Interannual fluctuations in connectivity among crab populations (Liocarcinus depurator) along the Atlantic-Mediterranean transition.

An interesting evolutionary question that still remains open is the connectivity between marine populations. Marine currents can favour the dispersal of larvae or adults, but they can also produce eddies and gyres generating oceanographic fronts, thus limiting gene flow. To address this subject, we selected the Atlantic-Mediterranean transition, where several fronts are located: Gibraltar Strait (GS), Almeria-Oran Front (AOF) and Ibiza Channel (IC). Seven populations of the marine crab Liocarcinus depurator (Cadiz, West and East Alboran, Alacant, Valencia, Ebro Delta and North Catalonia) located along this transition were analysed in six consecutive years (2014-2019) using a fragment of the COI (Cytochrome Oxidase subunit I) gene. All sequences (966) belonged to two well defined haplogroups: ATL (most abundant in Atlantic waters) and MED (predominant in Mediterranean waters). Following a geographic variation, the frequency of ATL decreased significantly from Cadiz to North Catalonia. However, this variation presented steps due to the effect of oceanographic restrictions/fronts. Significant effects were recorded for GS (2015, 2017, 2018 and 2019), AOF (all years except 2018) and IC (2016). The intensity and precise location of these fronts changed over time. Multivariate analyses distinguished three main population groups: Cadiz, Alboran Sea and the remaining Mediterranean populations. These findings could be relevant to properly define Marine Protected Areas and for conservation and fisheries policies.

Understanding discarding in trawl fisheries: A model based demersal case study with implications for mitigating and assessing impacts.

Despite research and public scrutiny over recent decades, discarding continues to be an issue for trawl fisheries. Previous research demonstrates that environmental, biological, operational, legislative and socioeconomic drivers affect a fisher's decision to discard an organism. Therefore, the reduction of fishery discards requires a better understanding of fishery-specific drivers. Despite considerable research and mitigation, further work is required to reduce discarding to acceptable levels (currently ~ 50% in Australia). To better understand the drivers of discarding, this study used a modelling approach to determine environmental and operational factors that drive discarding in the New South Wales (NSW) ocean prawn trawl fishery (OPT). Further, the study investigated the relationship between the discarded number of individuals from all functional species groups (i.e. elasmobranchs, crustaceans and fish combined) and the retained catch weight. This model was also run on just fish partly due to their disproportionally high contribution to the discard assemblage (e.g. 76% of all species or higher taxon) and importance (e.g. to the ecosystem and fisheries). The results quantified relationships of environmental and operational drivers of discarding and the relationship of fish discarding and retained catch weight was found to be linear. However, the identified relationships appear complicated and, whilst an important first step, more work is required to identify all drivers influencing discarding practices. We, in combination with previous research, suggest implementation of effort quotas may be a suitable management initiative to reduce discarding and its impact; at least whilst more research is conducted to better understand this complex process. Furthering our understanding of discarding is urgent given its global impact and the rate of discarding in the OPT.

A crew-operated data recording system for length-based stock assessment of Indonesia's deep demersal fisheries.

Deep demersal fisheries in Indonesia yielded close to 90,000 metric tons of snapper and grouper in 2019, landed by a fleet of approximately 10,000 fishing boats. Prior to the present study, information on these multi-species, dispersed, small- to medium-scale fisheries was scarce, while reliable species-specific data on catch and effort were non-existent. This data-deficiency made stock assessments and design of harvest control rules impossible. We developed a new data collection method, the Crew Operated Data Recording System (CODRS), to collect verifiable species- and length-composition data from catches across all segments of the fleet. CODRS engaged crews of 579 fishing vessels to take pictures of each fish in their catch, in combination with the deployment of a tracking device on their boats. Furthermore, we also conducted a frame survey to map the fleet across the entire Indonesian archipelago. Using more than 2 million CODRS images, we aimed to understand the basic characteristics and challenges within the fishery. We updated life-history parameters for the top 50 species in the fishery based on the maximum observed length-frequency distribution of the catch (i.e., asymptotic length, size at maturity, optimum fishing length, total mortality, and spawning potential ratio). Length-based stock assessments using the updated life-history parameters showed high risks of overfishing for most of the major target species, especially for snapper species with large maximum sizes. Our results indicated that effective management and harvest strategies are urgently needed across Indonesia's eleven Fishery Management Areas to prevent the collapse of these important fisheries.

Aspectos reproductivos de la raya látigo Hypanus longus (Garman, 1880) de los desembarques de la pesca artesanal en el Pacífico de Guatemala / Reproductive aspects of the longtail stingray Hypanus longus (Garman, 1880) from the landings of the artisanal fishery in the Pacific of Guatemala

La raya látigo Hypanus longus, ha pasado de ser una especie de captura incidental a una especie objetivo en la pesca artesanal del Pacífico de Guatemala. Esta actividad es realizada sin considerar criterios biológicos esenciales para su aprovechamiento sostenible. Aunado a ello, H. longus es una especie sensible, presentando características biológicas como: madurez sexual tardía, ciclos reproductivos largos y baja fecundidad. El presente estudio contribuye al conocimiento de la biología reproductiva de la raya látigo. Durante mayo de 2019 a marzo de 2020 se realizaron 11 muestreos de los desembarques de la pesca artesanal en la comunidad de Sipacate, Escuintla, en cada muestreo se registró el ancho de disco (AD), el peso, sexo y estado de maduración sexual de H. longus. En total se registraron 336 organismos, que presentaron una proporción sexual de 1:1, un AD para hembras de M = 82.33 cm, DS = 22.24 y de M = 76.91 cm, DS = 11.86 para machos. A partir de las evaluaciones externas e internas de los aparatos reproductores se determinó la talla de madurez sexual (L50), siendo de 88.2 y 79.3 cm AD para hembras y machos respectivamente. Finalmente, este estudio evidencio que el 65.68% de hembras y el 52.10% de machos son capturados por debajo de la L50, por lo cual se recomienda elaborar e implementar estra-tegias o medidas tendientes a la regulación de las prácticas pesqueras o artes de pesca que permitan la captura de organismos mayores a 95 cm de AD.

The whip ray Hypanus longushas gone from being a bycatch species to a target species in artisanal fisheries in the Pacific of Guatemala. This activity is carried out without considering essential biological criteria for its sustainable use. In addition, H. longusis a sensitive species, presenting biological characteristics such as late sexual maturity, long reproductive cycles and low fecundity. The present study contributes to the knowledge of the reproductive biology of the whip ray. During May 2019 to March 2020, 11 samplings were conducted from artisanal fishery landings in the community of Sipacate, Escuintla, in each sampling the disc width (AD), weight, sex and sexual maturation stage of H. longus were recorded. A total of 336 organisms were recorded, which pre-sented a sex ratio of 1:1, with a female AD of M = 82.33 cm, SD = 22.24 and M = 76.91 cm, SD = 11.86 for males. From the external and internal evaluations of the reproductive apparatus, the size at sexual maturity (L50) was determined to be 88.2 and 79.3 cm AD for females and males, respectively. Finally, this study showed that 65.68% of females and 52.10% of males are caught below L50, so it is recommended to develop and implement strategies or measures to regulate fishing practices or fishing gear that allow the capture of organisms larger than 95 cm AD.

Illegal, Unreported, and Unregulated Fisheries Threatening Shark Conservation in African Waters Revealed from High Levels of Shark Mislabelling in Ghana.

Mislabelling of fish and fish products has attracted much attention over the last decades, following public awareness of the practice of substituting high-value with low-value fish in markets, restaurants, and processed seafood. In some cases, mislabelling includes illegal, unreported, and unregulated (IUU) fishing, contributing to overexploit substitute species that are undetectable when sold under wrong names. This is the first study of DNA barcoding to assess the level of mislabelling in fish marketed in Ghana, focusing on endangered shark species. Genetic identification was obtained from 650 base pair sequences within the cytochrome c oxidase I (COI) gene. All except one of 17 shark fillets analysed were wrongly labelled as compared with none of 28 samples of small commercial pelagic fish and 14 commercial shark samples purchased in Europe. Several substitute shark species in Ghana are endangered (Carcharhinussignatus and Isurusoxyrinchus) and critically endangered (Squatina aculeata). Shark products commercialized in Europe (n = 14) did not reveal mislabelling, thus specific shark mislabelling cannot be generalized. Although based on a limited number of samples and fish markets, the results that reveal trade of endangered sharks in Ghana markets encourage Ghanaian authorities to improve controls to enforce conservation measures.

Environmentally triggered shifts in steelhead migration behavior and consequences for survival in the mid-Columbia River.

The majority of Columbia River summer-run steelhead encounter high river temperatures (near or > 20°C) during their spawning migration. While some steelhead pass through the mid-Columbia River in a matter of days, others use tributary habitats as temperature refuges for periods that can last months. Using PIT tag detection data from adult return years 2004-2016, we fit 3-component mixture models to differentiate between "fast", "slow", and "overwintering" migration behaviors in five aggregated population groups. Fast fish migrated straight through the reach on average in ~7-9 days while slow fish delayed their migration for weeks to months, and overwintering fish generally took ~150-250 days. We then fit covariate models to examine what factors contributed to the probability of migration delay during summer months (slow or overwintering behaviors), and to explore how migration delay related to mortality. Finally, to account for the impact of extended residence times in the reach for fish that delayed, we compared patterns in estimated average daily rates of mortality between migration behaviors and across population groups. Results suggest that migration delay was primarily triggered by high river temperatures but temperature thresholds for delay were lowest just before the seasonal peak in river temperatures. While all populations groups demonstrated these general patterns, we documented substantial variability in temperature thresholds and length of average delays across population groups. Although migration delay was related to higher reach mortality, it was also related to lower average daily mortality rates due to the proportional increase in reach passage duration being larger than the associated increase in mortality. Lower daily mortality rates suggest that migration delay could help mitigate the impacts of harsh migration conditions, presumably through the use of thermal refuges, despite prolonged exposure to local fisheries. Future studies tracking individual populations from their migration through reproduction could help illuminate the full extent of the tradeoffs between different migration behaviors.

Can we manage fisheries with the inherent uncertainty from eDNA?

Environmental (e)DNA, as a general approach in aquatic systems, seeks to connect the presence of species' genetic material in the water and hence to infer the species' physical presence. However, fisheries managers face making decisions with risk and uncertainty when eDNA indicates a fish is present but traditional methods fail to capture the fish. In comparison with traditional methods such as nets, electrofishing and piscicides, eDNA approaches have more sources of underlying error that could give rise to false positives. This has resulted in some managers to question whether eDNA can be used to make management decisions because there is no fish in hand. As a relatively new approach, the methods and techniques have quickly evolved to improve confidence in eDNA. By evaluating an eDNA based research programmes through the pattern of the eDNA signal, assay design, experimental design, quality assurance and quality control checks, data analyses and concurrent search for fish using traditional gears, the evidence for fish presence can be evaluated to build confidence in the eDNA approach. The benefits for fisheries management from adopting an eDNA approach are numerous but include cost effectiveness, broader geographic coverage of habitat occupancy, early detection of invasive species, non-lethal stock assessments, exploration of previously inaccessible aquatic environments and discovery of new species hidden beneath the water's surface. At a time when global freshwater and marine fisheries are facing growing threats from over-harvest, pollution and climate change, we anticipate that growing confidence in eDNA will overcome the inherent uncertainty of not having a fish in hand and will empower the informed management actions necessary to protect and restore our fisheries.

Industrial Applications of Dinoflagellate Phycotoxins Based on Their Modes of Action: A Review.

Dinoflagellates are an important group of phytoplanktons, characterized by two dissimilar flagella and distinctive features of both plants and animals. Dinoflagellate-generated harmful algal blooms (HABs) and associated damage frequently occur in coastal areas, which are concomitant with increasing eutrophication and climate change derived from anthropogenic waste and atmospheric carbon dioxide, respectively. The severe damage and harmful effects of dinoflagellate phycotoxins in the fishing industry have been recognized over the past few decades, and the management and monitoring of HABs have attracted much attention, leaving aside the industrial application of their valuable toxins. Specific modes of action of the organisms' toxins can effectively be utilized for producing beneficial materials, such as Botox and other therapeutic agents. This review aims to explore the potential industrial applications of marine dinoflagellate phycotoxins; furthermore, this review focuses on their modes of action and summarizes the available knowledge on them.

Protecting nursery areas without fisheries management is not enough to conserve the most endangered parrotfish of the Atlantic Ocean.

Marine protected areas (MPAs) are a primary strategy for marine conservation worldwide, having as a common goal the protection of essential habitats to enhance fish population recovery. However, MPAs alone may not be effective because species are not isolated from critical impacts occurring outside their boundaries. We evaluated how protecting critical nursery habitats affect the population of an important fishing target, using a 6-year database to predict juvenile hotspots and estimate population trends of the endemic and endangered parrotfish Scarus trispinosus within a mosaic of MPAs at the Abrolhos Bank, NE Brazil. We found that important nursery habitats are within no-take areas, but both juvenile and adult populations still show a declining trend over time. MPAs failed to ensure population maintenance and recovery likely due to overfishing in adjacent areas and the lack of compliance to management rules within multiple-use and within no-take MPAs. MPAs alone are not enough to protect ecologically important endangered species, but is still one of the only conservation strategies, particularly in developing countries. Our results shed light on the need for a wider adoption of more effective conservation policies in addition to MPAs, both in Brazil and in countries with similar governance contexts.

Mitigating seafloor disturbance of bottom trawl fisheries for North Sea sole Solea solea by replacing mechanical with electrical stimulation.

Ecosystem effects of bottom trawl fisheries are of major concern. Although it is prohibited to catch fish using electricity in European Union waters, a number of beam trawlers obtained a derogation and switched to pulse trawling to explore the potential to reduce impacts. Here we analyse whether using electrical rather than mechanical stimulation results in an overall reduction in physical disturbance of the seafloor in the beam-trawl fishery for sole Solea solea. We extend and apply a recently developed assessment framework to the Dutch beam-trawl fleet and show that the switch to pulse trawling substantially reduced benthic impacts when exploiting the total allowable catch of sole in the North Sea. Using Vessel Monitoring by Satellite and logbook data from 2009 to 2017, we estimate that the trawling footprint decreased by 23%, the precautionary impact indicator of the benthic community decreased by 39%, the impact on median longevity of the benthic community decreased by 20%, the impact on benthic biomass decreased by 61%, and the amount of sediment mobilised decreased by 39%. The decrease in impact is due to the replacement of tickler chains by electrode arrays, a lower towing speed and higher catch efficiency for sole. The effort and benthic physical disturbance of the beam-trawl fishery targeting plaice Pleuronectes platessa in the central North Sea increased with the recovery of the plaice stock. Our study illustrates the utility of a standardized methodological framework to assess the differences in time trends and physical disturbance between gears.

PeskAAS: A near-real-time, open-source monitoring and analytics system for small-scale fisheries.

Small-scale fisheries are responsible for landing half of the world's fish catch, yet there are very sparse data on these fishing activities and associated fisheries production in time and space. Fisheries-dependent data underpin scientific guidance of management and conservation of fisheries systems, but it is inherently difficult to generate robust and comprehensive data for small-scale fisheries, particularly given their dispersed and diverse nature. In tackling this challenge, we use open source software components including the Shiny R package to build PeskAAS; an adaptable and scalable digital application that enables the collation, classification, analysis and visualisation of small-scale fisheries catch and effort data. We piloted and refined this system in Timor-Leste; a small island developing nation. The features that make PeskAAS fit for purpose are that it is: (i) fully open-source and free to use (ii) component-based, flexible and able to integrate vessel tracking data with catch records; (iii) able to perform spatial and temporal filtering of fishing productivity by fishing method and habitat; (iv) integrated with species-specific length-weight parameters from FishBase; (v) controlled through a click-button dashboard, that was co-designed with fisheries scientists and government managers, that enables easy to read data summaries and interpretation of context-specific fisheries data. With limited training and code adaptation, the PeskAAS workflow has been used as a framework on which to build and adapt systematic, standardised data collection for small-scale fisheries in other contexts. Automated analytics of these data can provide fishers, managers and researchers with insights into a fisher's experience of fishing efforts, fisheries status, catch rates, economic efficiency and geographic preferences and limits that can potentially guide management and livelihood investments.

Using GIS and stakeholder involvement to innovate marine mammal bycatch risk assessment in data-limited fisheries.

Fisheries bycatch has been identified as the greatest threat to marine mammals worldwide. Characterizing the impacts of bycatch on marine mammals is challenging because it is difficult to both observe and quantify, particularly in small-scale fisheries where data on fishing effort and marine mammal abundance and distribution are often limited. The lack of risk frameworks that can integrate and visualize existing data have hindered the ability to describe and quantify bycatch risk. Here, we describe the design of a new geographic information systems tool built specifically for the analysis of bycatch in small-scale fisheries, called Bycatch Risk Assessment (ByRA). Using marine mammals in Malaysia and Vietnam as a test case, we applied ByRA to assess the risks posed to Irrawaddy dolphins (Orcaella brevirostris) and dugongs (Dugong dugon) by five small-scale fishing gear types (hook and line, nets, longlines, pots and traps, and trawls). ByRA leverages existing data on animal distributions, fisheries effort, and estimates of interaction rates by combining expert knowledge and spatial analyses of existing data to visualize and characterize bycatch risk. By identifying areas of bycatch concern while accounting for uncertainty using graphics, maps and summary tables, we demonstrate the importance of integrating available geospatial data in an accessible format that taps into local knowledge and can be corroborated by and communicated to stakeholders of data-limited fisheries. Our methodological approach aims to meet a critical need of fisheries managers: to identify emergent interaction patterns between fishing gears and marine mammals and support the development of management actions that can lead to sustainable fisheries and mitigate bycatch risk for species of conservation concern.

Morphological description of the first protozoeal stage of the deep-sea shrimps Aristeus antennatus and Gennadas elegans, with a key.

Accurate information on commercial marine species larvae is key to fisheries science, as their correct identification is the first step towards studying the species' connectivity patterns. In this study, we provide a complete morphological description of the first protozoeal stage of the valued deep-sea blue and red shrimp Aristeus antennatus and of the small mesopelagic shrimp Gennadas elegans. These two larval morphologies previously posed a risk of misidentification, thus hindering the study of A. antennatus larval ecology and dynamics in the context of fisheries science. Using specimens caught in the plankton at various locations in the Northwestern Mediterranean Sea and identification confirmed by molecular methods, the larvae of A. antennatus and G. elegans are distinguished from each other by the ornamentation of the antennula. A possible confusion in previous descriptions of Aristeidae larvae is addressed and a new key for the identification of Dendrobranchiata larvae provided.

Toward elimination of unwanted catches using a 100 mm T90 extension and codend in demersal mixed fisheries.

Most European fishing fleets will need to drastically reduce their unwanted catches to comply with new rules of the common fisheries policy. A more practical way to avoid increasing on-board sorting time and issues linked to storage capacity is to prevent unwanted catches in the first place. We assessed the selectivity properties of an experimental fishing gear that combined a 100 mm T90 cylinder with 130 meshes in the extension and a 100 mm T90 codend of 33 meshes (experimental gear) compared to a 100 mm diamond mesh extension and codend (control gear) during commercial trips using twin trawls. Analysis of the relative size composition of catches indicated a significantly higher escapement of small fish of several target species (e.g. Lepidorhombus whiffiagonis, Melanogrammus aeglefinus, Raja spp, and Lophius spp) and non-target species (e.g. Capros aper and Gurnards spp) from the T90 experimental trawl compared to the control trawl (n = 49 hauls), resulting in a significant reduction of unwanted catches of Gadidae, Triglidae, and Caproidae. In contrast, non-negligible commercial losses of small grade target gadoid species were observed. Mixed general linear models showed that the proportion of ray, haddock and anglerfish retained per length class decreased with increased tow duration. The T90 experimental gear will perform at a commercial level when targeting monkfish, megrim, rays and large haddock, however fishers are not likely to use this gear when targeting smaller-bodied species such as cephalopods, small haddock, whiting (Merlangius merlangus) and hake (Merluccius merluccius), because the gear is likely to allow large numbers to escape. Selectivity studies often focus on a short list of target species; however, catches of non-target species under quota can be problematic for some fisheries. For example, under the implementation of the Landing Obligation catches of boarfish could choke the French whitefish demersal fisheries in the Celtic sea, as France has no national quota for that species. The device tested constitutes an efficient solution to mitigate catches for such non-target schooling fish.

When an advantageous reproductive trait turns bad: Eggs of the threatened fish Genidens barbus as a natural bait in recreational fisheries.

This study describes a recreational fishing method focused on marine catfish, Genidens barbus (Endangered-EN), through the adoption of its eggs as a natural bait during its reproductive period in southern Brazilian ecosystems. Male G. barbus perform parental care, collecting eggs released by females after the fertilization process. Owing to this male behavioural pattern during the reproductive period, these individuals are easily caught in recreational fisheries that use eggs of the same species as a natural bait. The current adoption of G. barbus eggs as bait may intensify the fishing pressure on its populations.

Small is beautiful, but large is certified: A comparison between fisheries the Marine Stewardship Council (MSC) features in its promotional materials and MSC-certified fisheries.

The Marine Stewardship Council (MSC) sets a standard by which sustainable fisheries can be assessed and eco-certified. It is one of the oldest and most well-known fisheries certifications, and an estimated 15% of global fish catch is MSC-certified. While the MSC is increasingly recognized by decision-makers as an indicator for fishery success, it is also criticized for weak standards and overly-lenient third-party certifiers. This gap between the standard's reputation and its actual implementation could be a result of how the MSC markets and promotes its brand. Here we classify MSC-certified fisheries by gear type (i.e. active vs. passive) as well as by length of the vessels involved (i.e. large scale vs. small scale; with the division between the two occurring at 12 m in overall length). We compared the MSC-certified fisheries (until 31 December 2017) to 399 photographs the MSC used in promotional materials since 2009. Results show that fisheries involving small-scale vessels and passive gears were disproportionately represented in promotional materials: 64% of promotional photographs were of passive gears, although only 40% of MSC-certified fisheries and 17% of the overall catch were caught by passive gears from 2009-2017. Similarly, 49% of the photographs featured small-scale vessels, although just 20% of MSC-certified fisheries and 7% of the overall MSC-certified catch used small-scale vessels from 2009 to 2017. The MSC disproportionately features photographs of small-scale fisheries although the catch it certifies is overwhelmingly from industrial fisheries.

Noise exposure and effects on hearing in Brazilian fishermen.

BACKGROUND: Several health conditions among professional fishermen have been reported. Among the risks to the health of fishermen, it should be noted that high noise levels cause hearing loss and general health problems. OBJECTIVE: to investigate the effects of exposure to occupational noise on hearing in professional fishermen at the main large-scale commercial fishing center in Brazil. METHODS: A cross-sectional study, 466 Brazilian commercial fishermen participated in the study, all males, ages range 18-67 years. A total of 15 vessels were included in the study. The first phase involved assessment of the sound pressure levels (SPLs) in the vessels, the second phase involved the use of a questionnaire and audiological assessment. RESULTS: Most compartments registered SPLs greater than 80 dBA and the noisiest compartment was the engine-room, where the vessel pilot works. Among the fishermen, tinnitus was the most commonly reported symptom (48.63%). A higher prevalence of hearing loss was observed in engine-room keepers. Longer the length of time in service, and consequently, exposure to noise (in years), were associated with higher auditory thresholds. CONCLUSION: the tolerance limits to noise exposure were exceeded according to legislation. Fishing activities are associated with noise-induced hearing loss, with the risk increasing with the length of service.

Long-term observations from Antarctica demonstrate that mismatched scales of fisheries management and predator-prey interaction lead to erroneous conclusions about precaution.

Low catch limits for forage species are often considered to be precautionary measures that can help conserve marine predators. Difficulties measuring the impacts of fisheries removals on dependent predators maintain this perspective, but consideration of the spatio-temporal scales over which forage species, their predators, and fisheries interact can aid assessment of whether low catch limits are as precautionary as presumed. Antarctic krill are targeted by the largest fishery in the Southern Ocean and are key forage for numerous predators. Current krill removals are considered precautionary and have not been previously observed to affect krill-dependent predators, like penguins. Using a hierarchical model and 30+ years of monitoring data, we show that expected penguin performance was reduced when local harvest rates of krill were ≥0.1, and this effect was similar in magnitude to that of poor environmental conditions. With continued climate warming and high local harvest rates, future observations of penguin performance are predicted to be below the long-term mean with a probability of 0.77. Catch limits that are considered precautionary for forage species simply because the limit is a small proportion of the species' standing biomass may not be precautionary for their predators.