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Oceanic whitetip shark (Carcharhinus longimanus) is an important top predator in pelagic ecosystems currently classified as globally Critically Endangered by the International Union for the Conservation of Nature. This species is incidentally caught by fisheries targeting highly migratory tunas and billfishes throughout the Indian Ocean. Understanding the temporal, spatial and environmental factors influencing the capture of this species is essential to reduce incidental catches. In this study, we used generalized additive models to analyze the spatio-temporal distributions of the juvenile oceanic whitetip shark catches and the environmental conditions in the western Indian Ocean using observer data from 2010 to 2020 of the European Union and associated flags purse seine fishery. We found sea surface temperature and nitrate concentration to be the most important environmental variables predicting the probability of catching an oceanic whitetip shark. A higher probability of capture was predicted in areas where sea surface temperature was below 24°C and with low nitrate concentrations close to zero and intermediate values (1.5-2.5 mmol.m-3). We also found a higher probability of capture in sets on fish aggregating devices than in sets on free schools of tuna. The Kenya and Somalia basin was identified to have higher probabilities of capture during the summer monsoon (June to September) when upwelling of deep cold waters occurs. We provide the first prediction maps of capture probabilities and insights into the environmental preferences of oceanic whitetip shark in the western Indian Ocean. However, the causal mechanisms behind these insights should be explored in future studies before they can be used to design spatial management and conservation strategies, such as time-area closures, for bycatch avoidance.

Simple Summary: Blue shark species are at the top of the list of captured bycatch sharks in most tuna and tuna-like fisheries. As a consequence, their populations have been declining due to overfishing; thus, there is a need for the assessment of their stocks to better understand blue sharks' stock status. Most bycatch species lack sufficient data for traditional stock assessment models to be implemented. Blue sharks in the South Atlantic have been assessed in the past using a state-space production model. Given the development of new assessment models and the use of up-to-date data, their stock status was evaluated using a new state-space production model (CMSY++). We used different catch time series, abundance indices and priors to measure the intrinsic growth rate r to evaluate their influence on the outputs of CMSY++. We identified from many scenarios that the blue shark stock in the South Atlantic may be witnessing overfishing and is being overfished. CMSY++, an improved version of the CMSY approach developed from Catch-MSY which uses a Bayesian implementation of a modified Schaefer model and can predict stock status and exploitation, was used in the present study. Evaluating relative performance is vital in situations when dealing with fisheries with different catch time series start years and biological prior information. To identify the influences of data inputs on CMSY++ outputs, this paper evaluated the use of a nominal reported catch and a reconstructed catch dataset of the South Atlantic blue shark alongside different priors of the blue shark's productivity/resilience (r) coupled with different indices of abundance. Results from the present study showed that different catch time series start years did not have a significant influence on the estimation of the biomass and fishing reference points reported by CMSY++. However, uninformative priors of r affected the output results of the model. The developed model runs with varying and joint abundance indices showed conflicting results, as classification rates in the final year changed with respect to the type of index used. However, the model runs indicated that South Atlantic blue shark stock could be overfished (B2020/Bmsy = 0.623 to 1.15) and that overfishing could be occurring (F2020/Fmsy = 0.818 to 1.78). This result is consistent with the results from a previous assessment using a state-space surplus production model applied for the same stock in 2015. Though some potential could be observed when using CMSY++, the results from this model ought to be taken with caution. Additionally, the continuous development of prior information useful for this model would help strengthen its performance. [ABSTRACT FROM AUTHOR]

Oceanic whitetip shark (Carcharhinus longimanus) is an important top predator in pelagic ecosystems currently classified as globally Critically Endangered by the International Union for the Conservation of Nature. This species is incidentally caught by fisheries targeting highly migratory tunas and billfishes throughout the Indian Ocean. Understanding the temporal, spatial and environmental factors influencing the capture of this species is essential to reduce incidental catches. In this study, we used generalized additive models to analyze the spatio-temporal distributions of the juvenile oceanic whitetip shark catches and the environmental conditions in the western Indian Ocean using observer data from 2010 to 2020 of the European Union and associated flags purse seine fishery. We found sea surface temperature and nitrate concentration to be the most important environmental variables predicting the probability of catching an oceanic whitetip shark. A higher probability of capture was predicted in areas where sea surface temperature was below 24°C and with low nitrate concentrations close to zero and intermediate values (1.5-2.5 mmol.m-3). We also found a higher probability of capture in sets on fish aggregating devices than in sets on free schools of tuna. The Kenya and Somalia basin was identified to have higher probabilities of capture during the summer monsoon (June to September) when upwelling of deep cold waters occurs. We provide the first prediction maps of capture probabilities and insights into the environmental preferences of oceanic whitetip shark in the western Indian Ocean. However, the causal mechanisms behind these insights should be explored in future studies before they can be used to design spatial management and conservation strategies, such as time-area closures, for bycatch avoidance.

In this study we report the presence of the soft coral Verticillata castellviae at 947 m deep, off Buenos Aires Province, Argentina, which constitutes the northernmost record for this species. The specimen was collected as a bycatch species with a troncopyramidal trap during an experimental cruise devoted to the study of the red crab Chaceon notialis and the Patagonian lobsterette Thymops birsteini.

CMSY++, an improved version of the CMSY approach developed from Catch-MSY which uses a Bayesian implementation of a modified Schaefer model and can predict stock status and exploitation, was used in the present study. Evaluating relative performance is vital in situations when dealing with fisheries with different catch time series start years and biological prior information. To identify the influences of data inputs on CMSY++ outputs, this paper evaluated the use of a nominal reported catch and a reconstructed catch dataset of the South Atlantic blue shark alongside different priors of the blue shark’s productivity/resilience (r) coupled with different indices of abundance. Results from the present study showed that different catch time series start years did not have a significant influence on the estimation of the biomass and fishing reference points reported by CMSY++. However, uninformative priors of r affected the output results of the model. The developed model runs with varying and joint abundance indices showed conflicting results, as classification rates in the final year changed with respect to the type of index used. However, the model runs indicated that South Atlantic blue shark stock could be overfished (B2020/Bmsy = 0.623 to 1.15) and that overfishing could be occurring (F2020/Fmsy = 0.818 to 1.78). This result is consistent with the results from a previous assessment using a state-space surplus production model applied for the same stock in 2015. Though some potential could be observed when using CMSY++, the results from this model ought to be taken with caution. Additionally, the continuous development of prior information useful for this model would help strengthen its performance.

Electrical pulse trawling is an alternative to conventional beam trawling for common sole (Solea solea), with the potential for higher revenues and less impact on the marine ecosystem. Concerns exist, however, that benthic invertebrates might be seriously affected by pulse fishing. Even if direct injuries and mortality were limited, changes in behaviour might compromise their survival, with potentially large impacts on food webs. Here, we investigate effects of electrical pulses on locomotion behaviour and 14-days survival of six invertebrate species from four phyla that may encounter pulse fishing gears. Electrical stimulation consisted of a Pulsed Bipolar Current at 200 V m–1, 30 Hz, 0.33 ms pulse width, and 3 s duration. We quantified species-specific behaviours before, during, and after electrical stimulation and compared these to a non-exposed control group. Responses during stimulation varied from no visible effect (echinoderms) to squirming (sea mouse) and retractions (whelk and crustaceans). Within 30 s after stimulation, all animals resumed normal behavioural patterns, without signs of lasting immobilisation. Starfish, serpent star, whelk and sea mouse showed no change in movement patterns after stimulation, whereas flying crab and hermit crab showed significant changes in activity that were indicative of increased shelter behaviour. For none of the species, survival at 14-days after stimulation was negatively affected. These findings suggest that changes in locomotion behaviour due to electrical stimulation as used in pulse trawling are unlikely to substantially compromise survival of the investigated species.

Man-made floating objects in the surface of tropical oceans, also called drifting fish aggregating devices (DFADs), attract tens of marine species, including tunas and non-tuna species. In the Indian Ocean, around 80% of the sets currently made by the EU purse-seine fleet are on DFADs. Due to the importance and value of this fishery, understanding the habitat characteristics and dynamics of pelagic species aggregated under DFADs is key to improve fishery management and fishing practices. This study implements Bayesian hierarchical spatial models to investigate tuna and non-tuna species seasonal distribution based on fisheries-independent data derived from fishers’ echo-sounder buoys, environmental information (Sea Surface Temperature, Chlorophyll, Salinity, Eddie Kinetic Energy, Oxygen concentration, Sea Surface Height, Velocity and Heading) and DFAD variables (DFAD identification, days at sea). Results highlighted group-specific spatial distributions and habitat preferences, finding higher probability of tuna presence in warmer waters, with higher sea surface height and low eddy kinetic energy values. In contrast, highest probabilities of non-tuna species were found in colder and productive waters. Days at sea were relevant for both groups, with higher probabilities at objects with higher soak time. Our results also showed species-specific temporal distributions, suggesting that both tuna and non-tuna species may have different habitat preferences depending on the monsoon period. The new findings provided by this study will contribute to the understanding of the ecology and behavior of target and non-target species and their sustainable management.

Abstract: The objective of this work was to perform the chemical characterization of marine bonefish (Albula vulpes) and the development of fish burgers. Three formulations of fish burgers were prepared, containing 5, 8, and 10% cassava starch and functional ingredients (onion, garlic, and ground white pepper). Proximate composition, microbiological and pH analyses of the raw material, and fish burgers were performed, as well as the sensory analyses of the fish burgers. The yield and nutritional value of bonefish was found to be comparable with those of species of commercial value, with high-protein and low-lipid contents. The protein content of the fish burgers varied from 17.52 to 19.40 g 100 g-1 (raw), and from 20.74 to 24.25 g 100 g-1 (grilled); and the lipid contents ranged from 0.20 to 0.73 g 100 g-1 (raw), and from 0.36 to 0.77 g 100 g-1 (grilled). In the sensory tests, the formulations received scores between six and seven on the nine-point hedonic scale. Acceptance indexes were higher than 70% for all the assessed attributes. Therefore, the use of this underutilized species proves to be feasible.

Wahoo Acanthocybium solandri is a common bycatch pelagic species in oceanic fisheries targeting tuna and tuna-like species. Biology and environmental preferences are important parameters in understanding life history of fish species including wahoo. Despite the socio-economic importance of wahoo in many coastal countries, little is known about their biological and fisheries information in the Western and Central Pacific Ocean (WCPO). These parameters were analyzed on the basis of samples collected via the Chinese tuna long-line Fishery Observer Programme in 2012. Results obtained from this study show that the fork length (FL) of wahoo ranged from 59 to 169 cm with an average of 111.3 cm, and two dominant size groups were identified at 100 to 130 cm for males and 90 to 130 cm for females. Body size did not significantly differ between female and male wahoo specimens. Wahoo specimens expressed a positive allometric growth (b = 3.183), and the sex ratio was 1.9:1 (female/male), which differed significantly between both sexes. Only female wahoo were observed in catches of FL > 150 cm. The estimated lengths at 50% maturity (FL50) of female and male wahoo were 84 cm and 83 cm, respectively. Gonadosomatic index (GSI) of wahoo was at its peak in November, and on the basis of the stomach content analysis, wahoo mainly preyed on fish (84.64%), cephalopods (14.26%), and crustaceans (1.1%), found on the basis of prey number. The optimal swimming depth and water temperature of wahoo in the WCPO were found to range between 70 and 110 m and 23.1 and 24 ℃, respectively. The updated life history information presented in this work helps to address current data limitations and provides critical information for future assessments of wahoo stocks in the WCPO.

This paper presents an estimation of growth curves and spatiotemporal distributions of juvenile shortfin mako shark (Isurus oxyrinchus) in the western and central North Pacific Ocean using port sampling data collected from 2005 to 2013. The monthly length compositions show a clear transition of three modes in the size range of smaller than 150-cm precaudal length (PCL), which were believed to represent the growth of age-0 to age-2 classes, and they were then decomposed into age groups by fitting a Gaussian mixture distribution. Simulation data of lengths at monthly ages were generated from the mean and standard deviation of each distribution, and fit with a von Bertalanffy growth function. Parameters of the estimated growth curves for males and females were 274.4 and 239.4 cm PCL for the asymptotic length and 0.19 and 0.25 year-1 for the growth coefficient indicating apparently faster growth than previously reported. Generalised linear models were applied to age-0 to explore the seasonal changes of PCL by area. They were born during late autumn and winter off the coast of north-eastern Japan, an area known to have relatively high productivity compared with other pelagic areas, and gradually expanded their habitat eastward and northward with the seasons as they grew. Growth and spatiotemporal distribution of juvenile shortfin mako provide valuable information on their potential productivity, mechanisms of recruitment and movement. The aims of this study were to estimate the growth and to explore the distribution. The shortfin mako growth was faster than previously reported - sharks were born during autumn and winter off the coast of north-eastern Japan, and gradually expanded their habitat eastward and northward. [ABSTRACT FROM AUTHOR]

Based on the materials from a longline survey carried out in 2013 in the Weddell Sea, the bathymetric distribution of the Antarctic toothfish Dissostichus mawsoni, its size/weight and age composition, the maturity degree of its gonads, and its nutrition are analyzed. Individuals with a length of 63-170 cm and a weight of 3-59 kg, aged from 6 to 32 years, are recorded in the surveyed range of depths (786-1552 m). Compared with other Antarctic seas, small Antarctic toothfish (with a length of up to 70 cm) occur at deeper layers. The weight of large fish in the Weddell Sea (>100 cm) is lower than that of the individuals with the same size in the Ross Sea. It is assumed that this is due to a lower abundance and diversity of items of nutrition (four vs. ten fish species). [ABSTRACT FROM AUTHOR]

Since the late 1980s, a deep-sea fishery for Greenland halibut (Reinhardtius hippoglossoides) has been developing gradually in West Greenland. Deep-sea fish species are generally long-lived and characterized by late age of maturity, low fecundity, and slow growth, features that probably cause low resilience following overexploitation. In order to evaluate whether populations of nine potential bycatch species are negatively affected by the commercial fishery for Greenland halibut, scientific data from bottom-trawl surveys conducted in the same area and period as the commercial fishery were analysed. During the period 1988–2011, population abundance and size composition changed as catch and effort in the Greenland halibut fishery increased. Two species showed a significant decrease in abundance, and four populations showed a significant reduction in mean weight of individuals (p < 0.05). Correlation analyses show that most of the observed trends in abundance are probably not related to increasing fishing effort for Greenland halibut. The analysis did, however, show that most of the observed decreases in mean weight were significantly correlated with fishing effort during the 24-year period. [ABSTRACT FROM PUBLISHER]

Studies on fishers’ ecological knowledge (FEK) and local ecological knowledge (LEK) have rarely been undertaken for practical application in a management context. Here, we describe a methodology to access FEK that was designed under an ecosystem-based fisheries management framework. The procedure was adapted from the Delphi technique, which seeks experts’ consensus, and focused on several spatial and temporal issues related to the small-scale fisheries of the northern coast of São Paulo, Brazil (particularly, in Ubatuba, between 23°20′ S and 23°35′ S). Experienced fishers, considered as experts, were selected during a pilot phase to participate in two sequential rounds of semi-structured interviews at 3 main landing sites and 12 coastal fishing communities. The issues addressed were: (1) spatial and seasonal occurrence of mature females and juveniles of the main commercial species, (2) fishing grounds and bycatch species for each type of fishing gear, and (3) fishers’ suggestions for local fisheries management (e.g. mesh and size of gillnets, closure seasons, gear restrictions by fishing area). It was possible to identify consensus rates on the spatial and temporal issues, as well as on fishers’ management suggestions. The former allowed the construction of maps representing fishing grounds and the local spatial distribution of different fishery stocks strata. We illustrate the output by focusing on five fishery stocks: the seabob-shrimp Xiphopenaeus kroyeri, the whitemouth croaker Micropogonias furnieri, the inshore squid Loligo spp, the white shrimp Litopenaeus schimitti and the blue runner Caranx crysos. Overall, the results provided new guidelines for future local fisheries management and conservation initiatives. The methodology proved to be useful for the definition of essential fish habitats (EFHs), suggesting their potential application in other locations. [ABSTRACT FROM AUTHOR]

Fisheries stock assessments rely heavily on historical catch information to understand how a stock responds to exploitation and make meaningful forecasts under alternative management and environmental scenarios. However, for many bycatch species historical removals are virtually unknown, as a large portion of the catch was discarded at sea. For example, historical discard of elasmobranch species such as skates and sharks have been reported as 95 percent of the total catch based on available data. The longnose skate is one the most abundant groundfishes on the continental slope of the U.S. Pacific Coast by biomass, and the most abundant skate species in the Northeast Pacific Ocean. We developed a method to estimate catch of longnose skate on the U.S. West Coast based on the catch of Dover sole, a co-occurring targeted species with which longnose skate is caught. This method allowed us to reconstruct historical longnose skate catches back to the beginning of the bottom trawl fisheries and improve stock assessment for this species. We also examined the impact of using our method versus other common methods of catch reconstruction to inform stock assessment models, and found that the target-based predictive method produced results that more accurately reflected the life history and typical stock dynamics of elasmobranch taxa. Our method is not limited to the specific case of longnose skate and could be easily adapted for other species and areas. [ABSTRACT FROM AUTHOR]

• Species misidentification and lack of fishing gear data in official statistics. • Statistical stepwise procedure to estimate landed weight by species and effort. • Relevance of dedicated sampling programs for by-catch species. • Collaboration with fishermen as a source of relevant fisheries knowledge. To assess the exploitation status of marine resources and to formulate scientific advice for fisheries management, reliable fishery data are required. When dealing with data-poor stocks, like skates and rays (Rajiformes) caught by multispecies and multigear fisheries in Portugal, strategies need to be defined to surpass data limitations, like species misidentification and the lack of fishing gear information in landings data. This paper presents a stepwise statistical procedure, involving factor analysis for mixed data and flexible discriminant analysis, to estimate the total number of trips and the correspondent total landed weight by species. Interviews and self-sampling that took place under a pilot study (2011 – 2013) focused on skate and ray fisheries showed that collaborative research is a low cost and valuable tool to improve our knowledge on fisheries and their catches and may contribute to increase the accuracy. Given the persistence of species misidentification errors in the official statistics, the procedure here presented is currently used to report the Portuguese annual estimates of species-specific landed weight. This procedure may be considered to be applied to data deficient fishery bycatch resources for which dedicated sampling programs are not priority. [ABSTRACT FROM AUTHOR]

• SMART drumlines (SDLs) were deployed in combination with acoustic receivers. • Detections of tagged sharks were recorded before, during and after SDLs deployment. • Detections patterns of bull sharks were influenced by environmental parameters. • Neither baits nor fish caught on SDLs influence detections patterns of bull sharks. • The efficiency of SDLs as protective barriers against sharks was not demonstrated. Following a series of shark attacks, local authorities in Reunion Island developed an experimental shark control programme using innovative fishing gear, namely Shark Management Alert in Real Time (SMART) drumlines (SDL). From January to November 2014, four SDL were deployed 24 h per day, four days per week to target bull (Carcharhinus leucas) and tiger (Galeocerdo cuvier) sharks and to test the fishing efficacy of the SDL. Presence and residence time of 19 acoustically tagged bull and 19 tiger sharks, which had been tagged up to two years before the SDL deployment, were modelled against different SDL configurations, which included bait type and presence of bait or catches on the hooks, as well as environmental parameters before, during and after SLD deployment. There was insufficient acoustic data from the tiger sharks for any analyses. Bull sharks spent less time in nearshore waters when drumlines were deployed, and their presence was influenced by sea surface temperatures (SST), rainfall and time of day. There was no difference in the number of bull sharks detected in the SDL deployment area compared with surrounding sites. As SDL catch rates were only poorly correlated with presence of tagged sharks, their efficacy in catching sharks present in the area could not be accurately determined. Overall, the results show that SDL, deployed without chum and baited with small, whole, low-fat fish cannot be considered as "shark magnets", which could attract dangerous bull sharks inshore where they would pose a threat to the safety of surfers and other sea users. The detection of tagged bull sharks moving into and out of the SDL fishing area indicates that these fishing devices do not provide an impenetrable barrier to the passage of this potentially dangerous species. [ABSTRACT FROM AUTHOR]

Wahoo Acanthocybium solandri is a common bycatch pelagic species in oceanic fisheries targeting tuna and tuna-like species. Biology and environmental preferences are important parameters in understanding life history of fish species including wahoo. Despite the socio-economic importance of wahoo in many coastal countries, little is known about their biological and fisheries information in the Western and Central Pacific Ocean (WCPO). These parameters were analyzed on the basis of samples collected via the Chinese tuna long-line Fishery Observer Programme in 2012. Results obtained from this study show that the fork length (FL) of wahoo ranged from 59 to 169 cm with an average of 111.3 cm, and two dominant size groups were identified at 100 to 130 cm for males and 90 to 130 cm for females. Body size did not significantly differ between female and male wahoo specimens. Wahoo specimens expressed a positive allometric growth (b = 3.183), and the sex ratio was 1.9:1 (female/male), which differed significantly between both sexes. Only female wahoo were observed in catches of FL > 150 cm. The estimated lengths at 50% maturity (FL50) of female and male wahoo were 84 cm and 83 cm, respectively. Gonadosomatic index (GSI) of wahoo was at its peak in November, and on the basis of the stomach content analysis, wahoo mainly preyed on fish (84.64%), cephalopods (14.26%), and crustaceans (1.1%), found on the basis of prey number. The optimal swimming depth and water temperature of wahoo in the WCPO were found to range between 70 and 110 m and 23.1 and 24 °C, respectively. The updated life history information presented in this work helps to address current data limitations and provides critical information for future assessments of wahoo stocks in the WCPO. [ABSTRACT FROM AUTHOR]