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Operational interactions between odontocetes ( i.e., toothed whales) and longline gear are a global phenomenon that may threaten the conservation of odontocete populations and the economic viability of longline fisheries. This review attempts to define the issue, summarize the trends and geographical extent of its occurrence over the last half century, explore the potential impact on odontocetes and on fisheries, and describe potential acoustic and physical mitigation solutions. Reports of odontocete bycatch rates are highly variable (between 0.002 and 0.231 individuals killed per set) and at least 20 species may be involved. Information about marine mammal population size, migration patterns and life history characteristics are scarce, although at least one population may be in decline due to losses attributable to longline bycatch. Information about the financial impact of depredation on pelagic longline fisheries is also scarce, although estimates of daily fleet-wide losses range between US$1,034 and US$8,495 (overall fleet income was not reported). Such biological and financial losses may be unsustainable. Recent developments in acoustic and physical mitigation technologies have yielded mixed results. Acoustic mitigation technologies have no moving parts, although require complex electronics. To date, they are insufficiently developed and their efficacy has been difficult to assess. Physical mitigation technologies generally require complex moving parts, although they are relatively simple to develop and assess. Further development and testing remains necessary before widespread implementation would be possible. Development of these approaches should be prioritized and a 'toolbox' of various strategies and solutions should be compiled, because a single panacea to the problem is unlikely to emerge. [ABSTRACT FROM AUTHOR]

Estimating rare events from zero-heavy data (data with many zero values) is a common challenge in fisheries science and ecology. For example, loggerhead sea turtles (Caretta caretta) and leatherback sea turtles (Dermochelys coriacea) account for less than 1% of total catch in the U.S. Atlantic pelagic longline fishery. Nevertheless, the Southeast Fisheries Science Center (SEFSC) of the National Marine Fisheries Service (NMFS) is charged with assessing the effect of this fishery on these federally protected species. Annual estimates of loggerhead and leatherback bycatch in a fishery can affect fishery management and species conservation decisions. However, current estimates have wide confidence intervals, and their accuracy is unknown. We evaluate 3 estimation methods, each at 2 spatiotemporal scales, in simulations of 5 spatial scenarios representing incidental capture of sea turtles by the U.S. Atlantic pelagic longline fishery. The delta-lognormal method of estimating bycatch for calendar quarter and fishing area strata was the least biased estimation method in the spatial scenarios believed to be most realistic. This result supports the current estimation procedure used by the SEFSC. [ABSTRACT FROM AUTHOR]

The article examines the use of offset circle hooks with single baiting techniques in the U.S. pelagic longline fishery. It mentions that the catch of fishes did not differ in using such hook. It notes the decline in catch of Atlantic sailfish when using 18/0 non-offset single hooks with a mackerel bait compared to 10° offset circle hooks with threaded mackerel. It also emphasizes that single baiting also decreases target and escolar catch in yellowfin tuna sets.

The article examines the performance of non-offset and 10° offset circle hooks in commercial pelagic longline fishing (PLL) in the U.S. It mentions that the basis of their performance are catch rates, percent mortality, and the percentage of deep-hooked target and bycatch species. It emphasizes that the offset circle hook can reduce fishing efficiency compared to its non-offset type. It also notes higher mortality rate in blue marlin by using offset circle hooks than the non-offset one.

The article examines the effects of using circle hooks on seabird bycatch in the U.S. Atlantic pelagic longline fishery. It mentions the use of generalized linear models to examine such condition. It notes that the probability of catching seabirds is influenced by the combinations of hook type and size. It also emphasizes that the effectiveness of using circle hook is confounded by bait type, fishing location, and season.

The article investigates the changes in hook design and bait type on the catch rates in pelagic longlines of the western North Atlantic Ocean. It mentions the reduction of sea turtle bycatch by using circle hooks and mackerel bait. It notes the decline in swordfish catch and increase in the catch rate of blue shark by using 18/0 circle hooks with squid bait. It also emphasizes that mackerel bait decreases the catch of bigeye and albacore tuna and increase the catch of porbeagle.

The article discusses the views of the authors on the effect of the morphological elements on circle hooks on their performance in pelagic longline fisheries. They stress the need to test the aspects of tool's design that can affect its function and utility. They emphasize that several designs of the tool should be presented to fishermen when a commercial longline fleet considers to adopt it. They also assert that one should not depend solely on using such equipment to solve the bycatch issues.

The article examines the impact of the rapid switch from J-hooks to circle hooks on pelagic fish hooking survival rates in the U.S. longline fishery. It mentions the use of a repeated measures logistic regression approach to test the hypothesis of no change in the survival of the fish. It notes the variation in hooking survival by fishing zone for white marlin and albacore. It also emphasizes the potential of using circle hooks to increase hooking survival.

The article evaluates the effect of circle hooks and mackerel bait on pelagic longline catches and bycatch at the Grand Banks of the North Atlantic Ocean during 2002 to 2003. It mentions the importance of the hook in predicting anatomical hooking location. It notes that the odds of observing a dead fish boatside can be determined by soak time and hook. It also emphasizes that baiting with squid than mackerel, increases the odd of hooking swordfish and decreases the odd of hooking sharks.

The article evaluates the effect of hook type on the catch and length composition of target and non-target species in the pelagic longline fishery in Uruguay. It mentions the use of different hook types for both American- and Spanish-style longlines. It notes the high catch of albacore tuna, Thunnus alalunga, using circle hooks with both longlines. It also emphasizes the decline in the catch of pelagic stingray, Pteroplatytrygon violacea, in both longlines.

The article examines the effects of using 16/0 circle hooks on catch rates in albacore longline fisheries in the South Pacific Ocean. It mentions the use of a mix of hook sizes by the majority of longline vessels. It notes the absence of significant difference in catch by hook type and size in target species. It also emphasizes that catch rates are nominally lower for all fisheries using 16/0 hooks.

The article discusses the effect of using circle hooks on shark catchability and at-vessel mortality rates in longlines fisheries. It mentions the use of random effects meta-analysis and analysis of covariance in the study. It notes that using the tool on pelagic longlines did not affect the catch rates, but it reduced at-vessel mortality compared to the use of J-hooks. It also emphasizes the potential of circle hook to reduce bycatch mortality of sharks in such fishery.

The article discusses the use of circle hooks in the pelagic longline fishery for tunas and swordfish. It mentions that the use of the tool in the fishery leads to greater catch rates of target species and lower catch rates of bycatch species compared to standard J-hooks. It emphasizes the compared to J-hooks, circle hooks result in lower frequencies of internal hooking and trauma in billfish. It also stresses that despite these benefits, many anglers are reluctant to adopt circle hooks.

The article examines the catch rates in Hawaii-based longline fishery of tuna and false killer whales (FKW) using circle hooks. It mentions that the use of circle hooks resulted in mortalities and serious injuries to some FKW. It notes the absence of significant catch differences for bigeye tuna using strong circle hooks. It also emphasizes that in one instance, a FKW was released from a stronger circle hook.

Abstract: The risk of seabird–fishery interactions in the Western and Central Pacific Ocean (WCPO) was examined by analysing the overlap of seabird distributions with tuna and swordfish pelagic longline fisheries managed by the Western and Central Pacific Fisheries Commission (WCPFC) and its constituent members. The study used spatially-explicit Productivity–Susceptibility Analysis (PSA). Key data inputs were species productivity, fishing effort, likelihood of capture and species density by region. The outputs tailored results to the needs of fisheries- and wildlife-managers, indicating areas of greatest risk of species interactions, species of greatest concern for population impacts, and the flags or fisheries most likely to contribute to the risk. Large albatross species were found to be most likely to suffer population effects when exposed to longline fishing activity, followed by the larger petrels from the genuses Procellaria, Macronectes and Pterodroma. A mixture of coastal states with nesting seabird populations in their Exclusive Economic Zones (New Zealand, Australia and United States of America), distant water fishing nations (Japan, Taiwan) and flags of convenience (Vanuatu) contributed 90% of the risk to seabird populations. Recommendations include enhancing the level of fisheries observer monitoring in areas indicated as high to medium risk for seabird interactions, and consideration of spatial management tools, such as more intensive or more stringent seabird bycatch mitigation requirements in high- to medium-risk areas. The methods used, and similar studies conducted in the Atlantic Ocean could lead to improved targeting of monitoring resources, and greater specificity in the needs for seabird-mitigation measures. This will assist in reducing seabird mortality in longline fishing operations and with more effective use of resources for fishery managers in both domestic fisheries and RFMOs. [Copyright &y& Elsevier]

Abstract: For many shark species, little information exists about the stress response to capture and release in commercial longline fisheries. Recent studies have used hematological profiling to assess the secondary stress response, but little is known about how, and to what degree, these indicators vary interspecifically. Moreover, there is little understanding of the extent to which the level of relative swimming activity (e.g., sluggish vs. active) or the general ecological classification (e.g., coastal vs. pelagic) correlates to the magnitude of the exercise-induced (capture-related) stress response. This study compared plasma electrolytes (Na+, Cl−, Mg2+, Ca2+, and K+), metabolites (glucose and lactate), blood hematocrit, and heat shock protein (Hsp70) levels between 11 species of longline-captured sharks (n =164). Statistical comparison of hematological parameters revealed species-specific differences in response to longline capture, as well as differences by ecological classification. Taken together, the blood properties of longline-captured sharks appear to be useful indicators of interspecific variation in the secondary stress response to capture, and may prove useful in the future for predicting survivorship of longline-captured sharks where new technologies (i.e., pop-up satellite tags) can verify post-release mortality. [Copyright &y& Elsevier]

Abstract: Blood gasses of wild bonnethead, bull, and lemon sharks were measured with the i-STAT clinical analyzer with the CG4+ cartridge immediately after capture; and again immediately prior to release after tagging, handling and morphometric measurements were taken. Relative reference ranges of post-capture status were established. Among species, stress response to capture was similar for all parameters; however, pH declined and lactate concentrations rose over time, indicating continued insult from capture and/or response to additional handling stress. pCO2 rose faster for S. tiburo than for C. leucas, and lactate concentrations rose faster for S. tiburo than for N. brevirostris. All species caught in gillnets experienced lower pH and higher lactate concentrations than on longlines. Discriminant analysis justified the use of blood gas analysis to assess physiological stress induced by different capture methods. From these results, we recommend 1) that gear be monitored closely and sharks be removed immediately, or suboptimally, that gear is deployed for the shortest soak time possible; 2) longline over gillnet gear; and 3) extra caution with sensitive species (e.g., S. tiburo), which may include the administration of blood buffers and other therapeutics if a shark is beyond the limits of relative reference ranges reported here. [Copyright &y& Elsevier]

Abstract: Longline fishing is the most common elasmobranch capture method around the world, yet the physiological consequences of this technique are poorly understood. To quantify the sub-lethal effects of longline capture in the commonly exploited Caribbean reef shark (Carcharhinus perezi), 37 individuals were captured using standard, mid-water longlines. Hook timers provided hooking duration to the nearest minute. Once sharks were landed, blood samples were taken and used to measure a suite of physiological parameters. Control data were obtained by sampling an additional three unrestrained Caribbean reef sharks underwater at an established shark feeding site. The greatest level of physiological disruption occurred after 120–180min of hooking, whereas sharks exposed to minimal and maximal hook durations exhibited the least disturbed blood chemistry. Significant relationships were established between hooking duration and blood pH, pCO2, lactate, glucose, plasma calcium and plasma potassium. Longline capture appears more benign than other methods assessed to date, causing a shift in the stress response from acute at the onset of capture to a sub-acute regime as the capture event progresses, apparently facilitating a degree of physiological recovery. Continued investigation into the physiological response of elasmobranchs to longline capture is vital for the effective management of such fisheries. [Copyright &y& Elsevier]

This study addresses the growth dynamics of three size groups of juveniles graded from the same wild cohort of the Mediterranean blue mussel Mytilus galloprovincialis. Each size group was replicated and cultured independently from the others in culture bags suspended from a specific longline system devised for this task. The small size group of mussels showed an unexpected higher growth rate SGR (0.95 ± 0.07) than the intermediate size group (0.41 ± 0.08) or the large size group (0.32 ± 0.10) from the beginning of the experiment. Nevertheless, all three size groups grew more slowly with time and the initially large size group was conspicuously and significantly larger than the rest of size groups at the end of the experiment. Early selection of fast growers by grading on shell length is a straightforward approach to accelerate the fattening period. Speeding up harvest can be a natural tool to skip upwelling episodic blooms of toxic microalgae or to improve the final stock performance of cultured blue mussels. [ABSTRACT FROM PUBLISHER]

Abstract: We describe the results of a detailed monitoring program undertaken to understand the fishing practices and operational characteristics of longline gears deployed in the Australian Eastern Tuna and Billfish Fishery. Gear monitors were used to ascertain both the time-at-depth-profiles of the deployed longline hooks and the time- and depth-profiles of fish capture. Operational details and environmental conditions recorded by observers were also used to gain an understanding of factors influencing the depths attained by hooks and the shape of the longline. The results indicate that while hooks fish a range of depths down to around 400m the most common depths fished are relatively shallow, with 34 percent of all hooks deployed during the project period being between 40 and 60m. The depths to which hooks were observed to sink were found to be highly variable for a given longline configuration and hook-number, though the mean depths attained across sets were found to be reasonably well predicted by the longline catenary equation. Current-speed, hook-position and wind-speed were found to be the main factors influencing variation from the predicted depth. While the depth profiles fished by sets deploying less than 10 hooks-per-float were found to be similar, for sets deploying 10 or more hooks-per-float a near linear relationship was found in the mean depth fished by all hooks and the number of hooks-per-float. Finally, a procedure is outlined to estimate the availability-by-depth of the species caught and the resulting profiles were found to be similar to profiles obtained from studies using archival tags. The results of this study support the need to improve the information used to account for factors influencing the fishing effectiveness of longline gears and the use of set-based analyses to standardise catch rates. [Copyright &y& Elsevier]

Sablefish (Anoplopoma fimbria) are often caught incidentally in longline fisheries and discarded, but the extent of mortality after release is unknown, which creates uncertainty for estimates of total mortality. We analyzed data from 10,427 fish that were tagged in research surveys and recovered in surveys and commercial fisheries up to 19 years later and found a decrease in recapture rates for fish originally captured at shallower depths (210- 319 m) during the study, sustaining severe hooking injuries, and sustaining amphipod predation injuries. The overall estimated discard mortality rate was 11.71%. This estimate is based on an assumed survival rate of 96.5% for fish with minor hooking injuries and the observed recapture rates for sablefish at each level of severity of hook injury. This estimate may be lower than what actually occurs in commercial fisheries because fish are likely not handled as carefully as those in our study. Comparing our results with data on the relative occurrence of the severity of hooking injuries in longline fisheries may lead to more accurate accounting of total mortality attributable to fishing and to improved management of this species. [ABSTRACT FROM AUTHOR]

Abstract: The stress associated with commercial and recreational fishing of saithe (Pollachius virens Linnaeus) was investigated on fish caught with a rod and reel at the pier<10s or 4–5min at 100m depth and after 6–12h of soaking on a longline or chased to exhaustion for 15min. Results show that hooking caused an acute stress reaction accompanied by accumulating blood lactate and pCO2 levels accompanied by the acidification of the muscle. After 6–12h of soaking, the longlined had a significant increase in blood glucose levels, Na+, K+, hemoglobin content and hematocrit values. During soaking the longlined fish had restored their acid–base balance, having significant higher blood pH and HCO3 − levels, reflecting hyperventilation. Only one case of hypoxia was observed. None of the 767 investigated fish that was hauled onboard had died during soaking. We conclude that angling causes a long and short term stress effect on P. virens, but survival is related to animal capability to restore acid–base balance during soaking. [Copyright &y& Elsevier]

Summary Weight-length relationships were estimated for 27 demersal fish species of the Cape Verde archipelago. Samples were collected in October and November 2000 using longline gear in depths up to 600 m, and occasionally to 1200 m. The b values were within expected ranges, varying between 2.406 and 3.761, except for Syacium micrurum (1.574) and Paraconger notialis (4.476), which presented strong allometries instigated through further analysis. This work revises previous literature in the archipelago and provides the first reference on weight-length parameters for 10 fish species worldwide and for 21 species of the Cape Verde archipelago. [ABSTRACT FROM AUTHOR]

Field experiments were conducted to test the hypotheses that Pacific halibut (Hippoglossus stenolepis) display small-scale spatial structure within longline catches, relative to other species and empty hooks, or within-species based on sex or length. Sequential hook-by-hook inventories, along with length and sex data, were taken at thirty-one survey stations. Two-dimensional spatial statistics were used to test for 1) aggregation, defined as the clustering of individuals within a given demographic of size or sex over small intervals of distance; and 2) segregation, defined as the sequential occurrence of individuals within a given demographic of size or sex, uninterrupted by other observations, irrespective of the distance between individuals. Statistically significant structure was detected within catches that is more commonly associated with fish length than sex. Significant spatial structuring occurred at 60% of all stations tested. Significant aggregation of halibut of legal length for commercial retention (≥82 cm) was detected at 44% of stations and aggregation of sublegal-size halibut was detected at 11%. Male- and female-based aggregations were observed at 22% and 11% of stations, respectively. Significant segregation of females was observed at 20% of stations, male segregation occurred at 8% of stations, and segregation by size at 16% of stations. Understanding small-scale spatial structure within longline catches may help us interpret changes in survey and commercial catch data. If structure is generated by behavior, then observed size-at-age or relative sex-ratios may be biased relative to underlying distributions. Although physical processes such as gape limitation should remain stable over the time, dynamic processes may be spatially and temporally variable. [ABSTRACT FROM AUTHOR]

Abstract: The quality of Atlantic cod from one trawl catch and one longline catch, caught at the same time and location, was assessed and compared. In addition, the effect of ice storage in 7 days on quality parameters was investigated. No differences between the cod from the two catches were observed on microbial activity and drip loss. Trawl caught cod had decreased pH and increased TMA compared to longlined cod. Catch Damage Index showed that trawling gave increased damages compared to longlining, where trawling resulted in poor bleeding and bruises, while longlining resulted in gaffing damages. Both color and sensory analyses confirmed the poor bleeding of trawl caught cod. In addition, the longline caught cod had increased overall sensory quality and increased lightness. Water holding capacity was decreased in trawled cod compared to longlined cod together with increased protein denaturation measured by differential scanning calorimetry. Texture analysis showed increased firmness in longlined cod. Cod loins stored on ice for 7 days encountered decreased quality attributes evaluated by sensory methods, firmness, water holding capacity and lightness, while microbial growth, pH and protein denaturation of the loin increased. In this study, the catch of Atlantic cod caught by longline had a better overall quality compared to the catch of cod caught by trawl. [Copyright &y& Elsevier]

During an effort-regulated period from 1996 to 2002, unregistered annual increases of 0.3% of hooks fished per day were demonstrated for the Faroe Islands longline fishery. However, annual increases were higher (1.5%) during a preceding total allowable catch regulated period, thereby invalidating an expectation of the 1996 shift in regulations (output to input control) to have induced increases in the number of hooks set per day. Underlying this result is a substantial increase in total yearly effort (fishing days) and a shift in targeting behaviour from secondary to primary (high value) target species in response to the transition from output to input control. Interview data on technology were combined with logbook data and analysed with generalized linear modelling to demonstrate haddock () and Atlantic cod () catch-per-unit-effort increases of 51% and 26%, respectively, following the introduction of skewed hooks and swivel line. The technological introductions were not correlated to regulation shifts. So, rather than the management system in force, an ongoing technological development seems to be the principal driver of fishing power trends. The results highlight the need to explicitly address technological development and targeting behaviour when attempting to meet conservation objectives through input control of fisheries. [ABSTRACT FROM AUTHOR]

Relationships between albacore tuna ( Thunnus alalunga) longline catch per unit effort (CPUE) and environmental variables from model outputs in New Caledonia's Exclusive Economic Zone (EEZ) were examined through generalized linear models at a 1° spatial resolution and 10-day temporal resolution. At a regional (EEZ) scale, the study demonstrated that a large part of albacore CPUE variability can be explained by seasonal, interannual and spatial variation of the habitat. Results of the generalized linear models indicated that catch rates are higher than average in the northwestern part of the EEZ at the beginning of the year (January) and during the second half of the year (July-December). In the northwestern region of the EEZ, high CPUEs are associated with waters <20.5° in the intermediate layer and with moderate values of primary production. Longline CPUE also appeared to be dependent on prey densities, as predicted from a micronekton model. Albacore CPUE was highest at moderate densities of prey in the epipelagic layer during the night and for relatively low prey densities in the mesopelagic layer during the day. We also demonstrated that the highest CPUEs were recorded from 1986 to 1998, which corresponds to a period with frequent El Niño events. [ABSTRACT FROM AUTHOR]

Seabird bycatch by the longline fisheries of the Pacific Ocean is a major conservation concern. However, relatively few studies have examined the impacts of distant water longline fishing on the high seas due to the difficulty associated with deploying observers. Our study addresses this data gap by analyzing data from 2666 Taiwanese scientific observation data sets from 2002 to 2007 to calculate the seabird bycatch rate and to estimate the mortality of seabirds as a result of fishing activities by the entire fleet. A total of 379 seabirds were caught and 88% were albatross. A negative binomial distribution was used to represent the observed data based on spatial and temporal stratification, which yielded bycatch rates that ranged from 0.0003 to 0.2213 birds per 1000 hooks. The bycatch rates were highest in the areas between 25-45°N and 165°E-160°W between October and March and the areas between 25-35°S and 170°E-165°W between April and September. Using the observed data for bycatch rates and total fishing effort, the estimated number of seabird deaths caused by the Taiwanese fleet ranged from 1120 to 4290 birds annually. Increasing the observer coverage of specific fleets and areas, prioritizing observer programs and combined with international cooperation in research, would improve bycatch calculations. Seabird conservation efforts can be improved by monitoring fishing effort and the mandatory implementation of multiple mitigation measures. [ABSTRACT FROM AUTHOR]

A management simulation model was developed to test quota, trip limits and reduced longline hook numbers as alternatives to yearly seasonal (November) closure in South Australian snapper fisheries. Population dynamics equations and maximum-likelihood parameter estimates were supplied by an age- and length-based stock assessment model. The relative performance of tested management strategies was quantified by comparing change in egg production vs change in average catch, to optimise the trade-off between reproductive sustainability and catch foregone. Clusters of better-performing strategies were visually identifiable in management strategy scatterplots. These scatterplots display percentage change from the status quo in egg-production-per-female-recruit ( y-axis) vs percentage change in catch-per-recruit ( x-axis). Evaluated strategies fell into three distinct performance clusters. The best performing strategy extended November closure by 2 weeks. Strategies that retained the November closure performed uniformly better than those that removed it. Further simulation showed this resulted from non-closure strategies regulating only the commercial sector. [ABSTRACT FROM AUTHOR]

The smooth hammerhead shark Sphyrna zygaena (Sphyrnidae) is regularly caught as bycatch in pelagic longline fisheries, but is one of the least studied of all pelagic sharks. Recently, ICCAT (International Commission for the Conservation of Atlantic Tunas) issued recommendations underlining the need for more studies on the life history parameters of this and other pelagic shark species. To this end, the age and growth of S. zygaena were studied in the Eastern Equatorial Atlantic Ocean, in an area where growth parameters were not yet available for this species. Data from 139 specimens, caught between June and September 2009, ranging in size from 136 to 233 cm fork length (FL), were analysed. Preliminary trials were carried out to assess the most efficient growth band enhancement technique. These indicated that sectioning the vertebrae into 500 μm sections followed by staining with crystal violet produced the best results. Growth models were fitted using the traditional von Bertalanffy growth equation and a modification of this equation using a known size at birth. Growth models were compared using the Akaike information criterion (AIC). The von Bertalanffy growth equation seemed to be the most adequate model to describe growth in this species, with resulting growth parameters of Linf = 272 cm FL, k = 0.06 year for males and Linf = 285 cm FL, k = 0.07 year for females. In the first four years of life, S. zygaena grows 25 cm per year on average, but its growth slows down in later life. Future stock assessment models should incorporate these age and growth parameters for species management and conservation. [ABSTRACT FROM PUBLISHER]

The bigeye thresher, Alopias supercilious, is commonly caught as bycatch in pelagic longline fisheries targeting swordfish. Little information is yet available on the biology of this species, however. As part of an ongoing study, observers sent aboard fishing vessels have been collecting set of information that includes samples of vertebrae, with the aim of investigating age and growth of A. supercilious. A total of 117 specimens were sampled between September 2008 and October 2009 in the tropical northeastern Atlantic, with specimens ranging from 101 to 242 cm fork length (FL) (176 to 407 cm total length). The A. supercilious vertebrae were generally difficult to read, mainly because they were poorly calcified, which is typical of Lamniformes sharks. Preliminary trials were carried out to determine the most efficient band enhancement technique for this species, in which crystal violet section staining was found to be the best methodology. Estimated ages in this sample ranged from 2 to 22 years for females and 1 to 17 years for males. A version of the von Bertalanffy growth model (VBGF) re-parameterised to estimate L0, and a modified VBGF using a fixed L0 were fitted to the data. The Akaike information criterion (AIC) was used to compare these models. The VBGF produced the best results, with the following parameters: Linf = 293 cm FL, k = 0.06 y–1 and L0 = 111 cm FL for females Linf = 206 cm FL, k = 0.18 y–1 and L0 = 93 cm FL for males. The estimated growth coefficients confirm that A. supercilious is a slow-growing species, highlighting its vulnerability to fishing pressure. It is therefore urgent to carry out more biological research to inform fishery managers more adequately and address conservation issues. [ABSTRACT FROM PUBLISHER]

Abstract: Bycatch from pelagic longline fisheries has contributed to widespread population declines of turtles, sharks and other pelagic fishes. While large-scale estimates are needed to understand cumulative impacts on these highly migratory species, detailed information on targeting, setting, and discarding practices is needed to develop bycatch mitigation approaches. Data from qualitative fishers’ knowledge interviews with Canadian Atlantic pelagic longline captains was used to evaluate current bycatch estimation methods and to identify bycatch mitigation opportunities. Interviewed longline captains reported blue sharks (Prionace glauca) were common bycatch during swordfish-targeted sets, but were sometimes absent from tuna-targeted sets. Discrepancies between longline captains’ observations and bycatch assessment methods identified needed improvements to data collection methods. Longline captains reported innovative uses of turtle dehooking gear, which two-thirds of interviewed captains had used to release other bycatch species in addition to turtles. Longline captains reported techniques for discarding pelagic stingray (Pteroplatytrygon violacea), a common bycatch species in Pacific, Atlantic and Mediterranean pelagic longline fisheries. Therefore, such techniques could decrease fisheries impacts globally. While there can be major conservation benefits from fishers’ knowledge research, one-quarter of the active longline captains that we contacted declined interviews because they did not trust the larger research process. We urge conservation biologists to carefully design fishers’ knowledge research taking into account the often politicized context. Failure to do so may jeopardize future research and conservation efforts. [Copyright &y& Elsevier]

The article discusses alternative methods for estimating the total annual seabird bycatch by the U.S. Atlantic longline fishery since there is a lack of adequate observation data. Among the generalized additive models (GAM), the generalized linear models (GLM) and the GLM with special or spatio-temporally autocorrelated bycatch observations (s-GLM), GLM was chosen as having the best predictive accuracy. Influencing factors include the latitude, longitude, time of year and number of hooks.

Abstract: Taiwan is a major longline fishing nation with an interest in proactive conservation measures. Facing global concerns about the incidental catch in longline fisheries, Taiwan has focused on bycatch issues since the 2000s. This paper reviews the existing information on bycatch and the actions taken by Taiwan in the past ten years, including the establishment of observer programs, education and outreach, adoption of national plans of action and publicizing regulations for mitigation measures. This review suggests that continuing and improving the observer program, ensuring the compliance of mitigation measures, and encouraging information exchange and international cooperation will contribute to the conservation of non-commercial species of concern. [Copyright &y& Elsevier]

BSTRACT [ABSTRACT FROM AUTHOR]

We adapt Breiman’s non-negative garrote method to perform variable selection in non-parametric additive models. The technique avoids methods of testing for which no general reliable distributional theory is available. In addition, it removes the need for a full search of all possible models, something which is computationally intensive, especially when the number of variables is moderate to high. The method has the advantages of being conceptually simple and computationally fast. It provides accurate predictions and is effective at identifying the variables generating the model. To illustrate our procedure, we analyse logbook data on blue sharks (Prionace glauca) from the US pelagic longline fishery. In addition, we compare our proposal to a series of available alternatives by simulation. The results show that in all cases our methods perform better or as well as these alternatives. [ABSTRACT FROM AUTHOR]

The conclusions drawn from fisheries stock assessment models can depend strongly on the relative weights assigned to different data sets. However, there is no consensus amongst practitioners as to the best approach to data weighting. From a discussion of some key questions concerning data weighting in stock assessment models, I draw three guiding principles: ( i) do not let other data stop the model from fitting abundance data well; ( ii) when weighting age or length composition data, allow for correlations; and ( iii) do not down-weight abundance data because they may be unrepresentative. I propose an approach to data weighting based on these principles. Two factors that complicate this approach are that some decisions are inevitably subjective (which underlines the need for expert knowledge in stock assessment), and some technical problems are unresolved. [ABSTRACT FROM AUTHOR]

Abstract: Given the widely recognized need to better protect the oceans but limited resources to do so, methods for prioritizing potential protected area sites are important. This is particularly true for the open oceans, where few protected areas currently exist and data availability is limited. Here, we examine the relationship between the distributions of tuna and billfish species richness (an indicator of pelagic biodiversity), the human impact drivers of fishing pressure (quantified as cumulative removals) and sea surface temperature increase (quantified as the increase in large positive anomalies) in tropical to temperate oceans at the scale of a 5°×5° grid. We investigate relationships using Generalised Additive Models and Regression Tree analysis, and identify the top 50 “hotspot” cells for species richness and each of the two impact drivers. We find that both impact drivers significantly overlap with high species richness, but relationships are complex, non-linear and ocean-basin specific. Higher fishing pressure is associated with higher species richness in the Indian and Pacific Oceans, and this overlap is particularly prominent in the central Pacific, and in the Indian Ocean around Sri Lanka. In the Pacific and Atlantic Oceans, species richness is generally higher in areas that have seen lower levels of change in sea surface temperature and only one cell, near Easter Island, is a hotspot for species richness and sea surface temperature increase. While species richness and impact drivers overlap in some areas, there are many areas with high species richness and limited apparent impact. This suggests that area-based conservation strategies that aim to protect areas of high pelagic biodiversity may be achievable with limited displacement of fishing effort. [Copyright &y& Elsevier]

Our research aims to identify longline fishing gear modifications that can improve fishing selectivity and reduce incidental capture of non-target species. Catch rates and anatomical hook locations (AHL) were compared when using a 14/0 standard 'control' circle hook with a 0° offset and an experimental 'appendage' hook in a Costa Rican longline fishery. With the appendage, the maximum dimension of the appendage hook was increased by 10% and the minimum dimension of the hook by 19%. A total of 1,811 marine animals were captured during five fishing trips. By taxonomic groups, sea turtles represented the largest total catch (27%), followed by sharks (26%), rays (25%), mahimahi ( Coryphaena hippurus) (12%), and tunas and billfish (10%). Non-target and discard species, such as rays and sea turtles, accounted for over half of the total catch. Catch per unit effort (CPUE; number of individuals per 1,000 hooks) was higher with control hooks compared to appendage hooks for all species' categories except rays; appendage hooks caught 52% fewer sea turtles and 23% fewer tunas and billfish than standard hooks, which represents a significant reduction in bycatch of endangered and other species. No differences were found in the AHL for sea turtles, suggesting use of the appendage may not incur additional advantages regarding turtles' post-release survivorship. Despite lower catch rates for marketable species, such as sharks and mahimahi, use of the appendage resulted in dramatic reductions in catch rates of sea turtles. The results suggest that large scale adoption of hooks with a significantly wider hook dimension could be an effective conservation measure to maintain marine biodiversity while allowing for continued fishing. [ABSTRACT FROM AUTHOR]

Abstract: We quantified seasonal and interannual variability of pelagic and demersal fishes available to marine predators in southeastern Alaska focusing on prey of the Steller sea lion (Eumetopias jubatus). Estimates of abundance were determined from echo integration mid-water trawl and demersal longline surveys. The dominant species were walleye pollock (Theragra chalcogramma) (average biomass 9057t), Pacific hake (Merluccius productus) (1715t), Pacific herring (Clupea pallasii) (1176t), Pacific halibut (Hippoglossus stenolepis) (average catch rate 524kg per 1000 hooks), Pacific cod (Gadus macrocephalus) (177kg per 1000 hooks), sablefish (Anoplopoma fimbria) (120kg per 1000 hooks), and sandpaper skate (Bathyraja interrupta) (26kg per 1000 hooks). Of these species, seasonal differences in species abundance were detected for walleye pollock (p =0.03), Pacific cod (p =0.001) and sablefish (p <0.001) with walleye pollock the most abundant and widespread species year-round. Herring, hake, and juvenile (120–350mm) and adult (>350mm) pollock are pelagic species. Adult and juvenile pollock and hake were found in open water, while herring, young-of-the-year (<120mm) and the smallest juvenile pollock were found in bays. Herring of all ages concentrate in dense schools. Pollock and hake form scattered layers throughout open water with juvenile pollock shallower than adult pollock and adult pollock shallower than hake. Halibut, sablefish, skates, Pacific cod and arrowtooth flounder are demersal species; sablefish were deeper than the other demersal species. These seasonal and annual changes in prey availability affected prey selection of sea lions which shifted their diet in response. [Copyright &y& Elsevier]

Abstract: One of the biggest challenges of fisheries research is reducing the bycatch of unwanted species. The incidental fishing mortality of species with low reproductive rates, such as elasmobranchs (sharks, skates, and rays), is recognized as a key threat for their populations. In the present study, gear modifications related to the type of hook and position of the hook in the water column were tested to examine their effects on catch rates and mortality of elasmobranch species in both pelagic and coastal environments. Comparisons between circle (size 18/0, 0° offset) and J-style (size 9/0, 10° offset) hooks demonstrated that the circle hooks have a greater efficiency in reducing the mortality of most species caught, both in pelagic and coastal longline fisheries. Internal lodging of the hook was significantly less frequent for the individuals caught with circle hooks, which likely contributed to their higher survival rate at haulback. Additionally, circle hooks also increased the CPUE of elasmobranchs caught in the pelagic longline fishery, which was particularly evident for Carcharhinus falciformis and Prionace glauca. The position of the hook in the water column exhibited a strong influence on the species caught in the coastal bottom longline fishery. Suspending hooks in the middle of the water column reduced the bycatch of common demersal species, such as Carcharhinus acronotus, Ginglymostoma cirratum, and Dasyatis americana, while increasing the CPUE of potentially aggressive species, such as Galeocerdo cuvier and Carcharhinus leucas. The interaction of the type of hook utilized with its position in the water column appears to be an essential factor in the optimization of longline selectivity and minimization of bycatch mortality. [Copyright &y& Elsevier]

Abstract: Sailfish (Istiophorus platypterus) are of substantial economic importance to Taiwan because of their seasonal abundance (April to October, with a peak from May to July) off the island''s eastern coast. They are harvested by drift gill nets, set nets, harpoons, and as incidental bycatch by inshore longline fisheries. Although the biology of sailfish has been investigated in eastern Taiwan, there is a paucity of data on movement patterns. Pop-up satellite archival tags (PSATs) were used to study the vertical and horizontal movements of three sailfish in 2008. The fish were tagged near the southeastern coast of Taiwan and linear displacements ranged from 1050 to 1400km (~40kmday−1) from deployment to pop-up locations and all movements were confined to the East China Sea. Sailfish spent 88% of their time in the upper uniform mixed layer above 50m, but made more extensive vertical movements during the nighttime ( =60.61m±48.24 SD) than daytime ( =35.21m±35.37 SD). Depths and ambient water temperatures visited ranged from 0 to 214m and 30.0° to 17.8°C, respectively. However in all cases, the depth distribution appeared primarily limited by an 8°C change in water temperature. Diel diving patterns also suggested basking behavior. Sailfish behavior makes them particularly vulnerable to surface fishing gears. [Copyright &y& Elsevier]

Abstract: Bycatch mitigation approaches aim to either reduce the incidence of unwanted catch or reduce bycatch mortalities. In pelagic longline fisheries incidence of unwanted catch can be reduced by limiting the availability of baited hooks (e.g., within bycatch species’ preferred depths and water temperatures), whereas bycatch mortalities can be decreased by gear modifications and changes to fishing practices, e.g., by limiting soak time. To evaluate the effects of temperature, depth, and soak time on catch of target and bycatch species, temperature recorders were set along the length of the longline to characterize the environment at which hooks were fishing. Although few instrumented sets were fished, observations at the within set scale – specifically, that swordfish (Xiphias gladius) catch did not increase with longer soak times – led us to reexamine assumptions made in fleet-wide catch models. Swordfish catch did not increase with soak time in generalized linear models based on fisheries observer data collected from swordfish-targeted sets fished by the Canadian pelagic longline fleet in 2008 and 2009 (n =42 and n =78, respectively). Minimum soak time, from end of setting to start of hauling, was used in swordfish catch models. Total soak time is inappropriate for catch models because it includes haulback time, which increases as a function of catch. If landed catch does not increase as a function of soak time, then limiting longline soak time to reduce bycatch mortalities would not cause decreased swordfish catch nor result in economic losses for fishers. While minimum soak time limits would likely decrease bycatch mortality rates in swordfish longline fisheries, impacts on other aspects of the fishing process would need to be considered, such as negative impacts on fisher safety. [Copyright &y& Elsevier]

Straube, N., Kriwet, J. & Schliewen, U. K. (2010). Cryptic diversity and species assignment of large lantern sharks of the Etmopterus spinax clade from the Southern Hemisphere (Squaliformes, Etmopteridae). - Zoologica Scripta, 40, 61-75. Many species of the speciose deep-sea shark family Etmopteridae (lantern sharks) are a regular by-catch component of deepwater trawl and longline commercial fisheries. As for many elasmobranchs, the low fecundity, late sexual maturation and extreme longevity of the lantern sharks increase their susceptibility to overfishing. However, the taxonomic uncertainty within etmopterids and the poorly known patterns of dispersal of these shark species hampers the establishment of reasonable monitoring efforts. Here, we present the first molecular approach to clarify the taxonomy and distribution of a morphologically uniform group of lantern sharks comprising Etmopterus granulosus and closely related congeners by using nucleotide sequence data from the mitochondrial DNA cytochrome oxidase I gene and amplified fragment length polymorphisms. Samples were collected from several locations in the Southern Hemisphere, where the species occur. Our analyses reveal a high level of cryptic diversity. E. granulosus is not endemic to Chile, but instead has a widespread distribution in the Southern Hemisphere being synonymous to New Zealand Etmopterus baxteri. Conversely, specimens previously assigned to E. baxteri from off South Africa apparently represent a distinct species. Our results provide the basis for the re-description of E. granulosus and E. baxteri which will help in the establishment of useful monitoring and management strategies. [ABSTRACT FROM AUTHOR]

Ecological risk assessment is a useful methodology for assisting the management of fisheries from an ecosystem perspective. Atlantic tuna fisheries, managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), are economically important and interact with several bycatch species. In spite of these interactions, no comprehensive ecological risk assessment has been conducted for bycatch species caught in ICCAT fisheries. In this paper, we followed a two stage approach with the objective of assessing the relative risk of species being negatively impacted by Atlantic tuna fisheries. An analysis of the ICCAT bycatch species list (which includes all species reported to have interacted with different tuna fishing gears operating in the Atlantic) revealed that most of these species are caught in longline fisheries, followed by gillnets and purse seines. According to the IUCN red list, 7 species of the ICCAT bycatch list (3 coastal sharks, 3 sea turtles and one seabird) are categorized as critically endangered. In our study, and based on their life history characteristics, marine mammals and coastal sharks caught in ICCAT fisheries showed the highest intrinsic vulnerability values. A productivity susceptibility analysis for the European Union (EU) tropical tuna purse seine fleet and the United States (US) pelagic longline fleet revealed two groups with high relative risk scores. The first one included pelagic and coastal sharks, characterized by relatively low productivities, and the second one included teleosts, characterized by higher productivities but high susceptibility to purse seine and longline gears. Some alternative approaches to conduct productivity susceptibility analyses in the context of ecological risk assessments are discussed. [ABSTRACT FROM PUBLISHER]

Background: Seamounts have been identified as aggregating locations for pelagic biodiversity including tuna; however the topography and prevailing oceanography differ between seamounts and not all are important for tuna. Although a relatively common feature in oceanic ecosystems, little information is available that identifies those that are biologically important. Improved knowledge offers opportunities for unique management of these areas, which may advance the sustainable management of oceanic resources. In this study, we evaluate the existence of an association between seamounts and tuna longline fisheries at the ocean basin scale, identify significant seamounts for tuna in the western and central Pacific Ocean, and quantify the seamount contribution to the tuna longline catch. Methodology/Principal Findings: We use data collected for the Western and Central Pacific Ocean for bigeye, yellowfin, and albacore tuna at the ocean basin scale. GLMs were applied to a coupled dataset of longline fisheries catch and effort, and seamount location information. The analyses show that seamounts may be associated with an annual longline combined catch of 35 thousand tonnes, with higher catch apparent for yellowfin, bigeye, and albacore tuna on 17%, 14%, and 14% of seamounts respectively. In contrast 14%, 18%, and 20% of seamounts had significantly lower catches for yellowfin, bigeye and albacore tuna respectively. Studying catch data in relation to seamount positions presents several challenges such as bias in location of seamounts, or lack of spatial resolution of fisheries data. Whilst we recognize these limitations the criteria used for detecting significant seamounts were conservative and the error in identification is likely to be low albeit unknown. Conclusions/Significance: Seamounts throughout the study area were found to either enhance or reduce tuna catch. This indicates that management of seamounts is important Pacific-wide, but management approaches must take account of local conditions. Management of tuna and biodiversity resources in the region would benefit from considering such effects. [ABSTRACT FROM AUTHOR]

Research longline sampling was conducted seasonally from December 2006 to February 2009 to investigate the occurrence and population structure of the broadnose sevengill shark Notorynchus cepedianus in coastal areas of south-east Tasmania. Notorynchus cepedianus showed a consistent temporal trend in seasonal occurrence in Norfolk Bay characterized by high abundances in summer to near absence in winter. This pattern was less pronounced in the Derwent Estuary, where fish were still caught during winter. The absence of smaller total length ( L) classes (<80 cm) from the catches suggests that N. cepedianus are not using these coastal habitats as nursery areas. Of the 457 individuals tagged, 68 (15%) were recaptured. Time at liberty ranged from 6 days to almost 4 years and all but one of the recaptures were caught in its original tagging location, suggesting site fidelity. The large number of N. cepedianus in these coastal systems over summer indicates that these areas are important habitats for this species and that N. cepedianus may have a significant influence on community dynamics through both direct and indirect predator-prey interactions. [ABSTRACT FROM AUTHOR]

The operational efficiency of the longline hauler on an artisanal tuna fishing vessel from Margarita Island, Venezuela, was determined using the average setting velocity, average hauling velocity, hauler input tension (To) and traction strength (P). A direct relationship was found between the average gravity (qmed) on the long-line section and the hauler input tension (To). Considering a strength (Pmed) at the input of the longline hauler (S1), the roller tension (S3) decreases due to the force of H = 23.7 N exerted by the pressure roller, resulting in a strength of S4 = 0. The longline average setting velocity was 208 m min-1 (~ 333 hooks/hour) and its hauling velocity was 121 m min-1 (~ 160 hooks/hour), whereas hauler input tension (To) was 1013 N. Therefore, the new traction strength (P) fluctuated between 1.317 and 1.418 N. Based on torque output from the rollers of the longline hauler, the average hauling velocity (vmed) and the transmission relations (k1, k2), a required average strength (Nmed) of 5.3 hp (~ 3.95 kW) for longline retrieval was estimated. Thus, the hauling efficiency (Tp) by longline section was estimated to be 135.4 s. [ABSTRACT FROM AUTHOR]

Distribution and relative abundance of blue sharks (Prionace glauca) in the southwestern Atlantic Ocean was modeled based on catch-per-unit-effort (CPUE) per 1000 hooks and length frequencies of blue sharks caught by the Brazilian pelagic tuna longline fleet. As a measure of relative abundance, CPUE of blue sharks caught in 58 238 fishing sets by the Brazilian pelagic tuna longline fleet (national and chartered), from 1978 to 2009, was standardized by a Generalized Linear Model (GLM) using three different approaches: i) a negative binomial error structure (log link); ii) the traditional delta lognormal model; and iii) the Tweedie distribution, recently proposed to adjust models with a high proportion of zeros. A cluster analysis using the K-means method was used to identify target species and incorporate it as a factor into the GLM. Cluster analysis grouped the data into six different fishing clusters according to the percentage of target species. Target factor (cluster) was the most important factor explaining the variance in all three CPUE models. The Tweedie model showed a relatively better fit compared to the other models. Blue shark nominal and standardized CPUE showed a relatively stable trend from 1978 to 1995. From 1995 onwards, however, there was an increasing trend in the standardized CPUE, up to a maximum value in 2008. In general, nominal CPUE and standardized CPUE tracked well up until 2000, after which standardized CPUE’s values were at a noticeably lower level than nominal CPUE. Length frequency data were analyzed for 11 932 blue sharks measured as part of the Brazilian onboard observer program operating on the pelagic tuna longline fleet between 2006 and 2008, with sizes ranging from 91 to 224 cm fork length. Overall, blue shark size data showed clear spatial and seasonal distributions for males and females in the southwestern Atlantic Ocean, with juveniles predominantly concentrated in the most southerly latitudes. [ABSTRACT FROM PUBLISHER]