Angling,of,hybrid,sunfish,from,a,hatchery,pond,with,potential,implications,for,community,fisheries

Brin G.Blckwell, Mtthew J.Wrd, Todd M.Kufmn

aSouth Dakota Department of Game, Fish and Parks, 603 East 8th Avenue, Webster, SD, 57274, USA

bSouth Dakota Department of Game, Fish and Parks, 44437 139A Street, Waubay, SD, 57273, USA

Keywords:

Hybrid sunfish

Angling

Community fishing ponds

A B S T R A C T

Hatcheries are frequently called upon to produce catchable-sized fish for stocking community fishing ponds.Desirable attributes of fish selected for stocking into community ponds are that they are easy to produce in a hatchery system to sizes anglers are interested in catching and they provide anglers with high catch rates once stocked.Hybrid sunfish [male Bluegill (Lepomis macrochirus) ×female Green Sunfish (L.cyanellus)] have attributes that potentially make them attractive for use in community fishing ponds.We assessed initial angler catch rates of 100 stocked hybrid sunfish in a 0.12-ha hatchery pond and after being subjected to angling (four, 1-hr catch-and-release fishing events with five anglers).We also investigated whether catch rates would change following a supplemental stocking of an additional 100 hybrid sunfish (four, 1-hr catch-and-release fishing events with five anglers).The anal fin of each fish in the second stocking was hole punched to differentiate them from those of the first stocking and fish caught by anglers were hole punched in the caudal fin each time they were caught before being released back into the pond.Angler catch rates were highest during initial fishing events that followed stocking (9.2 fish/angler hr and 18.0 fish/angler hr) and substantially declined in subsequent events (≤3.4 fish/angler hr).Catches of the newly stocked fish and previously stocked fish contributed to the high catch following the supplemental stocking.Most (80 %) of the fish were caught in the first 30 min of each event and 45 % were caught during the first 10 min.Anglers were able to catch 88 % of the fish from the first stocking and 67 % from the second stocking at least once.No mortality occurred during the study as all fish were recovered when the pond was drained.Our results suggest that hybrid sunfish will potentially provide high initial catch rates following stocking into community ponds, but managers should expect reduced catch rates following initial fishing even without harvest.Additional stocking will be needed to provide periodic increases in angler catch rates even without harvest.

Community fishing programs provide an opportunity to counter nationwide declines in fishing participation and license sales (Balsman& Shoup, 2008).The goals of community fishing programs generally are to provide fishing opportunities, to recruit and retain anglers, and to educate people about fisheries and fishing (Hunt et al., 2008).Potential barriers to fishing are lessened with the development of community fisheries as they provide places to fish for people living in urban areas that do not require extensive travel or high expenditures to be successful.Fishing opportunities provided by five community fisheries near Brookings, South Dakota (SD), were found to enhance participation by young anglers (recruitment) while providing family-oriented recreation(retention and reactivation; Greiner et al., 2016).Similarly, Lucchesi et al.(2013) found Family Park Pond, SD, a community fishery located within the city of Sioux Falls, to have high angler use and they believed the fishery was a good tool for recruiting anglers.Recruitment and retention are often a main focus of community and urban fishing programs; however, involving individuals in fishing will potentially have broader impacts on the public’s perception and connection with nature.

Management of community fisheries often includes stocking catchable-size fish.Community fisheries stocked with catchable-size fish provide an immediate fishery (Brauhn & Kincaid, 1982).Selection of fish species for stocking should meet the desires of anglers and be species that are consistently available for stocking at a large enough size to attract anglers and at a reasonable cost (Brader, 2008).In SD,community fisheries are often stocked with adults of abundant underutilized species collected from nearby public lakes, and limited numbers of catchable-size fish raised in the hatchery system are also stocked.Species stocked as catchables in community fisheries in SD have included, but are not limited to, Black Bullhead (Ameiurus melas),Bluegill (Lepomis macrochirus), Channel Catfish (Ictalurus punctatus),Northern Pike (Esox lucius), Rainbow Trout (Oncorhynchus mykiss),White Bass (Morone chrysops), and Yellow Perch (Perca flavescens).The ability to meet the demand for catchable-size fish for stocking community fisheries in SD is a concern and has recently led to investigation of various fishes that can be efficiently produced and reared to catchable sizes in the state’s hatchery system.In addition to the rearing requirements, the stocked fish should provide anglers with high catch rates when stocked into community ponds.A catch rate of 1.0 fish/-angler hr is a common target of many community fishing ponds (Eades &Lang, 2012).

Catchable hybrid sunfish [male Bluegill ×female Green Sunfish(L.cyanellus)] have recently been considered for use in community fisheries in SD.Various sunfish crosses naturally occur where different sunfish species co-occur, and purposeful crosses of different species have been made for use in fisheries management.Male Bluegill ×female Green Sunfish hybrids (herein hybrid sunfish) are one of the more common sunfish hybrids used in fisheries management because they tend to have many desirable attributes (Brunson & Robinette, 1986).Several advantages of hybrid sunfish for use in pond management include being less prolific than Bluegills because the majority of the F1hybrid sunfish produced are males, hybrid vigor leads to increased growth, they are easy to culture, and they tend to be aggressive and relatively easy for anglers to catch (Brunson & Robinette, 1986; Crandall& Durocher, 1979; Lewis & Heidinger, 1978).Hybrid sunfish have commonly been used in pond management and are often stocked in combination with Largemouth Bass (Micropterus salmoides) to diversify angling opportunities.

The ease of their culture combined with a willingness to bite angler offerings potentially make hybrid sunfish a good choice for stocking community fishing ponds.High angler catch rates of fish in urban fishing programs are important as many urban anglers are not satisfied with their fishing experience if catches are low (Brader, 2008).Angler catch rates of stocked hybrid sunfish have been variable with stocking density and angler experience likely influencing observed catch rates.At Blackjack Pond (0.53 ha), Mississippi (MS) and Britt Pond (0.36 ha), MS,angler catches were high with mean catch rates of 12.2 fish/angler hr and 22.4 fish/angler hr reported after a 2-hr fishing period (Brunson &Robinette, 1986).Angler catch rates of hybrid sunfish were variable from 0.1-ha Oklahoma (OK) hatchery ponds stocked at six different rates(120–2000 fish/ha); the angler catch rates ranged from 1.0 to 35.6 fish/angler hr with catch rates exceeding 13.0 fish/angler hr when stocking rates were ≥500 fish/ha (Winkelman & Sager, 2004).

Although previous studies have looked at hybrid sunfish catches and have reported high angler catch rates, most of these studies were completed at more southerly latitudes.Additionally, most studies have only assessed hybrid sunfish catches during a single angling event shortly after stocking.We were interested in hybrid sunfish catch rates in a northern pond, whether changes in catches occurred after hybrid sunfish were subjected to catch-and-release angling and what influence supplemental stocking may have on angler catch rates.Even though our study was completed in a hatchery pond and catch-and-release angling was used, we believe that the results will have implications for stockings of hybrid sunfish in community fishing ponds.Specifically, our objectives for this study were to 1) assess the initial angler catch rates of hybrid sunfish and after being subjected to catch-and-release angling,and 2) determine if angler catch rates of hybrid sunfish increase following a supplemental stocking.

Hybrid sunfish were reared at Blue Dog State Fish Hatchery (Waubay, SD) in a 0.12-ha pond (mean depth =1.5 m).A pelleted diet(BioVita Fry, 1.5 mm pellets, Bio-Oregon, Longview, Washington) was fed to the fish twice daily during rearing and they were not subjected to angling.Fish used in the study were trapped from the rearing pond and stocked into a separate fishless, 0.12-ha pond (mean depth =1.5 m)where angler catch rates were assessed.The source of water for the hatchery ponds was unfiltered lake water from Blue Dog Lake, South Dakota.All fish used in the study were measured for total length (TL;mm) prior to stocking into the angling pond.The fish were not fed the pelleted diet once stocked into the angling pond because they would not be fed when stocked into community ponds.Food available to the stocked hybrid sunfish in the angling pond was likely composed of zooplankton and chironomids.Ward et al.(2011) found zooplankton and chironomids to be abundant in hatchery ponds at Blue Dog State Fish Hatchery.

One hundred (833/ha) hybrid sunfish were stocked into the 0.12-ha angling pond on August 5, 2020.Initial angling for the hybrid sunfish occurred on August 10, 2020 with subsequent angling events on August 11, 17, and 18, 2020.A second stocking of 100 (833/ha; total =1667/ha) hybrid sunfish was made on August 19, 2020.The anal fin of each fish in the second stocking was hole punched to differentiate these fish from those of the first stocking.Angling after the second stocking was initially completed on August 24, 2020 with additional angling events on August 25 and 31, 2020 and September 1, 2020.

Angling events took place in the morning and lasted 1 h with five anglers fishing during each event.All anglers were adults experienced with fishing and handling fish.The same five anglers were used during each fishing date with the exception of two occasions when a substitute angler having equal experience and fish handling skills was recruited.Fishing occurred only from shore and anglers were allowed to fish the entire pond perimeter.Terminal tackle was standardized to include an Aberdeen style hook (#6) with a small split-shot weight attached above;the baited hook was fished near the pond bottom below a bobber.A small piece of live night crawler (Lumbricus terrestris) was threaded on the hook for bait.This terminal tackle setup and bait was used because live worms fished near the bottom were found to catch more hybrid sunfish than artificial spinner baits and dry flies in two MS farm ponds(Brunson & Robinette, 1986).Additionally, this setup was recommended for use in fishing clinics because it is believed that participants will catch more fish with bobbers than without (Richters et al., 2008).

The caudal fin of each angled fish was hole punched each time it was caught before being released back into the pond.The number of holes corresponded to the number of times a fish was caught.The time(nearest min) each fish was caught, hooking location (i.e., anterior portion of mouth, esophagus, near eye), and number of caudal fin punches were recorded for each captured fish.Following the last fishing event, the pond was drained through a catch basin and hybrid sunfish present in the catch basin were enumerated to determine potential angling mortality.

The mean TL and 95 % CIs of each hybrid sunfish stocking were determined and TLs of the two stockings were compared using a twosamplet-test.Mean angler catch rates (fish/angler hr) and 95 % CIs were calculated for each angling event.Catch rates were compared across anglers and across fishing event dates using a repeated measures ANOVA and the Bonferroni test was used to determine differences in means when the ANOVA was significant.Winkelman and Sager (2004)provide an equation to predict angler catch rates of hybrid sunfish stocked at various densities{angler catch rate (fish/angler hr) =0.0173[stocking density (fish/ha)]+0.049}.We used our stocking densities to estimate what our angler catch rates would be after each stocking.The number of fish caught in each 10-min interval within an hour was summed across all fishing events and then the percentage of all fish caught in each 10-min interval was calculated.Chi-square tests were used to compare the percentages of fish caught across the 10-min intervals and for pairwise comparisons between the 10-min intervals.All statistical analyses were completed with SYSTAT13 (SYSTAT, 2009) and statistical significance was set at an α =0.05.To maintain an experimentwise error rate of α =0.05 for individual 10-min interval Chi-square tests, the significance level was determined by dividing 0.05 by the number of 10-min comparisons (i.e., 0.05/15 =0.003; Neumann& Allen, 2007).

The TL of hybrid sunfish in the two stockings was significantly different (t=2.83, df=198,p=0.005).The first 100 hybrid sunfish stocked ranged in TL from 103 to 132 mm with a mean TL of 117 mm(95 % CI =115–118) and the second 100 stocked fish ranged in TL from 103 to 125 with a mean TL of 114 mm (95 % CI =113–115).Biologically there likely was little difference in the size of fish in the two stockings.

Sixty-eight fish from the first 100 hybrid sunfish stocking were caught at least once prior to the second stocking and 67 from the second 100 stocked fish were caught a minimum of one time (Table 1).Following the second stocking, 28 of the original 100 stocked fish (12 had not been previously caught, 15 had previously been caught once,and one had previously been caught twice) were caught during the first fishing event along with 61 of the newly 100 stocked fish.Before the second stocking, ≤14 fish were caught during each of the previous three events.Eleven fish from the first stocking were caught multiple times prior to the second stocking and after the second stocking an additional 27 fish from the first stocking were caught multiple times during the eight angling events.Only four fish from the second stocking were caught multiple times.

Table 1The cumulative total number of times (i.e., 1x =first time caught, 2x =second time caught and 3x =third time caught) individual hybrid sunfish were caught during 1-hr fishing events ( five anglers) from a 0.12-ha pond at Blue Dog State Fish Hatchery, South Dakota following stocking of 100 hybrid sunfish on August 5, 2020 and August 19, 2020.

Most fish (96 %) were hooked in the anterior portion of their mouth,the hook point exited near the eye in six fish (3 %) and two fish (1 %)were hooked in their esophagus.The line was cut, and the hook left in the two fish hooked in their esophagus before being released.No mortality of hybrid sunfish occurred during the study as all stocked fish were accounted for when the pond was drained, and they all appeared to be healthy.

Mean catch rates across anglers for the entire study ranged from 3.3 fish/angler hr to 7.9 fish/angler hr and there was no statistical difference across anglers (F =2.35; df=4, 28;p=0.078).The mean catch rate across all eight fishing events was 5.0 fish/angler hr (SE =1.04), a mean of 4.0 fish/angler hr (SE =1.11) was obtained during the four events after the first stocking, and after the second stocking the mean catch rate was 6.0 fish/angler hr (SE =1.75) for the four events.A significant difference in angler catch rates was identified across the eight fishing events (F =14.04; df=7, 28;p ＜0.001; Fig.1).The highest catches occurred during each of the first fishing events after a stocking.Although the catch rates differed significantly across angling dates, the Bonferroni test revealed few differences; the catch rate on August 24 was significantly higher than those on August 11 and August 31.

Fig.1.Mean angler catch rate (fish/angler hr) by date of hybrid sunfish caught from a 0.12-ha pond at Blue Dog State Fish Hatchery, South Dakota during 1-hr catch-and-release fishing events ( five anglers) in 2020.One hundred hybrid sunfish were stocked on 8/5 prior to fishing and an additional 100 hybrid sunfish were stocked on 8/19.All caught fish were released so individual fish may have been caught multiple times.Different letters associated with means represent significant (p ≤0.05) differences and error bars are 95 % CI.

Based on our stocking rates, a catch rate of 14.4 fish/angler hr was predicted after our first stocking (833 fish/ha) and 28.9 fish/angler hr after our second stocking (1667 fish/ha).

A mean catch rate of 9.2 fish/angler hr (SE =3.48) was obtained during the first fishing event and catch rates then substantially declined during the next three events.After the addition of 100 fish, the mean catch rate increased to 18.0 fish/angler hr (SE =2.57) and again substantially declined following the first fishing event after stocking and remained lower.

The percentage of fish caught was greatest at the beginning of each fishing event.Most (80 %) fish were caught in the first 30 min of the fishing events, and nearly half (45 %) were caught in the first 10 min(Fig.2).Significant differences (χ2=144, df=5,p ＜0.001) in the percent of fish caught were identified across the six 10-min periods of the hour.The percentage of fish caught in the first 10 min wassignificantly higher than all other periods, and the percent caught in the second 10-min period was significantly higher than the 10-min periods that followed.No differences in percentage of fish caught occurred in the four 10-min periods between 20 and 60 min.

Fig.2.Percentage of total number (197) of hybrid sunfish caught during each 10-min interval during eight 1-hr catch-and-release fishing events ( five anglers)in 2020 from a 0.12-ha pond at Blue Dog State Fish Hatchery, South Dakota.Different letters designate significant (p ≤0.05) differences between the percentage of the total catch comprised by each 10-min interval.(For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

The initial high catch rates after stocking in our study and other studies potentially make hybrid sunfish a good choice for inclusion in community fishing ponds.High catches will help to keep the interest of anglers elevated while fishing in community fishing ponds.Variable catch rates for hybrid sunfish have been reported in studies completed further south (Brunson & Robinette, 1986; Winkelman & Sager, 2004)and our initial catch rates following stocking were similar to the higher values previously reported.Hybrid sunfish angler catch rates in community fishing ponds will likely be dependent on the numbers of fish stocked, angler experience, and how much time has passed since stocking occurred.

In addition to the high initial catch rates after stocking, our catch rates for each event averaged at least 1.0 fish/angler hr.Shupp (1972)suggested a catch rate of 0.5 fish/angler hr for community fishing programs.However, Eades and Lang (2012) believed that because of an increase in catch and release fishing that a catch rate of 1.0 fish/angler hr should be an acceptable target for angler satisfaction and continued participation.Furthermore, Harmon et al.(2018) suggest improved catch rates following stocking into a put-and-take fishery will result in improved angler satisfaction.Even though our catch rates generally exceeded 1.0 fish/angler hr there were multiple times when the anglers in our study became bored with fishing in the last 30 min of fishing events and wanted to quit before the hour was over.Expectations will vary by angler groups but providing high catch rates will help to keep anglers interested in fishing.

Stocking rates of hybrid sunfish into community fishing ponds will influence angler catch rates.A positive linear relationship was identified between hybrid sunfish stocking rates and angler catch rates by Winkelman and Sager (2004).Our angler catch rates were lower than those predicted at our two stocking rates (833 fish/ha; actual =9.2 fish/angler hr, predicted =14.4 fish/angler hr and 1667 fish/ha; actual =18.0 fish/angler hr, predicted =28.9 fish/angler hr), but did increase with stocking density.

Substantial declines in angler catch rates were observed in our fishing events that followed the initial fishing after stocking.Similarly,Harmon et al.(2018) found stocked Rainbow Trout catches to dramatically decrease during a 2-day period following stocking indicating the greatest boost in catch rates occurs immediately after stocking.Although a significant difference in angler catch rate was identified across days in our study, the mean comparisons failed to differentiate between days.The lack of a statistical difference was because of high variability among anglers during the fishing events.This occurred even though all of our anglers were highly experienced.All of our fish were accounted for when the pond was drained, thus mortality was not the reason for the reduced catch rates.Because few fish appeared to be injured (4 % were hooked deeper than the anterior portion of mouth) during fishing, we do not believe that injuries caused the reduced catches.

Learned hook avoidance has been suggested as a cause for reduced angler catch rates of several fish species.The catch rates of Rainbow Trout in five small lakes in British Columbia declined within 7–10 days under sustained fishing effort of catch-and-release fishing (Askey et al.,2006).Modeling results suggested that the highly catchable Rainbow Trout were quickly caught and then learned to avoid hooks.Common Carp (Cyprinus carpio) were found to develop hook avoidance from both direct hooking experiences and social hooking experiences (Wallerius et al., 2020).At Lake Wanahoo, Nebraska, it was believed that catch-and-release angling in the first 30 days the lake was open to fishing altered the behavior of Largemouth Bass and Northern Pike resulting in lower angler catches of these two species over time (Fedele,2017).Arlinghaus et al.(2017) suggest that individuals surviving catch and release may increase their timidness altering their catchability.It is likely that learned hook avoidance led to the reduced hybrid sunfish catches over time in our study.

The increase in catch rates we observed after the supplemental stocking was the result of catches of both the newly stocked fish and an increase in catches of previously stocked fish.The increase in catch of the previously stocked fish potentially indicates that some level of social facilitation of feeding occurred with the second stocking.The feeding of juvenile Chum Salmon (Oncorhynchus keta) was facilitated when exposed to visual cues emanating from feeding conspecifics (Ryder &Olla, 1991).It is possible the feeding of the recent stocked fish was recognized by their conspecifics which elicited their subsequent encounter with the angler bait and ultimately being caught.

Our use of only standardized terminal tackle and bait during our fishing may have contributed to our decline in catches because the fish could associate our gear with being caught.We would expect a variety of gears to be used by anglers fishing at community ponds and possibly hook avoidance would not occur.However, the use of 11 different lure types failed to maintain Largemouth Bass catch rates in six MS small impoundments managed with catch-and-release regulations (Wegener et al., 2018).Rock Bass (Ambloplites rupestris) were found to alter their behavior to avoid capture in response to exposure to fishing gear during a 7-day laboratory experiment (Fedele, 2017).Askey et al.(2006)believed that lakes exposed to fishing for the first time exhibit a short period of excellent angling that is followed by lower average catch rates,regardless of regulations.Unfortunately, we did not have the opportunity to repeat this study to see if a similar outcome (i.e., reduced catch rates) would occur, but the fact that catches dropped after each stocking indicates a similar outcome can be expected.The observed decline in catch rates could have negative implications on the use of hybrid sunfish in community ponds where high catch rates help to keep angler interest.Declines in catches of hybrid sunfish would also be expected where harvest occurs as fewer fish would be available to anglers as they are harvested from the population.

Supplemental stocking of hybrid sunfish will be needed to maintain angler catches of hybrid sunfish in community fishing ponds where harvest occurs.Previous studies have identified the need to restock hybrid sunfish because of their high harvest potential (Crandall &Durocher, 1979; Brunson & Robinette, 1986; Winkelman & Sager,2004).At Britt Pond, MS, anglers caught 66 % of the hybrid sunfish available (Brunson & Robinette, 1986) and 65 % of stocked hybrid sunfish were caught during a 2-hr youth fishing clinic in OK (Winkelman& Sager, 2004).Anglers at an Illinois state park lake removed 50 % of 10,800 hybrid sunfish in the first day of fishing and 82 % during the first 3 days (Childers, 1967).Anglers in our study were able to catch 88 % of the hybrid sunfish from the first stocking and 67 % from the second stocking.

Our results also indicate that supplemental stockings will be needed to provide periodic increases in angler catches where no or limited harvest occurs.However, the number of fish that can be stocked without running into biomass issues within the pond will need to be determined.It is possible that stocking a few individuals may facilitate the hybrid sunfish already present to bite angler offerings.Additional research should be completed to explore what stocking rate is needed to reinvigorate catch rates.

In addition to the catch rates declining following the initial fishing after stocking, the number of fish caught dropped substantially through the duration of individual fishing events.Most fish in our study were caught within the first 20 min.The drop in catches through the hour has implications for fishing clinics that extend for multiple hours or have anglers fishing in shifts.It may be hard to keep novice angler interested in fishing if the fish are not biting.Brunson and Robinette (1986) indicated that the aggressiveness of fish, even if not caught, may be a factor in encouraging anglers to continue to fish.We recommend all fishing clinic participants actively fish at the beginning of fishing for a clinic.

Community fisheries provide opportunities to recruit, retain, and reactivate anglers.Being able to provide catchable fish for stocking is an important component of the success of some community fisheries.In those ponds, the fish that are stocked should exhibit characteristics (e.g.,aggressive feeders) that make them easy to catch and be a species and size that anglers want to catch.Loss of interest in fishing will likely occur among beginning anglers if fish are not biting.Hybrid sunfish in our study were aggressive and easily caught when first stocked but their catches declined after exposure to angling.This reluctance to bite even occurred within hour-long fishing events.Our catch rates within a hatchery pond show that hybrid sunfish can potentially be used to provide short periods of high catch rates following stockings in community fishing ponds.Managers of community fishing ponds should expect reduced hybrid sunfish catch rates as fishing continues.When conducting fishing clinics, organizers should plan on hybrid sunfish catch rates being highest at the beginning of a clinic and stocking hybrid sunfish shortly before each clinic starts may ensure high catch rates.

CRediT authorship contribution statement

Brian G.Blackwell: Conceptualization, Methodology, Investigation,Resources, Formal analysis, Data curation, Writing – original draft.Matthew J.Ward: Conceptualization, Methodology, Resources,Writing – review & editing.Todd M.Kaufman: Conceptualization,Methodology, Writing – review & editing.

Acknowledgments

We are grateful to J.Broughton, C.Haabala, S.Kennedy, N.Pool, R.Rasmus, and R.Smidt for their assistance with the project.We thank G.Adams and M.Ermer for reviewing and improving an earlier version of this manuscript.