Culture trials of young green turtles, Chelonia mydas, in Torres Strait, northern Australia

Aquaculture, 11 (1977) 197-215 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

CULTURE TRIALS OF YOUNG GREEN TURTLES, IN TORRES STRAIT, NORTHERN AUSTRALIA

CHELONIA

197

MYDAS,

JOHN KOWARSKY Applied Ecology (Pty) Ltd, P.O. Box 26, Woden, A.C.T. 2606 (Australia) Present address: Department of Bioiogy, Capricornia Institute of Advanced Education, M.S. 76, Rockhampton, Qld. 4700 (Australia) (Received 28 March 1977)

ABSTRACT Kowarsky, J., 1977. Culture trials of young green turtles, Chelonia mydas, in Torres Strait, northern Australia. Aquaculture, 11: 197-215.. Survival and weight-change data for green turtles, Chelonia mydas, over the first 5 months of life are presented together with details of stocking densities and water turnover conditions under which turtles were held for that period. Evidence was obtained that poor water quality, rather than the degree of physical crowding, was the major adverse influence on the culture of these turtles.

INTRODUCTION

Concern has been expressed that farming or ranching of sea turtles may have adverse effects on natural populations (Ehrenfeld, 1974; Anonymous, 1975). Another source of concern is that such activities may affect indigenous people who rely upon sea turtles as a source of protein (Nietschmann, 1974; Weiss, 1975). In addition to these issues, there is a need for practical information about turtle culture before it is possible to assess completely the feasibility and acceptability of a proposed commercial turtle culture venture. The most successful culture project so far has been described in terms of its historical background and some production figures (Anonymous, 1974; Sefton, 1974; Reiger, 1975). Missing from the literature are details of conditions under which such turtles have been raised. This paper reports on work contributing baseline information on culture of young green turtles over the first 5 months of hatchling life. Small scale trials were conducted on Yorke Island (9” 45’ S, 143” 24’ E) between February and July 1976.

198

MATERIALS

AND METHODS

Turtles Group A turtles were Island (ll”36’ S, 144”l’ Group B turtles were 143” 52’ E) from 3 to 5 Simon (1975).

collected as newly emerged hatchlings on Raine E) from 29 January to 4 February 1976. collected as newly laid eggs on Bramble Cay (9”9’ S, January 1976 and subsequently tended according to

Water supply Water was pumped

from the sea as required.

Feeding Locally caught fish, including reef fish, mackerel and tuna formed the usual diet of all turtles. On two occasions the fish supply failed and turtles were fed “Pal” canned dog food which was accepted less enthusiastically than fish. Weighed quantities of filleted, skinned and diced fish (approximately l-cm cubes) were stored before use in a freezer. Measurements Excess water from each turtle was removed with a towel before weighing. Initially, weighings were made at weekly intervals; in the latter half of the experimental period they were made fortnightly. Turtles which had died were weighed as soon as possible after being reported. Carapace length was measured over the curve, along the mid-line, excluding marginal laminae front and rear. This measurement was used in preference to the generally used carapace length over the curve including the precentral and postcentral laminae as it was more easily and objectively taken. The relationship between the two measurements was as follows. Y = 1.1557 x - 0.0491, where Y = carapace and X = carapace

r = 0.9972,

sample size = 60,

length over curve including marginal laminae length over curve excluding marginal laminae

Experiments Experiment 1 Turtles from Group A were kept in a circular 3.1-m diameter plastic lined pool situated under a palm leaf roof which was about 2 m above ground level. Water changes were effected by transferring hatchlings to another freshly

199

filled pool by scoop net. When algal growth built up on the side and base of a pool it was drained and scrubbed. Following each water change, except for the last one of the day, a known quantity of food was placed in the pool. Immediately after the next water change, the quantity of food remaining was estimated visually so that the approximate quantity of food ingested could be calculated. The amount of food introduced at each feeding was adjusted to maintain a slight surplus. Water depth in the pool was increased, as turtles grew, to that judged not too deep to pose problems of food retrieval (fish pieces sank, and active diving by the hatchlings was necessary to feed). From the start of the experiment, on 9 February 1976 to 20 February 1976 the depth was 15 cm, from 21 February to 11 April 1976 the depth was 30 cm, and thereafter until the end of the experiment the depth was 45 cm. In the latter half of the experimental period trials were set up to investigate the effects of crowding without, ideally, concomitant changes in water quality. Some turtles were placed in floating enclosures in the same pool as the rest of the turtles. All turtles were given the same feeding and water change schedules. Because of changing numbers of turtles in Experiment 1, due to removal and/or addition of turtles used in other trials, estimates of real survival over a given period were calculated as the product of the daily survival figures, i.e. Percent

survival after ti days = 100 X S1 X Sz X . . . X S,

where S denotes the survival of turtles expressed as a fraction of the total turtles present at the start of the day, and ignoring addition or removal of live turtles on that day. At weighing times, all turtles in enclosures and a sample of 50 from outside enclosures were weighed. Carapace lengths of turtles outside enclosures were only measured at monthly intervals. Fig. 1 shows the enclosures, and their details of construction are given in Appendix A. Stocking density and water turnover figures are shown in Appendix B, and the available volume of water and surface area of tank per unit weight turtle are given in Appendices C and D, respectively.

Experiment 2 Turtles from Groups A and B were used. Holding units were plastic basins 59 cm long and 30.5 cm wide kept under a palm leaf roof. Group A turtles were in containers filled with 40 1 water (approximately 22 cm deep); from the start of this experiment, on 23 March, until 3 April 1976, Group B turtles were in containers with 20 1 water after which time they were also kept in 40-l containers. Three initial stocking densities under two water change schedules gave a total of six treatments for each group of turtles (Appendix E). All turtles were fed four times daily, the quantity of food given being aimed at giving slight excess at all times. At each water change turtles were removed, basins were emptied and refilled with fresh sea water and turtles were replaced. All basins

Fig. 1. (a) Turtles in Enclosure Al being transferred from one pool to another. (b) Enclo sures of the B-series floating in a circular pool.

207

were scrubbed daily. Stocking density and water turnover data are given in Appendices F and G, respectively. Appendix H shows the available surface area of tank per unit weight of turtle. Analysis of results No statistical analyses were made of survival figures because of the small numbers of replicates used. Examination of weight measurements of Experiment 1 turtles kept outside enclosures on 23 March (sample size = 148) and on 16 July 1976 (sample size = 50) showed that their distribution was not normal. Non-parametric statistical treatment was therefore appropriate. When comparing two samples the Mann-Whitney U test was used; when comparing more than two samples the Kruskal-Wallis one-way analysis of variance was used (see Siegel, 1956). Significance level was set at P < 0.05. RESULTS

Survival The relevant information for Experiment 1, for Group A turtles in Experiment 2, and for Group B turtles in Experiment 2 is displayed in Figs 2, 3 and 4, respectively.

*v 5

45

65

65 Age

105

125

-65 745

(days)

Fig. 2. Survival of Group A turtles in Experiment 1. Line denotes survival of turtles outside enclosures. X = introductipn of enclosure Al; Y = introduction of B-series enclosures.

405I

Al

3

25

45

1

1

I

65 Age

105

05

125

145

165 0

(days)

Fig. 3. Survival of Group A turtles in Experiment 2. Line denotes survival of turtles outside enclosures in Experiment 1.

100 .-.-

Baaaab ---

O go-

2,

0

0

0

“. \

.

.

.

cm-

al

. . .

L,

.

..a

‘3

-.cm

2 t

2 g

A

n “\

. 70-

.

*‘K. . .

Y

B

.

s E

\

1.

.

$’ 60.

B

.

.

D 50-

405

0

25

45

65

85

Age (days

105

0 0 125

145

165 I

1

Fig. 4. Survival of Group B turtles in Experiment 2. Line denotes survival of turtles outside enclosures in Experiment 1.

203

Two periods of comparatively intense mortality characterized the survival curve of turtles in Experiment 1; the first period was from about 45 to 75 days of age, and the second, less severe, was from about 105 to 145 days of age, Survival of turtles inside and outside enclosures was similar. The pattern of mortality of Group A turtles in Experiment 2 was generally similar to that of Experiment 1 turtles (from which stock they were taken) in that there were two periods of comparatively heavy mortality, the first up to about 75 days of age and the second after approximately 105 days of age. By contrast, the mortality of Group B turtles in Experiment 2 was distributed more uniformly over the whole experimental period. Survival of Group B turtles in Experiment 2 was inferior to survival of Group A turtles in the same experiment. In Experiment 2 there was heavier mortality of turtles subjected to three water changes daily than those given four water changes daily, with the exception of the turtles kept at the lowest stocking density. In Group A turtles at the two higher stocking densities, there was an indication of greater mortality in the more crowded containers.

Weight--length relationship The weight-length relationship for turtles kept outside enclosures Experiment 1 was calculated to be:

in

Y = 2.54 X - 0.24, N = 80, r = 0.99, where Y = log (weight in g), and X = log (carapace length in cm).

Death characteristics The weights of turtles dying were generally lower than the average live weight of turtles at the same time. This is illustrated in Fig. 5 for Experiment turtles kept outside enclosures. Examination of the log weight-log length linear regressions of living and dead turtles of Experiment 1 outside enclosures (Fig. 6) shows that the condition of turtles dying was inferior to that of living turtles. Two sets of observations appeared, associated with mortality in turtles. Firstly, particularly associated with the first more intense bout of mortality in Experiment 1, was an eye disease which in severe cases led to blindness. Lesions were also found on the head, neck and flippers. Secondly, many turtles dissected after death had foreign material such as fragments of Styrofoam (used initially as flotation material for enclosures) present in the gut which was usually otherwise empty.

Weight measurements The final weight frequency

distributions

of Group A turtles (at 164 days

1

It

519

I

590

571

t t+ t

+ t. : . + -:. ...:. .. + *: ‘:;::.: +

25

*: ‘::.“‘:

45

*

‘-‘:

65

105

65 Age

125

145

165

(days)

Fig. 5. Mean f 2 X S.E. weights (horizontal bar and vertical line, respectively) of live turtles kept outside enclosures in Experiment 1, compared with individual weights (dots) of dead turtles of the same group during the experimental period. 3.0 r Y = 254X

“OO6 I 06 I

07I

Log

-0.24,

0.8 I

carapace

r=099

09I

10 j

length

11 1

12 1

km)

Fig. 6. Weight-length relationship of live (continuous line, sample size = 80) and dead (broken line, sample size = 86) turtles in Experiment 1 outside enclosures.

205

c

x = 345

(b)

K = 312

Cc)

x=299

(II

~1,

0

100

200 Upper

300 limit

400 of

500 weight

600 class

700

800

900

1000

(g)

Fig. 7. Weight frequency histograms of Group A turtles at end of experimental period (all 164 days of age). (a) Outside enclosures in Experiment 1. (b) In enclosure Al, Experiment 1. (c) In B-series enclosures (data grouped) Experiment 1. (d) 4 water changes daily, originally 22/basin, Experiment 2. (e) 4 water changes daily, originally B/basin, Experiment 2. (f) 4 water changes daily, originally l/basin, Experiment 2. (g) 3 water changes daily, originally 22/basin, Experiment 2. (h) 3 water changes daily, originally 5/basin, Experiment 2. (i) 3 wamr changes daily, originally l/basin, Experiment 2.

of age) are displayed in Fig. 7; as there were no significant differences within the B-series enclosures in Experiment 1 these data were pooled. There was no significant difference between the weights of turtles outside enclosures and inside enclosure Al in Experiment 1, but both these treat-

206

ments were significantly different from the combined B-series data in that experiment. Within the six treatments to which Group A turtles were subjected in Experiment 2 there were significant weight differences. Within the higher water turnover treatments (four water changes daily) there were not significant weight differences: the combined data of these three treatments differed significantly from that of turtles kept outside enclosures in Experiment 1, but not from the weight data for the combined B-series enclosures in Experiment 1. Within the lower water turnover treatments (three water changes daily) a significant difference was found between weights of turtles in containers originally stocked at 22/basin, and the combined data for those stocked initially at 5 and l/basin. The final weight frequency distributions (at 132 days of age) of the six treatments to which Group B turtles were subjected in Experiment 2 are shown in Fig. 8. Within the treatments no significant weight differences were found; the combined data for these turtles differed significantly from the weights of Group A turtles of comparable age kept outside enclosures in Experiment 1.

(b)

Cd)

& F

L

_ -

1, , ,

0

50

100

150

(e)

%= 183

(f)

, x=

I,, 200

x= 209

250 Upper

300 llmlt

350 of

400

weight

450 class

210 , 500

, 550

, 600

(g) , 650

, 700

(g)

Fig. 8. Weight frequency histograms of Group B turtles in Experiment 2 at the end of experiment (132 days old) compared to that for Group A turtles outside enclosures in Experiment 1 of similar age (133 days old). (a) Outside enclosures in Experiment 1, Group A. (b) 4 water changes daily, originally 22/basin, Group B. (c) 4 water changes daily, originally B/basin, Group B. (d) 4 water changes daily, originally l/basin, Group B. (e) 3 water changes daily, originally 22/basin, Group B. (f) 3 water changes daily, originally 5/basin, Group B. (g) 3 water changes daily, originally l/basin, Group B.

207

Great variation in weight was present even within one treatment. For example, on 17 July 1976 weights of turtles in Experiment 1 kept outside enclosures ranged from 117 to 695 g (mean weight = 352 g). Conversion efficiency Table I shows estimates of food conversion efficiency of turtles kept in Experiment 1 prior to the introduction of enclosures in that experiment. Widely variable conversion factors were calculated; an indication of decreasing efficiency with increasing age was present. TABLE I Estimates of conversion efficiency of Group A green turtle hatchlings over a 73-day period in Experiment 1. At the commencement of the period turtles were 5 days old Period of 1976 9/2--1912 20/2413 5/3-- 913 10/3-16/3 1713 2213 23/3--3013 31/3714 8/4-1414 15/4-2214 g/2--22/4

Increment in mean weight (g) 16.71 24.95 11.57 10.88 13.07 10.03 10.67 16.73 11.17 125.8

Mass of food ingested per individual* (g)

Conversion factor

28.51 87.07 47.71 54.56 62.56 93.26 74.54 72.21 78.94

1.7 3.5 4.1 5.0 4.8 9.3 7.0 4.3 7.1

599.36

4.8

~~

* This was calculated by summing the daily average weight of food ingested per turtle for the days within the period. DISCUSSION

Survival Experiment 1 showed that the survival of young turtles, at the level of stocking density and water turnover used, was independent of a wide range of conditions of physical crowding and depths of containers. For example, turtles in enclosure Al were over six times more confined than those outside enclosures, and yet survival of the two groups was similar. Experiment 2 demonstrated the importance of the number of water changes given daily on the survival of turtles - only at the lowest stocking density did differential survival of the two water turnover treatments not occur. Effects of poor water quality could be expected to be least at the lowest stocking density. Results from the higher two stocking densities suggest

208

that daily water turnover per se was not the critical factor influencing survival - in both Group A and Group B turtles, those stocked initially at 5/basin and given three water changes daily had a daily water turnover about three times that of those stocked initially at 22/basin and given four water changes daily, and yet survival of the latter turtles was superior to that of the former. The difference between the two water change schedules was that, after turtles under both treatments had a water change and feed at 16.00 h, only those under the higher water turnover treatment were given another water change at 18.00 h; all that happened in the case of the lower water turnover treatment at this time was that remaining food pieces were removed from basins. Turtles in both treatments were then left for 14 h until 08.00 h the next morning when they were given a water change and feed. The results would thus suggest that maximum deterioration of water quality between 16.00 and 08.00 h the next day occurred in the two hours following 16.00 h, and that that occurring in the remaining 14 h was relatively insignificant. This could be explained by postulating that turtles exhibited a gastro-colic reflex, the gut being voided in response to feeding activity. Some difficulty was experienced in maintaining excess food in the most crowded basins in Experiment 2, because turtles on the surface obscured the basin floor and it was difficult to determine whether food was present or absent It is likely that rations available to turtles stocked initially at 22/basin were less than those available to turtles at other stocking densities. The inferior survival of Group B compared to Group A turtles may have been due to (i) genetic differences, (ii) effects of collection as eggs and subsequent artificial incubation, or (iii) effects of being placed in basins at an earlier age (19 days for Group B turtles compared with 48 days for Group A turtles). There have been some investigations of skin and eye lesions in tank-reared sea turtles. Rebel1 et al. (1975) found viral particles present in such lesions, while Witham (1973) reported successful treatment of necrotic skin lesions on tank-reared turtles with dilute KMn04. Growth

Because turtles which died were generally lighter than average live weight, the effect of such deaths would be to elevate the mean size of survivors, even if no real growth had occurred. It is thus important to consider survival information together with weight data before making inferences about comparative growth rates under various treatments. Because survival was similar, reasonable inferences can be made about the growth of turtles inside and outside enclosures in Experiment 1. It is apparent that growth, like survival, of turtles in this experiment was unaffected by a wide range of conditions of physical crowding and depths. However, the significant final weight difference between turtles in enclosure Al and

209

those in the B-series enclosures is difficult to explain, especially as both the available volume and surface area of water per unit weight turtle were slightly greater for the B-series enclosures turtles. One explanation could be that the structure of the B-series enclosures, being less open, could have restricted water exchange with the outside and resulted in a comparatively inferior water quality environment within the B-series enclosures. Better survival of Group A turtles in Experiment 2 under the higher water turnover treatment than survival of Group A turtles outside enclosures in Experiment 1 would tend, given equal growth rates, to result in the former turtles having a lighter average final weight than the latter. As this was in fact what was observed it is not possible to assume superior growth rates of the Experiment 1 turtles. Conversely, a real difference in growth rates between the three stocking density treatments under the higher water turnover schedule of Group A turtles in Experiment 2 may have been obscured by mortality effects. By similar reasoning, the outcome of all comparisons of final weights can be examined. Of these, observed weight differences between Group B turtles and Group A turtles of similar age kept outside enclosures in Experiment 1 can be accepted as indicating slower growth of Group B turtles. Similar explanations can be offered in this regard to those advanced to explain the inferior survival of Group B turtles. Conversion efficiency

The problem of size-selective mortality influencing the mean weight of survivors also occurred in these calculations, which must therefore be regarded as over-estimates of hatchiing food conversion capability. CONCLUSIONS

These trials have demonstrated the importance of the water change schedule in the culture of young green turtles. There was evidence that poor water quality, rather than the degree of physical crowding, was the major adverse influence on the turtles. Further research could be directed towards identifying harmful substances in the water, documenting the time course of the build-up of such substances and the concentrations at which they are harmful to turtles, and establishing strategies to maintain concentrations below these levels with minimal energy expenditure. For example, within a certain range of stocking densities, a given volume of water could probably be better used by keeping turtles in crowded conditions and changing the water often than by keeping turtles in relatively uncrowded conditions and changing the water infrequently. Knowledge of survival, weight changes, and conditions of culture of green turtles in the first 5 months of life should aid a more rational assessment of their culture potential.

210

ACKNOWLEDGEMENTS

The work described in this paper was undertaken while I was employed by Applied Ecology (Pty) Ltd to undertake research relating to the Company’s experimental turtle-farming project, and the Company provided all facilities utilized in the work. This paper is published with the permission of the Company which does not, however, accept responsibility for any opinions expressed herein. I am grateful to Mr Dan Mosby and his team who carried out the day-to-day running of the trials on Yorke Island. I thank Dr K.R. Allen, T. Kowarsky and Dr R.J. Rippingale for their constructive criticism of the manuscript in preparation. Some assistance towards the cost of preparation of this manuscript was provided by the Capricornia Institute of Advanced Education.

REFERENCES Anonymous, 1974. Turtle livestock culture: A new food technology. Food Eng., 46: 58-59. Anonymous, 1975. Utilization of marine turtles: revised principles and recommendations. IUCN Bull. (New Ser.), 6: 27. Ehrenfeld, D.W., 1974. Conserving the edible sea turtle: Can mariculture help? Am. Sci., 62: 23-31. Nietschmann, B., 1974. When the turtle collapses, the World ends. Nat. Hist., 83: 34--42. Rebell, G., Rywlin, A. and Haines, H., 1975. A Herpes-type agent associated with skin lesions of green sea turtles in aquaculture. Am. J. Vet. Res., 36: 1221- -1224. Reiger, G., 1975. Green turtle farming. Sea Frontiers, 21: 215-223. Sefton, N., 1974. Now they’re farming turtles. Oceans Mag., 7: 34-35. Siegel, S., 1956. Nonparametric Statistics for the Behavioural Sciences. McGraw-Hill, Kogakusha, Tokyo, 312 pp. Simon, M.H., 1975. The green sea turtle (Chelonia my&s); collection, incubation and hatching of eggs from natural rookeries. J. Zool., London, 176: 39-48. Weiss, B., 1975. Turtle farming. Oceans Mag., 8: 68. Witham, R., 1973. Focal necrosis of the skin in tank-reared sea turtles. J. Am. Vet. Med. Assoc., 163: 656.

211

APPENDIX A Details of enclosures used in Experiment 1 Enclosure

Description

Dimensions (cm) Length

Width

Depth

Initial number of turtles used

Date commenced

Al

Metal and wood frame, 2.5-cm wire mesh on sides, perforated aluminium floor 104

52

25

50

2214176

Bl

Plastic prawn (“lug”) basket

59

39.5

22

10

20/5/76

Plastic prawn (“lug”) basket

59

39.5

22

20

20/5/76

B3

Plastic prawn (“lug”) basket

59

39.5

13.5

10

2015176

B4

Plastic prawn (“lug”) basket

59

39.5

13.5

20

2015176

B2

APPENDIX B Stocking density and water turnover characteristics for Group A turtles maintained in Experiment 1 Period of 1976

Age at start of period (days)

Stock density at start of period (cc/g turtle)

Average number of water changes per day

Daily water turnover at start of period (cc/g)

912-1912 20/2413 513 913 10/3-1613 17/3-2213 23/3-3013 31/3714 a/4-14/4 1514 2214 23/4--2814 29/4-1215 13/5-1915 2015. -- 216 316-1616 17/6--2916 30/6-1617 1717 ,..

5 16 30 35 42 48 56 64 71 79 85 99 106 120 134 147 164

32 31 39 34 52 67 63 65 90 96 84 69 62 55 52 52 47

1.7 3.2 3.2 3.4 3.8 3.5 4.8 5.9 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0

54 100 126 115 198 235 302 381 539 573 503 416 371 329 313 311 281

212

APPENDIX C Available volume of water (cc/g turtle) for Group A turtles kept in enclosures compared with those outside during Experiment 1 Date 1976

2314 2914 1315 2015 316 1716 3016 1617

Outside enclosures

119 102 86 103 90 86 84 76

APPENDIX

B-Series combined

Within enclosures Al

Bl

B2

B3

B4

17 16 13 12 11 10 10 9

24 23 23 25 21

12 11 11 11 10

13 11 11 11 9

7 7 6 6 6

13 12 11 11 10

D

Available surface area (cm’/g turtle) for Group A turtles outside and inside enclosures during Experiment 1 Age (days)

Outside enclosures

Enclosure Al

Total B-series enclosures

106 120 134 147 164

2.01 1.76 1.67 1.65 1.48

0.49 0.43 0.41 0.42 0.36

0.71 0.66 0.63 0.62 0.58

APPENDIX

E

Details of treatments of turtles in Experiment

2

Group

Initial number of turtles per container

Daily number of water changes

A A A A A A B B B B B B

22 5 1 22 5 1 22 5 1 22 5 1

4 4 4 3 3 3 4 4 4 3 3 3

Number of replicates 2 5 5 2 4 5 1 2 5 2 2 5

Total 40

F

48 55 62 69 77 84 90 104 118 133 146 161

2313 3013 614 1314 2114 2814 415 1815

1616 2916 1417

116

Age (days)

18 17 17 16 14 13 12 11 10 9 9 9

22

Initial number/ basin

Date 1976

4

Daily water changes

Group A turtles

79 75 73 68 62 58 55 45 42 39 38 35

5

4

369 345 336 304 278 255 248 236 181 169 156 143

1

4

18 17 18 17 17 16 15 13 12 12 11 10

22

3

77 72 78 73 69 62 60 49 45 41 40 37

5

3

403 368 333 316 304 262 248 201 183 166 159 134 19 26 33 40 48 55 61 75 89 104 117 132

Age (days) 23 17 28 28 26 24 23 19 17 16 16 15

22

4

Group B turtles

97 89 150 130 118 108 106 89 82 80 71 65

5

4

Stocking density (cc/g turtle) of Group A and Group B turtles used in Experiment

APPENDIX

455 351 587 506 448 417 411 323 286 284 247 241

1

4

2

21 17 29 25 23 21 21 18 18 19 18 18

22

3

97

73 131 110 96 91 101 83 86 90 99 87

5

3

450 331 577 494 456 419 395 305 291 271 234 190

1

3

2313 3013 614 1314 2114 2814 415 18/5 l/6 1616 29/6 1417

70 68 68 63 56 51 49 42 40 36 36 35

22

Initial number/ basin

Date 1976

4

Daily water changes

317 298 291 272 250 231 219 181 169 154 151 138

5

4

1476 1380 1344 1215 1112 1020 993 942 726 676 622 574

1

4

Group A turtles

54 52 53 52 50 47 46 38 35 35 32 31

22

3

232 215 235 220 206 185 179 146 136 124 121 110

5

3

1208 1103 1000 949 913 787 744 603 549 499 477 401

1

3

90 68 113 110 103 94 90 77 66 63 63 59

22

4

356 601 519 470 432 423 356 328 318 286 260

390

5

4

Group B turtles

1821 1403 2349 2024 1791 1669 1644 1291 1142 1136 989 964

1

4

64 50 86 74 69 64 62 54 54 56 55 55

22

3

Water turnover (cc per g turtle per day) of Group A and Group B turtles used in Experiment

APPENDIX G 2

292 218 392 329 290 273 303 248 259 271 298 262

5

3

1349 992 1730 1481 1367 1256 1184 914 874 814 702 571

1

3

2313 3013 614 1314 2114 2814 415 1815 l/6 1616 2916 1417

0.79 0.76 0.76 0.71 0.63 0.57 0.55 0.47 0.45 0.41 0.40 0.39

22

Initial number/ basin

Date 1976

4

3.56 3.35 3.28 3.06 2.81 2.60 2.47 2.04 1.90 1.73 1.70 1.56

5

4

0.81 0.78 0.79 0.77 0.75 0.70 0.68 0.57 0.53 0.52 0.48 0.47

22

3

for Group

16.60 15.52 15.12 13.67 12.51 11.47 11.17 10.60 8.16 7.60 7.00 6.45

1

4

turtle)

A turtles

area (cm’/g

Group

surface

H

Daily water changes

Available

APPENDIX

3.48 3.23 3.52 3.30 3.10 2.78 2.68 2.20 2.04 1.86 1.82 1.66

5

3

A and Group

18.11 16.53 15.00 14.23 13.69 11.80 11.15 9.04 8.23 7.48 7.15 6.02

1

3

2.03 1.54 1.27 1.24 1.16 1.06 1.02 0.86 0.75 0.71 0.71 0.67

22

4

Group

8.76 8.02 6.76 5.84 5.29 4.86 4.76 4.01 3.69 3.58 3.21 2.92

B turtles

2

40.97 31.56 26.42 22.76 20.15 18.77 18.49 14.52 12.85 12.77 11.13 10.84

1

4

B turtles used in Experiment

1.92 1.49 1.30 1.10 1.03 0.96 0.93 0.81 0.81 0.85 0.82 0.82

22

3

8.76 6.56 5.88 4.93 4.33 4.09 4.54 3.72 3.88 4.07 4.47 3.93

5

3

40.47 29.77 25.95 22.20 20.49 18.83 17.76 13.71 13.11 12.21 10.53 8.56

1

3