Article

Examining the Severity of Roof-Hooking Injuries in Dolphinfish: a Comparison between Computed Tomography and Gross Necropsy

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Abstract

We describe hook trauma to the roof of the mouth in dolphinfish Coryphaena hippurus and compare computed tomography (CT) scanning to gross necropsy (GN) as a technique for diagnosing hooking injury in fish. Forty‐two dolphinfish carcasses spanning a range of hook injuries were collected and CT scanned, and 33 of these were evaluated using GN. Specimens were hooked either in the roof of the mouth, the eye via the roof or upper jaw, or the jaw (control group). In 75% of roof‐hooked individuals, GN revealed nondisplaced to comminuted fractures of the bones of the suspensorium, hematomas in and laceration of the extraocular muscles, and/or damage to the optic nerve. These injuries have the potential to compromise vision and therefore decrease post‐release survival rates of obligate sight‐feeding species such as dolphinfish. We evaluated the effectiveness of CT scanning to diagnose injury and found that CT could efficiently and accurately identify fractures and some soft tissue damage, but some injuries found in GN (e.g. optic nerve damage) were not observed on CT scans. Based on our findings, it is likely that mortality is greater in dolphinfish when hooked in the roof of the mouth than in the jaw. This study demonstrates a novel technique that was effective at diagnosing hooking injuries associated with the roof of the mouth. This article is protected by copyright. All rights reserved.

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... In contrast, cross-sectional imaging modalities, such as computed tomography (CT) and magnetic resonance imaging, allow for visualization of tissues without superimposition and for reconstruction of anatomy in multiple anatomic planes to detect lesions in fish that may not otherwise be visible with gross dissection or radiography alone (Rogers et al. 2008). For example, CT was able to detect potentially life-threatening injuries to the bones of the suspensorium, extraocular muscles, and/or optic nerve in Dolphinfish Coryphaena hippurus due to being hooked in the roof of the mouth (Mikles et al. 2019). For billfishes, CT has also been useful for investigating the fine skeletal structures in the rostrums of Blue Marlin and Swordfish Xiphias gladius (Habegger et al. 2015). ...
... The recovery prognosis for the hook-related fractures identified had the Blue Marlin been released was not assessed, though it is presumed to be better than the severe injuries reported in Dolphinfish hooked in the roof of the mouth (Mikles et al. 2019). The injuries in Blue Marlin may be less severe than in Dolphinfish because Blue Marlin have a larger skull and more robust skeletal structures than do Dolphinfish. ...
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Acute morbidity and mortality of marlins (family Istiophoridae) in hook‐and‐line fisheries have been studied; however, there has been little or no investigation of the skeletal injuries incurred from terminal tackles that could lead to decreased rates of postrelease survival. The objective of this study was to evaluate skeletal injuries in recreationally angled Atlantic Blue Marlin Makaira nigricans from the 2019 Big Rock Blue Marlin Tournament in Morehead City, North Carolina. We examined heads of six Blue Marlin that were angled using artificial lures rigged with J‐hooks and harvested for weigh‐in. The head of each Blue Marlin was scanned using computed tomography (CT) and examined with gross dissection. The CT interpretation revealed that two Blue Marlin had minimally displaced fractures of the maxilla, one of which also had a fracture to the lachrymal bone. These radiographic lesions were associated with penetrating hook injuries. The CT images also revealed degenerative changes within the quadrate‐articular joint in four Blue Marlin, which was associated with fish weight; the causes and consequences of these degenerative changes are unknown. Although the hooking‐related jaw fractures likely result in acute pain, their impact on postrelease morbidity is unknown and the impact on postrelease mortality is suspected to be small.
... In contrast, cross-sectional imaging modalities, such as computed tomography (CT) and magnetic resonance imaging, allow for visualization of tissues without superimposition and for reconstruction of anatomy in multiple anatomic planes to detect lesions in fish that may not otherwise be visible with gross dissection or radiography alone (Rogers et al. 2008). For example, CT was able to detect potentially life-threatening injuries to the bones of the suspensorium, extraocular muscles, and/or optic nerve in Dolphinfish Coryphaena hippurus due to being hooked in the roof of the mouth (Mikles et al. 2019). For billfishes, CT has also been useful for investigating the fine skeletal structures in the rostrums of Blue Marlin and Swordfish Xiphias gladius (Habegger et al. 2015). ...
... The recovery prognosis for the hook-related fractures identified had the Blue Marlin been released was not assessed, though it is presumed to be better than the severe injuries reported in Dolphinfish hooked in the roof of the mouth (Mikles et al. 2019). The injuries in Blue Marlin may be less severe than in Dolphinfish because Blue Marlin have a larger skull and more robust skeletal structures than do Dolphinfish. ...
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The behavior of fish around bait is poorly understood despite it being important for the fish catching process and estimating relative abundance. We used a fine-scale acoustic positioning system to quantify the movements of 26 red snapper (Lutjanus campechanus) around 120 bait deployments in 2019 at a natural reef site (~37-m deep) in North Carolina, USA. There were 39 instances of tagged red snapper approaching bait during four baiting days, some of which approached due to apparent sensory cues (28%) while most approached incidentally (72%). Tagged red snapper approached bait from initial distances of 1 to 1 147 m (median = 27 m; mean = 86 m), and took 0 – 77 min (mean = 22 min) to approach. Fish were more likely to approach bait if they were located close to, and down-current of, the bait at deployment. Our estimated effective fishing area of 2 290 m2 (within which >50% of red snapper responded to bait) could be used along with video counts and other information to estimate densities of red snapper.
... Mark-recapture methodologies including SCUBA are costly and time-consuming, and a validated proxy for estimating absolute mortality would be valuable to researchers. Laboratory examination of sacrificed individuals may be an inexpensive means of elucidating the extent of latent trauma and informing mortality estimates (Mikles et al., 2019). Gross necropsy has rarely been used in studies of discard survival of barotraumatized fishes (but see Burns and Restrepo, 2002;Neufeld and Spence, 2004;Rummer and Bennett, 2005) and has never to our knowledge been employed to directly compare prevalence of severe internal injuries to robust estimates of discard survival. ...
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The purpose of this study was to assess initial and delayed mortality of spotted seatrout Cynoscion nebulosus captured during live-release tournaments. Additionally, we examined spotted seatrout mortality as a function of season and anatomical hooking location. We assessed tournament-related mortality at 10 live-release fishing tournaments held in four Texas bays—Galveston, Matagorda, Aransas, and Upper Laguna Madre—from February 2004 to April 2006. Combined overall mean mortality was 22.9%, mean initial mortality (percent of dead fish brought to weigh-in) was 10.4%, mean delayed mortality (percent of fish that died in tournament holding tanks) was 14.1%, and delayed short-term mortality (percent of fish that died during a 14-d observation period in laboratory tanks) was 1.9%. To assess seasonal mortality, we examined a total of 364 spotted seatrout captured by hook and line from July 2004 to June 2005 using replicated 3.5-m 3 field enclosures for 72 h. Overall mortality for the seasonal study was 6%. Mortality rates were higher during spring (9%) and summer (10%) than during fall or winter (both 0%). Tournament organizers should avoid scheduling events during late spring and summer, when seasonal mortalities are the highest. To assess mortality as a function of anatomical hooking location, we examined a total of 479 spotted seatrout held in field enclosures after capture. We assigned hooking locations to four body regions: mouth, gills, esophagus, and external. Overall mortality for the anatomical hooking location study was 19%. Mortalities were higher for fish hooked in the esophagus (95%) and gills (75%) than for fish hooked in the mouth (10%) and externally (8%). Our results suggest that spotted seatrout mortality during live-release tournaments exceeds that observed under normal catch-and-release fishing practices and that posttournament delayed mortality is low. Anatomical hooking location is a major factor influencing mortality, but under normal fishing practices only about 12% of fish are hooked in locations that consistently cause mortality. Competitive sportfishing tournaments have contin-ued to increase in popularity over the last 30 years (Shupp 1979; Duttweiler 1985; Schramm et al. 1991b). In 1989, a survey conducted by the American Fisheries Society's Competitive Fishing Committee listed an annual total of 978 competitive saltwater fishing tournaments in North America, 33 of which were hosted in Texas (Schramm et al. 1991b). By 2003, the number of saltwater fishing tournaments held in Texas increased to 183 events (i.e., a 555% increase within 15 years; Oh et al. 2006). One of the most sought-after tournament sport fish in Texas is the spotted seatrout Cynoscion nebulosus, which was targeted in 36% of the Texas tournaments listed by Schramm et al. (1991b). Although numerous studies have examined tourna-ment-related mortality of freshwater fish, research is lacking for marine fish (Muoneke and Childress 1994). Negative impacts of competitive fishing tournaments on fishery resources have long concerned fishery managers, tournament organizers, and the general public (Barnhart 1989; Schramm et al. 1991a, 1991b; Radonski 2002). Concerns regarding intensified har-vest and sustainability of fish stocks have led many tournament organizers to adopt live-release formats that encourage anglers to keep their fish alive throughout the tournament (Nielsen 1985; Barnhart 1989; Fielder and Johnson 1994; Muoneke and Childress 1994; Radonski 2002). Clearly, mortality is reduced in live-release tournaments; however, post-release survival is of great concern (Plumb et al. 1988; Schramm et al. 1991a; Muoneke and Childress 1994). Unlike catch and release by recreational anglers, tournament anglers subject their fish to considerably more stress. Stressors include (1) the holding of fish in on-board live wells for extended periods of time, (2) the weigh-in process, (3) use of fish for photographic opportunities, and (4) release procedures. The addi-tional stress applied to tournament fish may increase the potential for postrelease mortality.
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Abstract  This study evaluates the performance of two types of non-offset circle hooks (traditional and non-traditional) and a similar-sized ‘J’ hook commonly used in the south Florida recreational live-bait fishery for Atlantic sailfish, Istiophorus platypterus (Shaw). A total of 766 sailfish were caught off south Florida (Jupiter to Key West, FL, USA) to assess hook performance and drop-back time, which is the interval between the fish's initial strike and exertion of pressure by the fisher to engage the hook. Four drop-back intervals were examined (0–5, 6–10, 11–15 and >15 s), and hook performance was assessed in terms of proportions of successful catch, undesirable hook locations, bleeding events and undesirable release condition associated with physical hook damage and trauma. In terms of hook performance, the traditionally-shaped circle hook had the greatest conservation benefit for survival after release. In addition, this was the only hook type tested that performed well during each drop-back interval for all performance metrics. Conversely, ‘J’ hooks resulted in higher proportions of undesirable hook locations (as much as twofold), bleeding and fish released in undesirable condition, particularly during long drop-back intervals. Non-traditional circle hooks had performance results intermediate to the other hook types, but also had the worst performance relative to undesirable release condition during the first two drop-back intervals. Choice of hook type and drop-back interval can significantly change hook wounding, and different models of non-offset circle hooks should not be assumed to perform equivalently.
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This study examined post-release survival in sand flathead (Platycephalus bassensis) and whether there were survival benefits from the use of circle hooks over conventional hook patterns. Anatomical hooking location was the major factor contributing to mortality, with an almost 100% survival rate for fish hooked in the lip, mouth or eye (shallow-hooked) compared with around 64% for fish hooked in the throat or gut (deep-hooked). Mortality in deep-hooked fish was generally associated with injuries to vital organs (gills, heart, liver) and survival was significantly lower if bleeding was associated with injury (54% compared with 85% for non-bleeders). Circle hooks resulted in significantly lower deep-hooking rates (1%) compared with conventional hook types (4-9%) and, based on catch rates, were at least as effective as conventional hook patterns. Estimated survival rates for line-caught sand flathead were high, over 99% for circle hooks and between 94 and 97% for conventional hooks. These findings support the efficacy of management strategies based on size and bag limits and the practice of catch-and-release fishing for sand flathead, as well as a potential conservation benefit from the use of circle hooks.
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Recreational fisheries are increasingly important sectors of tourism-based economies. In the last decade, new recreational fisheries have emerged that target species of varying conservation status including vulnerable, endangered, and unassessed species. In Guyana, catch-and-release angling tourism has begun to target arapaima, a genus of giant air-breathing fishes. Given the uncertain conservation status of this species and that no information is available to evaluate the sustainability of this activity, we sought to describe the responses of arapaima to recreational angling. We harnessed tri-axial accelerometer biologgers around the trunk of fish that had been captured and released by recreational anglers, allowing us to monitor post-release survival and behaviour, including surfacing, which is essential for this air-breathing fish to recover from exhaustion. Twenty-seven individuals were instrumented (162 ± 25 cm), 24 of which were considered survivors (89%) during the 47 ± 35 (SD) min monitoring period. Fish that died were observed to drown soon after release (i.e. within minutes), not surfacing to breathe air. Supervised machine learning classification of behaviours using a random forest algorithm identified surfacing events with 80% accuracy (i.e. out-of-bag error rate = 20%), which we applied to unobserved data periods to estimate breathing frequency after release, along with overall dynamic body acceleration (ODBA) as a proxy for activity. Neither mean breathing frequency nor ODBA were related to body size (total length), handling time (which incorporated facilitated recovery of individuals), nor time of capture (early or late in the dry season spanning water temperatures of 29.3–34.1 °C). The precise angling-related factors that led to arapaima mortality were unclear, but the frequency of mortality aligns with the mortality documented in other recreational fisheries. This mortality source can be incorporated into conservation plans and provide context to the impacts of recreational angling relative to the costs of legal or illegal harvest.
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The fishing characteristics of circle hooks and straight shank or "J" hooks were investigated in the pelagic longline fishery during two successive trips. In one trip, circle hooks and J-hooks of comparable size were alternated along the length of the longline on six sets of approximately 400 live-baited hooks each, allowing a preliminary comparison of catch per unit effort (CPUE), hooking location, and mortality between the two hook types. On a previous trip, records of hooking location and mortality were obtained for J-hooks on nine additional longline sets. Yellow fin tuna Thunnus albacares accounted for 60% of the catch; the remainder was composed of 15 other species, none of which was represented by more than eight individuals. There was higher CPUE for all species combined, using circle hooks (5.05 fish/100 hooks) as compared with using "J" hooks (2.28 fish/100 hooks). Similar results were observed with the catch of the target species (yellowfin tuna), for which CPUE was approximately 2.5 times higher with circle hooks (3.33 tuna/100 hooks) as compared with J-hooks. Circle hooks also resulted in a lower mortality for all species (31% versus 42%) and for the target species (21 % versus 39%). For all species, 95% of the fish taken on circle hooks were hooked in the jaw. Hooking location varied by species, but for all species combined, circle hooks consistently had a higher frequency of jaw hooking and a lower frequency of gut hooking than J-hooks. These preliminary results suggest that use of circle hooks in the pelagic longline fishery targeting yellowfin tuna may not only increase CPUE and survival of this species but also improve the survival of incidental catch and bycatch.
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The taxonomic diversity of bony fishes presents a seemingly endless diversity of forms that reflect the varied life history, ecology, and behavior of these animals. Matched to this taxonomic diversity, the skeletons of bony fishes also display a complex and diverse array of forms. The skeleton provides the architectural support for the musculature of the organism, while at the same time providing protection for internal organs and sensory systems. A solid understanding of the skeleton, therefore, is critical for studies of functional morphology and ecomorphology. In addition, because of its complex nature (comprising hundreds of individual bones and cartilages) the skeleton of bony fishes is rich in phylogenetic data and has been fundamental in the formulation of many compelling hypotheses regarding the evolutionary biology of fishes. It is this combination - phylogeny and function - that makes an understanding and appreciation of the skeleton of fishes central to so many aspects of the evolutionary and ecological biology of fishes generally. This article provides a brief overview of the skeletal structure of actinopterygians and fish-like sarcopterygians.
Chapter
What does the term ‘vision’ mean when applied to non-human animals, and how is the structure and function of a visual system adaptive for the animal that possesses it? These fundamental questions drive the visual ecologist and differentiate her or him from the photoecologist, who is interested in general sensitivity problems. How these questions are attacked will depend on the interests and expertise of the investigator, but ultimately all information regarding the properties of a particular visual system must be referred to the nature of the photic environment, the interactions of targets with the ambient light field, and the relevant visual tasks of the organism. Perhaps nowhere has this approach been more successfully applied than in studies defining the processes driving the evolution of visual systems in aquatic organisms. It follows that the visual ecologist must not only understand the biology, biophysics and perceptual qualities of vision, but must also have a basic understanding of optical physics and those properties of the medium that can influence the visible light field. We shall start with a discussion of basic optical quantities and hydrologic optics as they relate to vision, and then concentrate on three areas that are currently receiving particular attention by ‘fish’ visual ecologists: the near-ultraviolet light field, the polarized light field, and time-dependent changes in the light field produced by oceanic waves.
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We estimated survival rates of discarded black sea bass (Centropristis striata) in various release conditions using tag-recapture data. Fish were captured with traps and hook and line from waters 29-34mdeep off coastal North Carolina, USA, marked with internal anchor tags, and observed for release condition. Fish tagged on the bottom using SCUBA served as a control group. Relative return rates for trap-caught fish released at the surface versus bottom provided an estimated survival rate of 0.87 (95% credible interval 0.67-1.18) for surface-released fish. Adjusted for results from the underwater tagging experiment, fish with evidence of external barotrauma had a median survival rate of 0.91 (0.69-1.26) compared with 0.36 (0.17-0.67) for fish with hook trauma and 0.16 (0.08-0.30) for floating or presumably dead fish. Applying these condition-specific estimates of survival to non-tagging fishery data, we estimated a discard survival rate of 0.81 (0.62-1.11) for 11 hook and line data sets from waters 20-35m deep and 0.86 (0.67-1.17) for 10 trap data sets from waters 11-29 m deep. The tag-return approach using a control group with no fishery-associated trauma represents a method to accurately estimate absolute discard survival of physoclistous reef species.
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The mortality of discarded fish bycatch is an important issue in fisheries management and, because it is generally unmeasured, represents a large source of uncertainty in estimates of fishing mortality worldwide. Development of accurate measures of discard mortality requires fundamental knowledge, based on principles of bycatch stressor action, of why discarded fish die. To date, discard mortality studies in the field have focused on capture stressors. Recent laboratory discard experiments have demonstrated the significant role of environmental factors, size- and species-related sensitivity to stressors, and interactions of stressors, which increase mortality. In addition, delayed mortality was an important consideration in experimental design. The discard mortality problem is best addressed through a combination of laboratory investigation of classes of bycatch stressors to develop knowledge of key principles of bycatch stressor action and field experiments under realistic fishing conditions to verify our understanding and make predictions of discard mortality. This article makes the case for a broader ecological perspective on discard mortality that includes a suite of environmental and biological factors that may interact with capture stressors to increase stress and mortality.La mortalité des prises accessoires rejetées à l'eau est une question d'importance dans la gestion des pêches; parce qu'elle est rarement mesurée, elle représente une source considérable d'incertitude dans les estimations de la mortalité due à la pêche à l'échelle mondiale. L'élaboration de mesures précises de la mortalité des prises accessoires nécessite des connaissances fondamentales sur les causes de cette mortalité basées sur les modes d'action des facteurs de stress. À ce jour, les études se sont concentrées sur les stress reliés à la capture. Des études récentes en laboratoire ont souligné le rôle significatif des facteurs de l'environnement, de la sensibilité au stress spécifique à la taille et à l'espèce et des interactions entre les facteurs de stress, qui accroissent tous la mortalité. De plus, la mortalité retardée est un élément important du plan d'expériences. La meilleure façon d'aborder le problème de la mortalité des prises accessoires est par une combinaison d'études de laboratoire des différentes classes de facteurs de stress pour obtenir des connaissances sur les principes fondamentaux de leur mode d'action et par des expériences sur le terrain dans des conditions de pêche réalistes pour vérifier ces connaissances et faire des prédictions sur la moralité. Il faut donc utiliser dans l'étude de la mortalité des prises accessoires une perspective écologique élargie qui considère une série de facteurs environnementaux et biologiques qui peuvent interagir avec les facteurs de stress lors de la capture pour accroître le stress et la mortalité.[Traduit par la Rédaction]
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Post-release survival of line-caught pearl perch (Glaucosoma scapulare) was assessed via field experiments where fish were angled using methods similar to those used by commercial, recreational and charter fishers. One hundred and eighty-three individuals were caught during four experiments, of which >91% survived up to three days post-capture. Hook location was found to be the best predictor of survival, with the survival of throat- or stomach-hooked pearl perch significantly (P < 0.05) lower than those hooked in either the mouth or lip. Post-release survival was similar for both legal (≥35 cm) and sub-legal (<35 cm) pearl perch, while those individuals showing no signs of barotrauma were more likely to survive in the short term. Examination of the swim bladders in the laboratory, combined with observations in the field, revealed that swim bladders rupture during ascent from depth allowing swim bladder gases to escape into the gut cavity. As angled fish approach the surface, the alimentary tract ruptures near the anus allowing swim bladder gases to escape the gut cavity. As a result, very few pearl perch exhibit barotrauma symptoms and no barotrauma mitigation strategies were recommended. The results of this study show that pearl perch are relatively resilient to catch-and-release suggesting that post-release mortality would not contribute significantly to total fishing mortality. We recommend the use of circle hooks, fished actively on tight lines, combined with minimal handling in order to maximise the post-release survival of pearl perch.
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Bonefish (Albula spp.) are a group of species targeted by recreational anglers in shallow tropical and sub-tropical seas worldwide. Although bonefish angling is almost entirely catch-and-release, mortality can occur because the stress associated with angling and handling causes locomotory impairment that promotes post-release predation. We used tri-axial accelerometer loggers to compare the locomotor activity and behavior of bonefish exposed to angling-related stressors and immediately released (n = 10, 39.9 ± 1.1. cm FL), to those retained in a recovery bag for 15. min prior to release (n = 10, 39.6 ± 1.0. cm FL) in a tidal creek in Eleuthera, The Bahamas. We also validated the use of reflex action mortality predictors (RAMP) as an impairment index for evaluating bonefish condition upon release. Following release, bonefish were visually tracked for 30. min with floats to evaluate short-term survival, after which the accelerometer was retrieved. Bonefish held in recovery bags exhibited significantly less locomotory impairment immediately post-release, and higher maximum tail beat frequencies and amplitudes up to 15. min post-release, which was likely due to the time spent in the recovery bag. Bonefish in the recovery bag treatment also spent more time resting in possible refuge areas, which may facilitate further recovery and avoidance from predation. RAMP provided a gradient of impairment scores that were correlated with stressor duration. Retaining bonefish in recovery bags improved swimming abilities during the critical time period where the majority of post-release predation occurs, and one fish that was not placed in the recovery bag was preyed upon during the monitoring period. Further testing is needed to determine if the locomotory and behavioral benefits of retaining bonefish in recovery bags translate into improved survival from predation in more predator rich environments.
Article
Experiments to evaluate mortality of age I+ hatchery-reared landlocked Atlantic salmon (Salmo salar) caused by hooking with four terminal gear types were conducted at the Cobb Fish-cultural Station, Enfield, Maine in fall, 1972–1974. For the 3 study years, there was an overall mortality of only 3.3% for 1,200 salmon caught by angling, and a mortality of only 0.3% for control fish. Of the total mortality of angled fish, 42.5% occurred within the first 24 hours. Worm-hooked salmon suffered significantly greater mortality (5.7%) than fish caught on all hardware (single- and treble-hook data combined) (P < 0.001) and by single-hook hardware only (P < 0.01). Fly-hooked salmon mortality (4.6%) was significantly greater (P < 0.01) than mortality of fish hooked on all hardware. There was no significant difference in mortality between worm-hooked and fly-hooked salmon. Mortality caused by hooking with worms was primarily from fish hooked in the eye (76%) and gill or gill arch (12%). Fly-caught mortalities had been hooked mainly in the isthmus or tongue (42%), esophagus or stomach (25%), and eye (25%).
Article
We investigated short-term (48-h), postrelease mortality of spotted seatrout Cynoscion nebulosus caught in “run-around” gill nets or by hook and line in Tampa Bay, Florida, during October 1991–February 1993. Overall mortality of spotted seatrout caught by and released from hook and line was 4.6% and was influenced significantly by hooking location. More than 25% of gut-hooked fish died after release, whereas less than 2% of fish hooked in the eye, gill arch, jaws, or inside the mouth died. Overall mortality of fish captured in gill nets was 28.0% and was influenced significantly by water temperature. Mean mortalities were 10–40% at water temperatures of 16–23°C, and 47–69% at 28–31°C. In our study, fish captured in gill nets were more likely to die after release than were fish caught by hook and line. However, in absolute terms the number of spotted seatrout that died in Florida during 1992 after release from gill nets was about two orders of magnitude less than the number that died after release from hook and line. Under high levels of fishing effort, the mortality of released fish may substantially reduce the benefits of creel or harvest restrictions.
Article
Length‐limit regulations and promotion of catch‐and‐release fishing have become increasingly important management approaches for recreational fisheries. We review‐studies on catch‐and‐release (hooking) mortality gathered from the existing fisheries literature and from a survey of fisheries management agencies in all 50 states, the U.S. government, all Canadian provinces, and selected academic and research institutions. We identified hooking mortality estimates for 32 taxa. Most studies dealt with salmonids, centrarchids (especially black basses, Micropterus spp.), and percids (especially walleye, Stizostedion vitreum). Within and among species, differences in percent mortality were reported in association with bait type (artificial vs. natural), hook type (number of hooks, hook size, and barbs), season/ temperature, water depth (depressurization), anatomical location of hook wound, and individual size. Although most hooking mortalities occur within 24 h, the use of initial plus delayed mortality provides a more complete estimate of mortality. Single hooks (especially when used in conjunction with natural baits) resulted in higher mortalities than treble hooks. Environmental conditions (notably high water temperature and low dissolved oxygen) are important to overall mortality related to hooking, playing, and handling. Mortalities were highly variable; occasionally exceeding 30% among red drum (Sciaenops ocellatus), smallmouth bass (M. dolomieu), largemouth bass (M. salmoides), cutthroat trout (Oncorhynchus clarki), and catfishes (Ictaluridae), and 68% among spotted seatrout (Cynoscion nebulosus), bluegills (Lepomis macrocbirus), crappies, (Pomoxis spp.), striped bass (Morqne saxatilis), and coho salmon (O. kisutch). Lake trout (Salvelinus namaycush) and pikes (Esoddae) had mortalities under 15%. The many variables potentially affecting hooking mortality may make optimal management of particular species and water bodies difficult using regional‐level (e.g., statewide) management regulations.
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The mortality of discarded fish bycatch is an important issue in fisheries management and, because it is generally unmeasured, represents a large source of uncertainty in estimates of fishing mortality worldwide. Development of accurate measures of discard mortality requires fundamental knowledge, based on principles of bycatch stressor action, of why discarded fish die. To date, discard mortality studies in the field have focused on capture stressors. Recent laboratory discard experiments have demonstrated the significant role of environmental factors, size- and species-related sensitivity to stressors, and interactions of stressors, which increase mortality. In addition, delayed mortality was an important consideration in experimental design. The discard mortality problem is best addressed through a combination of laboratory investigation of classes of bycatch stressors to develop knowledge of key principles of bycatch stressor action and field experiments under realistic fishing conditions to verify our understanding and make predictions of discard mortality. This article makes the case for a broader ecological perspective on discard mortality that includes a suite of environmental and biological factors that may interact with capture stressors to increase stress and mortality.
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Most research on catch-and-release (C&R) in recreational fishing has been conducted from a disciplinary angle focusing on the biological sciences and the study of hooking mortality after release. This hampers understanding of the complex and multifaceted nature of C&R. In the present synopsis, we develop an integrative perspective on C&R by drawing on historical, philosophical, socio-psychological, biological, and managerial insights and perspectives. Such a perspective is helpful for a variety of reasons, such as 1) improving the science supporting successful fisheries management and conservation, 2) facilitating dialogue between managers, anglers, and other stakeholders, 3) minimizing conflict potentials, and 4) paving the path toward sustainable recreational fisheries management. The present work highlights the array of cultural, institutional, psychological, and biological factors and dimensions involved in C&R. Progress toward successful treatment of C&R might be enhanced by acknowledging the complexity inherent in C&R recreational fishing.
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Mortality rates were determined for common snook Centropomus undecimalis that had been hooked and released in different localities throughout southern Florida. Researchers and cooperative anglers caught, tagged, and retained 470 common snook ranging from 205 to 1,120 mm total length in 23 experiments during June 1991–April 1995. Live bait was used to capture 421 snook; 49 were caught with artificial lures. All snook were held in pens (9.1 × 2.4 × 1.2 m) for at least 48 h; 20.4% were held for 96 h (4 d), 30.8% were held for 120 h (5 d), and 3.2% were held for 288 h (12 d). Ten fish, or 2.13%, died within 24 h of capture. Hook location was the only variable that significantly affected release mortality rates (P < 0.0001); snook hooked in the throat or stomach (5.1% of the time) accounted for 40% of the total mortalities. No fish died in two separate control trials that examined the effects of handling, tagging, and holding common snook. These results should encourage resource managers to continue to use bag and size limits and closed seasons as tools to manage common snook populations. However, spawning aggregations that are heavily fished during the closed (fish cannot be retained) summer season may require additional protection because increasing effort could adversely affect reproductive output.
Article
The average hooking mortality per capture event for 630 trophy-sized wild brook trout Salvelinus fontinalis (mean total length, 33.9 cm) caught on five hardware lures was 4.3% during the first 48 h after capture. Mortality was 8.3% for brook trout caught on Mepps spinners and Cleo spoons equipped with a treble-pointed hook, whereas mortality was significantly lower (2.4% per hooking event; P < 0.05) for fish caught on the same lures with a single-pointed hook. The 10.9% mortality caused by treble-hook Mepps spinners was significantly higher than mortality caused by single-hook Cleo spoons (1.6%). Mortality for brook trout caught on single-hook Cleo spoons and single-hook Mepps spinners combined (2.4%) was also significantly lower (P < 0.05) than mortality offish caught on Mepps spinners with treble hooks. There was no mortality among 126 brook trout caught with Rapala lures rigged with two treble hooks. We believe that the differences in mortality of brook trout caught with different lures are primarily attributable to differences in the frequency and extent of damage to the gill arches and esophagus area. Certain lures were more likely to be engulfed deeply, particularly by larger fish, and thus were more likely to cause death. Lures that exhibit vigorous wobbling action when retrieved appear less likely to be deeply engulfed and consequently cause less mortality. Hooking mortality estimates for brook trout caught on Mepps and Cleo lures combined were positively and significantly correlated with size of fish (P < 0.003). The probability of death within 48 h of capture for profusely bleeding brook trout that were hooked in the gills or throat increased rapidly with increasing water tem- perature. Fish that did not bleed profusely after capture with treble-hooked Mepps and Cleo lures that did not penetrate the gill or throat region were unlikely to die as a result of temperature effects, unless temperatures were above approximately 14°C. The probability of death was not significantly associated with temperatures ranging from 5.6 to 17.8°C when brook trout were hooked with single- pointed hooks at anatomical sites other than the gills or throat and did not bleed heavily. Present regulations on Michigan's trophy trout lakes, which restrict lures to single-pointed hooks and forbid harvest of fish less than 38.1 cm in total length, appear quite adequate to minimize losses due to hooking mortality.
Article
Short-term hooking mortality was evaluated for three sparid species [Diplodus vulgaris (Geoffroy Saint-Hilaire), Sparus aurata L. and Spondyliosoma cantharus (L.)] in the Algarve, south Portugal. Fishes were caught from the shore during October 2009 at a fish farm reservoir (Ria Formosa), using three different hook sizes. The relationships between hooking mortality and seven independent variables were analyzed using logistic regression models. In all, 384 fishes representing the three target species were caught during the angling sessions. The most caught species was S. cantharus (n = 181; 100% undersized), followed by S. aurata (n = 137; 89% undersized) and D. vulgaris (n = 66, 97% undersized). Mortalities ranged between 0% for D. vulgaris and 12% for S. aurata (S. cantharus, 3%). For S. aurata, anatomical hooking location was the main predictor of mortality, with 63% of the fishes that died being deeply hooked. Our results support the current mandatory practices of releasing undersized fish for the studied species, given the low post-release mortality rates observed.
Article
The amount of exploitation in a fishery is typically controlled by regulatory harvest policies, of which the best for maximizing total yield is FMSY, the fishing rate that provides the maximum sustainable yield. However, estimation of FMSY can be difficult for many fisheries, and for this reason proxies such as the spawning-biomass-per-recruit rate (often denoted F%) have been adopted for some fisheries. Around 1992, the Pacific Fishery Management Council adopted an F35% harvest policy for U.S. West Coast groundfish. Recently, this policy has been questioned, along with the overall productivity of West Coast groundfish. Estimates of appropriate harvest rates and productivity are computed from stock assessment models, which often rely on poorly estimated values for natural mortality and at-sea discard levels. The effects of unaccounted discards and misspecified natural mortality on estimates of appropriate harvest rates were investigated using a basic catch-age model. A deterministic, generalized groundfish population was simulated using an average fishing mortality time series computed for 11 major West Coast groundfish species. The model results indicated that unaccounted, non-size-selective discards had no effect on subsequent harvest rate estimates, while unaccounted, size-selective discards of fish ranging up to 50% by weight resulted in a 30–40% higher F% in some cases. The largest changes in harvest policy resulted from lower spawner−recruit steepness parameters, younger ages of selection, and positively biased natural mortality values.
Article
Owing to concerns about the high incidence of past hooking injuries in Alagnak River rainbow trout Oncorhynchus mykiss, fish were captured with spin- and fly-fishing gear with barbed and barbless circle and “J” hooks to determine gear types contributing to injury. Landing and hook removal times were measured for a portion of fish captured, and the anatomical hooking location, hooking scar locations, bleeding intensity, angler experience, and fish size were recorded for all captured fish. Approximately 62% of fish captured experienced at least one new hooking injury, and 29% of fish had at least one past hooking injury. Small fish sustained higher new injury and bleeding rates, but large fish had higher past injury rates. Injury rates were higher for barbed J hooks, barbed J hooks took longer to remove, and fish caught by spin-fishing were injured more frequently than fish caught by fly-fishing. Fewer fly-fishing-caught fish were injured using circle hooks, and circle hooks tended to hook fish in only one location, generally in the jaw. Barbed J hooks were more efficient at landing fish, and J hooks were more efficient at landing fish than circle hooks. Novice anglers injured proportionally more fish than experienced anglers, primarily during hook removal. Landing time was positively correlated with fish size, and experienced anglers took longer to land fish than novices because they captured larger fish. These results suggest that a reduction in hooking injuries may be achieved by using circle hooks as an alternative to J hooks and barbless J hooks to reduce injury and handling time, yet catch efficiency for both methods would be reduced. Although fish captured with barbless J hooks and circle hooks had fewer injuries, it is important to note that each hook type also caused significant injury, and angler education is recommended to promote proper hook removal techniques.
Article
North Carolina's dolphin fishery was surveyed in 1961 and 1962 to evaluate its importance to the offshore sport-fishing industry, and to develop suitable and reliable techniques for sampling a marine sport-fishery. As a prelude to the investigation, characteristics of the prominent offshore charter-boat fishery are described. Duration of the sport-fishing season, species captured, fishing methods, and economical aspects of the fishery are discussed.In 1961, catch-forms, personal enumerations, and interviews with dockmasters were used to estimate the catch of party boats, private boats, and transient charter boats. Catch by these boats was approximately 3,150 fish. The activity of resident offshore charter boats operating from the principal North Carolina ports was sampled by use of log books. Complete catch records were returned from 20% of the 90 resident boats that habitually frequented offshore waters. Ports were stratified for statistical treatment into five areas on the basis of proximity and similarity of fishing grounds. Monthly estimates of fishing pressure and catch were calculated for each area. Catch by resident charter boats was estimated to be about 35,050 fish, or 92% of the total catch. Ninety-nine percent of this catch occurred during June through September. Merits of the offshore boat-day as a unit of fishing effort, and the inefficiencies inherent in the log-book survey are discussed. In 1962, the catch of party boats, private boats, and transient charter boats was estimated to be 3,000 fish. Resident offshore charter boats were again stratified into the five areas described in the 1961 survey. A complete enumeration of fishing activity was obtained at Hatteras, North Carolina (Area IV). At Areas I, II, III, and V, log books were distributed to captains who kept reliable records of fishing effort and success. The remaining boats were surveyed by a stratified random-sampling design. Secondary stratification divided the fishing season into four 1-month intervals, thereby producing a total of 16 strata. The original frame consisted of 9,028 total boat-days that were sampled to estimate fishing pressure and success by proportionally allocated postcards. In each stratum, total boat-days were divided into the following categories: offshore boat-days, bad-weather boat-days, and inshore or no-charter boat-days. Dolphin catch and its variance was determined for each stratum. Catch by resident charter boats was estimated to be 68,007 fish (96% of total catch). Ninety-five percent confidence limits were 59,790 and 76,220 fish. Fishing pressure was approximately double that of 1961; catch per unit of effort remained essentially constant, resulting in a two-fold increase in catch. Seasonal catch of a typical resident charter boat was about 700 fish. Inclement weather curtailed offshore activity during approximately 10% of the fishing season. Rate of postcard return was 39% (882 of 2,240 postcards originally distributed). Rate of return did not decrease as the fishing season progressed and did not appear to be a function of fishing effort.
Article
The mortality of anadromous coastal cutthroat trout Oncorhynchus clarki taken by anglers with worm-baited hooks of four different sizes, spinners with single hooks, spinners with treble hooks, and spinners with treble hooks baited with worms was investigated on the Stillaguamish and Snohomish rivers in Washington. In all but two comparisons mortality of cutthroat trout was greater (P < 0.05) from the four sizes of worm-baited hooks (39.5–58.1%) than from the three different spinner treatments (10.5–23.8%). The probability of killing fish was greater (P < 0.05) when fish were hooked in either the gill (95.5%), tongue (66.7%), esophagus (65.5%), or eye (53.8%) than in other anatomical locations. A group of untagged fish that were caught on worm-baited hooks but hooked only in the jaw or mouth were used as control fish to evaluate tagging mortality. The mortality of the untagged group (7.4%) was not greater than the mortality of fish caught on all terminal gear types and hooked in the upper or lower jaw (5.8%), suggesting that mortality from tagging was not an important factor. Mortality was positively related to bleeding at the time of hooking. Hooking a fish in a critical anatomical part was the most important factor causing subsequent mortality.
Article
Fish captured by recreational anglers are often released either voluntarily or because of harvest regulations in a process called ''catch-and-release''. Catch-and-release angling is thought to be beneficial for the conservation of fish stocks based on the premise that most of the fish that are released survive. However, expanding interest in animal welfare has promoted debate regarding the ethics of catch-and-release angling. There is a growing recognition that fish can consciously experience nociception and that they have some capacity to experience pain and fear. Indeed, empirical anatomical, physiological, and behavioural evidence supports the notion that fish could experience these two forms of suffering (i.e., pain and fear). Based on that premise, we examine existing catch-and-release research from a welfare perspective to determine the extent to which potential pain and suffering could be caused. There are numerous studies that provide analyses of the consequences of catch-and-release on the individual demonstrating physical injury, sublethal alterations in behaviour, physiology, or fitness, and mortality. Collectively, this research suggests that all recreational fishing results in some level of injury and stress to an individual fish. However, the severity of injury, magnitude of stress, and potential for mortality varies extensively in response to a variety of factors. Interestingly, this information can be used to identify strategies that anglers may adopt that minimize these effects through changes in either gear (e.g., type of hook, bait, or net) or angling practices (e.g., duration of fight and air exposure, fishing during extreme environmental conditions, fishing during the reproductive period). Although aspects of the catch-and-release angling experience cannot be refined (e.g., the need to physically hook the fish), we argue that informed anglers and fisheries managers can adopt practices to improve the welfare of angled fish. Although consideration of fish welfare is somewhat abstract to most anglers and fisheries managers, ultimately it benefits the individual fish, while simultaneously benefiting the fish population and fishery. Greater integration of welfare consideration into recreational and commercial fisheries should promote innovative solutions to minimize pain and suffering, which should also enhance conservation and management.
Article
Abstract The practice of catch and release (CR) as a fisheries management tool to reduce fishing mortality is widely applied in both freshwater and marine fisheries, whether from shifts in angler attitudes related to harvest or from the increasing use of harvest restrictions such as closed seasons or length limits. This approach assumes that for CR fishing policies to benefit the stock, CR will result in much lower mortality than would otherwise occur. There are many challenges in the design of CR studies to assess mortality, and in many practical settings it is difficult to obtain accurate and precise estimates. The focus of this article is on the design and quantitative aspects of estimating CR mortality, the need for a comprehensive approach that explicitly states all components of CR mortality, and the assumptions behind these methods. A general conceptual model for CR mortality that is applicable to containment and tagging-based studies with a slight modification is presented. This article reviews the design and analysis of containment and tagging studies to estimate CR mortality over both the short and long term and then compares these two approaches. Additionally, the potential population-level impacts of CR mortality are discussed. A recurring theme is the difficulty of designing studies to estimate CR mortality comprehensively and the need for additional research into both statistical model development and field study design.
Article
Abstract  Sharks, tunas and billfishes are fished extensively throughout the world. Domestic and international management measures (quotas, minimum sizes, bag limits) mandate release of a large, yet poorly quantified, number of these fishes annually. Post-release survivorship is difficult to evaluate, because standard methods are not applicable to large oceanic fishes. This paper presents information on the current approaches to characterising capture stress and survivorship in sharks, tunas and marlins. To assess mortality associated with capture stress, researchers must examine the cumulative impacts of physical trauma and physiological stress. Physical trauma, manifested as external and internal tissue and organ damage, is caused by fishing gear and handling. Gross examination and histopathological sampling have been used to assess physical trauma and to infer post-release survivorship. Exhaustive anaerobic muscular activity and time out of water cause physiological stress, which has been quantified in these fishes through the analyses of blood chemistry. Conventional, acoustic and archival tagging have been used to assess post-release survivorship in these species. Future studies relating capture stress and post-release survivorship could yield information that helps fishermen increase survivorship when practicing catch and release.
Article
Although computed tomography (CT) is used primarily for diagnosis in humans, it can also be used to diagnose disease in veterinary patients. CT and associated three-dimensional reconstruction have a role in diagnosis of a range of illnesses in a variety of animals. In a sea turtle with failure to thrive, CT showed a nodal mass in the chest, granulomas in the lungs, and a ball in the stomach. CT of a sea dragon with balance and movement problems showed absence of the swim bladder. In a sloth with failure to thrive, CT allowed diagnosis of a coin in the intestine. CT of a puffin with failure to thrive showed a mass in the chest, which was found to be a hematoma. In a smooth-sided toad whose head was tilted to one side and who was circling in that direction, CT showed partial destruction of the temporal bone. CT of a domestic cat with listlessness showed a mass with focal calcification, which proved to be a leiomyosarcoma. CT of a sea otter showed pectus excavatum, which is caused by the animal smashing oysters against its chest. In a Japanese koi with abdominal swelling, CT allowed diagnosis of a hepatoma.
Bluefin tuna project. Final Report for National Oceanic and Atmospheric Administration Award NA37FL0285
  • S Belle
Belle, S. 1997. Bluefin tuna project. Final Report for National Oceanic and Atmospheric Administration Award NA37FL0285. New England Aquarium, Edgerton Research Laboratory, Central Wharf, Boston, Massachusetts, p.62.
Diagnosis. Pages 107-124 in Handbook of evidence-based veterinary medicine
  • P D Cockcroft
  • M A Holmes
Cockcroft, P. D., and M. A. Holmes. 2003. Diagnosis. Pages 107-124 in Handbook of evidence-based veterinary medicine. Blackwell Publishing Ltd, Oxford, UK. Accepted Article This article is protected by copyright. All rights reserved.