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Survival of wild Atlantic salmon (Salmo salar) after catch and release angling in three Irish rivers
Fisheries Research 161 (2015) 252–260
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Fisheries Research journal homepage: www.elsevier.com/locate/fishres
Survival of wild Atlantic salmon (Salmo salar) after catch and release angling in three Irish rivers Patrick G. Gargan a,∗ , Trevor Stafford a , Finn Økland b , Eva B. Thorstad b a b
Inland Fisheries Ireland, 3044 Lake Drive, Citywest Business Campus, Dublin 24, Ireland Norwegian Institute for Nature Research (NINA), Trondheim, Norway
a r t i c l e
i n f o
Article history: Received 26 August 2013 Received in revised form 30 January 2014 Accepted 7 August 2014 Handling Editor George A. Rose Keywords: Atlantic salmon Angling Catch and release Survival
a b s t r a c t The practice of catch and release (C&R) in salmon rod fisheries has become increasingly common due to the widespread decline in salmon abundance in the North Atlantic over the past two decades. Many Irish Atlantic salmon rivers are only open for catch and release (C&R) angling since a change in salmon management in 2006. Success of Atlantic salmon surviving to contribute to the spawning stock following C&R was studied in three rivers. In total, 76 fish were tagged with radio transmitters post C&R angling. Survival to spawning was greater for fly caught (98%) than lure caught fish (55%). Hence, survival after C&R was dependent on gear type. Hook location may have influenced C&R mortality in the lure captured fish. All fish bleeding at the hook wound or hooked in the throat died. Simultaneous hooking in the upper and lower mouth may also have contributed to reduced survival. There was an overall net upstream movement post release with many salmon moving more than 10 km upstream. Results demonstrated that, when conducted using proper guidelines, survival of salmon after C&R can be high. Opening rivers to C&R angling can be successful as a tool to provide information on salmon stock status while not significantly impacting on salmon survival. © 2014 Elsevier B.V. All rights reserved.
1. Introduction The practice of catch and release (C&R) in Atlantic salmon rod fisheries has become increasingly common due to the population decline in the North Atlantic over the past decades (ICES, 2013). In some areas of Canada and USA, C&R has been practiced since 1984, and in more recent years it has been widely used in many European countries, both as a result of statutory regulation and through voluntary practice. Reported rates of C&R (expressed as % of the total reported rod catch) vary from 14% in Norway to as high as 73% in Scotland and 84% in Russia, reflecting varying management practices and angler and stakeholder attitudes among countries (ICES, 2013). C&R angling is a relatively recent phenomenon in Ireland. The rate of C&R in rod fisheries has increased from 5% of the total reported catch in 2004 to 35% in 2012, with an estimated 12,000 Atlantic salmon released in 2012. Since 2006, the management of Atlantic salmon in Ireland has been based on scientific assessment of all 141 salmon rivers, aiming at achieving river specific conservation limits (CL). Only the salmon surplus above the CL is available
∗ Corresponding author. E-mail address: paddy.gargan@fisheriesireland.ie (P.G. Gargan). http://dx.doi.org/10.1016/j.fishres.2014.08.005 0165-7836/© 2014 Elsevier B.V. All rights reserved.
for harvest. This has resulted in approximately 40% of rivers being open for harvest, a further 40% of rivers being clearly below the CL and closed to fishing, and with the last 20% of rivers being open to C&R angling only. C&R angling is permitted because there is lack on information on salmon runs, and the angling catch generated by C&R can be used in conjunction with a rod exploitation rate to provide an estimate of the overall salmon stock status. This estimate can be compared against the river specific CL to determine if it is being met. In addition to providing rod catch data, rivers open for catch and release angling generate economic activity and employment opportunities. While the angling methods permitted in the rivers open to C&R angling are restricted (use of single barbless hooks and no use of worm as bait), there is still a possibility of some mortality associated with C&R. For this reason, only rivers determined to be above a salmon fry threshold established by electro-fishing, or rivers estimated to be meeting >65% of CL, are open for C&R angling. However, concern has been expressed regarding the impact of catch and release angling on salmon mortality in rivers failing to meet conservation limits. With proper fish handling and water temperatures below 20 ◦ C, Atlantic salmon mortality after C&R may be low (Dempson et al., 2002; Thorstad et al., 2003). Most studies of the effects C&R in Atlantic salmon have been performed in North America, and many studies rely on fish being kept in tanks or cages after C&R, which
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may not be representative for fish being released back to the river (Thorstad et al., 2008). More realistic results may be obtained by tagging fish with radio or acoustic transmitters and recording the behaviour and survival of free-swimming fish in their natural environment after C&R (Donaldson et al., 2008). In previous studies using radio or acoustic transmitters, fly fishing has been the main angling method (Whoriskey et al., 2000; Jensen et al., 2010; Thorstad et al., 2003, 2007). However, gear type may influence survival rates (Arlinghaus et al., 2007). This study was undertaken to derive data on the success of Atlantic salmon surviving to contribute to the spawning stock following C&R. The aim was to test the management assumption that all released fish can be included in the estimate of the spawning stock in the rivers with C&R angling only. Information on angling methods were collected, and behaviour and survival after C&R were recorded by equipping individual fish with radio transmitters and releasing them immediately back to the river. Results from two different angling methods (spinning lures and flies) were compared, and results were related to gear type, playing time, handling time, where the fish were hooked, water temperature and fish length and sex. 2. Materials and methods 2.1. Study sites C&R angling was carried out on three Irish rivers, the Owenmore in county Mayo, the Mulkear in county Limerick and the Feale in county Kerry (Fig. 1). The Owenmore (precipitation area 341 km2 ,
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main stem channel of 20 km) is a productive spate river with an annual average rod catch (2009–2013) of 880 Atlantic salmon. The Mulkear (precipitation area 661 km2 , main stem channel of 23 km) is a large tributary of the Shannon catchment with an average annual rod catch (2009–2013) of 970 Atlantic salmon. The Feale (precipitation area 1151 km2 , main stem channel of 24 km) has an annual average rod catch (2009–2013) of 1350 Atlantic salmon. 2.2. Fish capture, tagging and release Tagging was conducted on the Owenmore River during August and September 2006 and 2007, on the Feale during September 2006 and on the Mulkear during September 2007. The salmon included in this study were tagged during or slightly after the peak period of salmon runs in these rivers. Fly fishing only was used to capture Atlantic salmon on the Owenmore, a combination of fly and lure fishing on the Feale and lure fishing only on the Mulkear (Table 1). Flies were artificial flies ranging in hook size from 10 to 14. The lures were spinning lures (Flying C type lures). Field staff were in the vicinity of anglers along the riverbank prior to tagging all fish. Anglers were instructed to play fish in the normal way and fish were landed using a standard landing net or directed into a purpose built polyester landing bag. The presence of a scientist did not alter the playing or landing of salmon during the study. Fish were exposed to air for less than 20 s. Capture method and the time taken from hooking to landing were recorded. Hooks were removed after noting hook size, the number of hooks imbedded and the position of the hooks. Fish were inserted into a cylinder tube filled with water, which allowed the head to be under water during tagging. Fish were inspected for damage or wounds which may have been inflicted by hooks. Fork length, sex and condition of fish were recorded. The fish were characterised as fresh run if they had a bright silvery colour, thin mucous layer and/or sea lice (Lepeophtheirus salmonis). Sea lice are marine parasites, and their presence usually indicates that the fish have been in fresh water less than a week (although some salmon lice may survive longer, Finstad et al., 1995). All fish (n = 76, Table 1) were one-sea-winter salmon (with the exception of one multi-sea-winter salmon from the Feale) in the 47–74 cm length range. The fish were tagged with model F2120 radio transmitters from Advanced Telemetry Systems (ATS), USA (flat with outline dimensions 21 mm × 52 mm × 11 mm, mass in air 15 g). Programmed battery life was seven months. Each transmitter had a unique frequency within the 173,200–173,500 MHz range. Similar transmitters had no effect on swimming performance of Atlantic salmon >45 cm in laboratory swim trials (Thorstad et al., 2000). Transmitters were attached externally to fish below the dorsal fin and secured with stainless steel wire. Time taken to tag each fish was recorded. After tagging, tags were checked for signal emission and fish were held in the water until fully recovered before being released. 2.3. Monitoring of tagged fish
Fig. 1. Location of the study rivers Owenmore, Mulkear and Feale and their precipitation areas in Ireland.
Tracking of tagged fish was conducted in October–January (i.e., until after spawning). Fish were tracked at a minimum of four weeks intervals on the Owenmore and on a weekly basis on the Feale and Mulkear using a 3-element Yagi antenna connected to a receiver (model R2000, ATS). Main channels and tributaries were radio tracked on foot or by boat. A vehicle was used to track fish where roads followed the river course. The entire catchment was monitored during each tracking survey with a few exceptions when high water did not allow tracking of lower main channel areas. Distances fish moved along rivers were calculated using Arc View 9.2 (Esri, USA).
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Table 1 Details on the characteristics of the tagged fish and angling details. Owenmore
Feale
Feale
Mulkear
Number of fish tagged Number of fish recorded post tagging Number of fish survived to spawning Gear type
52 48 47 (98%) Fly
12 12 12 (100%) Fly
3 3 2 (67%) Lure
9 8 4 (50%) Lure
Number by hook type and size (size 10:12:14:4) Single Double Trebble
0 13 (3:9:1:0) 39 (2:29:8:0)
9 (4:5:0:0) 2 (2:0:0:0) 1 (1:0:0:0)
3 (0:0:0:3) 0 0
0 0 9 (0:0:0:9)
Fish characteristics Fork length (mean, range, SD) Sex (number; male:female) Number (%) fresh run
58 (44–74, 6.3) 22:30 26 (50%)
59 (49–73, 7.0) 9:03 2 (17%)
60 (59–63, 2.3) 1:02 2 (67%)
56 (48–66, 5.5) 6:03 0 (0%)
Angling practices Water temperature at tagging (mean, range, SD) Time played in minutes (mean, range, SD) Time handled in minutes Total time playing and handling
13 (11–16, 1.3) 5.8 (3–9, 1.8) 2.2 8.0
13 (13–14, 0.5) 5.8 (4–8, 1.2) 2.3 8.1
14 (14–14, 0) 5.3 (5–6, 0.6) 2.0 7.3
10 (9–12, 1.22) 4.1 (3–6, 0.9) 2.1 6.2
Fish having moved upstream were deemed to have survived after C&R. Five fish (7%) were never recorded after tagging (Table 1). Possible explanations may be tag failure, unreported recaptures, or fish leaving the rivers. The five fish that disappeared were three males and two females, with mean fork length 61 cm (range 54–70, SD 8.4). The survival results are based on the 71 fish recorded after tagging. These fish were found during all tracking surveys, except 38% missing during one of the surveys and 12% missing during two of the surveys. One fish was not detected during three of the surveys, but when detected in December it had moved upstream 8.1 km from being tagged in September. 2.4. Data analyses Statistical comparisons between those fish dying and survivors were not performed due to the low number of fish suffering mortality. However, statistical comparisons were made between fly and lure captured fish to characterise the C&R fishery and examine if there were any differences between the angling methods relevant for fish performance and survival after C&R (all tagged fish included, sample sizes given in Tables 1 and 2). Data from the different rivers were combined as we have no reason a priori to expect that river characteristic would alter the interaction between survival and river site across treatment effects in a systematic fashion. Independent samples t-tests were used to test for possible differences between fly and lure captured fish in mean fork length, water temperature at C&R, playing time and handling time, assuming equal or unequal variances based on Levene’s test for equality of variances. One-way ANOVA was used to compare handling time between fish captured with single, double and treble hooks. Pearson chi square test was used to test for possible differences in frequencies among fly and lure captured fish (frequencies of fish captured on single, double and treble hooks and frequency of hook location), except chi square with continuity correction was used for 2 × 2 tables (frequency of males and females), or Fisher’s test when expected count was less than five in any of the cells (frequency of fresh run fish). Effect of fish length on playing time was tested using a linear regression. Statistical analyses were performed using SPSS Statistics version 21 (IBM, USA).
(radio transmitter signal detected at <100 m from release location) throughout all monitoring periods (Fig. 2). Two fish were stationary during the first monitoring period and recorded having moved downstream in subsequent periods. One fish moved downstream during the first and second monitoring period and then remained stationary (Fig. 2). Hence, all these six fish were presumed not to have survived. The survival rate was higher for fly caught (98%, 59 of 60) than for lure caught salmon (55%, 6 of 11) (Fisher’s exact test, p < 0.001, Table 1). The high survival of fly caught salmon was consistent over two years on the Owenmore (100% survival in 2006, 21 of 21 fish – and 96% survival in 2007, 26 of 27 fish), and between the Owenmore and the Feale (100% survival). No tagged salmon were reported recaptured by anglers in any of the rivers. The six fish presumed to have died after C&R were 3 males and 3 females with mean fork length 57 cm (range 53–63 cm, SD 3.7). One fish was characterised as fresh run. These fish were angled at a mean water temperature of 11 ◦ C (range 9–14 ◦ C, SD 2.1). Hence, sex
3. Results 3.1. Fish survival after catch and release Overall, 92% of the Atlantic salmon recorded after tagging survived post C&R (65 of 71 salmon, Table 1). Three fish were stationary
Fig. 2. Net displacement from the point of tagging for dead fish by date detected.
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Table 2 Characteristics of gear type, hook type and hooking location. Type of hook
Fly
Number of hooks Number of salmon hooked Hooking location (1, 2 or 3 hooks attached) Jaw (upper, lower) Maxillary bone Tongue, upper mouth Throat or belly Unknown (hook fell out)
Single 9 Single 6 2 0 0 1
a
Lure Double 15 Double (1:2) 7 (3:4) 5 (5:0) 2 (2:0) 0 1
Trebble 40 Trebble (1:2:3) 21 (14:7:0) 15 (8:7:0) 3 (2:1:0) 1 (1:0:0) 0
Single 3 Single 1 2 0 0 0
Trebble 9 Trebble (1:2:3) 7 (5:2a :0) 3 (3a :0:0) 0 1 (0:0:3) 0
To identify gear type and hooking location resulting in bleeding.
distribution, body length and water temperature at angling time did not differ between those not surviving and the tagged fish in general (Table 1 and below). The playing time (mean 4.5 min, range 4–6, SD 0.8), handling time (mean 2.0 min, range 2–2, SD 0) and total playing and handling time (mean 6.5 min, range 6–8, SD 0.8) for the mortalities were among the shorter periods in the total sample (Table 1 and below). Of the salmon that did not survive, one was captured by fly in the Owenmore and five on lures on the Mulkear and the Feale (Table 1). The fly captured salmon mortality (n = 1) was hooked in the upper jaw on a double barbed hook size 10. The lure captured salmon mortalities were captured on single barbless hooks, size 4 (n = 1), or on barbed treble hooks size 4 (n = 4). Of these lure captured salmon, one was hooked in the maxillary, one in the lower jaw, one in both the lower and upper jaw, one in both in the maxillary and in the upper jaw and one in the throat. Notably, the only two fish recorded as having bled at the hook wound in the entire data set were among the dead fish, as were the only fish hooked in the throat, and two of the three fish noted as being hooked in both the upper and lower mouth. 3.2. Characterisation of the fishery and angling methods There were no differences between fly caught and lure caught Atlantic salmon in fork length (t-test assuming equal variances, t = 0.66, p = 0.51), proportion males and females (chi-square test with continuity correction, 2 = 0.50, p = 0.48), or proportion of fish characterised as fresh run (Fisher’s exact test, p = 0.18) (Table 1). The water temperature at C&R was higher for fly caught than lure caught fish (mean 13 ◦ C vs. 11 ◦ C, t-test assuming unequal variances, t = 2.73, p = 0.019, Table 1). Of the fly caught salmon, 14% were captured on a single hook, 23% on a double hook and 63% on a treble hook (Table 1). Of the lure caught salmon, 25% were captured on a single hook and 75% on a treble hook (Table 1). There was no difference in proportion fish captured on single, double and treble hooks between fly caught and lure caught salmon (Pearson chi square test, df = 2, 2 = 3.58, p = 0.17). However, all lure caught salmon were captured using larger hooks (size 4) whereas hook size was smaller for fly caught salmon (size 10–14). In the Owenmore and Mulkear, all flies and lures had barbed hooks. In contrast, in the Feale, 67% of the flies (8 of 12) and 67% of the lures (2 of 3) had barbless hooks. For fish captured on flies with double hooks, 10 fish (67%) were hooked by one of the hooks, 4 fish (27%) by both hooks and for one fish the hook (7%) fell off at capture. For fish captured on flies with treble hooks, 25 fish (63%) were hooked by one hook and 15 fish (38%) by two hooks. For fish captured on lures with treble hooks, 5 fish (50%) were hooked by one hook, 4 fish (40%) by two hooks and 1 fish (10%) by all three hooks. Of the fly caught salmon, 53% were hooked in the upper or lower jaw, 34% in the maxillary bone, 8% in the tongue or upper mouth, 2% in the belly, and 3% lost the hook when landed (Table 2). Of the lure caught salmon, 50% were hooked in the upper or lower jaw,
42% in the maxillary bone and 8% in the throat (Table 2). There was no difference in distribution of hook locations between fly caught and lure caught salmon (Pearson chi square test, df = 4, 2 = 2.93, p = 0.60). The playing time (time from hooking to landing the fish) was generally short, on average 5.6 min (Table 1). Playing time increased with increasing fish length, but fish length explained only 11% of the variation in playing time (linear regression, r2 = 0.11, p = 0.004). Handling time (from landing to release) was on average 2.2 min, resulting in a total playing and handling time of average 7.8 min (Table 1). Playing time was longer for fly captured than lure captured salmon (t-test assuming unequal variances, t = 3.8, p = 0.001), whereas handling time did not differ between the groups (t-test assuming equal variances, t = 1.3, p = 0.19). In summary, total handling time was longer for fly captured than lure captured salmon (t-test assuming equal variances, t = 2.7, p = 0.009). Handling time did not differ between fish captured with single, double or treble hooks (one-way ANOVA, df = 2, F = 0.87, p = 0.43, all fish combined). Handling time did not differ between fish captured on barbed or barbless hooks (t-test assuming equal variances, t = −0.80, p = 0.43, all fish combined). Results were similar when fly and lure captured fish were tested separately (results not shown). 3.3. Fish behaviour after catch and release The fish that survived (n = 65) showed an overall net upstream movement post release (Figs. 3 and 4). Of the Owenmore fish that moved upstream, the majority travelled more than 3 km, with many fish moving more than 10 km upstream (Figs. 3 and 4). This is not unexpected as fish were captured in the lower and mid-main channel, and considerable spawning takes place in the upper main channel and head water tributaries. Three individuals moved several kilometres downstream after release, but subsequently moved upstream. The longest downstream migrations made by Owenmore fish were six fish in January, most likely after spawning. The net displacement since the previous detection event (Fig. 4) shows the type and extent of fish movements during the season. The majority of Feale salmon remained stationary or moved upstream in the first and second month after C&R (Figs. 3 and 4). An initial downstream migration was evident for four fish soon after release and three subsequently moved considerable distances upstream. Three of the four surviving salmon from the Mulkear moved upstream and were stationary during the entire study period (Figs. 3 and 4). Hook placement did not demonstrate marked differences in fish displacement after tagging (Fig. 5). 4. Discussion A high survival to spawning was recorded for fly caught Atlantic salmon (98%) in the present study, which is similar to results found in previous Atlantic salmon catch and release studies in Canada, Norway and Russia (92–100% survival, Dempson et al., 2002; Thorstad et al., 2007; Jensen et al., 2010; Whoriskey et al.,
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Fig. 3. The extent of net movements by date for individual fish which survived (n = 65).
2000). A lower survival rate (84%) was recorded in the Aberdeenshire Dee, Scotland (Webb, 1998). The high survival for fly caught salmon in the present study was consistent between years and rivers. However, the survival rates differed among gear types, as the survival rate for fish captured with spinning lures (55%) was much lower than for fly caught salmon. This is in accordance with results in a study of rainbow trout (Oncorhynchus mykiss), where fish caught by spinning lures were injured more frequently than fish caught by fly (Meka, 2004). The low number of fish suffering mortality in the present study did not allow for statistical comparisons between those dying and survivors. However, a descriptive inspection of the results did not reveal any particular characteristics of the individuals suffering mortality compared to survivors with respect to fish size, sex, water temperature, whether they were fresh run in the river or not, playing time, handling time, use of barbed vs. barbless hooks, or the use of single, double or treble hooks.
A notable difference between fly and lure captured Atlantic salmon, however, was the larger hooks used for all lure captured fish. Moreover, the only two fish bleeding at the hook wound in the entire sample were salmon mortalities captured by lure, as were the only fish hooked deep in the throat, and two of the three fish noted to be simultaneously hooked in the upper and lower mouth. Salmon most likely die after C&R from wounds caused from angling, or exhaustive exercise due to the extent of the intracellular acidosis within the muscle (Wood et al., 1983). The larger size of hooks used with spinning lures may have resulted in larger hook wounds, a greater extent of deep hooking and bleeding, and a greater extent of simultaneous hooking in the upper and lower mouth – and thereby a higher mortality. Meka (2004) similarly suggested that hook size may have been an important factor influencing the number of hook points penetrating rainbow trout during angling, which in turn caused increased injury to sensitive locations, associated bleeding, and subsequent mortality. Large hooks may be more difficult to
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Fig. 4. Net displacement of live fish since the previous detection event.
swallow than small hooks, but may cause greater tissue damage at the wound site (Pauley and Thomas, 1993; DuBois et al., 1994). Gjernes et al. (1993) speculated that the greater depth and gape of larger hooks may lead to deeper hook penetration and greater risk of contact with critical organs. As all fly captured fish were captured on small hook sizes compared to the larger hook size of fish captured by lures in the present study, it was not possible to isolate the effect of hook size alone. We suggest that hook size should be further investigated as a mortality factor after C&R. Bartholomew and Bohnsack (2005) found in their extensive review that catch-and-release angling mortality varied greatly among and within species, and that anatomical hooking location was the most important mortality factor. Other studies also indicate that anatomical hooking location and associated bleeding is the most important factor influencing mortality of angler-caught fish (e.g., Falk et al., 1974; Warner, 1976; Loftus et al., 1988; Nuhfer and Alexander, 1992; Arlinghaus et al., 2007). Simultaneous hooking in the lower and upper mouth may reduce oxygen uptake during
playing of the fish because it to some extent closes the mouth. We find no studies discussing simultaneously hooking in the lower and upper mouth in the scientific literature, but this is sometimes mentioned by anglers as a factor negatively impacting the condition of the salmon at release (E.B. Thorstad, personal observation). Hook characteristics and hook types are shown to impact the hooking locations and endpoints in C&R events in a number of studies, but the results vary widely among studies, perhaps due to interspecific variation (Muoneke and Childress, 1994; Cooke and Suski, 2005; Arlinghaus et al., 2007). Water temperature is an important factor in determining survival of Atlantic salmon after release, explaining 72% of the variation in survival from Atlantic salmon C&R angling (Dempson et al., 2002). Mortality after C&R angling may increase at high water temperatures, and temperatures above 18–20 ◦ C may have a negative effect on survival (Wilkie et al., 1996, 1997; Anderson et al., 1998; Dempson et al., 2002; Thorstad et al., 2003). The water temperatures in this study of 9–16 ◦ C were unlikely to impact on survival.
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Fig. 5. Net displacement of fish during the first fifty days plotted (with line of best fit with SE fitted in R using ggplot2) against hook placement.
Further, differences in water temperature cannot explain the differences in mortality between fly and lure captured salmon as the water temperature at C&R was lower and not higher for the lure salmon in general, and the temperature at C&R for individuals that failed to survive was among the lowest in the total sample. Catch-and-release mortality of rainbow trout and mountain whitefish (Prosopium williamsoni) increased when daily maximum water temperature was higher than 20 ◦ C and mortality of brown trout (Salmo trutta) increased when daily maximum water temperature was at or exceeded 23 ◦ C (Boyd et al., 2010). C&R took place in August and September in the present study and temperature may have a more significant effect during peak summer temperatures when water temperatures may reach 18 ◦ C or more. In 2012, 88% of the Irish salmon rod catch were caught between June and September, and 69% between July and September. This reflects the dominance of the one sea winter fish in the catch, and this study can therefore be considered as reflective of the time when the majority of the angling catch is taken in Ireland. The duration that a fish is angled may increase physiological disturbance, time needed to recover and mortality (Arlinghaus et al., 2007). Extended playing and handling times were a significant mortality factor in a review study of C&R angling mortality (Bartholomew and Bohnsack, 2005). The playing time increased with increasing fish size in the present study, in accordance with a previous Atlantic salmon study in Norway (Thorstad et al., 2003), but not to the extent that playing time seemed to affect survival. The fish that died were not among the largest salmon included in the study. Further, playing and handling time of the fish that died
were among the shorter periods in the total sample, indicating that playing time and handling did not explain the mortality. Air exposure is also associated with C&R-related physiological disturbance and mortality (Ferguson and Tufts, 1992; Schreer et al., 2005), and there may be interactive effects of air exposure duration and water temperature on survival and physiological disturbances (Gingerich et al., 2007; Gale et al., 2011). The results of Gingerich et al. (2007) indicate that at low to moderate water temperatures, extended air exposure may result in little mortality. However, at high water temperatures, short-term mortality (within 48 h) can be substantial, especially for fish that experience extended air exposure durations. Richard et al. (2013) found that water temperature negatively impacted reproductive success of salmon kept in the water, but in the temperature range of 12–17 ◦ C, air exposure time had a greater negative impact on fitness than water temperature. Depending on the temperature, reproductive success can be up to two or three times higher for salmon kept in the water compared with those exposed to air for 10 s and with those exposed to air for >10 s, respectively. Thus, the conditions in which C&R is conducted influence the success of the practice in terms of conservation. Consequently, Richard et al. (2013) conclude that precaution must be taken to limit C&R in warm water periods and avoid air exposure prior to release. Minimum air exposure, low to moderate water temperatures, short playing time and careful handling most likely contributed to the high survival post C&R in the present study. The time spent in the river prior to being angled did not seem to influence survival post C&R. A high proportion of fish captured was described as coloured, indicating that they had spent some time in
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freshwater, while 39% of the fish were characterised as fresh run. Physiological disturbance from angling and mortality may be larger in bright Atlantic salmon than in kelts (Brobbel et al., 1996), indicating that the stage of freshwater migration may be important for the effects of catch-and-release. However, similar to the results in the present study, Thorstad et al. (2007) did not find any differences in survival between newly ascended salmon and salmon that had stayed longer in the river before being caught and released. Another factor that can influence the impact of a hooking event is the presence or absence of barb on the hook (Muoneke and Childress, 1994; Cooke and Suski, 2005; Arlinghaus et al., 2007). Bartholomew and Bohnsack (2005) found that fish captured on barbed hooks had marginally higher mortality than those captured on barbless hooks. The use of barbless hooks can reduce handling time and air exposure, and may reduce tissue damage at the point of hook entry. There were no clear indications that the use of barbed vs. barbless hooks affected handling time or mortality in the present study, but the number of fish captured on barbless hooks was relatively low. Since the majority of data available support the notion that use of barbless hooks is beneficial for discards and can only benefit fish, the use of barbless hooks is generally recommended (Muoneke and Childress, 1994; Cooke and Suski, 2005; Arlinghaus et al., 2007). In Irish rivers open only for C&R angling, byelaws only permit the use of barbless hooks and in certain circumstances fly only angling. Previous studies of Atlantic salmon have shown that C&R may alter the upstream migration pattern and result in unusual delays, downstream movements, erratic displacement (Webb, 1998; Mäkinen et al., 2000; Thorstad et al., 2003, 2007) and may even reduce the ultimate distance a fish was willing to migrate (Tufts et al., 2000). While some downstream movement was evident in the month after release in the present study, most fish exhibited considerable upstream movement in subsequent months. For the river with the most data available, the Owenmore, salmon generally remained stationary or moved short distances upstream in the two months after tagging. The majority of upstream fish movement in December was over greater distances. Whoriskey et al. (2000) and Jensen et al. (2010) concluded that salmon behaviour seemed little altered after C&R angling. Webb (1998) concluded that, if treated with care, most freshrun and early summer salmon returned to the river by anglers behave normally and survive to spawn. The results of Bendock and Alexandersdottir (1993) in freshwater Chinook salmon fisheries in Alaska, Thorstad et al. (2003) and Dempson et al. (2002) for Atlantic salmon in Norway and Newfoundland, support the use of catch-and-release regulations as an effective management tool to reduce sport fishing mortality. Richard et al. (2013) also concluded that C&R is an effective management tool towards maintaining the socio-economic benefits from recreational fishing while ensuring a minimal impact on the exploited population, pending appropriate practices. Results from the present study concur with these findings. However, a small per cent mortality must be expected during C&R, even during fly fishing. Hooking location may have been one of the factors influencing C&R mortality in the present study. Fish bleeding from the hook wound and/or deeply hooked in the gills or throat had a low survival rate, and should therefore not be released. In rivers open for angling and harvesting salmon in Ireland in 2012, 37% of salmon were captured by fly fishing, 32% by lure and the remainder by worm and prawn fishing (Irish salmon logbook tagging scheme). For rivers where catch and release angling only was permitted, the percentage of salmon taken by fly fishing was 53%, while 33% were captured by lure fishing, both methods used with single barbless hooks. The three rivers in the present study were all above conservation limit and all angling methods were permitted. Results indicate that the management assumption that released Atlantic salmon can be included in the estimate of the
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spawning stock in Irish rivers with C&R angling only would be valid for fly captured (98% survival) but not for lure captured salmon (55% survival). Therefore, any interpretation on risks associated with catch and release fishing depend upon the characteristics of the fishery in terms of gear used, proportion of fish captured by gear type, angler release practices, and water temperatures when catch and release activities occur. Further studies are required regarding the appropriateness of allowing catch and release fishing using lures, and by allowing catch and release angling at water temperatures above 18 ◦ C. In conclusion, results showed that, when conducted using proper guidelines, and at low to moderate water temperatures, survival of fly captured salmon after C&R angling was high. The results generally demonstrated a careful treatment of the Atlantic salmon during C&R angling in these Irish rivers, with a short playing and handling time, minimum air exposure and a low occurrence of deep hooking (i.e., hooking in gills and throat). Hence, in rivers without a surplus of salmon above the conservation limit, permitting C&R angling using appropriate methods can be successful as a tool to provide information on salmon stock status while not significantly impacting on salmon survival. Acknowledgements The authors would like to thank the angling clubs on the Owenmore, Feale and Mulkear for their cooperation during this study and individual anglers who provided salmon for tagging and release. Inland Fisheries Ireland staff are acknowledged for their assistance during tagging and tracking on all three rivers. E.B. Thorstad was partly supported by the Norwegian Research Council project SalCaRe no. 216416/O10. Dr. Fred Whoriskey and Tony Holmes are acknowledged for their helpful comments on the revised version of the manuscript. References Anderson, W.G., Booth, R., Beddow, T.A., McKinley, R.S., Finstad, B., Økland, F., Scruton, D., 1998. Remote monitoring of heart rate as a measure of recovery in angled Atlantic salmon, Salmo salar (L.). Hydrobiologia 371/372, 233–240. Arlinghaus, R., Cooke, S.J., Lyman, J., Policansky, D., Schwab, A., Suski, C., Sutton, S.G., Thorstad, E.B., 2007. Understanding the complexity of catch-and-release in recreational fishing: an integrative synthesis of global knowledge from historical, ethical, social, and biological perspectives. Rev. Fish. Sci. 15, 75–167. Bartholomew, A., Bohnsack, J.A., 2005. A review of catch-and-release angling mortality with implications for no-take reserves. Rev. Fish Biol. Fish. 15, 129–154. Bendock, T., Alexandersdottir, M., 1993. Hooking mortality of Chinook salmon released in the Kenai River, Alaska. N. Am. J. Fish. Manage. 13, 540–549. Boyd, J.W., Guy, C.S., Horton, T.B., Leathe, S.A., 2010. Effects of catch-and-release angling on salmonids at elevated water temperatures. N. Am. J. Fish. Manage. 30, 898–907. Brobbel, M.A., Wilkie, M.P., Davidson, K., Kieffer, J.D., Bielak, A.T., Tufts, B.L., 1996. Physiological effects of catch and release angling in Atlantic salmon (Salmo salar) at different stages of freshwater migration. Can. J. Fish. Aquat. Sci. 53, 2036–2043. Cooke, S.J., Suski, C.D., 2005. Do we need species-specific guidelines for catch-andrelease recreational angling to effectively conserve diverse fishery resources? Biodivers. Conserv. 14, 1195–2005. Dempson, J.B., Furey, G., Bloom, M., 2002. Effects of catch and release angling on Atlantic salmon, Salmo salar L., of the Conne River, Newfoundland. Fish. Manage. Ecol. 9, 139–147. Donaldson, M.R., Arlinghaus, R., Hanson, K.C., Cooke, S.J., 2008. Enhancing catchand-release science with biotelemetry. Fish Fish. 9, 79–105. DuBois, R.B., Margenau, T.L., Stewart, R.S., Cunningham, P.K., Rasmussen, P.W., 1994. Hooking mortality of northern pike angled through ice. N. Am. J. Fish. Manage. 14, 769–775. Falk, M.R., Gillman, D.V., Dahlke, L.W., 1974. Comparison of Mortality Between Barbed and Barbless Hooked Lake Trout. Technical Report Series CEN/T-74-1. Department of Environmental Fisheries and Marine Services, Winnipeg, Manitoba. Ferguson, R.A., Tufts, B.L., 1992. Physiological effects of brief air exposure in exhaustively exercised rainbow trout (Oncorhynchus mykiss): implications for catch and release fisheries. Can. J. Fish. Aquat. Sci. 49, 1157–1162. Finstad, B., Bjørn, P.A., Nilsen, S.T., 1995. Survival of salmon lice, Lepeophtheirus salmonis Krøyer, on Arctic charr Salvelinus alpinus (L.) in fresh water. Aquacult. Res. 26, 791–795.
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Gale, M.K., Hinch, S.G., Eliason, E.J., Cooke, S.J., Patterson, D.A., 2011. Physiological impairment of adult sockeye salmon in fresh water after simulated capture-andrelease across a range of temperatures. Fish. Res. 112, 85–95. Gingerich, A.J., Cooke, S.J., Hanson, K.C., Donaldson, M.R., Hasler, C.T., Suski, C.D., Arlinghaus, R., 2007. Evaluation of the interactive effects of air exposure duration and water temperature on the condition and survival of angled and released. Fish. Res. 86, 169–178. Gjernes, T., Kronlund, A.R., Mulligan, T.J., 1993. Mortality of Chinook and Coho salmon in their first year of ocean life following catch and release by anglers. N. Am. J. Fish. Manage. 13, 524–539. ICES (International Council for the Exploration of the Sea), 2013. Report of the Working Group on North Atlantic Salmon (WGNAS). ICES CM 2013/ACOM:09. Jensen, J.L.A., Halttunen, E., Thorstad, E.B., Næsje, T.F., Rikardsen, A.H., 2010. Does catch-and-release angling alter the migratory behaviour of Atlantic salmon? Fish. Res. 106, 550–554. Loftus, A.J., Taylor, W.W., Keller, M., 1988. An evaluation of lake trout (Salvelinus namaycush) hooking mortality in the upper Great Lakes. Can. J. Fish. Aquat. Sci. 45, 1473–1479. Mäkinen, T.S., Niemelä, E., Moen, K., Lindström, R., 2000. Behaviour of gill-net and rod-captured Atlantic salmon (Salmo salar L.) during upstream migration and following radio tagging. Fish. Res. 45, 117–127. Meka, J.M., 2004. The influence of hook type, angler experience, and fish size on injury rates and the duration of capture in an Alaskan catch-and-release rainbow trout fishery. N. Am. J. Fish. Manage. 24, 1309–1321. Muoneke, M.I., Childress, W.M., 1994. Hooking mortality: a review for recreational fisheries. Rev. Fish. Sci. 2, 123–156. Nuhfer, A.J., Alexander, G.A., 1992. Hooking mortality of trophy-sized wild brook trout caught on artificial lures. N. Am. J. Fish. Manage. 12, 634–644. Pauley, G.B., Thomas, G.L., 1993. Mortality of anadromous coastal cutthroat trout caught with artificial lures and natural bait. N. Am. J. Fish. Manage. 13, 337–345. Richard, A., Dionne, M., Jinliang, W., Bernatchez, L., 2013. Does catch and release affect the mating system and individual reproductive success of wild Atlantic salmon (Salmo salar L.)? Mol. Ecol. 22, 187–200.
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Survival of wild Atlantic salmon (Salmo salar) after catch and release angling in three Irish rivers Patrick G. Gargan a,∗ , Trevor Stafford a , Finn Økland b , Eva B. Thorstad b a b
Inland Fisheries Ireland, 3044 Lake Drive, Citywest Business Campus, Dublin 24, Ireland Norwegian Institute for Nature Research (NINA), Trondheim, Norway
a r t i c l e
i n f o
Article history: Received 26 August 2013 Received in revised form 30 January 2014 Accepted 7 August 2014 Handling Editor George A. Rose Keywords: Atlantic salmon Angling Catch and release Survival
a b s t r a c t The practice of catch and release (C&R) in salmon rod fisheries has become increasingly common due to the widespread decline in salmon abundance in the North Atlantic over the past two decades. Many Irish Atlantic salmon rivers are only open for catch and release (C&R) angling since a change in salmon management in 2006. Success of Atlantic salmon surviving to contribute to the spawning stock following C&R was studied in three rivers. In total, 76 fish were tagged with radio transmitters post C&R angling. Survival to spawning was greater for fly caught (98%) than lure caught fish (55%). Hence, survival after C&R was dependent on gear type. Hook location may have influenced C&R mortality in the lure captured fish. All fish bleeding at the hook wound or hooked in the throat died. Simultaneous hooking in the upper and lower mouth may also have contributed to reduced survival. There was an overall net upstream movement post release with many salmon moving more than 10 km upstream. Results demonstrated that, when conducted using proper guidelines, survival of salmon after C&R can be high. Opening rivers to C&R angling can be successful as a tool to provide information on salmon stock status while not significantly impacting on salmon survival. © 2014 Elsevier B.V. All rights reserved.
1. Introduction The practice of catch and release (C&R) in Atlantic salmon rod fisheries has become increasingly common due to the population decline in the North Atlantic over the past decades (ICES, 2013). In some areas of Canada and USA, C&R has been practiced since 1984, and in more recent years it has been widely used in many European countries, both as a result of statutory regulation and through voluntary practice. Reported rates of C&R (expressed as % of the total reported rod catch) vary from 14% in Norway to as high as 73% in Scotland and 84% in Russia, reflecting varying management practices and angler and stakeholder attitudes among countries (ICES, 2013). C&R angling is a relatively recent phenomenon in Ireland. The rate of C&R in rod fisheries has increased from 5% of the total reported catch in 2004 to 35% in 2012, with an estimated 12,000 Atlantic salmon released in 2012. Since 2006, the management of Atlantic salmon in Ireland has been based on scientific assessment of all 141 salmon rivers, aiming at achieving river specific conservation limits (CL). Only the salmon surplus above the CL is available
∗ Corresponding author. E-mail address: paddy.gargan@fisheriesireland.ie (P.G. Gargan). http://dx.doi.org/10.1016/j.fishres.2014.08.005 0165-7836/© 2014 Elsevier B.V. All rights reserved.
for harvest. This has resulted in approximately 40% of rivers being open for harvest, a further 40% of rivers being clearly below the CL and closed to fishing, and with the last 20% of rivers being open to C&R angling only. C&R angling is permitted because there is lack on information on salmon runs, and the angling catch generated by C&R can be used in conjunction with a rod exploitation rate to provide an estimate of the overall salmon stock status. This estimate can be compared against the river specific CL to determine if it is being met. In addition to providing rod catch data, rivers open for catch and release angling generate economic activity and employment opportunities. While the angling methods permitted in the rivers open to C&R angling are restricted (use of single barbless hooks and no use of worm as bait), there is still a possibility of some mortality associated with C&R. For this reason, only rivers determined to be above a salmon fry threshold established by electro-fishing, or rivers estimated to be meeting >65% of CL, are open for C&R angling. However, concern has been expressed regarding the impact of catch and release angling on salmon mortality in rivers failing to meet conservation limits. With proper fish handling and water temperatures below 20 ◦ C, Atlantic salmon mortality after C&R may be low (Dempson et al., 2002; Thorstad et al., 2003). Most studies of the effects C&R in Atlantic salmon have been performed in North America, and many studies rely on fish being kept in tanks or cages after C&R, which
P.G. Gargan et al. / Fisheries Research 161 (2015) 252–260
may not be representative for fish being released back to the river (Thorstad et al., 2008). More realistic results may be obtained by tagging fish with radio or acoustic transmitters and recording the behaviour and survival of free-swimming fish in their natural environment after C&R (Donaldson et al., 2008). In previous studies using radio or acoustic transmitters, fly fishing has been the main angling method (Whoriskey et al., 2000; Jensen et al., 2010; Thorstad et al., 2003, 2007). However, gear type may influence survival rates (Arlinghaus et al., 2007). This study was undertaken to derive data on the success of Atlantic salmon surviving to contribute to the spawning stock following C&R. The aim was to test the management assumption that all released fish can be included in the estimate of the spawning stock in the rivers with C&R angling only. Information on angling methods were collected, and behaviour and survival after C&R were recorded by equipping individual fish with radio transmitters and releasing them immediately back to the river. Results from two different angling methods (spinning lures and flies) were compared, and results were related to gear type, playing time, handling time, where the fish were hooked, water temperature and fish length and sex. 2. Materials and methods 2.1. Study sites C&R angling was carried out on three Irish rivers, the Owenmore in county Mayo, the Mulkear in county Limerick and the Feale in county Kerry (Fig. 1). The Owenmore (precipitation area 341 km2 ,
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main stem channel of 20 km) is a productive spate river with an annual average rod catch (2009–2013) of 880 Atlantic salmon. The Mulkear (precipitation area 661 km2 , main stem channel of 23 km) is a large tributary of the Shannon catchment with an average annual rod catch (2009–2013) of 970 Atlantic salmon. The Feale (precipitation area 1151 km2 , main stem channel of 24 km) has an annual average rod catch (2009–2013) of 1350 Atlantic salmon. 2.2. Fish capture, tagging and release Tagging was conducted on the Owenmore River during August and September 2006 and 2007, on the Feale during September 2006 and on the Mulkear during September 2007. The salmon included in this study were tagged during or slightly after the peak period of salmon runs in these rivers. Fly fishing only was used to capture Atlantic salmon on the Owenmore, a combination of fly and lure fishing on the Feale and lure fishing only on the Mulkear (Table 1). Flies were artificial flies ranging in hook size from 10 to 14. The lures were spinning lures (Flying C type lures). Field staff were in the vicinity of anglers along the riverbank prior to tagging all fish. Anglers were instructed to play fish in the normal way and fish were landed using a standard landing net or directed into a purpose built polyester landing bag. The presence of a scientist did not alter the playing or landing of salmon during the study. Fish were exposed to air for less than 20 s. Capture method and the time taken from hooking to landing were recorded. Hooks were removed after noting hook size, the number of hooks imbedded and the position of the hooks. Fish were inserted into a cylinder tube filled with water, which allowed the head to be under water during tagging. Fish were inspected for damage or wounds which may have been inflicted by hooks. Fork length, sex and condition of fish were recorded. The fish were characterised as fresh run if they had a bright silvery colour, thin mucous layer and/or sea lice (Lepeophtheirus salmonis). Sea lice are marine parasites, and their presence usually indicates that the fish have been in fresh water less than a week (although some salmon lice may survive longer, Finstad et al., 1995). All fish (n = 76, Table 1) were one-sea-winter salmon (with the exception of one multi-sea-winter salmon from the Feale) in the 47–74 cm length range. The fish were tagged with model F2120 radio transmitters from Advanced Telemetry Systems (ATS), USA (flat with outline dimensions 21 mm × 52 mm × 11 mm, mass in air 15 g). Programmed battery life was seven months. Each transmitter had a unique frequency within the 173,200–173,500 MHz range. Similar transmitters had no effect on swimming performance of Atlantic salmon >45 cm in laboratory swim trials (Thorstad et al., 2000). Transmitters were attached externally to fish below the dorsal fin and secured with stainless steel wire. Time taken to tag each fish was recorded. After tagging, tags were checked for signal emission and fish were held in the water until fully recovered before being released. 2.3. Monitoring of tagged fish
Fig. 1. Location of the study rivers Owenmore, Mulkear and Feale and their precipitation areas in Ireland.
Tracking of tagged fish was conducted in October–January (i.e., until after spawning). Fish were tracked at a minimum of four weeks intervals on the Owenmore and on a weekly basis on the Feale and Mulkear using a 3-element Yagi antenna connected to a receiver (model R2000, ATS). Main channels and tributaries were radio tracked on foot or by boat. A vehicle was used to track fish where roads followed the river course. The entire catchment was monitored during each tracking survey with a few exceptions when high water did not allow tracking of lower main channel areas. Distances fish moved along rivers were calculated using Arc View 9.2 (Esri, USA).
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Table 1 Details on the characteristics of the tagged fish and angling details. Owenmore
Feale
Feale
Mulkear
Number of fish tagged Number of fish recorded post tagging Number of fish survived to spawning Gear type
52 48 47 (98%) Fly
12 12 12 (100%) Fly
3 3 2 (67%) Lure
9 8 4 (50%) Lure
Number by hook type and size (size 10:12:14:4) Single Double Trebble
0 13 (3:9:1:0) 39 (2:29:8:0)
9 (4:5:0:0) 2 (2:0:0:0) 1 (1:0:0:0)
3 (0:0:0:3) 0 0
0 0 9 (0:0:0:9)
Fish characteristics Fork length (mean, range, SD) Sex (number; male:female) Number (%) fresh run
58 (44–74, 6.3) 22:30 26 (50%)
59 (49–73, 7.0) 9:03 2 (17%)
60 (59–63, 2.3) 1:02 2 (67%)
56 (48–66, 5.5) 6:03 0 (0%)
Angling practices Water temperature at tagging (mean, range, SD) Time played in minutes (mean, range, SD) Time handled in minutes Total time playing and handling
13 (11–16, 1.3) 5.8 (3–9, 1.8) 2.2 8.0
13 (13–14, 0.5) 5.8 (4–8, 1.2) 2.3 8.1
14 (14–14, 0) 5.3 (5–6, 0.6) 2.0 7.3
10 (9–12, 1.22) 4.1 (3–6, 0.9) 2.1 6.2
Fish having moved upstream were deemed to have survived after C&R. Five fish (7%) were never recorded after tagging (Table 1). Possible explanations may be tag failure, unreported recaptures, or fish leaving the rivers. The five fish that disappeared were three males and two females, with mean fork length 61 cm (range 54–70, SD 8.4). The survival results are based on the 71 fish recorded after tagging. These fish were found during all tracking surveys, except 38% missing during one of the surveys and 12% missing during two of the surveys. One fish was not detected during three of the surveys, but when detected in December it had moved upstream 8.1 km from being tagged in September. 2.4. Data analyses Statistical comparisons between those fish dying and survivors were not performed due to the low number of fish suffering mortality. However, statistical comparisons were made between fly and lure captured fish to characterise the C&R fishery and examine if there were any differences between the angling methods relevant for fish performance and survival after C&R (all tagged fish included, sample sizes given in Tables 1 and 2). Data from the different rivers were combined as we have no reason a priori to expect that river characteristic would alter the interaction between survival and river site across treatment effects in a systematic fashion. Independent samples t-tests were used to test for possible differences between fly and lure captured fish in mean fork length, water temperature at C&R, playing time and handling time, assuming equal or unequal variances based on Levene’s test for equality of variances. One-way ANOVA was used to compare handling time between fish captured with single, double and treble hooks. Pearson chi square test was used to test for possible differences in frequencies among fly and lure captured fish (frequencies of fish captured on single, double and treble hooks and frequency of hook location), except chi square with continuity correction was used for 2 × 2 tables (frequency of males and females), or Fisher’s test when expected count was less than five in any of the cells (frequency of fresh run fish). Effect of fish length on playing time was tested using a linear regression. Statistical analyses were performed using SPSS Statistics version 21 (IBM, USA).
(radio transmitter signal detected at <100 m from release location) throughout all monitoring periods (Fig. 2). Two fish were stationary during the first monitoring period and recorded having moved downstream in subsequent periods. One fish moved downstream during the first and second monitoring period and then remained stationary (Fig. 2). Hence, all these six fish were presumed not to have survived. The survival rate was higher for fly caught (98%, 59 of 60) than for lure caught salmon (55%, 6 of 11) (Fisher’s exact test, p < 0.001, Table 1). The high survival of fly caught salmon was consistent over two years on the Owenmore (100% survival in 2006, 21 of 21 fish – and 96% survival in 2007, 26 of 27 fish), and between the Owenmore and the Feale (100% survival). No tagged salmon were reported recaptured by anglers in any of the rivers. The six fish presumed to have died after C&R were 3 males and 3 females with mean fork length 57 cm (range 53–63 cm, SD 3.7). One fish was characterised as fresh run. These fish were angled at a mean water temperature of 11 ◦ C (range 9–14 ◦ C, SD 2.1). Hence, sex
3. Results 3.1. Fish survival after catch and release Overall, 92% of the Atlantic salmon recorded after tagging survived post C&R (65 of 71 salmon, Table 1). Three fish were stationary
Fig. 2. Net displacement from the point of tagging for dead fish by date detected.
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Table 2 Characteristics of gear type, hook type and hooking location. Type of hook
Fly
Number of hooks Number of salmon hooked Hooking location (1, 2 or 3 hooks attached) Jaw (upper, lower) Maxillary bone Tongue, upper mouth Throat or belly Unknown (hook fell out)
Single 9 Single 6 2 0 0 1
a
Lure Double 15 Double (1:2) 7 (3:4) 5 (5:0) 2 (2:0) 0 1
Trebble 40 Trebble (1:2:3) 21 (14:7:0) 15 (8:7:0) 3 (2:1:0) 1 (1:0:0) 0
Single 3 Single 1 2 0 0 0
Trebble 9 Trebble (1:2:3) 7 (5:2a :0) 3 (3a :0:0) 0 1 (0:0:3) 0
To identify gear type and hooking location resulting in bleeding.
distribution, body length and water temperature at angling time did not differ between those not surviving and the tagged fish in general (Table 1 and below). The playing time (mean 4.5 min, range 4–6, SD 0.8), handling time (mean 2.0 min, range 2–2, SD 0) and total playing and handling time (mean 6.5 min, range 6–8, SD 0.8) for the mortalities were among the shorter periods in the total sample (Table 1 and below). Of the salmon that did not survive, one was captured by fly in the Owenmore and five on lures on the Mulkear and the Feale (Table 1). The fly captured salmon mortality (n = 1) was hooked in the upper jaw on a double barbed hook size 10. The lure captured salmon mortalities were captured on single barbless hooks, size 4 (n = 1), or on barbed treble hooks size 4 (n = 4). Of these lure captured salmon, one was hooked in the maxillary, one in the lower jaw, one in both the lower and upper jaw, one in both in the maxillary and in the upper jaw and one in the throat. Notably, the only two fish recorded as having bled at the hook wound in the entire data set were among the dead fish, as were the only fish hooked in the throat, and two of the three fish noted as being hooked in both the upper and lower mouth. 3.2. Characterisation of the fishery and angling methods There were no differences between fly caught and lure caught Atlantic salmon in fork length (t-test assuming equal variances, t = 0.66, p = 0.51), proportion males and females (chi-square test with continuity correction, 2 = 0.50, p = 0.48), or proportion of fish characterised as fresh run (Fisher’s exact test, p = 0.18) (Table 1). The water temperature at C&R was higher for fly caught than lure caught fish (mean 13 ◦ C vs. 11 ◦ C, t-test assuming unequal variances, t = 2.73, p = 0.019, Table 1). Of the fly caught salmon, 14% were captured on a single hook, 23% on a double hook and 63% on a treble hook (Table 1). Of the lure caught salmon, 25% were captured on a single hook and 75% on a treble hook (Table 1). There was no difference in proportion fish captured on single, double and treble hooks between fly caught and lure caught salmon (Pearson chi square test, df = 2, 2 = 3.58, p = 0.17). However, all lure caught salmon were captured using larger hooks (size 4) whereas hook size was smaller for fly caught salmon (size 10–14). In the Owenmore and Mulkear, all flies and lures had barbed hooks. In contrast, in the Feale, 67% of the flies (8 of 12) and 67% of the lures (2 of 3) had barbless hooks. For fish captured on flies with double hooks, 10 fish (67%) were hooked by one of the hooks, 4 fish (27%) by both hooks and for one fish the hook (7%) fell off at capture. For fish captured on flies with treble hooks, 25 fish (63%) were hooked by one hook and 15 fish (38%) by two hooks. For fish captured on lures with treble hooks, 5 fish (50%) were hooked by one hook, 4 fish (40%) by two hooks and 1 fish (10%) by all three hooks. Of the fly caught salmon, 53% were hooked in the upper or lower jaw, 34% in the maxillary bone, 8% in the tongue or upper mouth, 2% in the belly, and 3% lost the hook when landed (Table 2). Of the lure caught salmon, 50% were hooked in the upper or lower jaw,
42% in the maxillary bone and 8% in the throat (Table 2). There was no difference in distribution of hook locations between fly caught and lure caught salmon (Pearson chi square test, df = 4, 2 = 2.93, p = 0.60). The playing time (time from hooking to landing the fish) was generally short, on average 5.6 min (Table 1). Playing time increased with increasing fish length, but fish length explained only 11% of the variation in playing time (linear regression, r2 = 0.11, p = 0.004). Handling time (from landing to release) was on average 2.2 min, resulting in a total playing and handling time of average 7.8 min (Table 1). Playing time was longer for fly captured than lure captured salmon (t-test assuming unequal variances, t = 3.8, p = 0.001), whereas handling time did not differ between the groups (t-test assuming equal variances, t = 1.3, p = 0.19). In summary, total handling time was longer for fly captured than lure captured salmon (t-test assuming equal variances, t = 2.7, p = 0.009). Handling time did not differ between fish captured with single, double or treble hooks (one-way ANOVA, df = 2, F = 0.87, p = 0.43, all fish combined). Handling time did not differ between fish captured on barbed or barbless hooks (t-test assuming equal variances, t = −0.80, p = 0.43, all fish combined). Results were similar when fly and lure captured fish were tested separately (results not shown). 3.3. Fish behaviour after catch and release The fish that survived (n = 65) showed an overall net upstream movement post release (Figs. 3 and 4). Of the Owenmore fish that moved upstream, the majority travelled more than 3 km, with many fish moving more than 10 km upstream (Figs. 3 and 4). This is not unexpected as fish were captured in the lower and mid-main channel, and considerable spawning takes place in the upper main channel and head water tributaries. Three individuals moved several kilometres downstream after release, but subsequently moved upstream. The longest downstream migrations made by Owenmore fish were six fish in January, most likely after spawning. The net displacement since the previous detection event (Fig. 4) shows the type and extent of fish movements during the season. The majority of Feale salmon remained stationary or moved upstream in the first and second month after C&R (Figs. 3 and 4). An initial downstream migration was evident for four fish soon after release and three subsequently moved considerable distances upstream. Three of the four surviving salmon from the Mulkear moved upstream and were stationary during the entire study period (Figs. 3 and 4). Hook placement did not demonstrate marked differences in fish displacement after tagging (Fig. 5). 4. Discussion A high survival to spawning was recorded for fly caught Atlantic salmon (98%) in the present study, which is similar to results found in previous Atlantic salmon catch and release studies in Canada, Norway and Russia (92–100% survival, Dempson et al., 2002; Thorstad et al., 2007; Jensen et al., 2010; Whoriskey et al.,
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Fig. 3. The extent of net movements by date for individual fish which survived (n = 65).
2000). A lower survival rate (84%) was recorded in the Aberdeenshire Dee, Scotland (Webb, 1998). The high survival for fly caught salmon in the present study was consistent between years and rivers. However, the survival rates differed among gear types, as the survival rate for fish captured with spinning lures (55%) was much lower than for fly caught salmon. This is in accordance with results in a study of rainbow trout (Oncorhynchus mykiss), where fish caught by spinning lures were injured more frequently than fish caught by fly (Meka, 2004). The low number of fish suffering mortality in the present study did not allow for statistical comparisons between those dying and survivors. However, a descriptive inspection of the results did not reveal any particular characteristics of the individuals suffering mortality compared to survivors with respect to fish size, sex, water temperature, whether they were fresh run in the river or not, playing time, handling time, use of barbed vs. barbless hooks, or the use of single, double or treble hooks.
A notable difference between fly and lure captured Atlantic salmon, however, was the larger hooks used for all lure captured fish. Moreover, the only two fish bleeding at the hook wound in the entire sample were salmon mortalities captured by lure, as were the only fish hooked deep in the throat, and two of the three fish noted to be simultaneously hooked in the upper and lower mouth. Salmon most likely die after C&R from wounds caused from angling, or exhaustive exercise due to the extent of the intracellular acidosis within the muscle (Wood et al., 1983). The larger size of hooks used with spinning lures may have resulted in larger hook wounds, a greater extent of deep hooking and bleeding, and a greater extent of simultaneous hooking in the upper and lower mouth – and thereby a higher mortality. Meka (2004) similarly suggested that hook size may have been an important factor influencing the number of hook points penetrating rainbow trout during angling, which in turn caused increased injury to sensitive locations, associated bleeding, and subsequent mortality. Large hooks may be more difficult to
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Fig. 4. Net displacement of live fish since the previous detection event.
swallow than small hooks, but may cause greater tissue damage at the wound site (Pauley and Thomas, 1993; DuBois et al., 1994). Gjernes et al. (1993) speculated that the greater depth and gape of larger hooks may lead to deeper hook penetration and greater risk of contact with critical organs. As all fly captured fish were captured on small hook sizes compared to the larger hook size of fish captured by lures in the present study, it was not possible to isolate the effect of hook size alone. We suggest that hook size should be further investigated as a mortality factor after C&R. Bartholomew and Bohnsack (2005) found in their extensive review that catch-and-release angling mortality varied greatly among and within species, and that anatomical hooking location was the most important mortality factor. Other studies also indicate that anatomical hooking location and associated bleeding is the most important factor influencing mortality of angler-caught fish (e.g., Falk et al., 1974; Warner, 1976; Loftus et al., 1988; Nuhfer and Alexander, 1992; Arlinghaus et al., 2007). Simultaneous hooking in the lower and upper mouth may reduce oxygen uptake during
playing of the fish because it to some extent closes the mouth. We find no studies discussing simultaneously hooking in the lower and upper mouth in the scientific literature, but this is sometimes mentioned by anglers as a factor negatively impacting the condition of the salmon at release (E.B. Thorstad, personal observation). Hook characteristics and hook types are shown to impact the hooking locations and endpoints in C&R events in a number of studies, but the results vary widely among studies, perhaps due to interspecific variation (Muoneke and Childress, 1994; Cooke and Suski, 2005; Arlinghaus et al., 2007). Water temperature is an important factor in determining survival of Atlantic salmon after release, explaining 72% of the variation in survival from Atlantic salmon C&R angling (Dempson et al., 2002). Mortality after C&R angling may increase at high water temperatures, and temperatures above 18–20 ◦ C may have a negative effect on survival (Wilkie et al., 1996, 1997; Anderson et al., 1998; Dempson et al., 2002; Thorstad et al., 2003). The water temperatures in this study of 9–16 ◦ C were unlikely to impact on survival.
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Fig. 5. Net displacement of fish during the first fifty days plotted (with line of best fit with SE fitted in R using ggplot2) against hook placement.
Further, differences in water temperature cannot explain the differences in mortality between fly and lure captured salmon as the water temperature at C&R was lower and not higher for the lure salmon in general, and the temperature at C&R for individuals that failed to survive was among the lowest in the total sample. Catch-and-release mortality of rainbow trout and mountain whitefish (Prosopium williamsoni) increased when daily maximum water temperature was higher than 20 ◦ C and mortality of brown trout (Salmo trutta) increased when daily maximum water temperature was at or exceeded 23 ◦ C (Boyd et al., 2010). C&R took place in August and September in the present study and temperature may have a more significant effect during peak summer temperatures when water temperatures may reach 18 ◦ C or more. In 2012, 88% of the Irish salmon rod catch were caught between June and September, and 69% between July and September. This reflects the dominance of the one sea winter fish in the catch, and this study can therefore be considered as reflective of the time when the majority of the angling catch is taken in Ireland. The duration that a fish is angled may increase physiological disturbance, time needed to recover and mortality (Arlinghaus et al., 2007). Extended playing and handling times were a significant mortality factor in a review study of C&R angling mortality (Bartholomew and Bohnsack, 2005). The playing time increased with increasing fish size in the present study, in accordance with a previous Atlantic salmon study in Norway (Thorstad et al., 2003), but not to the extent that playing time seemed to affect survival. The fish that died were not among the largest salmon included in the study. Further, playing and handling time of the fish that died
were among the shorter periods in the total sample, indicating that playing time and handling did not explain the mortality. Air exposure is also associated with C&R-related physiological disturbance and mortality (Ferguson and Tufts, 1992; Schreer et al., 2005), and there may be interactive effects of air exposure duration and water temperature on survival and physiological disturbances (Gingerich et al., 2007; Gale et al., 2011). The results of Gingerich et al. (2007) indicate that at low to moderate water temperatures, extended air exposure may result in little mortality. However, at high water temperatures, short-term mortality (within 48 h) can be substantial, especially for fish that experience extended air exposure durations. Richard et al. (2013) found that water temperature negatively impacted reproductive success of salmon kept in the water, but in the temperature range of 12–17 ◦ C, air exposure time had a greater negative impact on fitness than water temperature. Depending on the temperature, reproductive success can be up to two or three times higher for salmon kept in the water compared with those exposed to air for 10 s and with those exposed to air for >10 s, respectively. Thus, the conditions in which C&R is conducted influence the success of the practice in terms of conservation. Consequently, Richard et al. (2013) conclude that precaution must be taken to limit C&R in warm water periods and avoid air exposure prior to release. Minimum air exposure, low to moderate water temperatures, short playing time and careful handling most likely contributed to the high survival post C&R in the present study. The time spent in the river prior to being angled did not seem to influence survival post C&R. A high proportion of fish captured was described as coloured, indicating that they had spent some time in
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freshwater, while 39% of the fish were characterised as fresh run. Physiological disturbance from angling and mortality may be larger in bright Atlantic salmon than in kelts (Brobbel et al., 1996), indicating that the stage of freshwater migration may be important for the effects of catch-and-release. However, similar to the results in the present study, Thorstad et al. (2007) did not find any differences in survival between newly ascended salmon and salmon that had stayed longer in the river before being caught and released. Another factor that can influence the impact of a hooking event is the presence or absence of barb on the hook (Muoneke and Childress, 1994; Cooke and Suski, 2005; Arlinghaus et al., 2007). Bartholomew and Bohnsack (2005) found that fish captured on barbed hooks had marginally higher mortality than those captured on barbless hooks. The use of barbless hooks can reduce handling time and air exposure, and may reduce tissue damage at the point of hook entry. There were no clear indications that the use of barbed vs. barbless hooks affected handling time or mortality in the present study, but the number of fish captured on barbless hooks was relatively low. Since the majority of data available support the notion that use of barbless hooks is beneficial for discards and can only benefit fish, the use of barbless hooks is generally recommended (Muoneke and Childress, 1994; Cooke and Suski, 2005; Arlinghaus et al., 2007). In Irish rivers open only for C&R angling, byelaws only permit the use of barbless hooks and in certain circumstances fly only angling. Previous studies of Atlantic salmon have shown that C&R may alter the upstream migration pattern and result in unusual delays, downstream movements, erratic displacement (Webb, 1998; Mäkinen et al., 2000; Thorstad et al., 2003, 2007) and may even reduce the ultimate distance a fish was willing to migrate (Tufts et al., 2000). While some downstream movement was evident in the month after release in the present study, most fish exhibited considerable upstream movement in subsequent months. For the river with the most data available, the Owenmore, salmon generally remained stationary or moved short distances upstream in the two months after tagging. The majority of upstream fish movement in December was over greater distances. Whoriskey et al. (2000) and Jensen et al. (2010) concluded that salmon behaviour seemed little altered after C&R angling. Webb (1998) concluded that, if treated with care, most freshrun and early summer salmon returned to the river by anglers behave normally and survive to spawn. The results of Bendock and Alexandersdottir (1993) in freshwater Chinook salmon fisheries in Alaska, Thorstad et al. (2003) and Dempson et al. (2002) for Atlantic salmon in Norway and Newfoundland, support the use of catch-and-release regulations as an effective management tool to reduce sport fishing mortality. Richard et al. (2013) also concluded that C&R is an effective management tool towards maintaining the socio-economic benefits from recreational fishing while ensuring a minimal impact on the exploited population, pending appropriate practices. Results from the present study concur with these findings. However, a small per cent mortality must be expected during C&R, even during fly fishing. Hooking location may have been one of the factors influencing C&R mortality in the present study. Fish bleeding from the hook wound and/or deeply hooked in the gills or throat had a low survival rate, and should therefore not be released. In rivers open for angling and harvesting salmon in Ireland in 2012, 37% of salmon were captured by fly fishing, 32% by lure and the remainder by worm and prawn fishing (Irish salmon logbook tagging scheme). For rivers where catch and release angling only was permitted, the percentage of salmon taken by fly fishing was 53%, while 33% were captured by lure fishing, both methods used with single barbless hooks. The three rivers in the present study were all above conservation limit and all angling methods were permitted. Results indicate that the management assumption that released Atlantic salmon can be included in the estimate of the
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spawning stock in Irish rivers with C&R angling only would be valid for fly captured (98% survival) but not for lure captured salmon (55% survival). Therefore, any interpretation on risks associated with catch and release fishing depend upon the characteristics of the fishery in terms of gear used, proportion of fish captured by gear type, angler release practices, and water temperatures when catch and release activities occur. Further studies are required regarding the appropriateness of allowing catch and release fishing using lures, and by allowing catch and release angling at water temperatures above 18 ◦ C. In conclusion, results showed that, when conducted using proper guidelines, and at low to moderate water temperatures, survival of fly captured salmon after C&R angling was high. The results generally demonstrated a careful treatment of the Atlantic salmon during C&R angling in these Irish rivers, with a short playing and handling time, minimum air exposure and a low occurrence of deep hooking (i.e., hooking in gills and throat). Hence, in rivers without a surplus of salmon above the conservation limit, permitting C&R angling using appropriate methods can be successful as a tool to provide information on salmon stock status while not significantly impacting on salmon survival. Acknowledgements The authors would like to thank the angling clubs on the Owenmore, Feale and Mulkear for their cooperation during this study and individual anglers who provided salmon for tagging and release. Inland Fisheries Ireland staff are acknowledged for their assistance during tagging and tracking on all three rivers. E.B. Thorstad was partly supported by the Norwegian Research Council project SalCaRe no. 216416/O10. Dr. Fred Whoriskey and Tony Holmes are acknowledged for their helpful comments on the revised version of the manuscript. References Anderson, W.G., Booth, R., Beddow, T.A., McKinley, R.S., Finstad, B., Økland, F., Scruton, D., 1998. Remote monitoring of heart rate as a measure of recovery in angled Atlantic salmon, Salmo salar (L.). Hydrobiologia 371/372, 233–240. Arlinghaus, R., Cooke, S.J., Lyman, J., Policansky, D., Schwab, A., Suski, C., Sutton, S.G., Thorstad, E.B., 2007. Understanding the complexity of catch-and-release in recreational fishing: an integrative synthesis of global knowledge from historical, ethical, social, and biological perspectives. Rev. Fish. Sci. 15, 75–167. Bartholomew, A., Bohnsack, J.A., 2005. A review of catch-and-release angling mortality with implications for no-take reserves. Rev. Fish Biol. Fish. 15, 129–154. Bendock, T., Alexandersdottir, M., 1993. Hooking mortality of Chinook salmon released in the Kenai River, Alaska. N. Am. J. Fish. Manage. 13, 540–549. Boyd, J.W., Guy, C.S., Horton, T.B., Leathe, S.A., 2010. Effects of catch-and-release angling on salmonids at elevated water temperatures. N. Am. J. Fish. Manage. 30, 898–907. Brobbel, M.A., Wilkie, M.P., Davidson, K., Kieffer, J.D., Bielak, A.T., Tufts, B.L., 1996. Physiological effects of catch and release angling in Atlantic salmon (Salmo salar) at different stages of freshwater migration. Can. J. Fish. Aquat. Sci. 53, 2036–2043. Cooke, S.J., Suski, C.D., 2005. Do we need species-specific guidelines for catch-andrelease recreational angling to effectively conserve diverse fishery resources? Biodivers. Conserv. 14, 1195–2005. Dempson, J.B., Furey, G., Bloom, M., 2002. Effects of catch and release angling on Atlantic salmon, Salmo salar L., of the Conne River, Newfoundland. Fish. Manage. Ecol. 9, 139–147. Donaldson, M.R., Arlinghaus, R., Hanson, K.C., Cooke, S.J., 2008. Enhancing catchand-release science with biotelemetry. Fish Fish. 9, 79–105. DuBois, R.B., Margenau, T.L., Stewart, R.S., Cunningham, P.K., Rasmussen, P.W., 1994. Hooking mortality of northern pike angled through ice. N. Am. J. Fish. Manage. 14, 769–775. Falk, M.R., Gillman, D.V., Dahlke, L.W., 1974. Comparison of Mortality Between Barbed and Barbless Hooked Lake Trout. Technical Report Series CEN/T-74-1. Department of Environmental Fisheries and Marine Services, Winnipeg, Manitoba. Ferguson, R.A., Tufts, B.L., 1992. Physiological effects of brief air exposure in exhaustively exercised rainbow trout (Oncorhynchus mykiss): implications for catch and release fisheries. Can. J. Fish. Aquat. Sci. 49, 1157–1162. Finstad, B., Bjørn, P.A., Nilsen, S.T., 1995. Survival of salmon lice, Lepeophtheirus salmonis Krøyer, on Arctic charr Salvelinus alpinus (L.) in fresh water. Aquacult. Res. 26, 791–795.
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