Elasmobranch fishing and trade in Sarawak,Malaysia, with implications for management

1. Many shark and ray (elasmobranch) species are threatened with extinction, due to overfishing and commercial trade
2. Sarawak is situated in Malaysian Borneo in the Coral Triangle: a global priority region for elasmobranch conservation. Malaysia is the world’s eighth largest elasmobranch fishing nation, and Sarawak is one of Malaysia’s largest fishing states, yet there are limited species-specific data on catch and trade of elasmobranchs to support conservation and fisheries management decisions.
3. This study presents landing site and market survey data, collected in Sarawak from January 2017 to December 2019. Geographical, temporal and operational trends in volumes of catch and trade are explored; the total volume, value and species composition of Sarawak's local elasmobranch markets is estimated; and simple size-based indicators are used to assess the sustainability of elasmobranch utilization for several conservation-priority and frequently traded species, including Critically Endangered and CITES-listed scalloped hammerhead sharks (Sphyrna lewini) and bottlenose wedgefish (Rhynchobatus australiae).
4. The results conservatively estimate that >26,500 elasmobranchs (~90,000 kg) are locally traded in Sarawak annually, worth ~US$125,000 per year at the market level.
5. Trade is dominated by small to medium-sized coastal requiem sharks (Carcharhinidae) and stingrays (Dasyatidae), with endangered and CITES-listed species making up 26% and 32% of total landings and trade, respectively.
6. High proportions of immature individuals were recorded, with evidence of overfishing for several species, based on simple size-based indicators.
7. Several options are outlined for improving management of elasmobranch fishing and trade in the future, including spatio-temporal closures and live release protocols, which could help to reduce the mortality of critically endangered species and implement CITES. Such measures could have large conservation impacts with limited socio-economic cost, since these species make up <5% of the total value of the elasmobranch market. However, management plans need to be co-designed with full participation of affected coastal communities in order to be ethical and effective.

     

Where land meets sea: Intertidal areas as key-habitats for sharks and rays

Intertidal habitats (i.e. marine habitats that are (partially) exposed during low tide) have traditionally been studied from a shorebird-centred perspective. We show that these habitats are accessible and important to marine predators such as elasmobranchs (i.e. sharks and rays). Our synthesis shows that at least 43 shark and 45 ray species, of which 54.5% are currently threatened, use intertidal habitats. Elasmobranchs use intertidal habitats mostly for feeding and as refugia, but also for parturition and thermoregulation. However, the motivation of intertidal habitat use remains unclear due to limitations to observe elasmobranch behaviour in these dynamic habitats. We argue that elasmobranch predators can play an important role in intertidal food webs by feeding on shared resources during high tide (i.e. ‘high-tide predators’), which are accessible and also consumed by terrestrial or avian predators during low tide (i.e. ‘low-tide predators’). In addition, elasmobranchs are able to change the bio-geomorphology of intertidal habitats by increasing habitat heterogeneity due to feeding activities and may also alter resource availability for other consumers. We discuss how the ecological role of elasmobranchs in intertidal habitats is being affected by the continued overexploitation of these species, and conversely, how the global loss of intertidal areas poses an additional threat to an already vulnerable taxonomic group. We conclude that studies on intertidal ecology should include both low-tide (e.g. shorebirds) and high-tide (e.g. elasmobranchs) predatory guilds and their ecological interactions. The global loss of elasmobranch predatory species and intertidal habitat provides additional compelling arguments for the conservation of these areas.     

Social ties explain catch portfolios of small‐scale fishers in the Caribbean

Small‐scale fisheries often involve weak management regimes with limited top‐down enforcement of rules and minimal support from legal institutions, making them useful model systems for investigating the role of social influence in determining economic and environmental outcomes. In such regimes, interpersonal relationships are expected to have a strong effect on a fisher's catch portfolio, the set of fish species targeted by an individual fisher. Here, we test three competing hypotheses about social influence using belief propagation network models and show that a peer‐to‐peer information‐sharing social network is key to explaining catch portfolios at a small‐scale fishery in Jamaica. We find that experience dictates the direction of influence among fishers in the social network, with older fishers and information brokers having distinct roles in shaping catch patterns for large‐ and small‐sized fish species, respectively. These findings highlight concrete opportunities for harnessing social networks in natural resource management. Our new approach to modelling social influence is applicable to many social–ecological systems with minimal legal and institutional support or those that rely heavily on bottom‐up participatory processes.     

Social networks in elasmobranchs and teleost fishes

Over the last decade, there has been an exponential increase in studies using social network analysis to describe the structure of animal societies. In this synthesis, we examine the contribution of social network analysis towards developing our understanding of the social organization of elasmobranchs and teleost fishes. We review and discuss the current state of knowledge of the mechanisms and functions underpinning social network structure in fishes with particular emphasis on cooperation, familiarity, site fidelity, population structure and the welfare of captive populations. We also discuss important methodological issues (e.g. how to identify and mark fish) and highlight new developments in this area of research and their implications for the study of fish behaviour. Finally, we outline promising future research areas for the application of social network analysis to teleost fishes and elasmobranchs.     

Population genetic divergence of bonnethead sharks Sphyrna tiburo in the western North Atlantic: Implications for conservation

1. Sharks are a priority for conservation because numerous species, including small-sized coastal species, are being heavily exploited by commercial and recreational fisheries. Understanding the genetic population structure of sharks is key to effective management, maximizing their evolutionary potential in a rapidly changing environment and preventing population declines.
2. Limited dispersal is an important factor promoting population divergence for several coastal shark species. The genetic variation in 14 microsatellite loci and 21,006 single nucleotide polymorphisms genotyped using restriction-site-associated DNA sequencing was analysed to assess the genetic structure of the bonnethead shark, Sphyrna tiburo, in the western North Atlantic.
3. Genetic differences were identified among three well-defined regions: the western Florida coast, the south-eastern US Atlantic coast, and the southern Gulf of Mexico. Results support previous studies based on mitochondrial DNA sequences in defining differences among these regions and suggest limitations of bonnethead sharks in routinely performing long-distance migrations.
4. The limited connectivity among regions explains the pattern of genetic divergence but also reported divergence at the species/subspecies level. These genetically discrete bonnethead populations have independent evolutionary histories that may include local adaptations to specific areas.
5. Bonnethead sharks are currently managed as two stocks in the USA owing to recent genetic, tagging, and life history studies; however, no stock assessments or management plans exist for Mexico. These results not only serve to reinforce US management strategies and provide critical data about the extent of gene flow and sex dispersal among populations, but also begin the process of effective management in the waters of Mexico to ensure the long-term productivity and resilience of this species. With an absence of gene flow between populations from US waters and the southern Gulf of Mexico, there is a need for management plans based upon independent biological and population dynamics data since limited or no opportunities for populations to interchange individuals may occur to re-establish population viability.

     

Naturally occurring lesions and micro-organisms in two species of free-living sharks: the spiny dogfish, Squalus acanthias L., and the smooth dogfish, Mustelus canis (Mitchill), from the north-western Atlantic

Twenty-three smooth dogfish, Mustelus canis L., and 20 spiny dogfish, Squalus acanthias (Mitchill), were examined for the presence of diseases. Sharks were collected from the north-western Atlantic between April and September 2000. Major organs were sampled for histopathology and bacterial cultures were taken from kidneys. Macroscopic lesions were infrequent and included intestinal cestodiasis and gastric and dermal erosions. Microscopic lesions were common in both shark species. Mustelus canis had numerous degenerative lesions involving the pancreatic ducts, seminiferous tubules and coronary vessels. The most frequent lesions in S. acanthias were parasitic and included pancreatic nematodiasis and biliary myxosporeosis. Additionally, both species had focal meningitis, encephalitis, dermatitis, gastritis, enteritis and glomerulomesangial thickening. Microscopic parasites included intestinal coccidiosis, unclassified gastric and testicular protozoa, skeletal muscle and renal tubular myxosporeans, a branchial trichodinid ciliate, olfactory and branchial trematodes, gastrointestinal cestodes and larval nematodes. Shewanella putrefaciens , Photobacterium sp., Vibrio sp., Pseudomonas sp. and Alteromonas sp. were isolated from kidneys of nine sharks. The role of the above lesions in the natural mortality and morbidity of the two shark species is unknown. The finding that apparently healthy sharks can harbour potentially debilitating lesions warrants the inclusion of histopathological studies in the management and conservation of sharks.     

An unfished area enhances a spiny lobster,Panulirus argus,fishery: implications for management and conservation within a Biosphere Reserve in the Mexican Caribbean

The Caribbean spiny lobster, Panulirus argus, Latreille, is the main source of income for the communities in the Sian Ka'an Biosphere Reserve Mexico. The fishery has recently been certified as sustainable by the Marine Stewardship Council provided that further stock assessment is carried out. A total of 379 lobsters were tagged in an unfished area offshore from the Bahía del Espíritu Santo fishing grounds to assess whether lobsters remained within these areas and were thus fully protected. The lobsters recaptured in the shallow area (5.3%) were sufficient to develop a multistate mark recapture model, which takes into account fishing and natural mortality, tag reporting rate and tag loss. This estimated that between 15 and 20% of all adult lobsters dwelling in the unfished area moved into the fishery and were subjected to exploitation. This study suggests that the offshore unfished area provides protection to the majority of the stock in this area while adding to and maintaining fishing yields within the inshore commercial fishery.     

You can swim but you can't hide: the global status and conservation of oceanic pelagic sharks and rays

• 1. Fishing spans all oceans and the impact on ocean predators such as sharks and rays is largely unknown. A lack of data and complicated jurisdictional issues present particular challenges for assessing and conserving high seas biodiversity. It is clear, however, that pelagic sharks and rays of the open ocean are subject to high and often unrestricted levels of mortality from bycatch and targeted fisheries for their meat and valuable fins.
• 2. These species exhibit a wide range of life‐history characteristics, but many have relatively low productivity and consequently relatively high intrinsic vulnerability to over‐exploitation. The IUCN — World Conservation Union Red List criteria were used to assess the global status of 21 oceanic pelagic shark and ray species.
• 3. Three‐quarters (16) of these species are classified as Threatened or Near Threatened. Eleven species are globally threatened with higher risk of extinction: the giant devilray is Endangered, ten sharks are Vulnerable and a further five species are Near Threatened. Threat status depends on the interaction between the demographic resilience of the species and intensity of fisheries exploitation.
• 4. 4. Most threatened species, like the shortfin mako shark, have low population increase rates and suffer high fishing mortality throughout their range. Species with a lower risk of extinction have either fast, resilient life histories (e.g. pelagic stingray) or are species with slow, less resilient life histories but subject to fisheries management (e.g. salmon shark).
• 5. 5. Recommendations, including implementing and enforcing finning bans and catch limits, are made to guide effective conservation and management of these sharks and rays.

Copyright © 2008 John Wiley & Sons, Ltd.     

A comparative analysis between recreational and artisanal fisheries in a Mediterranean coastal area

The biological impact and the social characteristics of different artisanal (professional) and recreational fishing techniques on the marine resources of a coastal Mediterranean area were compared. Data were from artisanal and recreational surveys carried out between 2006 and 2010. Competition between recreational (particularly spear fishing) and artisanal fishers for the natural resources is important as 52% of the 98 species surveyed were caught by both types of fishers. A total of 87 species were caught by all artisanal fishing gears together (of which 84% were retained and 16% discarded). Recreational fishing caught 58 species of which none was systematically discarded. The two fishing techniques that raise major environmental concerns are spear fishing (very selective in terms of species and/or sizes and high intrinsic vulnerability of catches) and trammel netting (highest number of species discarded and highest number of species endangered). Important challenges from the social standpoint were found that need to be taken into account in the management of coastal fisheries in the Mediterranean Sea including: progressive disappearance of the artisanal fisheries, ageing of the artisanal fisher populations and decline in the number of fishing gears used by artisanal fishers.     

The mitigation hierarchy for sharks: A risk‐based framework for reconciling trade‐offs between shark conservation and fisheries objectives

Sharks and their cartilaginous relatives are one of the world's most threatened species groups. The primary cause is overfishing in targeted and bycatch fisheries. Reductions in fishing mortality are needed to halt shark population declines. However, this requires complex fisheries management decisions, which often entail trade‐offs between conservation objectives and fisheries objectives. We propose the mitigation hierarchy (MH)—a step‐wise precautionary approach for minimizing the impacts of human activity on biodiversity—as a novel framework for supporting these management decisions. We outline a holistic conceptual model for risks to sharks in fisheries, which includes biophysical, operational and socioeconomic considerations. We then demonstrate how this model, in conjunction with the MH, can support risk‐based least cost shark conservation. Through providing examples from real‐world fishery management problems, we illustrate how the MH can be applied to a range of species, fisheries and contexts, and explore some of the opportunities and challenges hereto. Finally, we outline next steps for research and implementation. This is important in the context of increasing international regulation of shark fishing and trade, which must lead to reductions in shark mortality, while managing trade‐offs between conservation objectives and the socioeconomic value of fisheries.     

When large marine predators feed on fisheries catches: Global patterns of the depredation conflict and directions for coexistence

The sustainable mitigation of human–wildlife conflicts has become a major societal and environmental challenge globally. Among these conflicts, large marine predators feeding on fisheries catches, a behaviour termed “depredation,” has emerged concomitantly with the expansion of the world’s fisheries. Depredation poses threats to both the socio‐economic viability of fisheries and species conservation, stressing the need for mitigation. This review synthesizes the extent and socio‐ecological impacts of depredation by sharks and marine mammals across the world, and the various approaches used to minimize it. Depredation was reported in 214 fisheries between 1979 and 2019 (70% post‐2000) and affected fleets from 44 countries, in all sectors (commercial, artisanal and recreational), and in all major fishing techniques (nets, traps and hook‐and‐lines). A total of 68 predator species were involved in depredation (20 odontocetes, 21 pinnipeds and 27 sharks), and most (73%) were subject to either by‐catch and/or retaliatory killing from fishers when interacting with gear. Impacts on fishers were primarily associated with catch losses and gear damage but often lacked assessments. Deterrence was a major mitigation approach but also the least effective. Gear modifications or behavioural adaptation by fishers were more promising. This review highlights the need for improved monitoring, and interdisciplinary and integrated research to quantify the determinants and impacts of depredation in the socio‐ecological dimension. More importantly, as the conflict is likely to escalate, efforts directed towards changing perceptions and integrating knowledge through adaptive co‐management are raised as key directions towards coexistence between fisheries and large marine predators.     

Estimating the ecological,economic and social impacts of ocean acidification and warming on UK fisheries

Assessments of the combined ecological impacts of ocean acidification and warming (OAW) and their social and economic consequences can help develop adaptive and responsive management strategies in the most sensitive regions. Here, available observational and experimental data, theoretical, and modelling approaches are combined to project and quantify potential effects of OAW on the future fisheries catches and resulting revenues and employment in the UK under different CO₂ emission scenarios. Across all scenarios, based on the limited available experimental results considered, the bivalve species investigated were more affected by OAW than the fish species considered, compared with ocean warming alone. Projected standing stock biomasses decrease between 10 and 60%. These impacts translate into an overall fish and shellfish catch decrease of between 10 and 30% by 2020 across all areas except for the Scotland >10 m fleet. This latter fleet shows average positive impacts until 2050, declining afterwards. The main driver of the projected decreases is temperature rise (0.5–3.3 °C), which exacerbate the impact of decreases in primary production (10–30%) in UK fishing waters. The inclusion of the effect of ocean acidification on the carbon uptake of primary producers had very little impact on the projections of potential fish and shellfish catches (<1%). The <10 m fleet is likely to be the most impacted by‐catch decreases in the short term (2020–50), whereas the effects will be experienced more strongly by the >10 m fleet by the end of the century in all countries. Overall, losses in revenue are estimated to range between 1 and 21% in the short term (2020–50) with England and Scotland being the most negatively impacted in absolute terms, and Wales and North Ireland in relative terms. Losses in total employment (fisheries and associated industries) may reach approximately 3–20% during 2020–50 with the >10 m fleet and associated industries bearing the majority of the losses.     

Pathology associated with retained fishing hooks in blue sharks, Prionace glauca (L.), with implications for their conservation

Fishing hooks retained from previous capture events were found in 6 of 211 blue sharks, Prionace glauca (L.), landed in the summers of 1999 and 2000 by recreational fishermen off Long Island (New York, USA). The hooks were embedded within the distal oesophagus ( n =3), or perforated the gastric wall ( n =3) and lacerated the liver ( n =2). The hooks were surrounded by excessive fibronecrotic tissue which ablated the normal anatomical structures and in the three sharks with oesophageal hooks caused partial luminal obstruction. Accompanying lesions included oesophagitis, gastritis, hepatitis and proliferative peritonitis. Aeromonas sp. and Vibrio sp. were isolated from the peritoneal fluid of one shark with peritonitis and intralesional bacteria were seen on histological examination in all sharks. This is the first report of the prevalence and pathology of retained fishing hooks in a large number of wild-caught sharks.     

Melanomacrophages in three species of free-ranging sharks from the northwestern Atlantic, the blue shark Prionacae glauca (L.), the shortfin mako, Isurus oxyrhinchus Rafinesque, and the thresher, Alopias vulpinus (Bonnaterre)

The melanomacrophage aggregates or cells (MMC) are commonly used as biomarkers of exposure to pollution in fish, albeit their numbers and morphological characteristics can be influenced not only by environmental toxins but also by a range of physiological parameters and pathological conditions. Accordingly, before we can use MMC as biomarkers in any fish species, their normal, 'background' characteristics have to be established in apparently healthy fish. The knowledge of MMC in sharks is minimal. The aim of this study was to characterize MMC from 51 free-ranging, large pelagic sharks from the northwestern Atlantic, including shortfin mako, Isurus oxyrhinchus , thresher, Alopias vulpinus and blue shark, Prionacae glauca . The rationale of this study was twofold. First, because, sharks have life histories predisposing them to the accumulation of environmental toxins they constitute good sentinel species of the health of the global marine ecosystem. Second, because many shark populations are in decline or threatened by extinction, we need to expand our understanding of their health status in order to develop appropriate protective measures. All sharks were collected by sports fishing gear between June and August in 2007. Their health condition was assessed by necropsy, morphometrics, and by microscopic examination of gonads, livers, spleens and kidneys. Routine, haematoxylin and eosin and/or Pearl's reagent-stained paraffin embedded sections were studied by light microscopy. Our results provide the first data on the morphometric and morphological characteristics of MMC in viscera of apparently healthy free-ranging sharks from the northwestern Atlantic.     

Movements and diving behaviour of white-chinned petrels: Diurnal variation and implications for bycatch mitigation

1. Many seabirds dive to forage, and the ability to use this hunting technique varies according to such factors as morphology, physiology, prey availability, and ambient light levels. Proficient divers are more able to seize sinking baits deployed by longline fishing vessels and may return them to the surface, increasing exposure of other species. Hence, diving ability has major implications for mitigating incidental mortality (bycatch) in fisheries.
2. Here, the diving behaviour and activity patterns of the most bycaught seabird species worldwide, the white-chinned petrel (Procellaria aequinoctialis), tracked from Bird Island (South Georgia), are analysed. Three data sources (dives, spatial movements, and immersion events) are combined to examine diverse aspects of at-sea foraging behaviour, and their implications for alternative approaches to bycatch mitigation are considered.
3. The tracked white-chinned petrels (n = 14) mostly performed shallow dives (<3 m deep) of very short duration (<5 s), predominantly during darkness, but only 7 and 10% of landings in daylight and darkness, respectively, involved diving, suggesting that surface-seizing is the preferred foraging technique. Nonetheless, individuals were able to dive to considerable depth (max = 14.5 m) and at speed (max = 2.0 m·s⁻¹), underlining the importance of using heavy line-weighting to maximize hook sink rates, and bird-scaring lines (Tori lines) that extend for long distances behind vessels to protect hooks until beyond diving depths.

     

Spawning behaviour of amemasu charr,Salvelinus leucomaenis leucomaenis,with a discussion of the macroevolutionary patterns of postspawning behaviour in the Salmoninae

Abstract – Video cameras inside underwater housings were used to record the spawning behaviour of a subspecies of the white‐spotted charr, the amemasu charr (Salvelinus leucomaenis leucomaenis) in the Tokimae and Onbetsu Rivers, Hokkaido, Japan. Unlike other Salvelinus species, in which females use lateral swings of their bodies to ventilate and distribute eggs over gravel crevices (undulating) immediately after spawning, female amemasu charr covered their eggs with beats of their tails (cover digging). Cover digging right after spawning has previously been documented in Salmo, Oncorhynchus and Parahucho. Phylogenetic analysis of postspawning behaviours in the Salmoninae indicated that (i) resting then covering the eggs is plesiomorphic for the group, (ii) undulating replaced resting in the ancestor of Salvelinus, (iii) cover digging was advanced in the behavioural sequence to occur immediately after egg deposition in the ancestor of Parahucho + Salmo + Oncorhynchus and in the amemasu.     

Fishing for feed in China: Facts,impacts and implications

China is the world's largest capture fisheries and aquaculture producer. Over recent decades, China's domestic marine catch composition has changed markedly, from large volumes of a few high‐valued food species to multiple, small, low‐valued, species, a significant proportion of which is primarily used as animal, especially fish, feed. Despite the growing volume and economic importance of the feed catches, their species composition, catch volumes and socio‐environmental impacts are all poorly understood. Based on a nationwide survey of >800 fishing vessels, and the identification and measurement of >12,000 fish and invertebrate individuals, the present study provides an overview of the feed component of China's domestic marine catch, by volumes, species and sizes, and found it to be substantial and biologically unsustainable. Half of the trawler catch (3 million metric tons, mmt), or 35% of the total catch (4.6 mmt) in China's exclusive economic zone, are now comprised of low‐valued “feed‐grade fish”. The present study identified 218 fish species, 50 crustaceans and five cephalopods, and of these, 102 fish species were food species with 89% individuals in their juvenile size ranges. Feed‐grade fish were mainly used as aquaculture feed directly, or indirectly, through the feed industry after reduction to fishmeal and fish oil. The unparalleled scale and poor fisheries resource condition of China's domestic marine fisheries, in parallel with severe overfishing of juveniles, creates a demand for fundamental changes to fishery management practices, including a significant reduction of fishing effort to ensure productivity and ecosystem resilience.     

Effect of air exposure on scallop behaviour, and the implications for subsequent survival in culture

Scallop spat produced for continued culture normally requiretransportation between sites, and the associated stresses may causemortalities. In the present experiment, scallops of 40–55 mm shell heightwere emersed in air for time intervals up to 24 h and their behaviourexamined once re-immersed. Scallops were placed upside-down and thenumber of movements and the cumulative numbers righting in 5 min timeblocks were recorded. The greatest frequency for all behaviouralresponses was found at 15–17 °C in August. Responses were reducedin November and June (9–11 °C) and least at 5 °C in January.All effects of treatment, temperatures and season, and increases in airexposure were significantly different. Following the treatments, mortalitiesafter 10 days in culture was about 10–30% for scallops emersed for 18 and24 h in August and June. Scallops did not show significantly differentbehaviour whether they were emersed upright or inverted. However,scallops emersed at 15 °C had fewer responses than scallops held at <10 °C, so chilling during transport may prolong scallop vitality. Theresults suggest that air exposure >12 h should be avoided. At temperatures>9 °C, behavioural responses may be a simple and effective method toassess vitality which can assist in the management of scallop culture.     

Spatial patterns of recreational exploitation in eastern Australian ROFAs: implications for zonal management

Effective management of recreational fisheries requires information on fine‐scale spatial patterns of recreational exploitation. Such information is particularly important for specially designated regions such as recreational‐only fishing areas (ROFAs). Using data acquired through progressive counts and interview‐based surveys, this study quantitatively compared recreational effort, harvest‐per‐unit‐effort (HPUE) and species composition among zonal habitats in three representative estuarine ROFAs in eastern Australia. The zones compared were as follows: (1) entrance channels; (2) lake areas; (3) artificial reefs; (4) tributary creeks; (5) rivers; and (6) canals. In most cases, effort was concentrated in the lake zones, which had the greatest access to fisheries resources. The lake and channel zones were associated with some of the highest HPUEs for key taxa [Acanthopagrus spp. (hybrid complex of Acanthopagrus butcheri (Munro) × Acanthopagrus australis (Owen)), Platycephalus fuscus (Cuvier), Sillago ciliata (Cuvier) and Girella tricuspidata (Quoy & Gaimard)] and a greater number of highly sought‐after species. Drawing on specific examples from these findings, this paper concludes by illustrating how spatial information on exploitation gained from this type of research can be used to meet the fundamental goals of recreational fisheries management at fine spatial scales.     

Distribution,structure and function of Nordic eelgrass (Zostera marina) ecosystems: implications for coastal management and conservation

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