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Drying Temperature Effects on Fish Dry Mass Measurements
J. Great Lakes Res. 33:606–616 Internat. Assoc. Great Lakes Res., 2007
Drying Temperature Effects on Fish Dry Mass Measurements Brian F. Lantry* and Robert O’Gorman U.S. Geological Survey Biological Resources Division (USGS) Lake Ontario Biological Station 17 Lake St. Oswego, New York 13126 ABSTRACT. Analysis of tissue composition in fish often requires dry samples. Time needed to dry fish decreases as temperature is increased, but additional volatile material may be lost. Effects of 10°C temperature increases on percentage dry mass (%DM) were tested against 60°C controls for groups of lake trout Salvelinus namaycush, rainbow smelt Osmerus mordax, slimy sculpin Cottus cognatus, and alewife Alosa pseudoharengus. Lake trout %DMs were lower at greater temperatures, but not significantly different from 60°C controls. Rainbow smelt and slimy sculpin %DMs were lower at greater temperatures and differences were significant when test temperatures reached 90°C. Significant differences were not found in tests using alewives because variability in %DM was high between fish. To avoid inter-fish variability, 30 alewives were each dried successively at 60, 70, 80, and then 90°C and for all fish %DM declined at each higher temperature. In general, %DMs were lower at greater temperatures and after reaching a stable dry weight, fish did not lose additional mass if temperature remained constant. Results indicate that caution should be used when comparing dry mass related indices from fish dried at different temperatures because %DM was negatively related to temperature. The differences in %DM observed with rising temperature could account for substantial portions of the variability in reported energy values for the species tested. Differences in %DM means for the 60 vs. 80°C and 60 vs. 90°C tests for rainbow smelt and alewife could represent of from 8 to 38% of observed annual energy cycles for Lakes Ontario and Michigan. INDEX WORDS:
Drying time, energy density, lake trout, rainbow smelt, slimy sculpin, alewife.
INTRODUCTION Fish tissue is routinely dried prior to biochemical analysis or determination of energy content. The wide range of drying temperatures and processing methods used (Appendix Table 1) has potential to affect the results of individual studies and confound comparisons between studies. To our knowledge it has not been determined if drying temperatures, within the range from published studies, affect the final dry mass of fish. Dependence of the final dry mass on drying temperature may cause problems with individual estimates of energy content or tissue composition and with comparisons between samples dried at different temperatures. Error caused by using inappropriate or inconsistent drying temperatures can propagate as drying is used in developing dry mass dependent relations and then used again applying those relations. The *Corresponding
relation between percentage dry mass (%DM) and energy density in fish (Iles and Wood 1965, Craig 1977, Rottiers and Tucker 1982, Flath and Diana 1985, Hartman and Brandt 1995) has been used to circumvent labor intensive calorimetric measurements, simplifying estimation of energy density and allowing for increased sample sizes. With these relations established, %DM measurements have then been used to index fish condition and construct energy budgets (Rand et al. 1994, Lantry and Stewart 1993). Energy density relations were expected to be constant within species, however, differences have been observed between sample locations and studies (Hartman and Brandt 1995, Rand et al. 1994). Drying problems could affect development of energy density—%DM relations through incomplete drying which would bias caloric densities low and %DM high causing the relation to be lower due to both; or through additional volatilization of dry tissue which would cause a decrease in %DM and an increase in the relation. If fats were the material
author. E-mail: [email protected]
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Drying Temperature Effects volatilized they would somewhat offset the effect of a decrease in %DM because of their greater caloric density compared to protein. During the application of these relations incomplete drying of index samples would bias predicted energy values high whereas temperature induced volatilization of dry tissue would bias predicted values low. Using inappropriate, but equivalent temperatures in the development and application of relations would diminish accuracy with little affect on precision whereas using different temperatures could offset or enhance error. Knowing the appropriate drying temperature and the time needed to dry samples would aid in development and accuracy of dry mass related measurements and in determining if differences between studies were methodological. We routinely dry samples of four species of fish, juvenile (< 350 mm) lake trout (Salvelinus namaycush, Walbaum), rainbow smelt (Omerus mordax, Mitchill), slimy sculpin (Cottus cognatus, Richardson), and alewife (Alosa pseudoharengus, Wilson), to monitor seasonal and annual energetic condition. Initially 60°C was used as the standard drying temperature, but larger fish often required up to 2 weeks to reach a constant dry mass. Greater oven temperatures would decrease drying time, but only limited information existed concerning the effects higher temperatures had on final dry mass. Several methodological handbooks and a small number of published articles offered some advice on drying animal tissue. Some of the authors speculated that volatile fats are lost as drying temperatures approach 100°C, but did not test this idea (Busacker et al. 1990, Dowgiallo 1975, Crisp 1971, Giese 1967). Most of these authors indicated a range of 60 to 110°C was generally used to dry samples, but tests of the effects of using different drying temperatures were not presented. Dowgiallo (1975) indicated that samples dried at 60°C were usually a few percent higher in final dry mass than those dried at 100°C and advised the use of 60°C because volatile material may be lost at the higher drying temperature. Giese (1967) observed that at drying temperatures above 110°C marine invertebrate tissue changed color (“charred”) and the loss of volatile components in 48 h was up to 10% of the sample mass. Strange and Pelton (1987) compared fish dried at 60°C for 48 h with those dried first at 60°C for 24 h and then overnight at 105°C, but did not describe their methods and provided limited descriptions of their results. They indicated that fish dried at the 60°C for 48 h lost less mois-
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ture and hence had lower apparent energy content than those that finished drying at 105°C. Oliver et al. (1979) dried their fish at 105°C recognizing that some fatty acids volatilize at this temperature, but judged such loss of mass unimportant since lipids do not generally volatilize at 105°C. Although the advice from these authors is valuable, statistical comparisons between samples dried at different temperatures were absent. For many other studies (Appendix Table 1), the oven temperatures used to dry fish were typically between 60°C and 110°C (range: 40°C to 125°C). Various studies dried whole, sectioned, or ground samples. Lengths of drying varied considerably between studies with several using a 24-h period and giving no indication of how determination of a final dry mass was confirmed. The objective of this study was to examine whether increasing oven temperatures above 60°C led to changes in final dry mass percentage for fish. As part of an ongoing analysis, we had been drying fish to characterize mean seasonal energy density and fish-to-fish variability, so entire carcasses of individual fish were dried. Because we needed information that related to those drying procedures, in the current study we dried intact (≤ 100 mm) or sectioned (> 100 mm) individual fish at several temperatures within the range most typically used in published studies (60 to 110°C). METHODS Differences Among Groups Dried at Discrete Temperatures Lake trout about 19 months in age were obtained from three hatcheries: the New York State Department of Environmental Conservation hatchery at Bath, New York; the U.S. Fish and Wildlife Service Alleghany National Fish Hatchery at Warren, Pennsylvania; and The Ontario Ministry of Natural Resources Harwood Fish Culture Station, Harwood, Ontario, Canada. Rainbow smelt (hereafter referred to as smelt), slimy sculpin (hereafter referred to as sculpin), and alewife were collected with bottom trawls from Lake Ontario during April–October, 2003–2004. Upon collection, all fish were lightly coated with water and frozen immediately in sealed plastic bags. Collections dates and length ranges for all samples appear in Table 1. In preparation for drying at the laboratory, fish were thawed, excess water was blotted off the carcass, the body cavity was opened, and the stomach and intestine were manually cleared of food material. Each fish was
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TABLE 1. Mean percentage dry mass (%DM) for groups dried at discrete temperatures. Sample sizes are in parentheses following means for %DM. For lake trout and rainbow smelt, ANCOVA was used to compare %DM between groups with length as the covariate. No differences in slopes for either species were found, so least square means were used to evaluate temperature effects on %DM. ANOVA was used to compare %DM between groups for slimy sculpin and alewife. Length ranges and means appear in the same order as test temperatures. Asterisks indicate significant differences and MSE is mean square error. Sample Date Lake Trout: 28-Apr-04 28-Apr-04 28-Apr-04 26-Apr-05 24-Feb-05
Test Temp. (°C)
Total Length (mm)
Mean %DM
p-value
MSE
60 vs. 70 60 vs. 70 60 vs. 80 60 vs. 90 60 vs. 90
85–167, 105–153 116–179, 117–184 169–239, 148–248 111–166, 112–162 140–230, 141–227
21.61 (15), 21.21 (15) 24.42 (14), 24.13 (15) 26.08 (15), 25.57 (15) 21.59 (30), 21.37 (30) 27.02 (30), 26.68 (30)
0.143 0.358 0.081 0.335 0.071
0.524 0.722 0.576 0.771 0.514
Rainbow Smelt: 26-Apr-04 04-Jun-04 06-May-04 18-Oct-03 29-Jul-03
60 vs. 70 60 vs. 80 60 vs. 90 60 vs. 105 60 vs. 105
71–158, 69–145 60–155, 64–146 52–94, 54–96 54–132, 49–150 61–132, 68–127
22.48 (25), 22.46 (27) 20.25 (20), 19.90 (19) 20.54 (25), 19.60 (26) 22.98 (12), 22.01 (20) 22.27 (39), 20.48 (36)
0.962 0.515 0.037* 0.015* 0.035*
2.184 2.825 2.424 2.821 4.611
Slimy Sculpin: 22-Apr-04 06-Jun-04 04-Jun-04 21-Oct-04 29-Jul-03
60 vs. 70 60 vs. 70 60 vs. 80 60 vs. 80 60 vs. 90
73–94, 67–93 63–97, 63–101 63–114, 66–112 64–121, 78–130 62–95, 61–96
24.38 (10), 24.16 (10) 24.59 (14), 24.54 (14) 22.55 (15), 21.48 (15) 24.93 (30), 24.54 (30) 22.80 (24), 21.75 (23)
0.747 0.942 0.112 0.464 0.026*
2.220 2.517 3.198 4.353 2.466
Alewife: 16-Apr-04 16-Apr-04 26-Apr-04 16-Apr-04 06-May-04
60 vs. 70 60 vs. 80 60 vs. 80 60.vs. 90 60 vs. 90
136–167, 135–165 155–173, 151–172 132–173, 139–163 147–169, 146–172 128–166, 126–168
26.74 (12), 26.35 (12) 25.93 (9), 25.05 (10) 28.00 (30), 27.06 (30) 25.65 (10), 24.33 (10) 24.53 (30), 23.91 (30)
0.732 0.579 0.133 0.389 0.465
7.634 11.494 5.783 11.150 10.722
measured for total length (nearest mm) and mass (nearest 0.01 g) and placed whole (small fish ≤ 100 mm) or dorso-ventrally cut into 2 to 3 sections (fish > 100mm) into weighed aluminum dishes which were then placed into the oven. Dry weights were obtained immediately after removal of fish from the oven and samples were considered dry if masses of individual fish were within 0.01 g over 3 consecutive days. The balances used to measure weights, an AND Model FY300 and a Sartorius Model BL 1500S, had resolutions of 0.01 grams and repeatability’s of 0.01 and 0.015 g, respectively. Oven temperatures were monitored using calibrated Traceable® Full Scale Plus digital thermometers that had a resolution of 0.1°C and were accurate to 1.0°C. A test consisted of drying two similar groups of fish in separate ovens, one group dried at 60°C
(control) and the other dried at a higher temperature (70°C, 80°C, or 90 or 105°C, Table 1). Drying whole fish prohibited repeat sampling from one individual, so samples consisted of groups of individual fish dried separately. For each test, samples consisted of fish from one species caught in Lake Ontario at one location on one date or, for lake trout, came from a single raceway at one of three hatcheries on the same date. For each test, the two sample groups were drawn from the same sample and were made up of similar numbers of fish (n ranged from 9 to 30) encompassing the entire length range present. Percentage dry masses (%DM) were calculated for each fish by dividing the final dry mass by the initial wet mass and multiplying by 100. Because sample groups included fish from a range of sizes, linear regression was used to test for relations be-
Drying Temperature Effects tween length and %DM. When significant relations were detected, analysis of covariance (ANCOVA) was used to compare %DM between the sample groups with length as the covariate. When ANCOVAs indicated no differences between slopes, the least square means (LSM) were compared with t–tests. The LSM test examined differences between predicted %DM values from each regression at the mean length for the entire sample of fish used in each test. Analysis of variance (ANOVA) was used to compare mean %DM between the sample groups for species that showed no relation between length and %DM. Means were considered different at p-values ≤ 0.05. Low sample size provided limited power to detect differences in three tests that had relatively large differences between the sample group means (≈ 1% DM). Therefore, we repeated the three tests (60 vs. 80°C tests for sculpin and alewife, and 80 vs. 90°C test for alewife) because power analysis of sample size (α = 0.05 and 1 – β = 0.05; Neter et al. 1985) indicated sample group sizes should be increased to about 30 fish (all test results appear in Table 1). Differences Among Individuals Dried at Sequentially Greater Temperatures The effect of different drying temperatures on %DM for a single fish was examined by tracking masses of individual alewife as they were held at increasingly higher temperatures. To accomplish this, two 30-fish sample groups were dried to a constant mass, one at 60°C (sample A) and the other at 80°C (sample B), in two separate ovens. After a stable dry mass was obtained for each fish in sample A at 60°C, the oven temperature was raised sequentially to 70, 80, and then 90°C holding the fish at each temperature until a constant mass was achieved. Sample B was maintained at 80°C during the time period that sample A was taken through the cycle of temperatures from 60°C to 80°C. Maintaining sample B at 80°C allowed us to: 1) verify that dry masses remained stable at a constant temperature and 2) test whether the %DM obtained at 80°C differed between samples A and B. When sample A was raised to 90°C, sample B was also raised to 90°C to further verify that increasing temperature, and not some other time related event, was decreasing dry masses. The difference between the initial mean dry mass at 60°C for sample A, and those obtained for sample A at 70, 80, and 90°C were examined using a repeated measures ANOVA and those differences were examined for relations
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with fish length using linear regression. Regression relations between length and loss of dry mass were further examined by converting total dry mass lost per fish to mass specific values by dividing the mass lost by the initial dry mass obtained at 60°C and multiplying by 100 (percentage dry mass lost). For sample B, the mass specific dry mass lost was calculated by dividing the dry mass lost between 80 and 90°C by the initial value obtained at 80°C and multiplying by 100. RESULTS Differences Among Groups Dried at Discrete Temperatures Lake Trout Five tests were run for lake trout, two 60 vs. 70°C, one 60 vs. 80°C, and two 60 vs. 90°C (Table 1). Lake trout ranged in length from 85 to 286 mm, and length was positively related to %DM (r 2 s ranged from 0.22 to 0.85). Fish from each hatchery differed in length and length related %DM. Within all tests, ANCOVAs indicated slopes of length related regressions were not significantly different between sample groups. The LSMs were also not significantly different, although LSMs in the 60°C vs. 80°C test and one of the 60°C vs. 90°C tests were nearly significantly different (p = 0.08 and 0.07). For all tests, sample groups dried at 70 to 90°C were always lower in %DM than their respective 60°C control. Rainbow Smelt Five tests were run for smelt, one each with 60°C as the control and 70, 80, or 90°C as the test temperature and two 60 vs. 105°C tests (Table 1). Smelt samples included both juveniles and adults ranging in length from about 60 mm to 135 mm. For all samples length was positively related to %DM (r2s ranged from 0.22 to 0.71) and ANCOVAs indicated equal slopes within all tests for sample groups. The LSMs for the 60°C vs. 70°C and the 60°C vs. 80°C tests were not significantly different, although samples dried at > 60°C were always lower in %DM than the 60°C control. The LSMs for the 60°C vs. 90°C test and both of the 60°C vs. 105°C tests were significantly different. Smelt dried at 90°C and at 105°C were about 1% DM and 2% DM below values for fish dried at 60°C.
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Slimy Sculpin Five tests were run for sculpin, two each with 60°C as the control and 70 or 80°C as the test temperature and one 60 vs. 90°C test (Table 1). Sculpin samples included juveniles and adults from 61- to 130-mm long. Regression analyses indicated that for all samples length was not significantly related to %DM (r2 ≤ 0.16). Similar to lake trout and smelt, all %DM means from samples dried at > 60°C were lower than their 60°C controls. ANOVAs indicated that the means for sample pairs dried at 60°C vs. 70°C and at 60°C vs. 80°C were not significantly different, although the difference between the means for the first 60°C vs. 80°C test was nearly significant (p = 0.11, n = 15). Repeating the 60°C versus 80°C test with a larger sample size (n = 30) produced a less significant outcome (p = 0.464). The means for the 60°C vs. 90°C test were significantly different (p = 0.026). Sculpin dried at 90°C were about 1% DM below values for fish dried at 60°C. Alewife Five tests were run for alewife, one 60 vs. 70°C test, and two each with 60°C as the control and 80 or 90°C as the test temperature (Table 1). Alewife samples included adults from 126- to 173-mm long. Regression analyses indicated that length was not significantly related to %DM for the 60 vs. 70°C and the 60 vs. 90°C tests (r2 ≤ 0.089). For both 60 vs. 80°C tests, length was negatively related to %DM for fish dried at 60°C only (r2 = 0.684 and 0.235; slopes = 0.371 and 0.121). For the alewives dried at 80°C, length was not related to %DM (r2 = 0.004 and 0.025). ANOVAs were run for all tests and indicated no significant differences related to drying temperature. Comparison of means was confounded by high within sample group variability. Alewife had a greater within sample mean square error (MSE) in %DM (range: 5.7 to 11.2) than the other species tested (range: 0.5 to 4.6). Despite the lack of statistical significance the means for the higher temperature in each comparison were consistently lower than those from the 60°C control samples. Differences Among Individuals Dried at Sequentially Greater Temperatures In the sequential temperature test, each alewife from sample A lost dry mass at each increased temperature (Table 2). Repeated measures ANOVA for
TABLE 2. Mean percentage dry mass (%DM) for alewife dried at sequential temperatures. Sample A was dried to a constant mass at 60°C and then raised in 10°C steps (drying to constant mass at each step) to 90°C. Sample B was maintained in a separate oven at 80°C during the time sample A was dried at 60, 70 and 80°C and then both samples were simultaneously raised to 90°C. Sample size for A and B was 30 alewives each. Mean %DM was the mean for all 30 fish in each sample. The “%DM Diff.” was the difference between the mean %DM for sample A at 60°C and the mean %DM for each other temperature. Oven Temp. Sample (°C) A 60 A 70 A 80 A 90 B 80 B 90
Total Length Range (mm) 158–187 158–187 158–187 158–187 139–163 139–163
Mean %DM 27.88 27.72 27.61 27.47 27.01 26.94
%DM Diff. (= 60C – X) N/A 0.17 0.27 0.41 0.87 0.95
sample A indicated that after fish were first dried at 60°C, the mean amounts of additional mass lost at each temperature step (70, 80, and 90°C) were all significantly different (P < 0.0001) from one another. The final difference in dry mass lost between steps from 60°C to 90°C for sample A was positively related to fish length and averaged about 0.10 g or 0.41 %DM (Fig. 1). At each temperature step, the mass specific dry mass lost was also positively related to fish length (Fig. 2). For sample B mass specific dry mass lost between 80 and 90°C was not related to fish length (r2 = 0.005). Alewives from sample B, when maintained for 28 days at 80°C, reached constant dry mass within 5 days and lost only an average of 0.01g (n = 30, SE = 0.0013) between days 5 and 28. During the same time period, sample A alewives were sequentially dried at 60°C, 70°C, and 80°C and lost on average 0.07g (n = 30, SE = 0.0037). Final mean %DM for sample A at 80°C was 0.60 %DM greater than the value for sample B (both samples dried for the same amount of days). Sample A lost an average of 0.27 %DM after increasing the temperature from 60°C to 80°C, whereas the difference between the average %DM for sample B (dried at 80°C) and the average for sample A at 60°C was 0.87 %DM. This indicates that the additional dry mass lost by sequentially raising sample A from 60°C to 80°C was about three times less than what would have been
Drying Temperature Effects
FIG. 1. Relationships between total length and the amounts of dry mass lost by individual alewife in sample A of the sequential drying temperature experiment. Dry mass lost represents the difference between the initial dry mass obtained at 60°C and those values achieved at 70°C (∆), 80°C ( ■ ), ◆ ). Equations are listed in the same and 90°C (◆ order as the regression lines appear in the chart. lost if these fish were simply dried to a constant mass at 80°C initially. After maintaining a stable weight for 23 days at 80°C, sample B lost on average an additional 0.02 g of dry mass when it was raised from 80 to 90°C compared to an average loss of 0.03 g for sample A for the same temperature interval. DISCUSSION For all tests conducted within this study, the sample group means were consistently lower for the higher temperature in each test than for the 60°C control (Table 1). The differences in sample means ranged from 0.02 to 1.74 %DM which accounted for up to 6.3% of the fish’s total %DM. For lake trout, the difference between the means for the 60 vs. 80°C and one of the 60 vs. 90°C tests were nearly significant (p’s of 0.08 and 0.07), and for smelt and sculpin the difference in means became significant when test temperatures reached 90°C. Lipid concentration, energy density, and %DM in fish are often positively related to fish length (Rottiers and Tucker 1982, Rand et al. 1994, Madenjian et al. 2000). Regardless of fish size, %DM values for fish are related to energy density and lipid concentration (Craig 1977, Rottiers and Tucker 1982, Rand et al. 1994, Hartman and Brandt 1995, Owens and Noguchi 1998). In this study, lake trout and
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FIG 2. Relationships between total length and the mass specific dry mass lost for individual alewives in sample A for 70°C (∆), 80°C ( ■ ), and ◆) drying temperatures. Mass specific dry 90°C (◆ mass lost represents 100 multiplied by the quotient of dry mass lost and the initial dry mass obtained at 60°C. The dry mass lost was the difference between the dry mass obtained at 60°C and those values achieved at each greater temperature step. Equations are listed in the same order as the regression lines appear in the chart. smelt %DM values were positively related to fish length, whereas alewife and sculpin %DM values were not related to fish length. For alewife, relatively high variation in %DM values (current study) and lipid concentrations (Madenjian et al. 2000) may have hampered the detection of a %DM – length relation. Unlike our study, however, Madenjian et al. (2000) observed a significant relationship between lipid concentration and fish length (r2s = 0.42, 0.18 and 0.01) for slimy sculpin from Lake Michigan and the lengths of sculpin in their study were similar to those in our study. The absence of a %DM - length relationship in the current study may have been due to low sample size or perhaps the fat content of sculpin at different sizes does indeed vary less in Lake Ontario than in Lake Michigan. We do not have information on the length specific fat content of slimy sculpin in Lake Ontario. The lack of a %DM – length relationship for sculpin in the current study was consistent across samples and did not change with sample size, location, or date. The reason for the discrepancies for slimy sculpin between studies was not clear and warrants further investigation. Of the four species tested, alewife had the great-
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est within sample variability (Table 1) making it difficult to detect differences between sample group means within tests. Examining one group of alewives (sample A) dried at sequentially greater temperatures (60, 70, 80, and 90°C) avoided the confounding effect of the between fish variability. This test revealed that each alewife lost dry mass as drying temperature increased (Fig. 1). The mean dry mass for sample A when a stable dry mass was reached at 80°C, however, was about three times the value expected if the fish were dried at 80°C initially (i.e., sample B) without the temperature steps. A possible explanation for this disparity is that while drying sample A at 60°C, some fats liquefied and mixed with or coated material that would have volatilized at higher temperatures preventing some of that volatilization from happening. During this and previous work, the authors observed that some fat will liquefy at 60°C and leak out of the drying fish carcasses. Drying the fish in sample A at sequentially greater temperatures also affected the way fish size was related to the dry mass loss rate. For sample A, %DM was negatively related to fish size (r 2 = 0.26). Larger alewives, despite being lower in %DM, lost a greater proportion of their dry mass than did smaller alewives (Fig. 2). This indicated that the relative supply of the volatile(s) was greater or volatiles were lost at a greater rate for larger alewives. The percentage dry mass lost between 80 and 90°C for sample B was not related to fish length, indicating that the length related loss of volatiles observed in sample A occurred between 60 and 80°C. In addition to confirming that alewife were losing additional mass at higher drying temperatures, the sequential drying temperature test further indicated that once a stable dry mass was obtained it remained constant if temperature was unchanged. This result was important because it provided evidence that increases in temperature and not some other time-related event caused the further declines in dry mass. Decreases in dry mass at higher temperatures suggested that some material not volatile at lower temperatures (e.g., fats) was being lost. Temperature-induced losses in %DM observed in this study may appear inconsequential, but even these amounts can account for substantial portions of fish energy budgets. Adult smelt can undergo seasonal energy changes of about 1,314 J g –1 in Lake Ontario (Rand et al. 1994) and about 1,671 J g –1 in Lake Michigan (Foltz 1974, Rand et al. 1994). Adult alewife undergo wider changes than
smelt with values up to 2,476 J g–1 reported for Lake Ontario (Rand et al. 1994) and about 4,500 J g –1 for Lake Michigan (Stewart and Binkowski 1986). Rand et al. (1994) developed four separate regressions of energy density on %DM for Lakes Ontario and Michigan smelt and alewife which facilitated conversion of %DM values from the present study to energy density. Differences in the %DM means for smelt from the present study for the 90°C and 105°C tests ranged between 0.93 %DM and 1.74 %DM. Using the Lake Ontario smelt energy density regression, those differences equate to between 264 J g–1 and 490 J g–1 or 20% to 37% of the reported seasonal energy budget for smelt in Lake Ontario. Using the Lake Michigan regression those differences in %DM equate to between 347 J g–1 and 643 J g–1 or 21 to 38% of the seasonal energy cycle. The differences in means for %DM for alewife from the present study ranged from 0.88 %DM to 1.32 %DM for the 80°C and 90°C tests. Using the Lake Ontario alewife regression those differences in %DM equate to between 317 J g–1 and 404 J g–1 or 13% and 16% of the total seasonal energy cycle. Using the Lake Michigan regression those differences in %DM equate to between 341 J g–1 and 511 J g–1 or 8% and 11% of the seasonal energy cycle. The variability of methods and temperatures used to dry fish for energy determination has probably contributed to errors in determining true energy density relations for some fishes. Many authors that developed relations between energy density and %DM consider them species specific (Hartman and Brandt 1995, Rand et al. 1994), and there is little evidence to suggest that they should vary across locations. For alewife and smelt, however, the relations Rand et al. (1994) developed for Lake Michigan were lower than those for Lake Ontario. The Lake Ontario alewife and smelt were both dried at 60°C until a constant mass was reached over 3 consecutive days. In the samples from Lake Michigan, the alewife were dried at 50°C for 5 to 7 days (Flath and Diana 1985) and the smelt were dried for 48 h at 60°C (Foltz and Norden 1977). In the present study, adult alewives (≥ 135 mm) dried at 60°C required from 3 to 8 days to reach a constant mass. Adult sized smelt from the current study (≥ 100 mm) dried at 60°C required from 2 to 5 days to reach constant dry mass. Based on differences in drying times between studies for both species, the Lake Michigan fish may not have been completely dry when used in calorimetric analysis causing un-
Drying Temperature Effects derestimation of their energy density. In addition, the higher temperature at which Lake Ontario alewives were dried may have also contributed to the difference between studies. Similarly, Strange and Pelton (1987) compared fish dried at 60°C for 48 h with those dried at 60°C for 24 h and then 105°C overnight and found that the former had lower apparent energy content attributed to incomplete drying. During the present study, the goal of using greater drying temperatures was to shorten the time needed to reach constant dry masses. From our analyses, we were able to determine the approximate times needed to reach final dry mass at the different temperatures (Appendix Table 2). Compared to lake trout dried at 60°C, drying time was shortened at 70°C by about 2 to 4 days, at 80°C by about 2 to 5 days, and at 90°C by about 3 to 8 days. For smelt, the savings in drying time at temperatures above 60°C was generally 1 day or less. For sculpin and alewife, drying time did not decrease appreciably as oven temperature was increased. Another advantage of drying at temperatures > 60°C was that final dry mass was reached abruptly. In contrast, during the last few days of drying at 60°C, final dry mass was often reached slowly, fish often lost only 0.01 g d–1, and dry masses would at times fluctuate. More research is needed to determine whether fish lose additional moisture when dried at temperatures > 60°C or whether they lose some other volatile material (e.g., fats). In the interim, we caution against simple comparisons between %DM related measures from fish processed at temperatures ≥ 90°C and 60°C, and more conservatively the same caution would apply to those dried ≥ 80°C and 60°C. When drying fish to examine trends in energetic condition through time it may be adequate to choose a drying temperature between 60 and 80°C as long as methods remain consistent. Greater precision is, however, required for developing %DM – energy density relations. Application of energy density relations to %DMs from dried fish will be most precise when the temperatures used in both the development and applications of the relations are equivalent. Individual fish dry masses determined in this study, after being dried to a constant value at a constant temperature, did not decrease while the temperature remained constant and only decreased after oven temperatures were raised. This suggested that some material not volatile at the lower temperatures was vaporized as temperatures increased. Because water was volatile at the lowest
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temperature used in the tests (60°C), we suggest that the additional material lost at greater temperatures was probably fat. Until the composition of the volatiles is identified, we recommend 60°C as the appropriate drying temperature. ACKNOWLEDGMENTS We thank the staffs at the New York State Department of Environmental Conservation Fish Hatchery at Bath, N.Y., the U.S. Fish and Wildlife Service Alleghany National Fish Hatchery, in Warren, Penn., and the Ontario Ministry of Natural Resources Harwood Fish Culture Station, in Harwood, Ontario, Canada for providing lake trout for this study. We thank Jean Adams for providing statistical assistance, James Johnson and Charles Madenjian for their reviews of early versions of this manuscript, and the anonymous reviewers for their comments. This article is Contribution 1429 of the USGS Great Lakes Science Center. REFERENCES Bai, S. C., Nematipour, G.R., Perera, R.P., Jaramillo Jr., F., Murphy, B.R., and Gatlin III., D.M. 1994. Total body electrical conductivity for nondestructive measurement of body composition of red drum. Prog. Fish-Cult. 56:232–236. Bandow, F., and Anderson, C.S. 1993. Weight-length relationships, proximate composition, and winter survival of stocked walleye fingerlings. Minnesota. Department of Natural Resources Investigative Report 425, 1993. Barziza, D.E., and Gatlin III, D.M. 2000. An evaluation of total body electrical conductivity to estimate body composition of largemouth bass, Micropterus salmoides. Aquat. Living Resour. 13:439–447. Birkett, L. 1969. The nitrogen balance in plaice, sole and perch. J. Exp. Biol. 50:375–386. Brown, M.L., Gatlin III, D.M., and Murphy, B.R. 1993. Non-destructive measurement of sunshine bass, Morone chrysops (Rafinesque) X Morone saxatilis (Walbaum), body composition using electrical conductivity. Aquacult. Fish. Manage. 24:585–592. Bryan, S.D., Soupir, C.A., Duffy, W.G., and Freiburger, C.E. 1996. Caloric densities of three predatory fishes and their prey in Lake Oahe, South Dakota. J. Freshwat. Ecol. 11:153–161. Buijse, A.D., and Houthuijzen, R.P. 1992. Piscivory, growth, and size-selective mortality of age-0 pikeperch (Stizostedion lucioperca). Can. J. Fish. Aquat. Sci. 49:894–902. Busacker, G.P., Adelman, I.R., and Goolish, E.M. 1990. Growth. In Methods For Fish Biology, C.B. Schreck
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and P.B. Moyle, eds., pp. 363–387. Bethesda, MD: American Fisheries Society. Craig, J.F. 1977. The body composition of adult perch, Perca fluviatilis in Windermere, with reference to seasonal changes and reproduction. J. Anim. Ecol. 46:617–632. ——— , Kenley, M.J., and Talling, J.F. 1978. Comparative estimations of the energy content of fish tissue from bomb calorimetry, wet oxidation and proximate analysis. Freshwat. Biol. 8:585–590. Crisp, D.J. 1971. Energy flow measurements. In Handbook No.16, Methods for the Study of Marine Benthos, N.A. Holme and A.D. McIntyre, eds., pp. 197–279. IPB (International Biological Programme). Diana, J.S., and Salz, R. 1990. Energy storage, growth, and maturation of yellow perch from different locations in Saginaw Bay, Michigan. Trans. Am. Fish. Soc. 119:976–984. Dowgiallo, A. 1975. Chemical composition of an animal’s body and its’ food. In Handbook No.24, Methods for Ecological Bioenergetics, W. Grodzinski, R.Z. Klekowski, and A. Duncan, eds., pp. 160–199. IBP (International Biological Programme). Eggleton, M.A., and Schramm, Jr., H.L. 2002. Caloric densities of selected fish prey organisms in the lower Mississippi River. J. Freshwat. Ecol. 17:409–414. Fagan, J.A., and Fitzpatrick, L.C. 1978. Allocation of secondary production to growth and reproduction by gizzard shad Dorosoma cepedianum (Clupeidae) in Lake Lewisville, Texas. Southwest. Nat. 23:247–262. Flath, L.E., and Diana, J.S. 1985. Seasonal energy dynamics of the alewife in southeastern Lake Michigan. Trans. Am. Fish. Soc. 114:328–337. Foltz, J.W. 1974. Food consumption and energetics of the rainbow smelt, Osmerus mordax (Mitchill), in Lake Michigan. M.Sc. thesis, University of Wisconsin-Milwaukee. ——— , and Norden, C.R. 1977. Seasonal changes in food consumption and energy content of smelt (Osmerus mordax) in Lake Michigan. Trans. Am. Fish. Soc. 106:230–640. Gerking, S.D. 1955. Influence of rate of feeding on body composition and protein metabolism of bluegill sunfish. Physiol. Zool. 28:267–282. Giese, A.C. 1967. Some methods for study of the biochemical constitution of marine invertebrates. Oceanogr. Mar. Biol. Annu. Rev. 5:159–186. Groves, T.D.D. 1970. Body composition changes during growth in young sockeye (Oncorhynchus nerka) in fresh water. J. Fish. Res. Board Can. 27:929–942. Hartman, K.J., and Brandt, S.B. 1995. Estimating energy density of fish. Trans. Am. Fish. Soc. 124:347–355. Hayes, D.B., and Taylor, W.W. 1994. Changes in the composition of somatic and gonadal tissues of yellow perch following white sucker removal. Trans. Am. Fish. Soc. 123:204–216.
Henderson, B.A., Trivedi, T., and Collins, N. 2000. Annual cycle of energy allocation to growth and reproduction of yellow perch. J. Fish Biol. 57:122–133. Iles, T.D., and Wood, R.J. 1965. The fat/water relationship in North Sea herring (Clupea harengus), and its possible significance. J. Mar. Biol. Assoc. U. K. 45:353–356. Jaramillo, Jr., F., Bai, S.C., Murphy, B.R., and Gatlin, III, D.M. 1994. Application of electrical conductivity for non-destructive measurement of channel catfish, Ictalurus punctatus, body composition. Aquat. Living Resour. 7:87–91. Jonas, J.L., Kraft, C.E, and Margenau, T.L. 1996. Assessment of seasonal changes in energy density and condition in age-0 and age-1 muskellunge. Trans. Am. Fish. Soc. 125:203–210. Kelso, J.R.M. 1972. Conversion, maintenance, and assimilation for walleye, Stizostedion vitreum vitreum, as affected by size, diet, and temperature. J. Fish. Res. Board Can. 29:1181–1192. ——— . 1973. Seasonal energy changes in walleye and their diet in West Blue Lake, Manitoba. Trans. Am. Fish. Soc. 102:363–368. Lantry, B.F., and Stewart, D.J. 1993. Ecological energetics of rainbow smelt in the Laurentian Great Lakes— an interlake comparison. Trans. Am. Fish. Soc. 122:951–976. Madenjian, C.P., Elliott, R.F., DeSorcie, T.J., Stedman, R.M., O’Connor, D.V., and Rottiers, D.V. 2000. Lipid concentrations in Lake Michigan fishes: seasonal, spatial, ontogenetic, and long-term trends. J. Great Lakes Res. 26:427–444. Meakins, R.H. 1976. Variations in the energy content of freshwater fish. J. Fish Biol. 8:221–224. Neter, J., Wasserman, W., and. Kutner, M.H. 1985. Applied linear statistical models, 2nd ed. Homewood, IL: Irwin. Oliver, J.D., Holeton, G.F., and Chua, K.E. 1979. Overwinter mortality of fingerling smallmouth bass in relation to size, relative energy stores, and environmental temperature. Trans. Am. Fish. Soc. 108:130–136. Owens, R.W., and Noguchi, G.E. 1998. Intra-lake variation in maturity, fecundity, and spawning of slimy sculpin (Cottus cognatus) in southern Lake Ontario. J. Great Lakes Res. 24:383–391. Pangle, K.L., Sutton, T.M., Kinnunen, R.E, and Hoff, M.H. 2004. Overwinter survival of juvenile lake herring in relation to body size, physiological condition, energy stores, and food ration. Trans. Am. Fish. Soc. 133:1235–1246. Pierce, R.J., Wissing, T.E., Jaworski, J.G., Givens, R.N., and Megrey, B.A. 1980. Energy storage and utilization patterns of gizzard shad in Acton Lake, Ohio. Trans. Am. Fish. Soc. 109:611–616. Post, J.R., and Parkinson, E.A. 2001. Energy allocation
Drying Temperature Effects strategy in young fish: allometry and survival. Ecology 82:1040–1051. Pratt, T.C., and Fox, M.G. 2002. Influence of predation risk on the overwinter mortality and energetic relationships of young-of-year walleyes. Trans. Am. Fish. Soc. 131:885–898. Rand, P.S., Lantry, B.F., O’Gorman, R., Owens, R.W., and Stewart, D.J. 1994. Energy density and size of pelagic prey fishes in Lake Ontario, 1978–1990: Implications for Salmonine Energetics. Trans. Am. Fish. Soc. 123:519–534. Rottiers, D.V., and Tucker, R.M. 1982. Proximate composition and caloric content of eight Lake Michigan fishes. USFWS Technical Papers 108. Simpkins, D.G., Hubert, W.A., Del Rio, C.M., and Rule, D.C. 2003. Physiological responses of juvenile rainbow trout to fasting and swimming activity: effects on body composition and condition indices. Trans. Am. Fish. Soc. 132:576–589. Stewart, D.J., and Binkowski, F.P. 1986. Dynamics of consumption and food conversion by Lake Michigan
APPENDIX TABLE 1. composition. Authors Gerking Birkett Groves Kelso Kelso Meakins Craig Foltz and Norden Craig et al. Fagan and Fitzpatrick Oliver et al. Pierce et al. Rottiers and Tucker Flath and Diana Strange and Pelton Tanasichuk and Mackay Diana and Salz Buijse and Houthuijzen Bandow and Anderson Brown et. al. Bai et al. Hayes and Taylor Jaramillo et al. Rand et al. Hartman and Brandt Bryan et al. Jonas et al.
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alewives: an energetics-modeling synthesis. Trans. Am. Fish. Soc. 115:643–661. Strange, R.J., and Pelton, J.C. 1987. Nutrient content of clupeid forage fishes. Trans. Am. Fish. Soc. 116:60–66. Sutton, S.G., Bult, T.P., and Haedrich, R.L. 2000. Relationships among fat weight, body weight, water weight, and condition factors in wild Atlantic salmon parr. Trans. Am. Fish. Soc. 129:527–538. Tanasichuk, R.W., and Mackay, W.C. 1989. Quantitative and qualitative characteristics of somatic and gonadal growth of yellow perch (Perca flavescens) from Lac Ste. Anne, Alberta. Can. J. Fish. Aquat. Sci. 46:989–994. Vondracek, B., Giese, B.D., and Henry, M.G. 1996. Energy density of three fishes from Minnesota waters of Lake Superior. J. Great Lakes Res. 22:757–764. Submitted: 2 May 2007 Accepted: 29 March 2007 Editorial handling: Donald J. Stewart
Survey of studies that dried fish tissue for calorimetry or analysis of proximate Publication date 1955 1969 1970
Drying temp. (°C) 105C 40-50 70
1972 1973 1976 1977 1977 1978 1978 1979 1980 1982 1985 1987 1989 1990 1992 1993 1993 1994 1994 1994 1994 1995 1996 1996
105 105 90 80 60 80 65 105 60 100 50 105 70 80 Freeze-dried 80 100 125 75-80 125 60-65 70 60 65-70
Dry weight end point detection constant weight constant weight constant weight (vacuum oven) constant weight constant weight ? constant weight 48 h ? constant weight 20-26 h constant weight constant weight constant weight 24 h constant weight constant weight constant weight constant weight 3h 24 h 3h constant weight constant weight 24 h constant weight
Sample preparation whole ? ? whole whole whole sectioned sectioned sectioned sectioned whole whole homogenized whole or sectioned homogenized sectioned whole or homogenized sectioned homogenized homogenized homogenized sectioned homogenized whole or sectioned whole homogenized homogenized (Continued)
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APPENDIX TABLE 1. Authors Vondracek et al. Barziza and Gatlin Henderson et al. Sutton et al. Post and Parkinson Eggleton and Schramm Pratt and Fox Simpkins et al. Pangle et al.
(Continued). Publication Date 1996 2000 2000 2000 2001 2002 2002 2003 2004
Drying Temp. (°C) 80 125 105 94 50 60 90 60 100
Dry weight end point detection constant weight 3h 24 h 16 h 96 h 72-96 h (vacuum oven) 48 h constant weight 24 h
Sample preparation homogenized homogenized homogenized whole whole homogenized homogenized sectioned whole
APPENDIX TABLE 2. Drying times (days) to the final dry weight (excluding the final two days of drying) at different temperatures for lake trout, rainbow smelt, slimy sculpin and alewife. Species Lake trout Lake trout Lake trout Lake trout Lake trout Lake trout Lake trout Lake trout Lake Trout Lake Trout Lake Trout Smelt Smelt Smelt Smelt Smelt Smelt Smelt Smelt Smelt Sculpin Sculpin Sculpin Sculpin Sculpin Alewife Alewife Alewife Alewife Alewife Alewife Alewife Alewife
Drying Temp. (°C) 60 60 60 60 70 70 80 80 80 90 90 60 60 60 70 70 80 80 105 105 60 60 60 80 80 60 60 70 70 80 80 90 90
Total Length (mm) 116–153 mm 154–186 mm 198–216 mm 231–239 mm 117–163 mm 168–184 mm 148–197 mm 196–213 mm 242–248 mm 141–180 mm 182–227 mm < 100 mm 100–125 mm 125–160 mm < 125 mm 124–145 mm < 111 mm 120–146 mm < 100mm 100–125 mm < 85 mm 85–100 mm 111–115 mm < 85 mm 86–115 mm < 100 mm 135–175 mm < 100 mm 140–165 mm < 100 mm > 123 mm < 110 mm 145–175 mm
Time (days) to dry weight 5–6 d 7–12 d 13 d 15 d 4d 5d 6–8 d 8–10 d 15 d 4d 7d 1–2 d 2–3 d 4–5 d 1d 3d 1–2 d 3–5 d 1d 1–3 d 1d 2d 2–3 d 1d 2d 1d 3–8 d 1d 3–4 d 1d 3d 1–2 d 5–6 d
Drying Temperature Effects on Fish Dry Mass Measurements Brian F. Lantry* and Robert O’Gorman U.S. Geological Survey Biological Resources Division (USGS) Lake Ontario Biological Station 17 Lake St. Oswego, New York 13126 ABSTRACT. Analysis of tissue composition in fish often requires dry samples. Time needed to dry fish decreases as temperature is increased, but additional volatile material may be lost. Effects of 10°C temperature increases on percentage dry mass (%DM) were tested against 60°C controls for groups of lake trout Salvelinus namaycush, rainbow smelt Osmerus mordax, slimy sculpin Cottus cognatus, and alewife Alosa pseudoharengus. Lake trout %DMs were lower at greater temperatures, but not significantly different from 60°C controls. Rainbow smelt and slimy sculpin %DMs were lower at greater temperatures and differences were significant when test temperatures reached 90°C. Significant differences were not found in tests using alewives because variability in %DM was high between fish. To avoid inter-fish variability, 30 alewives were each dried successively at 60, 70, 80, and then 90°C and for all fish %DM declined at each higher temperature. In general, %DMs were lower at greater temperatures and after reaching a stable dry weight, fish did not lose additional mass if temperature remained constant. Results indicate that caution should be used when comparing dry mass related indices from fish dried at different temperatures because %DM was negatively related to temperature. The differences in %DM observed with rising temperature could account for substantial portions of the variability in reported energy values for the species tested. Differences in %DM means for the 60 vs. 80°C and 60 vs. 90°C tests for rainbow smelt and alewife could represent of from 8 to 38% of observed annual energy cycles for Lakes Ontario and Michigan. INDEX WORDS:
Drying time, energy density, lake trout, rainbow smelt, slimy sculpin, alewife.
INTRODUCTION Fish tissue is routinely dried prior to biochemical analysis or determination of energy content. The wide range of drying temperatures and processing methods used (Appendix Table 1) has potential to affect the results of individual studies and confound comparisons between studies. To our knowledge it has not been determined if drying temperatures, within the range from published studies, affect the final dry mass of fish. Dependence of the final dry mass on drying temperature may cause problems with individual estimates of energy content or tissue composition and with comparisons between samples dried at different temperatures. Error caused by using inappropriate or inconsistent drying temperatures can propagate as drying is used in developing dry mass dependent relations and then used again applying those relations. The *Corresponding
relation between percentage dry mass (%DM) and energy density in fish (Iles and Wood 1965, Craig 1977, Rottiers and Tucker 1982, Flath and Diana 1985, Hartman and Brandt 1995) has been used to circumvent labor intensive calorimetric measurements, simplifying estimation of energy density and allowing for increased sample sizes. With these relations established, %DM measurements have then been used to index fish condition and construct energy budgets (Rand et al. 1994, Lantry and Stewart 1993). Energy density relations were expected to be constant within species, however, differences have been observed between sample locations and studies (Hartman and Brandt 1995, Rand et al. 1994). Drying problems could affect development of energy density—%DM relations through incomplete drying which would bias caloric densities low and %DM high causing the relation to be lower due to both; or through additional volatilization of dry tissue which would cause a decrease in %DM and an increase in the relation. If fats were the material
author. E-mail: [email protected]
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Drying Temperature Effects volatilized they would somewhat offset the effect of a decrease in %DM because of their greater caloric density compared to protein. During the application of these relations incomplete drying of index samples would bias predicted energy values high whereas temperature induced volatilization of dry tissue would bias predicted values low. Using inappropriate, but equivalent temperatures in the development and application of relations would diminish accuracy with little affect on precision whereas using different temperatures could offset or enhance error. Knowing the appropriate drying temperature and the time needed to dry samples would aid in development and accuracy of dry mass related measurements and in determining if differences between studies were methodological. We routinely dry samples of four species of fish, juvenile (< 350 mm) lake trout (Salvelinus namaycush, Walbaum), rainbow smelt (Omerus mordax, Mitchill), slimy sculpin (Cottus cognatus, Richardson), and alewife (Alosa pseudoharengus, Wilson), to monitor seasonal and annual energetic condition. Initially 60°C was used as the standard drying temperature, but larger fish often required up to 2 weeks to reach a constant dry mass. Greater oven temperatures would decrease drying time, but only limited information existed concerning the effects higher temperatures had on final dry mass. Several methodological handbooks and a small number of published articles offered some advice on drying animal tissue. Some of the authors speculated that volatile fats are lost as drying temperatures approach 100°C, but did not test this idea (Busacker et al. 1990, Dowgiallo 1975, Crisp 1971, Giese 1967). Most of these authors indicated a range of 60 to 110°C was generally used to dry samples, but tests of the effects of using different drying temperatures were not presented. Dowgiallo (1975) indicated that samples dried at 60°C were usually a few percent higher in final dry mass than those dried at 100°C and advised the use of 60°C because volatile material may be lost at the higher drying temperature. Giese (1967) observed that at drying temperatures above 110°C marine invertebrate tissue changed color (“charred”) and the loss of volatile components in 48 h was up to 10% of the sample mass. Strange and Pelton (1987) compared fish dried at 60°C for 48 h with those dried first at 60°C for 24 h and then overnight at 105°C, but did not describe their methods and provided limited descriptions of their results. They indicated that fish dried at the 60°C for 48 h lost less mois-
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ture and hence had lower apparent energy content than those that finished drying at 105°C. Oliver et al. (1979) dried their fish at 105°C recognizing that some fatty acids volatilize at this temperature, but judged such loss of mass unimportant since lipids do not generally volatilize at 105°C. Although the advice from these authors is valuable, statistical comparisons between samples dried at different temperatures were absent. For many other studies (Appendix Table 1), the oven temperatures used to dry fish were typically between 60°C and 110°C (range: 40°C to 125°C). Various studies dried whole, sectioned, or ground samples. Lengths of drying varied considerably between studies with several using a 24-h period and giving no indication of how determination of a final dry mass was confirmed. The objective of this study was to examine whether increasing oven temperatures above 60°C led to changes in final dry mass percentage for fish. As part of an ongoing analysis, we had been drying fish to characterize mean seasonal energy density and fish-to-fish variability, so entire carcasses of individual fish were dried. Because we needed information that related to those drying procedures, in the current study we dried intact (≤ 100 mm) or sectioned (> 100 mm) individual fish at several temperatures within the range most typically used in published studies (60 to 110°C). METHODS Differences Among Groups Dried at Discrete Temperatures Lake trout about 19 months in age were obtained from three hatcheries: the New York State Department of Environmental Conservation hatchery at Bath, New York; the U.S. Fish and Wildlife Service Alleghany National Fish Hatchery at Warren, Pennsylvania; and The Ontario Ministry of Natural Resources Harwood Fish Culture Station, Harwood, Ontario, Canada. Rainbow smelt (hereafter referred to as smelt), slimy sculpin (hereafter referred to as sculpin), and alewife were collected with bottom trawls from Lake Ontario during April–October, 2003–2004. Upon collection, all fish were lightly coated with water and frozen immediately in sealed plastic bags. Collections dates and length ranges for all samples appear in Table 1. In preparation for drying at the laboratory, fish were thawed, excess water was blotted off the carcass, the body cavity was opened, and the stomach and intestine were manually cleared of food material. Each fish was
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TABLE 1. Mean percentage dry mass (%DM) for groups dried at discrete temperatures. Sample sizes are in parentheses following means for %DM. For lake trout and rainbow smelt, ANCOVA was used to compare %DM between groups with length as the covariate. No differences in slopes for either species were found, so least square means were used to evaluate temperature effects on %DM. ANOVA was used to compare %DM between groups for slimy sculpin and alewife. Length ranges and means appear in the same order as test temperatures. Asterisks indicate significant differences and MSE is mean square error. Sample Date Lake Trout: 28-Apr-04 28-Apr-04 28-Apr-04 26-Apr-05 24-Feb-05
Test Temp. (°C)
Total Length (mm)
Mean %DM
p-value
MSE
60 vs. 70 60 vs. 70 60 vs. 80 60 vs. 90 60 vs. 90
85–167, 105–153 116–179, 117–184 169–239, 148–248 111–166, 112–162 140–230, 141–227
21.61 (15), 21.21 (15) 24.42 (14), 24.13 (15) 26.08 (15), 25.57 (15) 21.59 (30), 21.37 (30) 27.02 (30), 26.68 (30)
0.143 0.358 0.081 0.335 0.071
0.524 0.722 0.576 0.771 0.514
Rainbow Smelt: 26-Apr-04 04-Jun-04 06-May-04 18-Oct-03 29-Jul-03
60 vs. 70 60 vs. 80 60 vs. 90 60 vs. 105 60 vs. 105
71–158, 69–145 60–155, 64–146 52–94, 54–96 54–132, 49–150 61–132, 68–127
22.48 (25), 22.46 (27) 20.25 (20), 19.90 (19) 20.54 (25), 19.60 (26) 22.98 (12), 22.01 (20) 22.27 (39), 20.48 (36)
0.962 0.515 0.037* 0.015* 0.035*
2.184 2.825 2.424 2.821 4.611
Slimy Sculpin: 22-Apr-04 06-Jun-04 04-Jun-04 21-Oct-04 29-Jul-03
60 vs. 70 60 vs. 70 60 vs. 80 60 vs. 80 60 vs. 90
73–94, 67–93 63–97, 63–101 63–114, 66–112 64–121, 78–130 62–95, 61–96
24.38 (10), 24.16 (10) 24.59 (14), 24.54 (14) 22.55 (15), 21.48 (15) 24.93 (30), 24.54 (30) 22.80 (24), 21.75 (23)
0.747 0.942 0.112 0.464 0.026*
2.220 2.517 3.198 4.353 2.466
Alewife: 16-Apr-04 16-Apr-04 26-Apr-04 16-Apr-04 06-May-04
60 vs. 70 60 vs. 80 60 vs. 80 60.vs. 90 60 vs. 90
136–167, 135–165 155–173, 151–172 132–173, 139–163 147–169, 146–172 128–166, 126–168
26.74 (12), 26.35 (12) 25.93 (9), 25.05 (10) 28.00 (30), 27.06 (30) 25.65 (10), 24.33 (10) 24.53 (30), 23.91 (30)
0.732 0.579 0.133 0.389 0.465
7.634 11.494 5.783 11.150 10.722
measured for total length (nearest mm) and mass (nearest 0.01 g) and placed whole (small fish ≤ 100 mm) or dorso-ventrally cut into 2 to 3 sections (fish > 100mm) into weighed aluminum dishes which were then placed into the oven. Dry weights were obtained immediately after removal of fish from the oven and samples were considered dry if masses of individual fish were within 0.01 g over 3 consecutive days. The balances used to measure weights, an AND Model FY300 and a Sartorius Model BL 1500S, had resolutions of 0.01 grams and repeatability’s of 0.01 and 0.015 g, respectively. Oven temperatures were monitored using calibrated Traceable® Full Scale Plus digital thermometers that had a resolution of 0.1°C and were accurate to 1.0°C. A test consisted of drying two similar groups of fish in separate ovens, one group dried at 60°C
(control) and the other dried at a higher temperature (70°C, 80°C, or 90 or 105°C, Table 1). Drying whole fish prohibited repeat sampling from one individual, so samples consisted of groups of individual fish dried separately. For each test, samples consisted of fish from one species caught in Lake Ontario at one location on one date or, for lake trout, came from a single raceway at one of three hatcheries on the same date. For each test, the two sample groups were drawn from the same sample and were made up of similar numbers of fish (n ranged from 9 to 30) encompassing the entire length range present. Percentage dry masses (%DM) were calculated for each fish by dividing the final dry mass by the initial wet mass and multiplying by 100. Because sample groups included fish from a range of sizes, linear regression was used to test for relations be-
Drying Temperature Effects tween length and %DM. When significant relations were detected, analysis of covariance (ANCOVA) was used to compare %DM between the sample groups with length as the covariate. When ANCOVAs indicated no differences between slopes, the least square means (LSM) were compared with t–tests. The LSM test examined differences between predicted %DM values from each regression at the mean length for the entire sample of fish used in each test. Analysis of variance (ANOVA) was used to compare mean %DM between the sample groups for species that showed no relation between length and %DM. Means were considered different at p-values ≤ 0.05. Low sample size provided limited power to detect differences in three tests that had relatively large differences between the sample group means (≈ 1% DM). Therefore, we repeated the three tests (60 vs. 80°C tests for sculpin and alewife, and 80 vs. 90°C test for alewife) because power analysis of sample size (α = 0.05 and 1 – β = 0.05; Neter et al. 1985) indicated sample group sizes should be increased to about 30 fish (all test results appear in Table 1). Differences Among Individuals Dried at Sequentially Greater Temperatures The effect of different drying temperatures on %DM for a single fish was examined by tracking masses of individual alewife as they were held at increasingly higher temperatures. To accomplish this, two 30-fish sample groups were dried to a constant mass, one at 60°C (sample A) and the other at 80°C (sample B), in two separate ovens. After a stable dry mass was obtained for each fish in sample A at 60°C, the oven temperature was raised sequentially to 70, 80, and then 90°C holding the fish at each temperature until a constant mass was achieved. Sample B was maintained at 80°C during the time period that sample A was taken through the cycle of temperatures from 60°C to 80°C. Maintaining sample B at 80°C allowed us to: 1) verify that dry masses remained stable at a constant temperature and 2) test whether the %DM obtained at 80°C differed between samples A and B. When sample A was raised to 90°C, sample B was also raised to 90°C to further verify that increasing temperature, and not some other time related event, was decreasing dry masses. The difference between the initial mean dry mass at 60°C for sample A, and those obtained for sample A at 70, 80, and 90°C were examined using a repeated measures ANOVA and those differences were examined for relations
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with fish length using linear regression. Regression relations between length and loss of dry mass were further examined by converting total dry mass lost per fish to mass specific values by dividing the mass lost by the initial dry mass obtained at 60°C and multiplying by 100 (percentage dry mass lost). For sample B, the mass specific dry mass lost was calculated by dividing the dry mass lost between 80 and 90°C by the initial value obtained at 80°C and multiplying by 100. RESULTS Differences Among Groups Dried at Discrete Temperatures Lake Trout Five tests were run for lake trout, two 60 vs. 70°C, one 60 vs. 80°C, and two 60 vs. 90°C (Table 1). Lake trout ranged in length from 85 to 286 mm, and length was positively related to %DM (r 2 s ranged from 0.22 to 0.85). Fish from each hatchery differed in length and length related %DM. Within all tests, ANCOVAs indicated slopes of length related regressions were not significantly different between sample groups. The LSMs were also not significantly different, although LSMs in the 60°C vs. 80°C test and one of the 60°C vs. 90°C tests were nearly significantly different (p = 0.08 and 0.07). For all tests, sample groups dried at 70 to 90°C were always lower in %DM than their respective 60°C control. Rainbow Smelt Five tests were run for smelt, one each with 60°C as the control and 70, 80, or 90°C as the test temperature and two 60 vs. 105°C tests (Table 1). Smelt samples included both juveniles and adults ranging in length from about 60 mm to 135 mm. For all samples length was positively related to %DM (r2s ranged from 0.22 to 0.71) and ANCOVAs indicated equal slopes within all tests for sample groups. The LSMs for the 60°C vs. 70°C and the 60°C vs. 80°C tests were not significantly different, although samples dried at > 60°C were always lower in %DM than the 60°C control. The LSMs for the 60°C vs. 90°C test and both of the 60°C vs. 105°C tests were significantly different. Smelt dried at 90°C and at 105°C were about 1% DM and 2% DM below values for fish dried at 60°C.
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Slimy Sculpin Five tests were run for sculpin, two each with 60°C as the control and 70 or 80°C as the test temperature and one 60 vs. 90°C test (Table 1). Sculpin samples included juveniles and adults from 61- to 130-mm long. Regression analyses indicated that for all samples length was not significantly related to %DM (r2 ≤ 0.16). Similar to lake trout and smelt, all %DM means from samples dried at > 60°C were lower than their 60°C controls. ANOVAs indicated that the means for sample pairs dried at 60°C vs. 70°C and at 60°C vs. 80°C were not significantly different, although the difference between the means for the first 60°C vs. 80°C test was nearly significant (p = 0.11, n = 15). Repeating the 60°C versus 80°C test with a larger sample size (n = 30) produced a less significant outcome (p = 0.464). The means for the 60°C vs. 90°C test were significantly different (p = 0.026). Sculpin dried at 90°C were about 1% DM below values for fish dried at 60°C. Alewife Five tests were run for alewife, one 60 vs. 70°C test, and two each with 60°C as the control and 80 or 90°C as the test temperature (Table 1). Alewife samples included adults from 126- to 173-mm long. Regression analyses indicated that length was not significantly related to %DM for the 60 vs. 70°C and the 60 vs. 90°C tests (r2 ≤ 0.089). For both 60 vs. 80°C tests, length was negatively related to %DM for fish dried at 60°C only (r2 = 0.684 and 0.235; slopes = 0.371 and 0.121). For the alewives dried at 80°C, length was not related to %DM (r2 = 0.004 and 0.025). ANOVAs were run for all tests and indicated no significant differences related to drying temperature. Comparison of means was confounded by high within sample group variability. Alewife had a greater within sample mean square error (MSE) in %DM (range: 5.7 to 11.2) than the other species tested (range: 0.5 to 4.6). Despite the lack of statistical significance the means for the higher temperature in each comparison were consistently lower than those from the 60°C control samples. Differences Among Individuals Dried at Sequentially Greater Temperatures In the sequential temperature test, each alewife from sample A lost dry mass at each increased temperature (Table 2). Repeated measures ANOVA for
TABLE 2. Mean percentage dry mass (%DM) for alewife dried at sequential temperatures. Sample A was dried to a constant mass at 60°C and then raised in 10°C steps (drying to constant mass at each step) to 90°C. Sample B was maintained in a separate oven at 80°C during the time sample A was dried at 60, 70 and 80°C and then both samples were simultaneously raised to 90°C. Sample size for A and B was 30 alewives each. Mean %DM was the mean for all 30 fish in each sample. The “%DM Diff.” was the difference between the mean %DM for sample A at 60°C and the mean %DM for each other temperature. Oven Temp. Sample (°C) A 60 A 70 A 80 A 90 B 80 B 90
Total Length Range (mm) 158–187 158–187 158–187 158–187 139–163 139–163
Mean %DM 27.88 27.72 27.61 27.47 27.01 26.94
%DM Diff. (= 60C – X) N/A 0.17 0.27 0.41 0.87 0.95
sample A indicated that after fish were first dried at 60°C, the mean amounts of additional mass lost at each temperature step (70, 80, and 90°C) were all significantly different (P < 0.0001) from one another. The final difference in dry mass lost between steps from 60°C to 90°C for sample A was positively related to fish length and averaged about 0.10 g or 0.41 %DM (Fig. 1). At each temperature step, the mass specific dry mass lost was also positively related to fish length (Fig. 2). For sample B mass specific dry mass lost between 80 and 90°C was not related to fish length (r2 = 0.005). Alewives from sample B, when maintained for 28 days at 80°C, reached constant dry mass within 5 days and lost only an average of 0.01g (n = 30, SE = 0.0013) between days 5 and 28. During the same time period, sample A alewives were sequentially dried at 60°C, 70°C, and 80°C and lost on average 0.07g (n = 30, SE = 0.0037). Final mean %DM for sample A at 80°C was 0.60 %DM greater than the value for sample B (both samples dried for the same amount of days). Sample A lost an average of 0.27 %DM after increasing the temperature from 60°C to 80°C, whereas the difference between the average %DM for sample B (dried at 80°C) and the average for sample A at 60°C was 0.87 %DM. This indicates that the additional dry mass lost by sequentially raising sample A from 60°C to 80°C was about three times less than what would have been
Drying Temperature Effects
FIG. 1. Relationships between total length and the amounts of dry mass lost by individual alewife in sample A of the sequential drying temperature experiment. Dry mass lost represents the difference between the initial dry mass obtained at 60°C and those values achieved at 70°C (∆), 80°C ( ■ ), ◆ ). Equations are listed in the same and 90°C (◆ order as the regression lines appear in the chart. lost if these fish were simply dried to a constant mass at 80°C initially. After maintaining a stable weight for 23 days at 80°C, sample B lost on average an additional 0.02 g of dry mass when it was raised from 80 to 90°C compared to an average loss of 0.03 g for sample A for the same temperature interval. DISCUSSION For all tests conducted within this study, the sample group means were consistently lower for the higher temperature in each test than for the 60°C control (Table 1). The differences in sample means ranged from 0.02 to 1.74 %DM which accounted for up to 6.3% of the fish’s total %DM. For lake trout, the difference between the means for the 60 vs. 80°C and one of the 60 vs. 90°C tests were nearly significant (p’s of 0.08 and 0.07), and for smelt and sculpin the difference in means became significant when test temperatures reached 90°C. Lipid concentration, energy density, and %DM in fish are often positively related to fish length (Rottiers and Tucker 1982, Rand et al. 1994, Madenjian et al. 2000). Regardless of fish size, %DM values for fish are related to energy density and lipid concentration (Craig 1977, Rottiers and Tucker 1982, Rand et al. 1994, Hartman and Brandt 1995, Owens and Noguchi 1998). In this study, lake trout and
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FIG 2. Relationships between total length and the mass specific dry mass lost for individual alewives in sample A for 70°C (∆), 80°C ( ■ ), and ◆) drying temperatures. Mass specific dry 90°C (◆ mass lost represents 100 multiplied by the quotient of dry mass lost and the initial dry mass obtained at 60°C. The dry mass lost was the difference between the dry mass obtained at 60°C and those values achieved at each greater temperature step. Equations are listed in the same order as the regression lines appear in the chart. smelt %DM values were positively related to fish length, whereas alewife and sculpin %DM values were not related to fish length. For alewife, relatively high variation in %DM values (current study) and lipid concentrations (Madenjian et al. 2000) may have hampered the detection of a %DM – length relation. Unlike our study, however, Madenjian et al. (2000) observed a significant relationship between lipid concentration and fish length (r2s = 0.42, 0.18 and 0.01) for slimy sculpin from Lake Michigan and the lengths of sculpin in their study were similar to those in our study. The absence of a %DM - length relationship in the current study may have been due to low sample size or perhaps the fat content of sculpin at different sizes does indeed vary less in Lake Ontario than in Lake Michigan. We do not have information on the length specific fat content of slimy sculpin in Lake Ontario. The lack of a %DM – length relationship for sculpin in the current study was consistent across samples and did not change with sample size, location, or date. The reason for the discrepancies for slimy sculpin between studies was not clear and warrants further investigation. Of the four species tested, alewife had the great-
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est within sample variability (Table 1) making it difficult to detect differences between sample group means within tests. Examining one group of alewives (sample A) dried at sequentially greater temperatures (60, 70, 80, and 90°C) avoided the confounding effect of the between fish variability. This test revealed that each alewife lost dry mass as drying temperature increased (Fig. 1). The mean dry mass for sample A when a stable dry mass was reached at 80°C, however, was about three times the value expected if the fish were dried at 80°C initially (i.e., sample B) without the temperature steps. A possible explanation for this disparity is that while drying sample A at 60°C, some fats liquefied and mixed with or coated material that would have volatilized at higher temperatures preventing some of that volatilization from happening. During this and previous work, the authors observed that some fat will liquefy at 60°C and leak out of the drying fish carcasses. Drying the fish in sample A at sequentially greater temperatures also affected the way fish size was related to the dry mass loss rate. For sample A, %DM was negatively related to fish size (r 2 = 0.26). Larger alewives, despite being lower in %DM, lost a greater proportion of their dry mass than did smaller alewives (Fig. 2). This indicated that the relative supply of the volatile(s) was greater or volatiles were lost at a greater rate for larger alewives. The percentage dry mass lost between 80 and 90°C for sample B was not related to fish length, indicating that the length related loss of volatiles observed in sample A occurred between 60 and 80°C. In addition to confirming that alewife were losing additional mass at higher drying temperatures, the sequential drying temperature test further indicated that once a stable dry mass was obtained it remained constant if temperature was unchanged. This result was important because it provided evidence that increases in temperature and not some other time-related event caused the further declines in dry mass. Decreases in dry mass at higher temperatures suggested that some material not volatile at lower temperatures (e.g., fats) was being lost. Temperature-induced losses in %DM observed in this study may appear inconsequential, but even these amounts can account for substantial portions of fish energy budgets. Adult smelt can undergo seasonal energy changes of about 1,314 J g –1 in Lake Ontario (Rand et al. 1994) and about 1,671 J g –1 in Lake Michigan (Foltz 1974, Rand et al. 1994). Adult alewife undergo wider changes than
smelt with values up to 2,476 J g–1 reported for Lake Ontario (Rand et al. 1994) and about 4,500 J g –1 for Lake Michigan (Stewart and Binkowski 1986). Rand et al. (1994) developed four separate regressions of energy density on %DM for Lakes Ontario and Michigan smelt and alewife which facilitated conversion of %DM values from the present study to energy density. Differences in the %DM means for smelt from the present study for the 90°C and 105°C tests ranged between 0.93 %DM and 1.74 %DM. Using the Lake Ontario smelt energy density regression, those differences equate to between 264 J g–1 and 490 J g–1 or 20% to 37% of the reported seasonal energy budget for smelt in Lake Ontario. Using the Lake Michigan regression those differences in %DM equate to between 347 J g–1 and 643 J g–1 or 21 to 38% of the seasonal energy cycle. The differences in means for %DM for alewife from the present study ranged from 0.88 %DM to 1.32 %DM for the 80°C and 90°C tests. Using the Lake Ontario alewife regression those differences in %DM equate to between 317 J g–1 and 404 J g–1 or 13% and 16% of the total seasonal energy cycle. Using the Lake Michigan regression those differences in %DM equate to between 341 J g–1 and 511 J g–1 or 8% and 11% of the seasonal energy cycle. The variability of methods and temperatures used to dry fish for energy determination has probably contributed to errors in determining true energy density relations for some fishes. Many authors that developed relations between energy density and %DM consider them species specific (Hartman and Brandt 1995, Rand et al. 1994), and there is little evidence to suggest that they should vary across locations. For alewife and smelt, however, the relations Rand et al. (1994) developed for Lake Michigan were lower than those for Lake Ontario. The Lake Ontario alewife and smelt were both dried at 60°C until a constant mass was reached over 3 consecutive days. In the samples from Lake Michigan, the alewife were dried at 50°C for 5 to 7 days (Flath and Diana 1985) and the smelt were dried for 48 h at 60°C (Foltz and Norden 1977). In the present study, adult alewives (≥ 135 mm) dried at 60°C required from 3 to 8 days to reach a constant mass. Adult sized smelt from the current study (≥ 100 mm) dried at 60°C required from 2 to 5 days to reach constant dry mass. Based on differences in drying times between studies for both species, the Lake Michigan fish may not have been completely dry when used in calorimetric analysis causing un-
Drying Temperature Effects derestimation of their energy density. In addition, the higher temperature at which Lake Ontario alewives were dried may have also contributed to the difference between studies. Similarly, Strange and Pelton (1987) compared fish dried at 60°C for 48 h with those dried at 60°C for 24 h and then 105°C overnight and found that the former had lower apparent energy content attributed to incomplete drying. During the present study, the goal of using greater drying temperatures was to shorten the time needed to reach constant dry masses. From our analyses, we were able to determine the approximate times needed to reach final dry mass at the different temperatures (Appendix Table 2). Compared to lake trout dried at 60°C, drying time was shortened at 70°C by about 2 to 4 days, at 80°C by about 2 to 5 days, and at 90°C by about 3 to 8 days. For smelt, the savings in drying time at temperatures above 60°C was generally 1 day or less. For sculpin and alewife, drying time did not decrease appreciably as oven temperature was increased. Another advantage of drying at temperatures > 60°C was that final dry mass was reached abruptly. In contrast, during the last few days of drying at 60°C, final dry mass was often reached slowly, fish often lost only 0.01 g d–1, and dry masses would at times fluctuate. More research is needed to determine whether fish lose additional moisture when dried at temperatures > 60°C or whether they lose some other volatile material (e.g., fats). In the interim, we caution against simple comparisons between %DM related measures from fish processed at temperatures ≥ 90°C and 60°C, and more conservatively the same caution would apply to those dried ≥ 80°C and 60°C. When drying fish to examine trends in energetic condition through time it may be adequate to choose a drying temperature between 60 and 80°C as long as methods remain consistent. Greater precision is, however, required for developing %DM – energy density relations. Application of energy density relations to %DMs from dried fish will be most precise when the temperatures used in both the development and applications of the relations are equivalent. Individual fish dry masses determined in this study, after being dried to a constant value at a constant temperature, did not decrease while the temperature remained constant and only decreased after oven temperatures were raised. This suggested that some material not volatile at the lower temperatures was vaporized as temperatures increased. Because water was volatile at the lowest
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temperature used in the tests (60°C), we suggest that the additional material lost at greater temperatures was probably fat. Until the composition of the volatiles is identified, we recommend 60°C as the appropriate drying temperature. ACKNOWLEDGMENTS We thank the staffs at the New York State Department of Environmental Conservation Fish Hatchery at Bath, N.Y., the U.S. Fish and Wildlife Service Alleghany National Fish Hatchery, in Warren, Penn., and the Ontario Ministry of Natural Resources Harwood Fish Culture Station, in Harwood, Ontario, Canada for providing lake trout for this study. We thank Jean Adams for providing statistical assistance, James Johnson and Charles Madenjian for their reviews of early versions of this manuscript, and the anonymous reviewers for their comments. This article is Contribution 1429 of the USGS Great Lakes Science Center. REFERENCES Bai, S. C., Nematipour, G.R., Perera, R.P., Jaramillo Jr., F., Murphy, B.R., and Gatlin III., D.M. 1994. Total body electrical conductivity for nondestructive measurement of body composition of red drum. Prog. Fish-Cult. 56:232–236. Bandow, F., and Anderson, C.S. 1993. Weight-length relationships, proximate composition, and winter survival of stocked walleye fingerlings. Minnesota. Department of Natural Resources Investigative Report 425, 1993. Barziza, D.E., and Gatlin III, D.M. 2000. An evaluation of total body electrical conductivity to estimate body composition of largemouth bass, Micropterus salmoides. Aquat. Living Resour. 13:439–447. Birkett, L. 1969. The nitrogen balance in plaice, sole and perch. J. Exp. Biol. 50:375–386. Brown, M.L., Gatlin III, D.M., and Murphy, B.R. 1993. Non-destructive measurement of sunshine bass, Morone chrysops (Rafinesque) X Morone saxatilis (Walbaum), body composition using electrical conductivity. Aquacult. Fish. Manage. 24:585–592. Bryan, S.D., Soupir, C.A., Duffy, W.G., and Freiburger, C.E. 1996. Caloric densities of three predatory fishes and their prey in Lake Oahe, South Dakota. J. Freshwat. Ecol. 11:153–161. Buijse, A.D., and Houthuijzen, R.P. 1992. Piscivory, growth, and size-selective mortality of age-0 pikeperch (Stizostedion lucioperca). Can. J. Fish. Aquat. Sci. 49:894–902. Busacker, G.P., Adelman, I.R., and Goolish, E.M. 1990. Growth. In Methods For Fish Biology, C.B. Schreck
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and P.B. Moyle, eds., pp. 363–387. Bethesda, MD: American Fisheries Society. Craig, J.F. 1977. The body composition of adult perch, Perca fluviatilis in Windermere, with reference to seasonal changes and reproduction. J. Anim. Ecol. 46:617–632. ——— , Kenley, M.J., and Talling, J.F. 1978. Comparative estimations of the energy content of fish tissue from bomb calorimetry, wet oxidation and proximate analysis. Freshwat. Biol. 8:585–590. Crisp, D.J. 1971. Energy flow measurements. In Handbook No.16, Methods for the Study of Marine Benthos, N.A. Holme and A.D. McIntyre, eds., pp. 197–279. IPB (International Biological Programme). Diana, J.S., and Salz, R. 1990. Energy storage, growth, and maturation of yellow perch from different locations in Saginaw Bay, Michigan. Trans. Am. Fish. Soc. 119:976–984. Dowgiallo, A. 1975. Chemical composition of an animal’s body and its’ food. In Handbook No.24, Methods for Ecological Bioenergetics, W. Grodzinski, R.Z. Klekowski, and A. Duncan, eds., pp. 160–199. IBP (International Biological Programme). Eggleton, M.A., and Schramm, Jr., H.L. 2002. Caloric densities of selected fish prey organisms in the lower Mississippi River. J. Freshwat. Ecol. 17:409–414. Fagan, J.A., and Fitzpatrick, L.C. 1978. Allocation of secondary production to growth and reproduction by gizzard shad Dorosoma cepedianum (Clupeidae) in Lake Lewisville, Texas. Southwest. Nat. 23:247–262. Flath, L.E., and Diana, J.S. 1985. Seasonal energy dynamics of the alewife in southeastern Lake Michigan. Trans. Am. Fish. Soc. 114:328–337. Foltz, J.W. 1974. Food consumption and energetics of the rainbow smelt, Osmerus mordax (Mitchill), in Lake Michigan. M.Sc. thesis, University of Wisconsin-Milwaukee. ——— , and Norden, C.R. 1977. Seasonal changes in food consumption and energy content of smelt (Osmerus mordax) in Lake Michigan. Trans. Am. Fish. Soc. 106:230–640. Gerking, S.D. 1955. Influence of rate of feeding on body composition and protein metabolism of bluegill sunfish. Physiol. Zool. 28:267–282. Giese, A.C. 1967. Some methods for study of the biochemical constitution of marine invertebrates. Oceanogr. Mar. Biol. Annu. Rev. 5:159–186. Groves, T.D.D. 1970. Body composition changes during growth in young sockeye (Oncorhynchus nerka) in fresh water. J. Fish. Res. Board Can. 27:929–942. Hartman, K.J., and Brandt, S.B. 1995. Estimating energy density of fish. Trans. Am. Fish. Soc. 124:347–355. Hayes, D.B., and Taylor, W.W. 1994. Changes in the composition of somatic and gonadal tissues of yellow perch following white sucker removal. Trans. Am. Fish. Soc. 123:204–216.
Henderson, B.A., Trivedi, T., and Collins, N. 2000. Annual cycle of energy allocation to growth and reproduction of yellow perch. J. Fish Biol. 57:122–133. Iles, T.D., and Wood, R.J. 1965. The fat/water relationship in North Sea herring (Clupea harengus), and its possible significance. J. Mar. Biol. Assoc. U. K. 45:353–356. Jaramillo, Jr., F., Bai, S.C., Murphy, B.R., and Gatlin, III, D.M. 1994. Application of electrical conductivity for non-destructive measurement of channel catfish, Ictalurus punctatus, body composition. Aquat. Living Resour. 7:87–91. Jonas, J.L., Kraft, C.E, and Margenau, T.L. 1996. Assessment of seasonal changes in energy density and condition in age-0 and age-1 muskellunge. Trans. Am. Fish. Soc. 125:203–210. Kelso, J.R.M. 1972. Conversion, maintenance, and assimilation for walleye, Stizostedion vitreum vitreum, as affected by size, diet, and temperature. J. Fish. Res. Board Can. 29:1181–1192. ——— . 1973. Seasonal energy changes in walleye and their diet in West Blue Lake, Manitoba. Trans. Am. Fish. Soc. 102:363–368. Lantry, B.F., and Stewart, D.J. 1993. Ecological energetics of rainbow smelt in the Laurentian Great Lakes— an interlake comparison. Trans. Am. Fish. Soc. 122:951–976. Madenjian, C.P., Elliott, R.F., DeSorcie, T.J., Stedman, R.M., O’Connor, D.V., and Rottiers, D.V. 2000. Lipid concentrations in Lake Michigan fishes: seasonal, spatial, ontogenetic, and long-term trends. J. Great Lakes Res. 26:427–444. Meakins, R.H. 1976. Variations in the energy content of freshwater fish. J. Fish Biol. 8:221–224. Neter, J., Wasserman, W., and. Kutner, M.H. 1985. Applied linear statistical models, 2nd ed. Homewood, IL: Irwin. Oliver, J.D., Holeton, G.F., and Chua, K.E. 1979. Overwinter mortality of fingerling smallmouth bass in relation to size, relative energy stores, and environmental temperature. Trans. Am. Fish. Soc. 108:130–136. Owens, R.W., and Noguchi, G.E. 1998. Intra-lake variation in maturity, fecundity, and spawning of slimy sculpin (Cottus cognatus) in southern Lake Ontario. J. Great Lakes Res. 24:383–391. Pangle, K.L., Sutton, T.M., Kinnunen, R.E, and Hoff, M.H. 2004. Overwinter survival of juvenile lake herring in relation to body size, physiological condition, energy stores, and food ration. Trans. Am. Fish. Soc. 133:1235–1246. Pierce, R.J., Wissing, T.E., Jaworski, J.G., Givens, R.N., and Megrey, B.A. 1980. Energy storage and utilization patterns of gizzard shad in Acton Lake, Ohio. Trans. Am. Fish. Soc. 109:611–616. Post, J.R., and Parkinson, E.A. 2001. Energy allocation
Drying Temperature Effects strategy in young fish: allometry and survival. Ecology 82:1040–1051. Pratt, T.C., and Fox, M.G. 2002. Influence of predation risk on the overwinter mortality and energetic relationships of young-of-year walleyes. Trans. Am. Fish. Soc. 131:885–898. Rand, P.S., Lantry, B.F., O’Gorman, R., Owens, R.W., and Stewart, D.J. 1994. Energy density and size of pelagic prey fishes in Lake Ontario, 1978–1990: Implications for Salmonine Energetics. Trans. Am. Fish. Soc. 123:519–534. Rottiers, D.V., and Tucker, R.M. 1982. Proximate composition and caloric content of eight Lake Michigan fishes. USFWS Technical Papers 108. Simpkins, D.G., Hubert, W.A., Del Rio, C.M., and Rule, D.C. 2003. Physiological responses of juvenile rainbow trout to fasting and swimming activity: effects on body composition and condition indices. Trans. Am. Fish. Soc. 132:576–589. Stewart, D.J., and Binkowski, F.P. 1986. Dynamics of consumption and food conversion by Lake Michigan
APPENDIX TABLE 1. composition. Authors Gerking Birkett Groves Kelso Kelso Meakins Craig Foltz and Norden Craig et al. Fagan and Fitzpatrick Oliver et al. Pierce et al. Rottiers and Tucker Flath and Diana Strange and Pelton Tanasichuk and Mackay Diana and Salz Buijse and Houthuijzen Bandow and Anderson Brown et. al. Bai et al. Hayes and Taylor Jaramillo et al. Rand et al. Hartman and Brandt Bryan et al. Jonas et al.
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alewives: an energetics-modeling synthesis. Trans. Am. Fish. Soc. 115:643–661. Strange, R.J., and Pelton, J.C. 1987. Nutrient content of clupeid forage fishes. Trans. Am. Fish. Soc. 116:60–66. Sutton, S.G., Bult, T.P., and Haedrich, R.L. 2000. Relationships among fat weight, body weight, water weight, and condition factors in wild Atlantic salmon parr. Trans. Am. Fish. Soc. 129:527–538. Tanasichuk, R.W., and Mackay, W.C. 1989. Quantitative and qualitative characteristics of somatic and gonadal growth of yellow perch (Perca flavescens) from Lac Ste. Anne, Alberta. Can. J. Fish. Aquat. Sci. 46:989–994. Vondracek, B., Giese, B.D., and Henry, M.G. 1996. Energy density of three fishes from Minnesota waters of Lake Superior. J. Great Lakes Res. 22:757–764. Submitted: 2 May 2007 Accepted: 29 March 2007 Editorial handling: Donald J. Stewart
Survey of studies that dried fish tissue for calorimetry or analysis of proximate Publication date 1955 1969 1970
Drying temp. (°C) 105C 40-50 70
1972 1973 1976 1977 1977 1978 1978 1979 1980 1982 1985 1987 1989 1990 1992 1993 1993 1994 1994 1994 1994 1995 1996 1996
105 105 90 80 60 80 65 105 60 100 50 105 70 80 Freeze-dried 80 100 125 75-80 125 60-65 70 60 65-70
Dry weight end point detection constant weight constant weight constant weight (vacuum oven) constant weight constant weight ? constant weight 48 h ? constant weight 20-26 h constant weight constant weight constant weight 24 h constant weight constant weight constant weight constant weight 3h 24 h 3h constant weight constant weight 24 h constant weight
Sample preparation whole ? ? whole whole whole sectioned sectioned sectioned sectioned whole whole homogenized whole or sectioned homogenized sectioned whole or homogenized sectioned homogenized homogenized homogenized sectioned homogenized whole or sectioned whole homogenized homogenized (Continued)
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APPENDIX TABLE 1. Authors Vondracek et al. Barziza and Gatlin Henderson et al. Sutton et al. Post and Parkinson Eggleton and Schramm Pratt and Fox Simpkins et al. Pangle et al.
(Continued). Publication Date 1996 2000 2000 2000 2001 2002 2002 2003 2004
Drying Temp. (°C) 80 125 105 94 50 60 90 60 100
Dry weight end point detection constant weight 3h 24 h 16 h 96 h 72-96 h (vacuum oven) 48 h constant weight 24 h
Sample preparation homogenized homogenized homogenized whole whole homogenized homogenized sectioned whole
APPENDIX TABLE 2. Drying times (days) to the final dry weight (excluding the final two days of drying) at different temperatures for lake trout, rainbow smelt, slimy sculpin and alewife. Species Lake trout Lake trout Lake trout Lake trout Lake trout Lake trout Lake trout Lake trout Lake Trout Lake Trout Lake Trout Smelt Smelt Smelt Smelt Smelt Smelt Smelt Smelt Smelt Sculpin Sculpin Sculpin Sculpin Sculpin Alewife Alewife Alewife Alewife Alewife Alewife Alewife Alewife
Drying Temp. (°C) 60 60 60 60 70 70 80 80 80 90 90 60 60 60 70 70 80 80 105 105 60 60 60 80 80 60 60 70 70 80 80 90 90
Total Length (mm) 116–153 mm 154–186 mm 198–216 mm 231–239 mm 117–163 mm 168–184 mm 148–197 mm 196–213 mm 242–248 mm 141–180 mm 182–227 mm < 100 mm 100–125 mm 125–160 mm < 125 mm 124–145 mm < 111 mm 120–146 mm < 100mm 100–125 mm < 85 mm 85–100 mm 111–115 mm < 85 mm 86–115 mm < 100 mm 135–175 mm < 100 mm 140–165 mm < 100 mm > 123 mm < 110 mm 145–175 mm
Time (days) to dry weight 5–6 d 7–12 d 13 d 15 d 4d 5d 6–8 d 8–10 d 15 d 4d 7d 1–2 d 2–3 d 4–5 d 1d 3d 1–2 d 3–5 d 1d 1–3 d 1d 2d 2–3 d 1d 2d 1d 3–8 d 1d 3–4 d 1d 3d 1–2 d 5–6 d