Search

Objective: The Striped Bass Morone saxatilis is one of the most sought‐after recreational fish species along the US Atlantic coast. Regulations and a strong conservation ethic among anglers make Striped Bass among the most frequently released coastal marine fishes. A recent rule requires anglers to use circle hooks when targeting Striped Bass with natural baits, yet the conservation benefit of this action remains unclear. Methods: We used acoustic telemetry to monitor the fate of Striped Bass that were recreationally caught with baited hooks (n = 349) and to estimate the influence of various biological (fish size), fishery (fight time, handling time, hook location, bait type, and hook type), and environmental (water temperature and air temperature) variables on postrelease survival. Result: A semi‐quantitative score of fish release condition was the single best predictor of mortality. A broader dataset that included untagged fish (n = 716) was used to identify the best predictors of fish release condition, which included hook location and handling time. Conclusion: Contrary to expectations, the circle hooks used in this study did not result in lower release mortality than conventional J‐hooks. Impact statementStriped Bass are a popular recreational sport fish in the United States, with most fish being caught and released. To increase the survival of released fish, anglers are now required to use circle hooks when fishing with bait. This study found that using circle hooks does not increase the survival of released Striped Bass. [ABSTRACT FROM AUTHOR]

Pelagic stingray (Pteroplatytrygon violacea) is the only species of stingray (Dasyatidae) that utilizes both pelagic and demersal habitats. It is the main bycatch species in pelagic longline fisheries targeting bluefin tuna (Thunnus thynnus) in the Gulf of Lions. In the Mediterranean Sea, their stock structure, behavioural ecology and movements are unknown. For the first time in the Mediterranean, 17 individuals (39–60 cm disc width) were tagged with pop-up satellite archival transmitting tags using a novel method of tag attachment to investigate horizontal and vertical movements. The tags were attached for between two and 60 days. Between the months of July and October, pelagic stingray occupied a temperature range of 12.5–26.6 °C, and a depth range extending from the surface to 480 m. Monthly trends in catch-per-unit-effort (CPUE) of pelagic stingray peaked in August and decreased by late autumn. Pelagic stingray may aggregate on the continental shelf during summer and move southwards in early autumn, and this movement pattern is considered in relation to the reproductive cycle and overwintering. At-vessel mortality was low, but there was varying evidence of post-release mortality, indicating the need for further work. Future work and options for bycatch mitigation are also discussed. [ABSTRACT FROM AUTHOR]

The Caribbean spiny lobster (Panulirus argus) fishery in Florida, valued at millions of dollars annually, relies mostly on wooden-slat traps baited with live, sublegal-size lobsters to attract legal-size individuals. However, this practice leads to confinement-related mortality due to starvation and depredation. We investigated the escape rates and mortality of bait lobsters using long-term deployable cameras, documenting behavior of bait lobsters in traps. Although previous research found that long-term confinement of these bait lobsters results in their poor health and mortality, these estimates of mortality relied on periodic observations of traps that could not differentiate causes and timing of mortality. To identify how the long-term confinement of bait lobsters affects their likelihood for escape or mortality, we deployed traps with one lobster for each of the following treatments: healthy/fed or starved for 2, 4, or 6 weeks. Long-term deployable cameras and infrared lights mounted on traps were used to observe the fate (i.e., escape or mortality) of these lobsters over a 2-week trap soak period typical in the fishery. We conducted 12 deployments of 103 total traps over 1 year and found that escape varied with duration of lobster starvation. Our study confirmed escape rates from past studies (1.26 ± 0.43 % of lobsters per day) and revealed "serial confinement," where escaped lobsters re-entered traps, potentially prolonging their confinement and mortality risk. Starvation, caused by long-term confinement, resulted in increased mortality, with smaller lobsters (<68 mm carapace length) facing higher risk of mortality. Video documentation allowed for the first time to differentiate between starvation mortality and depredation within traps; depredation by octopuses (Octopus briareus) and triggerfish (Ballistes spp.) posed a substantial threat, reducing trap catch efficiency. Our video documentation showed that the presence of dead lobsters in traps further decreased catch rates for the duration (∼5d) the carcass remained in the trap, underscoring the negative impact on fishery yield. Our findings emphasize the need for the fishery to explore management strategies to mitigate mortality of sublegal-size lobsters in traps due to long-term confinement, including trap reduction, use of escape gaps, and shorter trap soak times, akin to successful practices in other spiny lobster fisheries. The study highlights the utility of long-term deployable cameras in assessing trap functioning and catch dynamics, offering insights for sustainable management of Florida's lobster fishery while preserving its cultural and economic significance. ● Presence of a dead lobster reduced a trap's effective soak period by 33 %. ● Escape and carcass decay rates were similar to studies using periodic observations. ● Daily lobster catch rates decreased as soak time increased. ● Lobsters < 68 mm carapace length were at greater risk of starvation mortality. ● Escape was greater for the healthier lobsters and lowest for starved lobsters. [ABSTRACT FROM AUTHOR]

Despite the importance of Rapana fisheries in the Black Sea region, few studies have focused on the non-target species, and determined discard rates from hauls on the deck, with no data on organisms that entered and subsequently escaped the fishing net during the dredge fishing. Rapana venosa is harvested along the entire coast of the Black Sea using dredging or beam-trawl fishing. This study adopted the cover net method to assess the composition and proportion of non-target escapees in Rapana fisheries by dredging along the western coast of the Black Sea. In this method, the dredge net bag (codend net) is covered with a second net bag that has a smaller mesh size to retain those individuals escaping from the dredge net bag. Up to 87% of the total ∼1.4×106 individuals per km (ind. km−2) cover net catches belonged to non-target species. Overall, 24 non-target species were caught in the cover net, with 46% of species belonging to the Teleostei (mostly flatfishes), 21% Malacostraca, 17% Bivalvia, 8% Gastropoda, 4% Amphibia, and 4% Ascidiacea. On the other hand, up to 6.8% of the total ∼0.16×106 ind. km−2 catches of the codend net (dredge net) belonged to non-target species. Compared to the cover net, a total of seven non-target species were retained in the codend net, and six of them belonged to Bivalvia. This study demonstrated an apparent negative impact of Rapana fisheries, particularly on escapees that often go unaccounted for their vulnerability to stress and physical damage. [ABSTRACT FROM AUTHOR]

Despite the implementation of technical management measures to facilitate stock recovery of European sea bass, Dicentrarchus labrax (L.), the survival rate of discarded hook‐and‐line caught sea bass remains unknown. This makes the effectiveness of management measures that result in discarding difficult to assess. Therefore, a questionnaire was distributed to 421 UK‐based commercial hook‐and‐line fishers (65 respondents) to characterise how sea bass are caught, handled and released. Responses suggested fishing was selective with a reported estimated mean discard rate of 12.9% (±3.3% SE). Low rates of foul and deep hooking, and short periods of air exposure were reported. Combined with data from a post‐release mortality experiment using hook‐and‐line caught captive sea bass, a fleet‐wide discard survival rate of 89.3% (±2.6% SE) was calculated for the UK commercial hook‐and‐line sea bass fishery. This survival rate suggests that technical management measures, for example minimum conservation reference sizes and catch limits, could be effective tools for managing the sea bass hook‐and‐line fishery. [ABSTRACT FROM AUTHOR]

Globally, it is estimated that around 10% of the fish that are caught are discarded. This is considered to be a wasteful human marine activity since these fish are often dead or dying. To reduce the high discard rates of commercial fisheries, the European Union (E.U.) has enacted a landing obligation that includes the ability to exempt “species for which scientific evidence demonstrates high survival rates”. Therefore, discard survival studies (henceforth DSSs) have become one of the most politically prioritized fisheries research areas in European fisheries. International expert groups have produced guidance reports to promote best practices and to harmonize the methodologies. Nevertheless, there has not been any focus on how to implement animal welfare (AW) regulations experimentally. Discard survival studies are “frontrunners” in fisheries science research areas that are embedded by animal research welfare requirements and are expected to be more restrictive in the future because of an increased public focus on fish welfare. This paper focuses on AW regulations in relation to conducting DSSs, but the outreach is much broader. We investigate experimental procedures by bringing in relevant examples, using output results, and relating this information to relevant AW guidelines and regulations by focusing on implementing 3R principles.

Abstract Background Pacific halibut support high-value commercial and sport fisheries in the north Pacific Ocean, making survival of Pacific halibut bycatch in trawl fisheries an important management concern. We present a method for characterizing activity and inferring survival of Pacific halibut based on accelerometer data from Pop-up Satellite Archival Tags (PSATs). A PSAT attached to a fish with a dart and tether floats freely above the fish in a vertical orientation when the fish is stationary, but switches to a more horizontal orientation when towed behind an active fish. We hypothesized that characteristic changes in PSAT orientation associated with activity could be detected by accelerometers and summarized for transmission by PSATs to provide valuable information on fish activity. Results We developed procedures for inferring survival of Pacific halibut with accelerometer PSATs based on a progression of analysis steps that linked PSAT orientation, PSAT acceleration data, and Pacific halibut activity patterns. Relationships between PSAT orientation and Pacific halibut activity were confirmed by observations of PSAT orientation on Pacific halibut swimming in the laboratory and comparisons with depth data from tags on free-ranging Pacific halibut. We developed two metrics summarizing 1 Hz acceleration data for transmission to the Argos satellite network. The “knockdown” metric records abrupt changes in vertical acceleration, indicating both initiation of swimming bouts and sustained swimming behavior, and is robust to the effects of tidal currents. The “%tilt” metric records the amount of time the tag tilts past a vertical orientation threshold and captures the proportion of each time bin that the fish is active. These PSAT metrics revealed diel behavior and three activity modes present in free-ranging Pacific halibut that allowed inference of survival when compared to PSAT data from fish carcasses and weighted tags. Conclusions Accelerometer PSAT metrics developed in this study revealed Pacific halibut activity patterns, and thus survival, and may be extended to other fish species. Economical accelerometer PSATs can allow larger sample sizes that enhance bycatch survival studies while detecting fish activity in flat study areas. PSAT advantages over other survival estimation methods include providing outcomes for all specimens during exposure to natural conditions.

Mortality of fish discarded from commercial fisheries is often estimated by using viability keys to parse fish into different categories with unique estimated survival outcomes. In this study we examined the relationships of environmental and physiological parameters and viability classifications of Pacific halibut (Hippoglossus stenolepis) released from commercial longline gear using three distinct hook-release methods. Our results indicate that the hook release method used strongly influenced viability, with careful shake and gangion cut resulting in minimal injuries leading to discarded fish characterized as having excellent viability. In contrast hook stripping resulted in most released fish having moderate or poor viability. Physiological parameters (lactate, hematocrit) were strong indicators of Pacific halibut assigned to the dead viability category. In addition to being captured at greater depth and lower sea bottom temperature, dead categorized fish were associated with high plasma lactate levels and lower hematocrit, attributed to sand flea intrusion. Reducing the use of hook strippers and limiting soak times in areas of known sand flea activity are likely to improve viability outcomes of Pacific halibut released from commercial longline gear. Discard survival and understanding of the factors affecting it remain critical to successful long-term management of Pacific halibut, as sustainable fishing levels are adjusted yearly for estimated mortality consistent with recent fishing discards. • Understanding environmental and physiological influences on discard mortality is critical to sound management. • Hook release method has a significant influence on the survivability of Pacific halibut discarded in commercial fisheries. • Physiological parameters (lactate, hematocrit) are strong indicators of the poorest viability classifications. • Pacific halibut in the dead viability category had high plasma lactate levels and low hematocrit. • Reducing hook stripper use and limiting soak time in presence of sand fleas improves viability of Pacific halibut released from longline gear. [ABSTRACT FROM AUTHOR]

Geopositioning underwater acoustic telemetry was used to test whether rapid recompression with weighted return-to-depth (descender) devices reduced discard mortality of red snapper (n  =   141) and gray triggerfish (n  =   26) captured and released at 30–60 m depths at two 15 km2 study sites in the northern Gulf of Mexico. Cox proportional hazards modelling indicated red snapper released with descender devices had significantly lower discard mortality within the first 2 d (95% CI = 18.8–41.8% for descender-released vs. 44.0–72.4% for surface-released, unvented fish), while there was no significant effect of descender devices on discard mortality of gray triggerfish. Predation by large pelagic predators was estimated to account 83% of red snapper and 100% of gray triggerfish discard mortality. Discard mortality due to predation has likely been overlooked in previous mark-recapture, laboratory, and enclosure studies, suggesting cryptic population losses due to predation on discards may be underestimated for red snapper and gray triggerfish. Large-area three-dimensional positioning acoustic telemetry arrays combined with collaboration and data sharing among acoustic telemetry researchers have the potential to advance our knowledge of the processes affecting discard mortality in reef fishes and other taxa. [ABSTRACT FROM AUTHOR]

Abstract A key factor affecting survival of fish which are captured at depth and subsequently released is barotrauma. Barotrauma are a suite of injuries which occur as a result of the decreasing ambient pressure experienced by a fish during capture and are caused by expanding swim bladder gas and formation of gas embolisms. Snapper (Chrysophrys auratus) are of key importance to both commercial and recreational fisheries in southern Australia and are often released after capture suffering from barotrauma. Previous research has yielded inconsistent results for survival of C. auratus after suffering barotrauma, in part due to influences related to capture, 'cage' effects and the use of only very short term post-catch and release monitoring. This study therefore used laboratory hyperbaric chambers to simulate the pressure changes associated with capture to investigate whether barotrauma was a direct cause of mortality in C. auratus. The influences of depth and repressurization on mortality, behaviour and symptoms due to barotrauma could therefore be examined in a controlled environment independent of capture and 'cage' effects combined with long-term monitoring (220 d) post-simulation. In a pilot experiment C. auratus (n = 12) were depressurized from 8 bar (≈70 m depth), before being repressurized after 2 min at 1 bar (atmospheric pressure) resulting in agitated in-chamber behaviours and abdominal distension as a result of swim bladder perforation, but 100% survival. A second experiment depressurized C. auratus from 4 bar (≈30 m depth); one treatment group (n = 32) were repressurized after 10 min again resulting in behaviour and symptoms indicative of swim bladder perforation and 100% survival, the other group (n = 32) was left at 1 bar and exhibited many additional external and internal barotrauma symptoms and suffered 16% mortality. Despite the death of a single control individual, statistical analyses found a significant effect of treatment on mortality. Mortality occurred within 15 min of depressurization and the cause of death was consistent with the formation of gas embolisms. Staged post-mortems performed on C. auratus that had been depressurized from 4 bar to induce swim bladder perforation indicated that swim bladders were healed sufficiently to hold gas after just 2 d. C. auratus were shown to be a remarkably robust species to the effects of barotrauma, particularly if repressurized quickly (<10 min) after capture and this resilience is likely reflective of their characteristic semi-pelagic physiology. This study also demonstrated the usefulness of laboratory hyperbaric chambers to examine the long term (>200 d) effects of depressurization on deep water fish species independent of capture and 'cage' effects. [ABSTRACT FROM AUTHOR]

Highlights • The utility of escape gaps for mitigating the ghost fishing of derelict portunid traps was assessed. • Escape gaps and/or holes in traps reduced catches of Portunus armatus by >93% during up to 10-week soaks. • Fewer Portunus armatus were injured or died in derelict traps with escape gaps or holes than those without. • Retroactively fitted escape gaps are warranted to minimise ghost fishing. Abstract Owing to concerns about derelict portunid traps perpetually fishing ('ghost fishing') in southeastern Australia, the utility of escape gaps for minimising temporal catching efficiencies, and damage and mortality, among key species was investigated. Replicate baited traps with (i) no escape gaps ('conventional'), (ii) three escape gaps ('escape-gap' traps), or (iii) three holes where escape gaps would have been if they were biodegradable ('open-hole' traps) were deployed and retrieved after short (one and two weeks), medium (four and six weeks) and long soaks (eight and 10 weeks). No trap had bait remaining after any soak. Total catches comprised 17 species, but 70% was blue swimmer crabs, Portunus armatus —most (78%) of which were smaller than a proposed new legal size (≥65 mm carapace length). Many (62%) P. armatus were injured (typically missing one or two appendages), but had few mortalities (total of 5%). Compared to conventional traps, the escape-gap and open-hole traps retained significantly fewer undersized P. armatus across all soaks (by 93 and 96%) and there were less total injuries (by 86 and 97%) and mortalities trap–1 (by 80 and 85%). Irrespective of the trap, catches of total and undersized P. armatus and injuries trap–1 were greater after short (all by up to 3×) than medium or long soaks. Several traps had broken mesh bars, which was negatively associated with P. armatus catches and injuries. Only three other species had mortalities (n = 7). The data support using escape gaps for minimising ghost fishing among derelict portunid traps. [ABSTRACT FROM AUTHOR]

Abstract: In southeastern Australia, some commercial fishers sort their catches of trapped Portunus armatus in ice slurries to pacify and facilitate discarding sub‐legal and ovigerous individuals, but with unknown mortality. To estimate mortality, during 90 trap lifts, 101 and 110 small P. armatus were sorted dry and in ice slurries, respectively (over 0.5–10.0 min). All discards were individually caged and monitored with 32 similar‐sized control animals (caught by benign methods) for 48 hr. Irrespective of handling, only eight discarded P. armatus were physically damaged. None of the controls died, compared with 1 and 13% of the dry‐ and ice‐slurry sorted conspecifics. The probability of mortality was estimated at 0.005 immediately after emptying the traps and remained temporally constant for dry‐sorted individuals, but was positively associated with time in the ice slurries, reaching 50% at 9 min. Minimising sorting in ice slurries to <2 min should cause minimal impact to P. armatus, although other unaccounted mortalities (e.g., predation) and sublethal effects warrant assessment. [ABSTRACT FROM AUTHOR]

European sea bass (Dicentrarchus labrax) is an important target species for recreational and commercial fisheries. In recent years, the spawning stock biomass has declined markedly in some areas, and strict management measures have been introduced. However, the development of appropriate stock assessment and fisheries management has been hampered by a lack of information on post-release mortality. This study investigated post-release mortality of sea bass captured with common recreational fishing gear under experimental conditions in an aquaculture facility over 10 d. Three experiments investigated: (i) the effects of different bait types; (ii) the impact of prolonged air exposure; and (iii) the impact of deep hooking on post-release mortality. By combining the experimental results with country-specific information on sea bass angling practices, estimates of post-release mortality are provided for the northern sea bass stock. No mortality was observed for sea bass captured on artificial baits. The use of natural baits resulted in a mortality of 13.9% (95% CI  = 4.7–29.5%), which was associated with deep hooking, hooking injuries, and prolonged air exposure. The use of artificial baits and short air exposure (≤30 s) increased survival probability, whereas deep hooking resulted in 76.5% (95% CI  = 50.0–93.2%) mortality. Depending on country-specific angling practices, post-release mortality estimates ranged from 2.8% to 9.1% (mean = 5.0%, 95% CI  = 1.7–14.4%) for northern sea bass. Despite these relatively low mortality estimates, post-release mortality should be considered in stock assessments as its cumulative impact may be high. Moreover, post-release mortality can be reduced by implementing species-specific best practice guidelines. [ABSTRACT FROM AUTHOR]

Several anguillid eel species have experienced severe population declines over the past decades, particularly the European eel ( Anguilla anguilla ), which is listed as critically endangered by the International Union for Conservation of Nature. To reduce fishing mortality, many European countries have introduced strict recreational eel fishing regulations increasing regulatory catch-and-release (C&R) practice. Despite high release rates, only limited information exists on the potential consequences of C&R on eels. A field experiment was conducted with pre-tagged eels in a semi-natural environment to investigate lethal and sublethal impacts of C&R. The experiment was combined with a citizen science study evaluating the effects of different hooks on catch rates, fish size, and hooking location to develop best practice guidelines. Short-term mortality (≤72 h) ranged from 0.0–18.2%, and adjusted long-term mortality (>72 h) from 0.0–46.2% depending on treatments, resulting in adjusted total mortality rates between 8.4% and 64.4% at the end of the study period (≥43 d). The only significant predictor of mortality was the occurrence of bleeding from hooking injuries. Deep hooking was common, and only few deep-hooked eels for which the fishing line was cut and the hook left in place shed the hook after release. However, no significant effect of C&R on eel condition was found. The citizen science study showed that anglers can significantly decrease the catch of small eels, and thus release rates, by using large J-hooks. Furthermore, large J-hooks or circle hooks reduced the likelihood of deep hooking compared to small J-hooks. Post-release mortality of eels caught in recreational fisheries needs to be considered in future stock assessments and management plans to ensure conservation of the European eel. This study also highlights the strength of combining citizen science with experimental studies to develop best practice guidelines promoting fish conservation. [ABSTRACT FROM AUTHOR]

Discard mortality (DM) estimates are vitally important to fisheries management. Commercial fishery DM estimates, for example, can help calculate total fishing mortality and biologically acceptable catch limits. The winter skate, Leucoraja ocellata , is the only species within the US portion of the western North Atlantic that is targeted in the skate wing fishery. However, due primarily to fishery regulations, this species is also routinely discarded at sea when daily quotas are reached. While already examined in mobile fishing gears (i.e. bottom otter trawls), DM has not been addressed for the western North Atlantic skate species captured in the sink gillnet fishery, and a conservative 50% DM is used across the species of the skate complex in the management processes. Given this data gap, we estimate the DM of winter skate in sink gillnets under standard commercial fishing conditions. The study methods employed address the issue of cryptic mortality (drop out of dead skates from the gear and depredation prior to retrieval), which can bias DM estimates low for bycatch in passive gear. The degree of injury sustained during capture and handling was found to be a statistically significant predictor of mortality. Overall mean DM rates reached an asymptote within 170 h of captivity, with estimates of 11% and 17% for females and males, respectively. Based on these results, the species appears more resilient to sink gillnet capture and release than previously thought. However, cryptic fishing mortality appeared to be high for extended soak times and likely represents an important focus of future research and management actions. [ABSTRACT FROM AUTHOR]

Due primarily to regulatory factors, skates (family Rajidae) account for nearly half the total bycatch discarded during commercial fishing operations in the U.S. portion of the Northwest Atlantic Ocean. In this region the New England scallop dredge fishery has the second highest skate discard rate; however, no information regarding their resiliency to interaction with this gear type exists. To gain insight into species-specific mortality rates, 295 tows were conducted throughout six research cruises (2012–2013 fishing season), with a total of 4216 skates (little skate, Luecoraja erinacea , winter skate, Leucoraja ocellata , and barndoor skate, Dipturus laevis ) evaluated and scored using reflex impairment and injury (i.e., overt physical trauma) indicators. To quantify mortality rates associated with these indicators, 334 skates were retained in an on-deck refrigerated flow-through seawater system and monitored every six-hours until the end of a trial. This study also assessed the effect of fishing conditions/practices and individual traits on post-release mortality. Data suggest that species-specific differences exist wherein winter skate are likely the most resilient (45.4% mortality) to capture and handling, little skate have a moderate capacity to deal with these pressures (62.7% mortality), and barndoor skate appear to be the most susceptible (99.9% mortality). In addition, little and winter skate mortality rates were both influenced by tow duration, while fishing depth and temperature gradient had an effect on little skate and air exposure on winter skate. [ABSTRACT FROM AUTHOR]

There is a lack of information available on octopuses in Alaskan waters and because of this lack of data, catch limits are set based on historical incidental catch rates or survey biomass estimates that are likely to be overly conservative. This issue is further exacerbated by the fact that catch accounting for octopuses assumes 100% mortality for all octopuses caught whether retained or discarded. We examined the delayed mortality of the giant Pacific octopus, Enteroctopus dofleini , captured in Pacific cod, Gadus microcephalus , pot fisheries in the Gulf of Alaska. Octopuses captured as bycatch during commercial fishing operations were held on the vessel and brought back to the laboratory to assess delayed mortality over a period of 21 days. The relationship between survivorship and injury presence, sex, maturity, weight, season of capture, air temperature, water depth, and pot soak time were examined using generalized linear models. In addition, the relationship between injury presence and the same parameters were examined. Survivorship ranged from 77.8% to 93.6% during each of three fishing seasons and was significantly related to injury presence. Injury presence ranged from 10.0% to 63.2% during each season and was related to season with an increase in injuries during the fall. These data indicate the conservative assumption of 100% bycatch mortality for octopus is not appropriate for some fisheries, in particular those utilizing pot gear. [ABSTRACT FROM AUTHOR]

Predicting discard mortality of species from fishery operations is essential for developing accurate stock assessments and determining sustainable fishery practices. The Florida stone crab, Menippe mercenaria , is a highly exploited fishery resource in which only the claws are harvested and declawed legal-size and both intact ovigerous females and under-size (i.e., sublegal) crabs are discarded alive. A technique for assessing discard mortality—the reflex action mortality predictor (RAMP) method—defines the relationship between the severity of reflex impairment observed in an animal and the likelihood of mortality. We successfully adapted the RAMP method to the Florida stone crab with the ultimate goal of furthering knowledge of delayed mortality of discarded sublegal animals in the fishery. We identified eight reliable reflex behaviors, then exposed 230 sublegal M. mercenaria to three treatments in laboratory conditions: no trauma (control, n = 25), physiological trauma (five different time periods of desiccation, n = 20–22 per treatment), or physical trauma (being dropped from five different heights, n = 19–21 per treatment). Crabs were evaluated and scored based on the impairment of reflexes immediately before and after treatment and again at the end of a 14-day holding period. Stone crabs survived the range of desiccation treatments but were sensitive to the damage sustained during dropping treatments. Analysis using a logistic exposure model revealed that reflex impairment and the height from which crabs were dropped were strong predictors of daily survival (i.e., probability of surviving a single day) with 76.5% correct predictions. Other variables (sex, carapace width, degree of external injury, and side of the body upon which the reflexes were tested) appeared only to minimally influence daily survival. When reflexes of sublegal crabs were scored immediately after removal from traps fished for two weeks in field conditions, RAMP revealed low reflex impairment, indicating that the impact of the traps was negligible. Therefore, the RAMP method should be a beneficial tool in assessing discard mortality rates of sublegal crabs, along with the efficacy of current handling and holding techniques in the stone crab fishery. [ABSTRACT FROM AUTHOR]

The European Commission landing obligation, including species-specific "high survival" exemptions, has established a need for accurate dis- card survival estimates. This study presents the first discard survival estimates on-board Dutch commercial pulse trawlers. During seven, six, and one fishing trip(s), respectively, undersized plaice (Pleuronectes platessa), sole (Solea solea), and dab (Limanda limanda) were collected, assessed for vitality and subsequently monitored up to 21 days. Uncorrected for any potential impacts from predation, tagging, research-related handling, or holding conditions overall survival for plaice (n = 349), sole (n = 226), and dab (n = 187) was assessed as 15% [95% CI: 11-19%], 29% [95% CI: 24-35%], and 16% [95% CI: 10-26%] respectively. Survival was mainly effected by water temperature and factors linked to the fishing vessel. Fish length was not found to affect survival. Catch processing time and haul duration affected plaice survival but not sole. Vitality index, which averages reflex impairment and external damage scores, correlated with survival and may be developed as a proxy for discard survival. Compared to tickler-chain beam trawlers, pulse trawlers showed relatively higher discard survival under fishing conditions pertinent to these studies. [ABSTRACT FROM AUTHOR]

Fishery observer data collected from June 2006 through December 2015 in the Gulf of Mexico commercial reef fish fishery were examined to determine if any covariates available affected immediate discard mortality for six species: red grouper Epinephelus morio , red snapper Lutjanus campechanus , vermilion snapper Rhomboplites aurorubens , gag grouper Mycteroperca microlepis , scamp grouper Mycteroperca phenax , and speckled hind Epinephelus drummondhayi . Using logistic regression models, this study predicted immediate discard mortality was positively correlated with increased depths, seasons associated with warmer water temperatures, and external evidence of barotrauma. Additionally, bottom longline gear increased the predicted probability of immediate mortality compared to vertical line gear for all species except vermilion snapper. Air bladder venting significantly decreased the predicted probability of immediate mortality for all species except speckled hind. Future research incorporating tag-recapture data into the current observer program for the commercial reef fish fishery is vital to assess if condition assessment at release can be relied on as an accurate proxy for long-term survival. This research provides information that managers could potentially use to make more informed decisions when implementing measures such as changes to existing size limits, venting requirements, and seasonal, area, or gear restrictions intended to reduce unwanted discard mortality. [ABSTRACT FROM AUTHOR]

By 2019, the Common Fisheries Policy will prohibit discarding in all European fisheries of any pelagic, demersal or shellfish species for which removals are managed by TACs and quotas or minimum sizes. However, the regulation allows for exemptions from the prohibition for species for which scientific evidence demonstrates high survival rates associated with discarding. Producing reliable evidence of high survival typically requires long and costly studies involving tagging or captivity. This paper proposes to use the capacity to resist air exposure, a key stressor for discarded animals, as a proxy for survival that can be used to prioritize candidate species for more in-depth discard survival studies. The time required to induce mortality (TM) in air-exposed fish was estimated for ten discarded species under commercial fishing conditions for two artisanal French otter trawlers in the Bay of Biscay and in the English Channel. European seabass, plaice, sole and skates had extended TM values on average, suggesting that these species are good candidates. The three species observed in both regions (plaice, sole and skates) had larger TM values in the English Channel experiment compared to the Bay of Biscay experiment. Among the four measured external conditions that could influence TM (air temperature, fish length, tow depth and tow duration), the air temperature was the most important and the factor that most distinguished the two experiments. [ABSTRACT FROM AUTHOR]

Octopus are caught incidentally in several US federally-managed trawl, longline, and pot fisheries in Alaska. The majority caught are giant Pacific octopus Enteroctopus dofleini . Recent changes in fisheries management in Alaska have resulted in the creation of an octopus species complex with annual catch limits, leading to increased interest in management and catch accounting for this data-poor assemblage. This study characterized the incidental octopus catch in Alaska groundfish fisheries and the mortality rate of octopus caught and discarded at sea. Onboard fisheries observers collected data on octopus weight, sex, and condition at discard in a variety of Alaska groundfish fisheries from 2006 to 2011. A field study aboard a commercial pot-fishing vessel examined delayed mortality resulting from the capture process in giant Pacific octopus during routine pot fishing. Octopus incidental catch varied widely in size and condition at capture for various fishing gear types. Vessels fishing using pot gear captured larger octopus than vessels using longline or trawl gear. Initial condition at capture was best in pot gear, with over 90% of octopus discarded from pot vessels alive in excellent condition. Octopus taken in trawl gear had the highest immediate mortality rate, with 68–94% dead or injured at discard. Giant Pacific octopus held for 24–60 h following pot capture showed no signs of delayed mortality or decline in condition. These results suggest that assuming 100% mortality of discarded octopus may overestimate fishing impacts. [ABSTRACT FROM AUTHOR]

Estimates of post-release mortality (PRM) rates for discarded bycatch are largely unknown across marine fisheries and represent a substantial source of uncertainty when estimating total fishery mortality. One way to predict PRM is through the use of reflex action mortality predictors (RAMP), whereby the presence or absence of target reflexes and known post-release fate are used to create a delayed mortality model. We employed reflex impairment assessments in concert with post-capture caging and video monitoring to predict 5-d PRM rates for the deepsea giant isopod Bathynomus giganteus, a common bycatch species in numerous deepwater fisheries worldwide, and also considered the factors contributing to mortality. Mortality rates 5 d post-capture ranged from 50 to 100% and both RAMP scores and time at the surface were significant predictors of mortality, although our conclusions regarding the effect of surface time are limited. In-cage video documented little movement within the 24-h monitoring period following capture, and it appeared that surviving individuals often fed within the holding period after cage deployment. Our results suggest that PRM in B. giganteus is common and that this unaccounted source of mortality should be quantified for other deep-sea crustaceans captured as bycatch. [ABSTRACT FROM AUTHOR]

In recent years, the recreational contribution to the total catch of Atlantic cod (Gadus morhua) in the Gulf of Maine (GOM) has increased with recreational discards outnumbering recreational landings by 2:1.However, the discard mortality (DM) rate of cod released in the recreational fishery remains poorly understood, thus contributing to the uncertainty in stock assessments and fishery management plans. The current study examined the capture-related factors most detrimental to codDMin theGOMrecreational rod-and-reel fishery. Atlantic cod (n = 640; 26.0-72.0 cm) were angled from June-October 2013 on southern Jeffreys Ledge in thewesternGOMusing fishing gear representative of the local recreational fishery.A subset (n = 136)was also taggedwith pressure-sensing acoustic transmitters before being releasedinto anacoustic receiver array (n = 31)deployedto monitor survivalupto94days. Toproperly model DMupto the fishery-wide level, all codwere visually assessedforcapture-relatedinjuries accordingto a four-level injury score index. Mean tackle-specific DM rates of 15.4 and 21.2% were estimated for bait- and jig-captured cod, respectively, with an overall 16.5% mean DM rate for the 2013 GOM recreational cod fishery. Twenty-nine cod tagged with acoustic transmitters were identified as dead, where the majority (90%) died within 16 h post-capture. Upon evaluation with a specifically adapted parametric survival analysis, greater incidence of mortality was attributed to the capture and handling process (rather than release) for moderately and severely injured cod. Based on the capture-related factors associated with the highest injury rates, we recommend minimizing fight and handling times, avoiding areas with small cod, educating inexperienced anglers, and favouring bait over jigs to mitigate mortality. Results will continue to inform the development of fishery management plans and enhance survival through dissemination of "best practice" techniques to fishery stakeholders. [ABSTRACT FROM AUTHOR]

Under the "high survival" exemption of the European landing obligation or discard ban, monitoring vitality and survival of European flatfish becomes relevant to a discard-intensive beam trawl fishery. The reflex action mortality predictor (RAMP) method may be useful in this context. It involves scoring for the presence or absence of natural animal reflexes to generate an impairment score which is then correlated with post-release or discard mortality. In our first experiment, we determined suitable candidate reflexes for acclimated, laboratory-held European plaice (Pleuronectes platessa) and common sole (Solea solea). In a second experiment, we quantified reflex impairment of commercially trawled-and-handled plaice and sole in response to commercial fishing stressors. In a third experiment, we tested whether a combined reflex impairment and injury (vitality) score of plaice was correlated with delayed post-release mortality to establish RAMP. Five-hundred fourteen trawled-and-discarded plaice and 176 sole were assessed for experimentally confirmed reflexes such as righting, evasion, stabilise, and tail grab, among others. Of these fish, 316 plaice were monitored for at least 14 d in captivity, alongside 60 control plaice. All control fish survived, together with an average of 50% (± 29 SD) plaice after being trawled from conventional, 60 min trawls and sorted on-board a coastal beam trawler. Stressors such as trawl duration, wave height, air, and seawater temperature were not as relevant as a vitality score and total length in predicting post-release survival probability. In the second experiment where survival was not assessed, reflex impairment of plaice became more frequent with prolonged air exposure. For sole, a researcher handling-and-reflex scoring bias rather than a fishing stressor may have confounded results. Scoring a larger number of individuals for injuries and reflexes from a representative selection of trawls and trips may allow for a fleet-scale discard survival estimate to facilitate implementation of the discard ban. [ABSTRACT FROM AUTHOR]

Conservation concerns and new management policies such as the implementation of ecosystem-based approaches to fisheries management are motivating an increasing need for estimates of mortality associated with commercial fishery discards and released fish from recreational fisheries. Traditional containment studies and emerging techniques using electronic tags on fish released to the wild are producing longitudinal mortality-time data from which discard or release mortalities can be estimated, but where there may also be a need to account analytically for other sources of mortality. In this study, we present theoretical and empirical arguments for a parametric mixture-distribution model for discard mortality data. We show, analytically and using case studies for Atlantic cod (Gadus morhua), American plaice (Hippoglossoides platessoides), and winter skate (Leucoraja ocellata), how this model can easily be generalized to incorporate different characteristics of discard mortality data such as distinct capture, post-release and natural mortalities, and delayed mortality onset. In simulations over a range of conditions, the model provided reliable parameter estimates for cases involving both discard and natural mortality. These results support this modelling approach, indicating that it is well suited for data from studies in which fish are released to their natural environment. The model was found to be less reliable in simulations when there was a delay in discard mortality onset, though such an effect appears only in a minority of existing discard mortality studies. Overall, the model provides a flexible framework in which to analyse discard mortality data and to produce reliable scientific advice on discard mortality rates and possibilities for mitigation. [ABSTRACT FROM AUTHOR]

Fish and invertebrates that are unintentionally captured during commercial fishing operations and then released back into the ocean suffer mortality at unknown rates, introducing uncertainty into the fishery management process. Attempts have been made to quantify discard mortality rates using reflex action mortality predictors or RAMP which use the presence or absence of a suite of reflexes to predict discard mortality. This method was applied to snow crab, Chionoecetes opilio, during the 2010-2012 fisheries in the Bering Sea. Discard mortality in the fishery is currently assumed to be 50% in stock assessment models, but that rate is not based on empirical data and is widely recognized to be in need of refinement. Over 19 000 crab were evaluated using the RAMP method. The estimated discard mortality rate was 4.5% (s.d. = 0.812), significantly below the rate used in stock assessment models. Predicted discard mortality rates from the 2010 to 2012 study were strongly correlated with the air temperature at the St Paul Island airport in the Pribilof Islands. Using this relationship, the discard mortality rate from 1991 to 2011 was estimated at 4.8% (s.d. = 1.08). [ABSTRACT FROM AUTHOR]

The spiny lobster fishery in Florida uses live, sublegal-size lobsters as bait in the approximately 450,000 traps currently permitted in the fishery. Live baits increase the catch of traps, yet confinement in traps compromises lobster health and causes mortality. We conducted a field experiment to test the suitability of traps fitted with escape gaps to address a priority need for reducing catch and mortality of sublegal-size lobsters and other species in Florida's spiny lobster trap fishery. We then modeled the potential effect of escape gaps on the Florida commercial spiny lobster trap fishery (via a Monte Carlo simulation technique) to identify the effect on fishery harvest. We measured catch rates and mortality of lobsters in traps with or without a 54 mm escape gap and baited with either a live sublegal-size lobster, a live legal-size lobster, or left unbaited. The relationship between catch in traps fitted with escape gaps vs. catch in control traps determined from the field experiment was applied to commercial fishery landings data from 2010 to 2018 and used to model changes in harvest as result of implementing escape gaps and baiting with a legal-size lobster. We found that traps with escape gaps nearly eliminated catch of sublegal-size lobsters in traps, which would lower mortality caused by such confinement and potentially allow hundreds of thousands of lobsters to remain in the population. Alternatively, replacing live bait lobsters every two weeks reduced bait mortality by half in our field experiment; thus, mortality of sublegal-size lobsters used as bait in the fishery could be reduced through frequent release of bait lobsters. Escape gaps also reduced fish bycatch, including some in the snapper-grouper management complex. Traps with escape gaps and baited with legal-size lobsters caught ~27% ± 16% fewer legal-size lobsters than control lobster traps baited with a sublegal-size lobster. However, these traps caught as many legal-size lobsters as control lobster traps baited with sublegal-size lobsters when lobster abundance was high, demonstrating that self-baiting of traps is density dependent. Although traps with escape gaps caught fewer legal-size lobsters per trap, fishery modeling indicated that increased survival of sublegal-size lobsters could increase landings by the second to fourth year after implementation of escape gaps, depending on which model assumptions are used to predict landings. • Escape gaps reduced sublegal-size lobster mortality rates by 87%. • Escape gap use could release hundreds of thousands of lobsters back to the wild. • Use of escape gaps is expected to increase annual lobster harvest after 2–4 years. • Escape-gap traps with a legal-size lobster caught 27% less than control traps. • Under high lobster abundance escape-gap trap catch equaled that of control traps. [ABSTRACT FROM AUTHOR]

Highlights: [•] Postrecompression survival of two physoclists from deep capture depth was studied. [•] At capture, the external signs of severe barotrauma were similar for both species. [•] Survival (48h) of the two rockfishes diverged sharply as capture depth increased. [•] Yelloweye rockfish survival remained high while canary rockfish dropped to 25%. [Copyright &y& Elsevier]

A new technique to ameliorate the effects of barotrauma was tested based on observations of pink snapper, Pagrus auratus (Forster), inadvertently piercing their everted stomach with their teeth and releasing trapped swim bladder gases. This technique was termed buccal venting and involved piercing the everted stomach protruding into the buccal cavity or out of the mouth with a 16-gauge hypodermic needle (a practice previously not encouraged). Short-term (~3 days) survival of buccal-vented fish was not significantly different from laterally vented fish nor untreated controls. Both buccal and lateral venting techniques were shown to cause no harm and allowed fish to return to depth. The short-term (1-3 days) post-release survival of line caught snapper was 88% with no significant difference in survival across three depth ranges tested (37-50, 51-100 and 101-180 m). Survival of sublegal pink snapper (<35 cm TL) was not significantly different (P > 0.05) from that of legal-sized fish (≥35 cm TL). Healing of the swim bladder was observed in 27% of pink snapper dissected after ≤3 days in captivity, and healing of stomachs was observed in 64% of pink snapper that had been buccal vented. Relatively high post-release survival rates of line caught pink snapper may offer some protection for snapper stocks where high fishing pressure and legal size restrictions result in the majority of the catch having to be released. [ABSTRACT FROM AUTHOR]

Highlights: [•] Low survival for sole and plaice, high for cod and skates in beam trawl discards. [•] Benthic invertebrates largely survive discarding in beam trawl fishery. [•] Injuries predict survival of invertebrates, skates and plaice, not of sole and cod. [•] Model predictions indicate species-specific duration of survival experiments. [•] Small fish specimens have low chances of surviving discarding. [ABSTRACT FROM AUTHOR]

We developed a simulation framework to explore the combined effects of harvest slot regulations, reductions in recreational discard mortality rate, and alternate bycatch accountability approaches on fishery management performance measures representing a broad range of stakeholder interests in a multi-sector marine fishery. Simulation results indicated reductions in recreational discard mortality rate, alone or combined with harvest slot regulations, may result in longer recreational fishing seasons, increased recreational catch rates, reduced dead discarded biomass, and an increase in the population of reproductively valuable older fish. Based on application to Gulf of Mexico red snapper (Lutjanus campechanus), we demonstrate the trade-offs among competing management objectives and illustrate how reduced recreational discard mortality rates and allocation of catch quotas between recreational and commercial sectors based on total dead biomass versus landed catch alone can influence the efficacy of regulatory actions. We suggest increased use of simulation analyses is warranted to aid fisheries management decision making and can spur development of performance measures that better communicate trade-offs among the diverse objectives of stakeholders in multi-sector marine fisheries. [ABSTRACT FROM AUTHOR]

Highlights: [•] Gags Mycteroperca microlepis released in a recreational fishery were observed. [•] Release conditions were related to subsequent mark-recapture rates. [•] It was necessary to control for variable reporting and recapture rates. [•] Relative survival was reduced for gags released in fair and poor condition. [•] Overall estimated discard mortality was low in shallow water and increased with depth [ABSTRACT FROM AUTHOR]

Highlights: [•] Owing to quota breaches, adult plaice and sole are sometimes discarded by beam trawlers in the English Channel. [•] Un-partitioned discard mortality was estimated at between ∼20 and 63% for plaice and 24 and 47% for sole. [•] Spawning plaice and small fish of both species suffered the greatest fatalities. [•] Mitigation strategies are warranted. [ABSTRACT FROM AUTHOR]

Abstract: Identification of variables that can be used to predict discard mortality is an important step towards improving estimates of total fishery removals. I explored the utility of capture depth, six external signs of barotrauma, two behavioral responses, and an impairment index that summed the physical and behavioral impairment associated with rapid decompression at predicting the submergence success of hook-and-line captured yelloweye (n =95) and quillback (n =65) rockfish that were released at the water''s surface. Random forests classification models were used to identify the relative importance of predictor variables (n =11) for each species and to explore the ability of these variables to accurately predict individual submergence success. Capture depth was identified as the most important variable in predicting yelloweye rockfish submergence but provided little improvement to the quillback rockfish model. The impairment index and the barotrauma sign associated with maximal gas retention were identified as important predictor variables for both yelloweye and quillback rockfish. These findings suggest that the impairment index, unlike capture depth, was able to account for individual variability in submergence success or failure of quillback rockfish. [Copyright &y& Elsevier]

Abstract: Obtaining a representative estimate of discard mortality for population and ecosystem assessments is very challenging. This can only rarely be done directly by recovering tagged discarded individuals. Instead, semi-quantitative measures of individual fish vitality or physical condition, obtained by onboard observers prior to discarding, can be used. Such vitality measures can be a good indicator of discard mortality, and by virtue of the data collection method, should also reflect the condition of discards throughout the fishery. Furthermore, vitality can be predicted using covariates known to affect discard mortality, allowing for a more general assessment. We argue that a representative mortality rate can be estimated using the product of at least two probabilities: that of belonging to a particular vitality class, conditional on the factors experienced during capture and catch handling; and the probability of surviving the event, conditional on pre-release vitality. Here we estimate mortalities for five fish taxa captured in southern Gulf of St. Lawrence fisheries. The conditional survival probabilities were obtained using survival analysis of data from experiments in which fish were captured using commercial fishing methods and held to assess short-term mortality (2–3 days). The analysis included a mixture model with a fraction of unaffected individuals, which appears appropriate for data from bycatch mortality studies. Based on this study and the mechanistic interpretation of the mixture model, short-term monitoring of discard mortality may be sufficient to characterize longer term impacts in a number of taxa. [Copyright &y& Elsevier]

Abstract: Fish bycatch discard mortality is one of the most significant issues influencing marine fisheries management worldwide. Discard mortality studies to date rely on potentially biased on-deck evaluation of immediate mortality or reflex impairment, and evaluation of delayed mortality through holding captured fish for varying lengths of time to determine survival. Telemetry of ultrasonically tagged fish provides a technique for evaluating fish bycatch discard mortality, and especially latent mortality, under natural conditions in the sea. For summer flounder (Paralichthys dentatus), along the eastern United States, an 80% discard mortality is assumed but not verified. To determine the mortality of discarded fish, both live (n =41; excellent condition=4, good condition=16, poor condition=21) and dead (n =16) summer flounder from commercial fishery-length tows were tagged and released in a fixed hydrophone array (mean depth of 8.8m) on 15 September 2009 off Brigantine, NJ. We were able to re-detect both live and dead fish within the array and during mobile tracking for approximately 24h before a storm. Fish of poor initial health and known dead fish were redetected after the storm in a concentrated area inshore of the release site and were presumed dead. Live fish exited the array offshore, as is typical in the fall migration. The final discard mortality estimate, combining on-deck mortality (32.7%) and latent mortality (49.0%), was 81.7% similar to current estimates. Latent mortality contributed at least as much to total discard mortality as on-deck mortality, confirming assumptions of earlier assessments. Several new telemetry metrics can lead to a better understanding of these important latent effects. [Copyright &y& Elsevier]

Abstract: The conundrum probed here is the seeming divergence in outcomes of the management program presently in place in the Mid-Atlantic Bight for summer flounder; namely that increasing restrictions on catch to limit quota exceedances and maintain satisfaction in the fishing experience for the angler may not be simultaneously achievable. The corollary quandary is the loss of the bag limit as an operative management tool, as efforts to restrain landings became increasingly burdensome, thereby placing inordinate reliance on the size limit (and season). To investigate options that might promote increased angler gratification and reduce discard mortality without eliciting quota exceedances, we examine a number of alternative management strategies that might (a) bring bag limits back into the manager''s repertoire, (b) trade discards for landings, thereby increasing angler gratification, and (c) provide an increased number of fish per unit of landings weight, thereby realizing for the angler a greater number of kept fish. Options investigated include standard bag-and-size limits, boat limits, dual-size limits implemented with both a minimum and maximum size, slot limits, and a cumulative-size limit in which landings are restrained by a total number of inches of landed fish. Comparing all fishery options reveals that dual-size, slot, and cumulative-size limits provide the best resolution to the posed conundrum. Dual-size and slot limits improve landings relative to fishing mortality, but the cumulative-size limit outperforms both by a substantial degree. The options in part permit increased landings relative to discards and this moves discard mortality to landings, a useful outcome. However, the probability of mortality due to discard is low in summer flounder and, thus, relatively little gain occurs in simply minimizing discards. Rather, successful management options are those that permit effort to be transferred from larger fish to smaller fish, thus reducing total weight landed relative to total number. The cumulative-size limit is the most successful approach in accomplishing this feat. [Copyright &y& Elsevier]

The article presents the study on the comparison of blue shark (Prionace glauca) mortality estimates in the Atlantic and Pacific oceans. It states that the bycatch mortality in the Pacific is higher than reported by Moyes and colleagues in 2006 and Musyl and colleagues in 2009. It says that the report by Moyes and colleagues on zero hooking mortality of the sharks was possibly due to at least in part to a fishing strategy that enhanced the survival and did not showed the Hawaiian or Pacific commercial fisheries. Other types of blue shark mortalities being compared from the studies include finning, handling and tagging mortality, and post-release mortality. Moreover, the study suggests that the study design of Moyes and colleagues reduces its considerable scientific value.

Broadhurst, M. K., Millar, R. B., and Uhlmann, S. S. 2009. Using a double codend to reduce discard mortality. – ICES Journal of Marine Science, 66: 2077–2081.Traditional technical strategies for mitigating collateral fishing mortality have involved improving gear selectivity (to reduce bycatch) and, more recently, concomitant changes to onboard handling procedures to reduce some of the negative impacts to the remaining discards. A less common approach is to modify gears physically to minimize deleterious catching mechanisms and subsequent mortalities during fishing. This study aimed to investigate the utility of the latter category of modifications for penaeid trawls by separating a codend into two compartments (termed a double codend) to alleviate interactions between catches. Compared with a conventional design, the double codend significantly reduced the immediate (from 17.1 to 13.8%) and short-term (22.5 to 17.1%) mortalities of discarded juvenile school prawns (Metapenaeus macleayi). The effectiveness of the double codend remained independent of other factors known to affect the fate of discarded juvenile M. macleayi, including cloud cover and, owing to minimal variability, the weight of the total catch. However, irrespective of the codend configuration, overall mortalities were also positively correlated with the quantity of jellyfish. We conclude that when combined with modifications to improve selectivity and appropriate onboard handling strategies, compartmentalizing codend catches could cumulatively reduce unaccounted fishing mortality. [ABSTRACT FROM PUBLISHER]

Abstract: This paper discusses the potential for implementing individual transferable quota (ITQ) schemes in commercial recreational fisheries, focusing particularly on charter and headboat fisheries. After a brief discussion of ITQs in commercial fisheries, the paper discusses the manner in which rents get dissipated in commercial recreational fisheries. Fishing mortality in recreational fisheries is determined as a joint outcome of angler behavior and trip supply. In the recreational sector under open access conditions, there are likely to be too many vessels providing too many trips at prices that are too low. Vessel input configurations are likely to be distorted in a manner that generates excessive fishing mortality. Designing ITQs for recreational fisheries requires consideration of issues not prominent in the design of commercial fisheries. Among the most important is the manner in which angler preferences and types affect overall mortality from both landings and discards. While catch and release fisheries and pure food fish recreational fisheries are relatively easy to manage with recreational ITQs, fisheries with both angler types present difficult monitoring problems that add complexities to ITQ design. Various ways to design programs that account for both landings and discard mortalities and that generate incentives for anglers and vessel owners to reduce discard mortality are discussed. [Copyright &y& Elsevier]

The article focuses on the bycatch mortality rate of blue sharks Prionace glauca. It notes that bycatch of non-commercial, unretained species can result to their injury or death. It cites a study wherein it reported that more than one million tons of fish were discarded yearly in U.S. waters alone. It conducts a study using archival satellite pop-up tags and found out that overall blue shark bycatch mortality was estimated at 35%. Moreover, it also mentions that bycatch mortality is classified into capture mortality and post-release mortality.

Uhlmann, S. S., Broadhurst, M. K., Paterson, B. D., Mayer, D. G., Butcher, P., and Brand, C. P. 2009. Mortality and blood loss by blue swimmer crabs (Portunus pelagicus) after simulated capture and discarding from gillnets. – ICES Journal of Marine Science, 66: 455–461.Two laboratory experiments were carried out to quantify the mortality and physiological responses of juvenile blue swimmer crabs (Portunus pelagicus) after simulated gillnet entanglement, air exposure, disentanglement, and discarding. In both experiments, all but control blue swimmer crabs were entangled in 1-m2 gillnet panels for 1 h, exposed to air for 2 min, subjected to various treatments of disentanglement ranging between the forceful removal of none, one, two, and four appendages, then “discarded” into individual experimental tanks and monitored for 10 d. In Experiment 1, mortalities were associated with the number of appendages removed and the occurrence of unsealed wounds. In Experiment 2, live blue swimmer crabs were sampled for blood at 2 min and 6, 24, and 72 h post-discarding to test for the effects of disentanglement and appendage removal on total haemocyte counts, clotting times, protein levels (by refractive index), and blood ion concentrations. Compared with blue swimmer crabs that had sealed or no wounds, those with unsealed wounds had lower total haemocyte counts, protein, and calcium concentrations and increased clotting times and magnesium and sodium levels. Induced autotomy, as opposed to the arbitrary, forceful removal of appendages has the potential to minimize the mortality and stress of discarded, juvenile blue swimmer crabs. [ABSTRACT FROM PUBLISHER]

Simple Summary: Due to the implementation of a landing obligation in fisheries in the European Union (EU), with an exemption for species with "high survival", discard survival studies (henceforth DSSs) have become one of the most politically prioritized fisheries research areas in European fisheries. In contrast to most fisheries science research areas, DSSs are embedded by the EUs animal research welfare directive. This is a challenge, and there has not been any focus on how to implement animal welfare (AW) regulations experimentally in DSSs. This paper focuses on AW regulations in relation to conducting DSSs, but the outreach is much broader. We investigate experimental procedures by bringing in relevant examples, using the output results, and relating this information to relevant AW guidelines and regulations by focusing on implementing 3R principles. Globally, it is estimated that around 10% of the fish that are caught are discarded. This is considered to be a wasteful human marine activity since these fish are often dead or dying. To reduce the high discard rates of commercial fisheries, the European Union (E.U.) has enacted a landing obligation that includes the ability to exempt "species for which scientific evidence demonstrates high survival rates". Therefore, discard survival studies (henceforth DSSs) have become one of the most politically prioritized fisheries research areas in European fisheries. International expert groups have produced guidance reports to promote best practices and to harmonize the methodologies. Nevertheless, there has not been any focus on how to implement animal welfare (AW) regulations experimentally. Discard survival studies are "frontrunners" in fisheries science research areas that are embedded by animal research welfare requirements and are expected to be more restrictive in the future because of an increased public focus on fish welfare. This paper focuses on AW regulations in relation to conducting DSSs, but the outreach is much broader. We investigate experimental procedures by bringing in relevant examples, using output results, and relating this information to relevant AW guidelines and regulations by focusing on implementing 3R principles. [ABSTRACT FROM AUTHOR]

The paucity of data on discard mortality in the commercial blue crab fishery contributes significant uncertainty to stock assessments. The reflex action mortality predictor (RAMP) method is used to predict mortality of commercially fished species by establishing a relationship between reflex impairment and the likelihood of mortality (RAMP curve). The present study adapted the RAMP method to commercially fished blue crabs in two unique habitats in Florida, the Tampa Bay estuary and the St. Johns River. The euryhaline nature of blue crabs permits the fishery to operate in myriad habitats, which adds complexity to cumulative effects that influence discard mortality. A total of 697 crabs were assessed, and a RAMP curve was generated. Logistic regression analyses determined that reflex impairment score, injury score, and salinity are strong predictors of discard mortality, with 91% of predictions correct. For every 1-unit increase in reflex impairment and injury score, mortality was 2.71 and 1.65 times more likely, respectively. Additionally, for every 1-SD (11.35 ppt) increase in salinity, mortality was 2.17 times more likely. Crab size, sex, water temperature, and emersion time minimally influenced mortality. The present study is the first crustacean RAMP research that included water quality and demonstrated that its inclusion increases the predictability of discard mortality. The RAMP curve can be used as a tool to estimate discard mortality aboard commercial vessels and discard mortality in future stock assessments. [ABSTRACT FROM AUTHOR]

Abstract: A purpose-built, water-filled sorting tray was compared against a conventional dry tray for its utility in reducing discard mortality across a range of conditions in an Australian estuarine penaeid-trawl fishery, including the limits of typical delays in starting sorting (2 vs. 15 min). During nine days of fishing, up to 10 replicate deployments were done for each sorting method and delay. Bycatches (44 389 teleosts comprising 15 species) were assessed for their immediate mortalities, before 1346 live individuals (10 species) were released (to simulate discarding) into replicate cages and monitored for their short-term mortalities over five days. Appropriate controls were included for the most abundant economically-important species, yellowfin bream, Acanthopagrus australis. Most trawled-and-discarded teleosts followed a pattern of minimal differences in immediate mortalities between sorting methods for the short delay, but generally fewer deaths in the water tray than in the conventional tray during the longer delay. However, owing to a dominant and slightly protracted influence of the trawling process, comparable rates of deaths were observed for caged fish irrespective of their post-capture treatment. Mixed-effects logistic models applied to four key species (A. australis; silver biddy, Gerres subfasciatus; southern herring, Herklotsichthys castelnaui; and Port Jackson glassfish, Ambassis jacksoniensis) revealed that in addition to the method and delay in sorting, the weights of total catch and jellyfish, salinity and the size of fish also had significant impacts on mortality. For the longer delay in sorting in the water tray, the influences of some of the other factors were negated so that total mortalities of three of the modelled species were reduced by almost one quarter. We conclude that while unaccounted fishing mortality can be reduced via changes to onboard sorting procedures, this approach should only be applied ancillary to efficient gear selectivity. [Copyright &y& Elsevier]