Catch and Release Mortality Striped Bass

PROJECT 5: BYCATCH AND INDIRECT LOSS QUANTIFICATION

                                                                                Prepared by: Rudy Lukacovic

Hooking Mortality of Deep and Shallow-Hooked Striped Bass Under Different

Environmental Conditions in Chesapeake Bay. II. 

Introduction

                Recreational catch-and-release mortality of striped bass Morone saxatilis is caused by two main factors: physical injury and physiological stress. Anatomical location of the hook wound (physical injury) isthe most important factor in hooking mortality (Muoneke and Childress 1994).  Hook wound location is influenced by hook type and size, bait size, the use of natural baits over artificial lures, angler experience and fish behavior (Harrel 1988; Hysmith et al. 1993, Diodoti and Richards 1996).

                Stress related mortality among released striped bass has been shown to be most affected by three interactive factors: temperature, salinity and fish size (RMC 1990, Lukacovic and Uphoff 1997). High temperatures, low salinities and large fish size can contribute to increased mortality. Temperature, salinity, and fish size were cited as major risk factors when Maryland’s striped bass catch-and-release policy was formulated in 1994 because field studies showed release mortality averaged 1.8% at salinities of 7.7-8.3ppt, 38.8% at 0.7-4.2ppt, and 70.4% at 0.0 ppt for fish caught on artificial lures at water temperatures exceeding 25^oC (RMC 1990).

                The Atlantic States Marine Fisheries Commission uses a constant 8% mortality rate as an estimate of catch-and-release losses from the recreational fishery in their striped bass stock assessment. A 5% estimate formed the basis of Maryland’s revised catch-and-release policy (King 1994). However release mortality among striped bass caught in Chesapeake Bay may not be constant and may vary with deep hooking rates of different techniques. Shallow-hooked striped bass caught at high salinities from June through October in Chesapeake Bay died at a rate of 3.5%, while 53.1% of striped bass deeply hooked with J-style bait hooks died  (Lukacovic 2000).

                Anglers catch and release fish for a variety of reasons; fish may not be legal size or they may be out of season, or caught and released outright as recreation.  High survival of released fish is fundamental for successful management of catch-and-release fisheries.  Catch-and-release mortality may reduce effectiveness of minimum size limits, but does not necessarily negate their usefulness (Waters and Huntsman 1986).  Measurement of release losses is an important  component of  stock assessments when many fish are released (Muoneke and Childress 1994).  If release mortality rates are higher than assumed, then estimates of fishing mortality may be too low and estimates of stock size too high.

                A substantial recreational catch-and-release fishery for striped bass has developed along the Atlantic Coast because of large population size, high minimum length limits, and low creel limits (Atlantic States Marine Fisheries Commission or ASMFC 1995; Diodoti and Richards 1996).  Releases along the Atlantic Coast rose from 38% of the catch in the early 1980s to 93% by the early 1990s (Diodoti and Richards 1996).  Releases accounted for 91% of the Atlantic coast’s recreational catch during 1998 (United States Department of Commerce’s Marine Recreational Fisheries Statistics Survey or USDOC MRFSS, 1997).

                Since catch-and-release mortality rates cannot be assumed to be constant, a predictive model of deep and shallow hooking mortality under different environmental conditions would improve understanding of factors influencing catch-and-release mortality and monitoring and estimation of catch-and-release losses. The information collected in 1999, and reported in Federal Aid Report F-54-R, was oriented towards developing such a model by measuring release mortality over the course of the entire season at two locations with significantly different salinities.  Drought conditions in 1999 resulted in minimal salinity differences between sites. Data collected in 2000 was directed toward upper bay areas that would have lower salinity.

Methods

                Eight paired two-day trials comparing hook styles were run during spring and summer 2000. Love Point, at the mouth of the Chester River was fished on June 19-20, July 10-11, August 7-8, and September 11, 2000 (Figure 1). The upper bay in the area of Pooles Island was fished on June 26-27, July 24-25, August 28-29 and September 25-26, 2000.

                Striped bass were caught by chumming. Chumming was chosen because it was the most likely sportfishing technique that would provide samples of both deep and shallow hooked fish. Chumming is a traditional method of bait fishing for striped bass (Burton 1966). A boat is anchored and ground fish or clams are distributed into the water to attract fish. Hooks are baited with a piece of cut bait, usually the same as the attractant, and drifted back into the dispersed chum (Burton 1966). Charter boats, hired through the Maryland Charter Boat Association, were used to chum for striped bass. Sixty-seven volunteer anglers, representing a cross-section of angling experience, caught striped bass for this study. They used medium-weight spinning or casting rods equipped with 12-20 pound test monofilament line. Standard J-style bait hooks were used the first day of each 2-day trial and non-offset circle hooks were used the second. Hook sizes were kept constant for each fishing day. Circle hooks were sized similar to standard bait hooks used the previous day. Anglers used 3/0 bait hooks the first day of each trial and 9/0 non-offset circle hooks the second day. Ground Atlantic menhaden Brevoortia tyrannus were used as chum and cut pieces of menhaden were used as bait.

                Fish were played normally and landed either with a dip net or by hand. If a fish was shallow hooked (defined as hooked in the lip, mouth or gills), the hook was removed and the fish was marked with a hole punch through the lower lobe of the caudal fin. If a fish was deep hooked (hooked past the gills, i.e. point of penetration could not be seen) the hook was left in place, the line was cut as close to the hook as possible and a hole was punched through the upper lobe of the caudal fin. Each fish was then placed in aerated tanks on board a transport vessel.

                Water temperature (EC), salinity (E/BB) and dissolved oxygen (mg/l) were recorded several times each day at the surface, mid-depth, and bottom at the fishing site. Temperature and dissolved oxygen in the transport tank were monitored and maintained at the most optimal level documented for each parameter in the water column profile. These measurements were also monitored at the net pens. Air temperature (EC) was recorded several times each fishing day.

                Striped bass captured at Love Point were taken to net pens near C. J. Langenfelder & Son, Inc. at the northern tip of Kent Island. Fish captured in the Pooles Island area  were taken to net pens at the Coast Guard Station at Stillpond. Net pens were 4.6 m (15 ft) square and 3.7 m (12 ft) deep and were constructed of #252 knotless nylon. They were suspended by a floating wood and styrofoam frame at both locations. Captured fish were transferred into pens using soft rubber nets. Ten striped bass was the minimum number used in any single day trial and 50 was to be the maximum.

                Pens were checked and water quality measured every day for three days. Dead fish were removed, measured and hook location (hole punch position) was recorded. All dead fish marked as deep hooked were necropsied to determine internal damage. Shallow hooked fish that died were examined for mechanical damage from hooks that may have impacted gills and then slipped forward during the fight. Nets were emptied following 3 days of observation and survivors released after they were measured and had hook location (hole punch position) recorded.

                Additional hook location data was collected on4otherdays. These fish were caught as part of supplemental hooking mortality studies and were angled in an identical manner to fish in this study. Fish length, hook type and hook wound location was recorded on all striped bass landed and is included to supplement hook location data only.

                                                                                Results

                Standard J-style bait hooks were used by 36 anglers on 12 days of fishing. They caught 467 striped bass of which 264 were used in the mortality study (Table 1). Non-offset circle hooks were used by 35 anglers on 11 days of fishing.  They caught 392 striped bass and 241 were used in the mortality study. Striped bass caught on these days that were not used  in the mortality trials were included to supplement hook location data. Numbers of striped bass caught per day varied from 3 to 124. Two trials were canceled due to insufficient numbers of fish (n=3 and 6). The first trial at Still Pond was aborted due to high mortality from suspected salinity shock. Three other trials were canceled due to weather and one was terminated due to vandalism and theft. No trial was conducted with less than 10 fish.

                Length frequencies of striped bass caught with J-style bait hooks were similar to those striped bass caught with circle hooks (Figure 2). Striped bass caught with J-style hooks averaged 383 mm (15.1 in) total length and ranged from 220 mm (8.7 in) to 851 mm (33.5 in). Striped bass caught with circle hooks averaged 370 mm (14.7 in). They ranged in size from 239 mm (9.4 in) to 553 mm (21.8 in). Fish averaged as much as 105 mm (4.1 in) smaller during the early summer (late June to mid-July) of 2000 compared to the same period in 1999. Fish size in August, September and October was similar to fish caught in 1999. 

                Average size of striped bass caught each day ranged from 315 mm (12.4 in) to 463 mm (18.2 in; Table 2.). Fish averaged larger than the legal minimum size of 457 mm (18 in) on only one day all season (July 10 at Love Point). The portion of each day’s catch that exceeded the minimum size averaged less than 25%. On only two of 18 fishing days did 50% of the catch exceeded the minimum size limit. Fish did not exceeded the minimum size on two days. Overall only 11.5% of the fish caught all season were in excess of 457 mm (18 in).                

                Hook sizes were held constant each day. Because fish size did not change appreciably over the course of the study, hook sizes (3/0 J-style and 9/0 circle) remained constant all season. Striped bass were deep hooked 15.0% of the time (N= 467) with J-style bait hooks but only 5.6% of the time (N=392) when circle hooks were used. Sub-legal striped bass, those less than 457 mm (18 in), were deep hooked 10.9% of the time (N=393) with J-style hooks but only 3.3% of the time (N=357) with circle hooks.

                Monthly deep hooking rates were highest in September and lowest in October for both styles of hook (Figure 3). The use of J-style hooks did not produce the seasonal difference in deep hooking reduction from spring to fall, seen in Lukacovic 2000.

                Daily deep hooking frequencies with J-style hooks varied from 0.0% to 33.3% while daily deep hooking frequencies with circle hooks varied from 0.0% to 16.8% (Table 3). No fish were deep hooked with circle hooks on four fishing days, whereas J-style hooks deep hooked fish on all but one day.

                Deep hooking mortality differed by hook style. Striped bass deep-hooked with J-style bait hooks died at a rate of 58.3% (N=70). Striped bass deep hooked with non-offset circle hooks died at a rate of 33.3% (N=22).

                All deep hooked fish that died were necropsied to determine hook location at death and to document internal mechanical damage. Post mortem examination of dead fish, deep hooked with J-style hooks (N=14), consistently (as in previous Maryland DNR studies) exhibited profuse internal hemorrhage from puncture wounds to liver and/or heart. All deep hooked J-style hooks were oriented either ventrally or laterally in the visceral cavity. Dead fish, deep-hooked with circle hooks (N=5), also showed  significant internal hemorrhage, tears in the esophagus and stomach, but not puncture wounds to liver or heart. All deep hooked circle hooks were oriented laterally in the visceral cavity. No fish were landed with hooks in their gills.

                Mortality of shallow hooked fish all season was 3.5% for J-style hooks (N=171) and 3.5% for circle hooks (N=226). Shallow hooking mortality was 1.0% in June (N=100), highest in July at 5.5% (N=145) and 3.3% in August (N=91)  (Figure 4).  Shallow hooking mortality data is not available for September due to weather cancellations and vandalism. Daily shallow hooking mortality varied between trials from 0.0% (N=44, 46, and 47) to 13.3% (N=30).

                Salinity at Love Point ranged daily from 5.1-7.4 ppt in June to 9.2-10.3 ppt in September. Daily salinity in the vicinity of  Pooles Island during the study, ranged from1.6-4.5 ppt in June to 2.0-7.9 pptin August. Shallow hooking mortality was evaluated at three salinity ranges between 1.6 ppt and 10.3 ppt. At salinities of 1.6-2.5 ppt shallow hooking mortality was 2.5% (N=157). At salinities of 5.1-6.3 ppt shallow hooking mortality was 4.7% (N=149) and at salinities of 9.2-9.4 mortality of shallow hooked striped bass was 3.3% (N=92).

                Most mortality, 82%, occurred in less than 6 hours and91% occurred in less than 24 hours during this experiment (Figure 5). All mortality occurred within 48 hours.

                All striped bass that were placed in net pens were accounted for either by documentation of mortality or at time of release with two exceptions.  One deep hooked fish in August at Still Pond was unaccounted for and 13 fish on September 11 at Love Point were missing.         

Discussion

                Deep hooking mortality rates were slightly higherthis year than last year for both styles of hooks possibly reflecting a size-related influence (Figure 6). Striped bass caught this year averaged smaller than fish caught for last year’s study. Striped bass caught in1999 averaged 422 mm (16.6 in) while those caught in 2000 averaged 377 mm (14.8 in). The size range of fish caught during 2000 (220-851 mm; 8.7-33.5 in) was also smaller than last year (267-930 mm; 10.5-36.6 in).Fish size did not change appreciably over the course of the season as it had in most other years. Larger fish, generally available in June and July, were not present in their usual abundance during 2000 (Figure 7).Fish size has been a factor influencing several aspects of catch-and-release mortality including deep hooking rates, and both deep and shallow hooking mortality (Lukacovic 2000). Smaller fish seen in greater abundance this year may be less resilient to physical trauma associated with deep hooking (e.g. loss of blood, etc.).  Fish size has also been anecdotally correlated with fish behavior (C. Rosendale, personal communication).

                Overall deep-hooking frequency in 2000 was nearly three times lower when non-offset circle hooks were used (5.6%) instead  of J-style bait hooks (15.0%; Figure 8). A four-fold reduction in deep hooking rates was documented during the 1999 study by the use of circle hooks (3.4%) compared to J-style bait hooks (17.2%).  Deep hooking rates of striped bass declined form 46% with J-style bait hooks to 11% with non-offset circle hooks on two consecutive days in June 1997 (Lukacovic and Uphoff 1997). In 1996, striped bass were deep hooked 24% of the time with standard bait hooks compared to 4% with non-offset circle hooks (K.Lockwood, Maryland Fisheries Service, personal communication).

                Seasonal differences in deep hooking rates with J-style bait hooks  were not observed this year as they were in the 1999 study (Figure 9). Higher deep hooking rates with J-style bait hooks were observed in late June/mid-July in the 1999 study compared to September and October. Monthly deep hooking rates with J-style bait hooks declined during the 1999 season from 40.8% in June to 7.4% in October. This was thought to be linked with fish size and possibly with seasonal behavioral differences such as feeding aggression. Deep hooking rates of striped bass caught in Chesapeake Bay using J-style bait hooks were 19.0% in October 1996 and were 54.2% in June 1997 and these differences were related with fish size (Lukacovic and Uphoff 1997). Deep hooking with J-style bait hooks declined from 28.6% in spring to 5.3% during the fall (Lukacovic 1998). It has been observed that differential behavior, i.e. aggressiveness, can be associated with fish size (C. Rosendale, personal communication). Smaller, younger individuals are considerably more abundant in any normal population than larger individuals and hence must be more competitive or aggressive when feeding (C. Rosendale, personal communication).

                During 1999, deep-hooked fish that died averaged slightly smaller in size than the average deep-hooked fish on all days, except when air temperatures were above 35EC (95EF). Mortality of striped bass deep hooked with J-style bait hooks consistently averaged near 50%. Lukacovic and Uphoff (1997) reported deep hooking mortality to be 41.0% during fall and 56.3% during spring. During 1995, striped bass were hooked in specific deep and shallow anatomical locations and held under controlled conditions for 60 days in experiments at the Cooperative Oxford Laboratory. (K. Lockwood, Maryland Fisheries Service, personal communication). Deeply-hooked fish (gullet and stomach) died at a rate of 57.5% after 7 days. Mortality for esophagus-hooked hybrid striped bass (Morone saxatilis x M. Chrysops) was 55.3% (Walters 1997).

                Necropsies of striped bass deep-hooked with J-style bait hooks that died in this study showed the point oriented ventrally or laterally 100% (N=14) of the time. Lukacovic (1999) reported J-style bait hooks were oriented ventrally 67.4% (N=43) of the time. Lukacovic and Uphoff (1997) reported that hooks were oriented ventrally 77.5% (N=40) of the time in dead striped bass deep hooked with standard bait hooks. Non-offset circle hooks orient the point away from the direction of travel when the line is pulled tight. The point does not penetrate organs as a standard bait hook with its point facing in the direction of travel. Only five striped bass deep hooked with circle hooks died, but necropsies showed tears in the esophagus were caused by the outside bend of the hook not the point. Dissections of striped bass deep hooked with standard bait hooks showed points penetrating liver and/or heart in most cases. Long term survival of deep hooked striped bass is not well documented.   

                 Mortality rates of shallow-hooked fish were identical for both styles of hook (3.5%), indicating that hook style had no effect on stress-related mortality. Combined shallow-hooking mortality for both styles of hook in 1999 was also 3.5%. All shallow hooked fish that died were examined to determine any mechanical damage (other than hook wound) that may have contributed to mortality. None was documented. External hook wounds that were visible at time of release appeared mildly inflamed on some fish.

                Stress related mortality among released striped bass has been shown to be most affected by three interactive factors: temperature, salinity and fish size (RMC 1990, Lukacovic and Uphoff 1997). High temperatures, low salinities and large fish size can contribute to increased mortality.

                Shallow hooking mortality was highest in July 2000 (5.5%) as it was in July 1999 (11.8%; Figure 10). Even though air temperatures during the 2000 study did not exceed 35.0EC (95EF) on any fishing day, shallow hooking mortality on two days in July was 13.3% and 11.1%. Average total length of striped bass and percent of legal fish caught those two days was greater than all other days all season. The interactive compounding of two physiological stressors, warm water temperatures and larger fish size, could have resulted in increased mortality.

                RMC (1990) estimated shallow-hooking mortality of striped bass was 2% at water temperatures of 27EC (80.6EF) and salinity of 8 ppt. Mortality increased to 39% at salinities of 0.5 – 4.2 ppt, and to 70% in fresh water (0.0 ppt; RMC 1990). Lukacovic and Uphoff (1997) reported that mortality among shallow hooked striped bass declined from 11.6% in June to 5.5% in October due to increased salinity and decreased water temperature and fish size. Tomasso et al. (1996) reported mortality of shallow hooked striped bass in freshwater was 11.7% in summer and 5.7% in fall.

                Temperature, salinity, and fish size are major risk factors associated with physiological stress and were cited as such when Maryland’s striped bass catch-and-release policy was formulated in 1994. Mortality of shallow hooked striped bass was not high (3.5%) at salinities encountered during the 2000 study. Mortality was 2.5% (n=157) at salinities of 1.6-2.5 ppt, 4.7% (n=149) at 5.1-6.3 ppt and 3.3% (n=92) at 9.2-9.4 ppt. Mortality of shallow hooked striped bass did not exceed 5% at any salinity range encountered in 1999 or 2000 except when air temperatures were greater than 35.0EC (95EF).

                In the absence of salinity (0.0 ppt), water temperature greatly influenced shallow hooking mortality on the Susquehanna Flats (Lukacovic and Florence, 1998).  Mortality of striped bass caught with artificial lures was 1.6% at 13.8-15.0EC (57-59EF), 3.7% at 16.2-16.6EC (61-62EF), and 15.9% at 17.6- 21.9EC (63.6 – 71.3EF). Even low concentrations of salinity seem to greatly enhance survival of physiologically stressed fish. Maryland Fisheries Service hatchery personnel routinely add salt to transport tanks when transporting striped bass (C. Stence, MD DNR, personnel communication). Striped bass collected by electrofishing, or from pound nets, at salinities less than 1.0 ppt and transported to the state hatchery have survival rates approaching 100% if salinity is increased to 5 ppt in the transport tank.

                Death of fish in this study, as in most other of catch-and-release mortality studies, occurred rapidly. More than 82% occurred in the first 6 hours and 91% had occurred within 24 hours. During 1999, more than 75% of deaths were documented in less than 6 hours and 97% occurred within 24 hours. Nelson (1998) reported 73% of the mortality of striped bass used in his experiment occurred in 24 hours. Lukacovic and Uphoff (1997) reported that 90% of mortality occurred within 24 hours in June and 93% in October. All release mortality of American shad Alosa sapidissima was observed within 24 hours (Lukacovic 1998).  This strongly suggests that mortality of these fish mostly is reflective of hooking injury or angling stress, not confinement, because mortality is rapid and all fish that survived were extremely vigorous at release. Caging mortality would be expressed over time as fish languished in confinement.

                 In this, and other catch-and-release mortality studies, significant differences in mortality have been consistently documented between deep and shallow-hooked fish. Anatomical location of the hook wound is the single most important factor in hooking mortality (Mouneke and Childress 1994). Non-offset circle hooks have been shown in several studies to reduce frequency of deep-hooking. These studies have also shown that deep-hooking mortality is approximately twice as low as with non-offset circle hooks than with offset standard J-style bait hooks. Overall mortality (combining deep-hooking rates with deep-hooking mortality) in 1999 was reduced from 9.1% to 0.8% and was reduced from 8.7% to 1.9% in 2000 by the use of non-offset circle hooks. 

                References

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Diodoti, P.J. and R.A. Richards. 1996. Mortality of striped bass hooked and released in salt water. Transactions of the American Fisheries Society 125:300-307.

Harrel, R.M. 1988. Catch-and-release mortality of striped bass caught with artificial lures and baits. Proceedings of the Annual Conference Southeastern Association of Fish and Wildlife Agencies 41(1987):70-75.

Hysmith, B.T., J.H. Moczygemba, and G.R. Wilde. 1993. Hooking mortality of striped bass in Lake Texoma, Texas-Oklahoma. Proceedings of the Annual Conference Southeastern Association of Fish and Wildlife Agencies 46(1992):413-420.

King, H. 1994. Policy for catch-and-release fishing. Memorandum: Maryland Department of Natural Resources, Tidewater Administration, Annapolis, Maryland.

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Lukacovic, R. 1999. Hook location, size distribution and percentage of striped bass caught and released by various angling techniques in Chesapeake Bay. In: Weinrich, D.R., P.G. Piavis, B.H. Pyle, A.A. Jarzynski, J.C. Walstrum, R.A. Sadzinski, E.J. Webb, H.W. Rickabaugh, E. Zlokovitz, J.P. Mower, R. Lukacovic, K.A. Whiteford. Stock assessment of selected resident and migratory recreational finfish species within Maryland’s Chesapeake Bay. Federal Aid Project F-54-R. Annual Report, Department of the Interior, Fish and Wildlife Service.

Lukacovic, R. 2000. Hooking mortality of deep and shallow hooked striped bass under different environmental conditions in Chesapeake Bay. In: Weinrich, D.R., P.G. Piavis, B.H. Pyle, A.A. Jarzynski, J.C. Walstrum, R.A. Sadzinski, E.J. Webb, H.W. Rickabaugh, E. Zlokovitz, J.P. Mower, R. Lukacovic, K.A. Whiteford. Stock assessment of selected resident and migratory recreational finfish species within Maryland’s Chesapeake Bay. Federal Aid Project F-54-R. Annual Report, Department of the Interior, Fish and Wildlife Service.

Lukacovic, R. and B. Florence. 1999. Mortality rate of striped bass caught and released with artificial lures during spring on the Susquehanna Flats. Maryland Department of Natural Resources, Annapolis, Maryland.

Lukacovic, R. and J. Uphoff. 1997. Hook location, fish size and seasonality as factors influencing mortality of striped bass caught with bait in Chesapeake Bay. Maryland Department of Natural Resources Technical Memo No. 16, Annapolis, Maryland.

Muoneke, M.I. and M.W. Childress. 1994. Hooking mortality: a review for recreational fisheries.

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Nelson, K. 1998. Hooking mortality of striped bass in the Roanoke River, North Carolina. North American Journal of Fisheries Mangement 18:25-30.

RMC, Inc. 1990. An evaluation of angler induced mortality of striped bass in Maryland. Completion Report (P.L. 89-304, AFC-18-1) to National Marine Fisheries Service, Gloucester, Massachusetts.

Tomasso, A.O. and J.J. Isely. 1996. Physiological responses and mortality of striped bass angled in freshwater. Transactions of the American Fisheries Society 125:321-325.

Walters, D.A. 1997. Impact of hooking mortality on hybrid striped bass. Final Report for Federal Aid in Sport Fish Restoration Project F-69-P. Division of Wildlife, Ohio Department of Natural Resources, Xenia, Ohio.