Showing papers by "National Marine Fisheries Service published in 2019"

Impacts of historical warming on marine fisheries production.

Abstract: Climate change is altering habitats for marine fishes and invertebrates, but the net effect of these changes on potential food production is unknown. We used temperature-dependent population models to measure the influence of warming on the productivity of 235 populations of 124 species in 38 ecoregions. Some populations responded significantly positively (n = 9 populations) and others responded significantly negatively (n = 19 populations) to warming, with the direction and magnitude of the response explained by ecoregion, taxonomy, life history, and exploitation history. Hindcasts indicate that the maximum sustainable yield of the evaluated populations decreased by 4.1% from 1930 to 2010, with five ecoregions experiencing losses of 15 to 35%. Outcomes of fisheries management-including long-term food provisioning-will be improved by accounting for changing productivity in a warmer ocean.

Krill ( Euphausia superba ) distribution contracts southward during rapid regional warming

Abstract: High-latitude ecosystems are among the fastest warming on the planet1. Polar species may be sensitive to warming and ice loss, but data are scarce and evidence is conflicting2–4. Here, we show that, within their main population centre in the southwest Atlantic sector, the distribution of Euphausia superba (hereafter, ‘krill’) has contracted southward over the past 90 years. Near their northern limit, numerical densities have declined sharply and the population has become more concentrated towards the Antarctic shelves. A concomitant increase in mean body length reflects reduced recruitment of juvenile krill. We found evidence for environmental controls on recruitment, including a reduced density of juveniles following positive anomalies of the Southern Annular Mode. Such anomalies are associated with warm, windy and cloudy weather and reduced sea ice, all of which may hinder egg production and the survival of larval krill5. However, the total post-larval density has declined less steeply than the density of recruits, suggesting that survival rates of older krill have increased. The changing distribution is already perturbing the krill-centred food web6 and may affect biogeochemical cycling7,8. Rapid climate change, with associated nonlinear adjustments in the roles of keystone species, poses challenges for the management of valuable polar ecosystems3. As the southwest Atlantic sector of the Southern Ocean has warmed, the distribution of a key species, Antarctic krill, has contracted southwards. This has occurred in tandem with a decline in recruitment of juveniles, linked to increasingly positive anomalies of the Southern Annular Mode.

Sex-dependent dominance maintains migration supergene in rainbow trout

Abstract: Males and females often differ in their fitness optima for shared traits that have a shared genetic basis, leading to sexual conflict. Morphologically differentiated sex chromosomes can resolve this conflict and protect sexually antagonistic variation, but they accumulate deleterious mutations. However, how sexual conflict is resolved in species that lack differentiated sex chromosomes is largely unknown. Here we present a chromosome-anchored genome assembly for rainbow trout (Oncorhynchus mykiss) and characterize a 55-Mb double-inversion supergene that mediates sex-specific migratory tendency through sex-dependent dominance reversal, an alternative mechanism for resolving sexual conflict. The double inversion contains key photosensory, circadian rhythm, adiposity and sex-related genes and displays a latitudinal frequency cline, indicating environmentally dependent selection. Our results show sex-dependent dominance reversal across a large autosomal supergene, a mechanism for sexual conflict resolution capable of protecting sexually antagonistic variation while avoiding the homozygous lethality and deleterious mutations associated with typical heteromorphic sex chromosomes.

Understanding PCR Processes to Draw Meaningful Conclusions from Environmental DNA Studies.

Abstract: As environmental DNA (eDNA) studies have grown in popularity for use in ecological applications, it has become clear that their results differ in significant ways from those of traditional, non-PCR-based surveys. In general, eDNA studies that rely on amplicon sequencing may detect hundreds of species present in a sampled environment, but the resulting species composition can be idiosyncratic, reflecting species’ true biomass abundances poorly or not at all. Here, we use a set of simulations to develop a mechanistic understanding of the processes leading to the kinds of results common in mixed-template PCR-based (metabarcoding) studies. In particular, we focus on the effects of PCR cycle number and primer amplification efficiency on the results of diversity metrics in sequencing studies. We then show that proportional indices of amplicon reads capture trends in taxon biomass with high accuracy, particularly where amplification efficiency is high (median correlation up to 0.97). Our results explain much of the observed behavior of PCR-based studies, and lead to recommendations for best practices in the field.

Bottom trawl surveys in the northern Bering Sea indicate recent shifts in the distribution of marine species

Abstract: The climate regime in the eastern Bering Sea has recently been dominated by a pattern of multi-year stanzas, in which several successive years of minimal sea-ice formation and warm summer temperatures (e.g., 2002–2005, 2014–2017) alternate with several years of relatively extensive sea-ice formation and cold summer temperatures (e.g., 2006–2013). This emerging climate pattern may be forcing long-term changes in the spatial distributions of the Bering Sea’s marine fauna. The National Marine Fisheries Service’s Alaska Fisheries Science Center recently conducted two bottom trawl surveys covering the entire Bering Sea shelf from the Alaska Peninsula to the Bering Strait. The first, in the summer of 2010, was conducted during a cold year when the majority of the continental shelf was covered by a pool of cold (< 2 °C) water. The second, in the summer of 2017, was during a warmer year with water temperatures above the long-term survey mean. These two surveys recorded significantly different spatial distributions for populations of several commercially important fish species, including walleye pollock (Gadus chalcogrammus), Pacific cod (Gadus macrocephalus), and several flatfish species, as well as jellyfishes. Population shifts included latitudinal displacement as well as variable recruitment success. The large-scale distributional shifts reported here for high-biomass species raise questions about long-term ecosystem impacts, and highlight the need for continued monitoring. They also raise questions about our management strategies for these and other species in Alaska’s large marine ecosystems.

Contrasting genomic shifts underlie parallel phenotypic evolution in response to fishing

Abstract: Humans cause widespread evolutionary change in nature, but we still know little about the genomic basis of rapid adaptation in the Anthropocene. We tracked genomic changes across all protein-coding genes in experimental fish populations that evolved pronounced shifts in growth rates due to size-selective harvest over only four generations. Comparisons of replicate lines show parallel allele frequency shifts that recapitulate responses to size-selection gradients in the wild across hundreds of unlinked variants concentrated in growth-related genes. However, a supercluster of genes also rose rapidly in frequency and dominated the evolutionary dynamic in one replicate line but not in others. Parallel phenotypic changes thus masked highly divergent genomic responses to selection, illustrating how contingent rapid adaptation can be in the face of strong human-induced selection.

Disease epidemic and a marine heat wave are associated with the continental-scale collapse of a pivotal predator (Pycnopodia helianthoides).

Abstract: Multihost infectious disease outbreaks have endangered wildlife, causing extinction of frogs and endemic birds, and widespread declines of bats, corals, and abalone. Since 2013, a sea star wasting disease has affected >20 sea star species from Mexico to Alaska. The common, predatory sunflower star (Pycnopodia helianthoides), shown to be highly susceptible to sea star wasting disease, has been extirpated across most of its range. Diver surveys conducted in shallow nearshore waters (n = 10,956; 2006–2017) from California to Alaska and deep offshore (55 to 1280 m) trawl surveys from California to Washington (n = 8968; 2004–2016) reveal 80 to 100% declines across a ~3000-km range. Furthermore, timing of peak declines in nearshore waters coincided with anomalously warm sea surface temperatures. The rapid, widespread decline of this pivotal subtidal predator threatens its persistence and may have large ecosystem-level consequences.

Realizing resilience for decision-making

Abstract: Researchers and decision-makers lack a shared understanding of resilience, and practical applications in environmental resource management are rare. Here, we define social-ecological resilience as a property of social-ecological systems that includes at least three main characteristics — resistance, recovery and robustness (the ‘three Rs’). We define socio-economic resilience management as planning, adaptation and transformational actions that may influence these system characteristics. We integrate the three Rs into a heuristic for resilience management that we apply in multiple management contexts to offer practical, systematic guidance about how to realize resilience.

Responses of the Northern Bering Sea and Southeastern Bering Sea Pelagic Ecosystems Following Record-Breaking Low Winter Sea Ice

Abstract: Bering Sea sea ice during winter 2017–2018 was the lowest ever recorded. Ecosystem effects of low ice have been observed in the southeastern Bering Sea, but never in the northern Bering Sea. Observations in both systems included weakened water column stratification, delayed spring bloom, and low abundances of large crustacean zooplankton. Summer Cold Pool presence was extremely limited. Young walleye pollock production and condition were similar to prior warm years, though catches of other pelagic forage fishes were low. Summer seabird die‐offs were observed in the northern Bering Sea, and to lesser extent in the southeastern Bering Sea, and reproductive success was poor at monitored colonies. Selected bottom‐up responses to lack of sea ice in the north were similar to those in the south, potentially providing environmental indicators to project ecosystem effects in a lesser studied system. Results offer a potential glimpse of the broader Bering Sea pelagic ecosystem under future low‐ice projections. Plain Language Summary During the winter of 2017–2018, there was a lack of winter sea ice in the northern and southeastern Bering Sea. This was unprecedented, and its implications were unknown, especially for the northern Bering Sea. Ecosystem surveys showed that oceanic plants and animals at the base of the food web were delayed in their spring production and food quality was generally low. Abundances of young walleye pollock, a commercial species important to the global fish market, were average in 2018, but catches of other forage fishes were lower. Seabird die‐offs in the northern Bering Sea were extensive. If heat‐related ecosystem changes previously observed in the southeastern Bering Sea ecosystem are now happening in the northern Bering Sea, disruptions to food webs and increased die‐offs could occur if oceans continue to warm in the future.

Conceptualizing Ecological Responses to Dam Removal: If You Remove It, What's to Come?

Abstract: One of the desired outcomes of dam decommissioning and removal is the recovery of aquatic and riparian ecosystems. To investigate this common objective, we synthesized information from empirical studies and ecological theory into conceptual models that depict key physical and biological links driving ecological responses to removing dams. We define models for three distinct spatial domains: upstream of the former reservoir, within the reservoir, and downstream of the removed dam. Emerging from these models are response trajectories that clarify potential pathways of ecological transitions in each domain. We illustrate that the responses are controlled by multiple causal pathways and feedback loops among physical and biological components of the ecosystem, creating recovery trajectories that are dynamic and nonlinear. In most cases, short-term effects are typically followed by longer-term responses that bring ecosystems to new and frequently predictable ecological condition, which may or may not be similar to what existed prior to impoundment.

Major Shifts in Pelagic Micronekton and Macrozooplankton Community Structure in an Upwelling Ecosystem Related to an Unprecedented Marine Heatwave

Abstract: The community structure of pelagic zooplankton and micronekton may be a sensitive indicator of changes in environmental conditions within the California Current ecosystem. Substantial oceanographic changes in 2015 and 2016 due to the anomalously warm ocean conditions associated with the ‘warm blob’ and a major El Nino perturbation resulted in onshore and northward advection of warmer and more stratified surface waters resulting in reduced upwelling. Data from fine-mesh pelagic trawl surveys conducted off Oregon and Washington during early summer of 2011 and 2013-2016 were examined for interannual changes in spatial distribution and abundance of fish and invertebrate taxa. Overall species diversity was highest in 2015 and lowest in 2011, but 2016 was similar to the other years, although the evenness was somewhat lower. The community of taxa in both 2015 and 2016 was significantly different from the previously sampled years. Crustacean plankton densities (especially Euphausiidae) were extremely low in both years, and the invertebrate composition became dominated mostly by gelatinous zooplankton. Fishes and cephalopods showed mixed trends overall, but some species such as age-0 Pacific hake were found in relatively high abundances mainly along the shelf break in 2015 and 2016. These results suggest dramatically different pelagic communities were present during the recent warm years with a greater contribution from offshore taxa, especially gelatinous taxa, during 2015 and 2016. The substantial reorganization of the pelagic community has the potential to lead to major alterations in trophic functioning in this normally productive ecosystem.

The importance of migratory connectivity for global ocean policy

Abstract: The distributions of migratory species in the ocean span local, national and international jurisdictions. Across these ecologically interconnected regions, migratory marine species interact with anthropogenic stressors throughout their lives. Migratory connectivity, the geographical linking of individuals and populations throughout their migratory cycles, influences how spatial and temporal dynamics of stressors affect migratory animals and scale up to influence population abundance, distribution and species persistence. Population declines of many migratory marine species have led to calls for connectivity knowledge, especially insights from animal tracking studies, to be more systematically and synthetically incorporated into decision-making. Inclusion of migratory connectivity in the design of conservation and management measures is critical to ensure they are appropriate for the level of risk associated with various degrees of connectivity. Three mechanisms exist to incorporate migratory connectivity into international marine policy which guides conservation implementation: site-selection criteria, network design criteria and policy recommendations. Here, we review the concept of migratory connectivity and its use in international policy, and describe the Migratory Connectivity in the Ocean system, a migratory connectivity evidence-base for the ocean. We propose that without such collaboration focused on migratory connectivity, efforts to effectively conserve these critical species across jurisdictions will have limited effect.

Decline towards extinction of Mexico's vaquita porpoise (Phocoena sinus).

Abstract: The vaquita (Phocoena sinus) is a small porpoise endemic to Mexico. It is listed by IUCN as Critically Endangered because of unsustainable levels of bycatch in gillnets. The population has been monitored with passive acoustic detectors every summer from 2011 to 2018; here we report results for 2017 and 2018. We combine the acoustic trends with an independent estimate of population size from 2015, and visual observations of at least seven animals in 2017 and six in 2018. Despite adoption of an emergency gillnet ban in May 2015, the estimated rate of decline remains extremely high: 48% decline in 2017 (95% Bayesian credible interval (CRI) 78% decline to 9% increase) and 47% in 2018 (95% CRI 80% decline to 13% increase). Estimated total population decline since 2011 is 98.6%, with greater than 99% probability the decline is greater than 33% yr-1. We estimate fewer than 19 vaquitas remained as of summer 2018 (posterior mean 9, median 8, 95% CRI 6-19). From March 2016 to March 2019, 10 dead vaquitas killed in gillnets were found. The ongoing presence of illegal gillnets despite the emergency ban continues to drive the vaquita towards extinction. Immediate management action is required if the species is to be saved.

World Octopus Fisheries

Abstract: Recent studies have shown that coastal and shelf cephalopod populations have increased globally over the last six decades. Although cephalopod landings are dominated by the squid fishery, which represents nearly 80% of the worldwide cephalopod catches, octopuses and cuttlefishes represent ∼10% each. Total reported global production of octopuses over the past three decades indicates a relatively steady increase in catch, almost doubling from 179,042 t in 1980 to 355,239 t in 2014. Octopus fisheries are likely to continue to grow in importance and magnitude as many finfish stocks are either fully or over-exploited. More than twenty described octopus species are harvested from some 90 countries worldwide. The current review describes the major octopus fisheries around the globe, providing an overview of species targeted, ecological and biological features of exploited stocks, catches and the key aspects of management.

Assessing bottom trawling impacts based on the longevity of benthic invertebrates

Abstract: Bottom trawling is the most widespread human activity directly affecting seabed habitats. Assessment and effective management of the effects of bottom trawling at the scale of fisheries requires an understanding of differences in sensitivity of biota to trawling. Responses to disturbance are expected to depend on the intrinsic rate of increase in populations (r), which is expected to be linearly related to the reciprocal of longevity. We examine the relationship between the longevity of benthic invertebrates and their response to bottom trawling; both in terms of the immediate mortality following a trawl pass and their subsequent rates of recovery. We collate all available data from experimental and comparative trawling studies, and test how longevity influences these aspects of sensitivity. The shortest lived organisms ( 1 year decreased by ~9% immediately following a trawl pass. The effect of bottom trawling in comparative studies increased with longevity, with a 2–3× larger effect on biota living >10 years than on biota living 1–3 years. We attribute this difference to the slower recovery rates of the long-lived biota. The observed relationship between the intrinsic rate of population increase (r, our metric of recovery rate) and the reciprocal of longevity matches theoretical expectation and predicts that the sensitivity of habitats to bottom trawling is higher in habitats with higher proportions of long-lived organisms. Synthesis and applications. Where the longevity of a species or the longevity distribution of a community is known or can be inferred, our estimates of depletion and intrinsic rate of increase can be combined with high-resolution maps of trawling intensity to assess trawling impacts at the scale of the fishery or other defined unit of assessment. Our estimates of r may also be used to estimate recovery times following other forms of seabed disturbance.

It's about time: A synthesis of changing phenology in the Gulf of Maine ecosystem.

Abstract: The timing of recurring biological and seasonal environmental events is changing on a global scale relative to temperature and other climate drivers. This study considers the Gulf of Maine ecosystem, a region of high social and ecological importance in the Northwest Atlantic Ocean and synthesizes current knowledge of (a) key seasonal processes, patterns, and events; (b) direct evidence for shifts in timing; (c) implications of phenological responses for linked ecological-human systems; and (d) potential phenology-focused adaptation strategies and actions. Twenty studies demonstrated shifts in timing of regional marine organisms and seasonal environmental events. The most common response was earlier timing, observed in spring onset, spring and winter hydrology, zooplankton abundance, occurrence of several larval fishes, and diadromous fish migrations. Later timing was documented for fall onset, reproduction and fledging in Atlantic puffins, spring and fall phytoplankton blooms, and occurrence of additional larval fishes. Changes in event duration generally increased and were detected in zooplankton peak abundance, early life history periods of macro-invertebrates, and lobster fishery landings. Reduced duration was observed in winter-spring ice-affected stream flows. Two studies projected phenological changes, both finding diapause duration would decrease in zooplankton under future climate scenarios. Phenological responses were species-specific and varied depending on the environmental driver, spatial, and temporal scales evaluated. Overall, a wide range of baseline phenology and relevant modeling studies exist, yet surprisingly few document long-term shifts. Results reveal a need for increased emphasis on phenological shifts in the Gulf of Maine and identify opportunities for future research and consideration of phenological changes in adaptation efforts.

Ten tips for developing interdisciplinary socio-ecological researchers

Abstract: Interdisciplinary research and collaborations are essential to disentangle complex and wicked global socio-ecological challenges. However, institutional structures and practices to support interdisciplinary research are still developing and a shared understanding on how best to develop effective interdisciplinary researchers (particularly at early career stages) is lacking. Barriers to interdisciplinary approaches, which include diverse disciplinary ‘languages’, research time constraints and limited guidance on how to achieve interdisciplinarity in practice, further challenge this understanding. To help overcome these barriers, this paper provides practical advice for early career researchers and their mentors, as well as senior researchers and lab leaders, in the form of 10 tips: ‘Develop an area of expertise’; ‘Learn new languages’; ‘Be open-minded’; ‘Be patient’; ‘Embrace complexity’; ‘Collaborate widely; ‘Push your boundaries’; ‘Consider if you will engage in interdisciplinary research’; ‘Foster interdisciplinary culture’; and ‘Champion interdisciplinary researchers’. They are presented here to empower present and future generations of interdisciplinary researchers in their endeavour to solve contemporary socio-ecological challenges worldwide.

Advances in research on the impacts of anti-submarine sonar on beaked whales.

Abstract: Mass stranding events (MSEs) of beaked whales (BWs) were extremely rare prior to the 1960s but increased markedly after the development of naval mid-frequency active sonar (MFAS). The temporal and spatial associations between atypical BW MSEs and naval exercises were first observed in the Canary Islands, Spain, in the mid-1980s. Further research on BWs stranded in association with naval exercises demonstrated pathological findings consistent with decompression sickness (DCS). A 2004 ban on MFASs around the Canary Islands successfully prevented additional BW MSEs in the region, but atypical MSEs have continued in other places of the world, especially in the Mediterranean Sea, with examined individuals showing DCS. A workshop held in Fuerteventura, Canary Islands, in September 2017 reviewed current knowledge on BW atypical MSEs associated with MFAS. Our review suggests that the effects of MFAS on BWs vary among individuals or populations, and predisposing factors may contribute to individual outcomes. Spatial management specific to BW habitat, such as the MFAS ban in the Canary Islands, has proven to be an effective mitigation tool and mitigation measures should be established in other areas taking into consideration known population-level information.

oSCR: a spatial capture–recapture R package for inference about spatial ecological processes

Abstract: Spatial capture–recapture (SCR) methods have become widely applied in ecology. The immediate adoption of SCR is due to the fact that it resolves some major criticisms of traditional capture–recapture methods related to heterogeneity in detectabililty, and the emergence of new technologies (e.g. camera traps, non‐invasive genetics) that have vastly improved our ability to collection spatially explicit observation data on individuals. However, the utility of SCR methods reaches far beyond simply convenience and data availability. SCR presents a formal statistical framework that can be used to test explicit hypotheses about core elements of population and landscape ecology, and has profound implications for how we study animal populations. In this software note, we describe the technical basis and analytical workflow of oSCR, an R package for analyzing spatial encounter history data using a multi‐session sex‐structured likelihood. The impetus for developing oSCR was to create an accessible and transparent analysis tool that allows users to conveniently and intuitively formulate statistical models that map directly to fundamental processes of interest in spatial population ecology (e.g. space use, resource selection, density and connectivity). We have placed an emphasis on creating a transparent and accessible code base that is coupled with a logical workflow that we hope stimulates active participation in further technical developments.

Progress on Implementing Ecosystem-Based Fisheries Management in the United States Through the Use of Ecosystem Models and Analysis

Abstract: Worldwide fisheries management has been undergoing a paradigm shift from a single-species approach to ecosystem approaches. In the U.S., NOAA has adopted a policy statement and Road Map to guide the development and implementation of ecosystem-based fisheries management (EBFM). NOAA’s EBFM policy supports addressing the ecosystem interconnections to help maintain resilient and productive ecosystems, even as they respond to climate, habitat, ecological, and social and economic changes. Managing natural marine resources while taking into account their interactions with their environment and our human interactions with our resources and environment requires the support of ecosystem science, modeling, and analysis. Implementing EBFM will require using existing mandates and approaches that fit regional management structures and cultures. The primary mandate for managing marine fisheries in the U.S. is the Magnuson-Stevens Fishery Conservation and Management Act. Many tenets of the Act align well with the EBFM policy; however, incorporating ecosystem analysis and models into fisheries management processes has faced procedural challenges in many jurisdictions. In this paper, we review example cases where scientists have had success in using ecosystem analysis and modeling to inform management priorities, and identify practices that help bring new ecosystem science information into existing policy processes.

Microbiome differences in disease-resistant vs. susceptible Acropora corals subjected to disease challenge assays.

Abstract: In recent decades coral gardening has become increasingly popular to restore degraded reef ecosystems. However, the growth and survivorship of nursery-reared outplanted corals are highly variable. Scientists are trying to identify genotypes that show signs of disease resistance and leverage these genotypes in restoring more resilient populations. In a previous study, a field disease grafting assay was conducted on nursery-reared Acropora cervicornis and Acropora palmata to quantify relative disease susceptibility. In this study, we further evaluate this field assay by investigating putative disease-causing agents and the microbiome of corals with disease-resistant phenotypes. We conducted 16S rRNA gene high-throughput sequencing on A. cervicornis and A. palmata that were grafted (inoculated) with a diseased A. cervicornis fragment. We found that independent of health state, A. cervicornis and A. palmata had distinct alpha and beta diversity patterns from one another and distinct dominant bacteria. In addition, despite different microbiome patterns between both inoculated coral species, the genus Sphingomonadaceae was significantly found in both diseased coral species. Additionally, a core bacteria member from the order Myxococcales was found at relatively higher abundances in corals with lower rates of disease development following grafting. In all, we identified Sphingomonadaceae as a putative coral pathogen and a bacterium from the order Myxococcales associated with corals that showed disease resistant phenotypes.

The ocean’s movescape: fisheries management in the bio-logging decade (2018–2028)

Abstract: &NA; Although movement has always played an important role in fisheries science, movement patterns are changing with changing ocean conditions. This affects availability to capture, the spatial scale of needed governance, and our food supply. Technological advances make it possible to track marine fish (and fishermen) in ways not previously possible and tracking data is expected to grow exponentially over the next ten years ‐ the bio‐logging decade. In this article, we identify fisheries management data needs that tracking data can help fill, ranging from: improved estimates of natural mortality and abundance to providing the basis for short‐term fisheries closures (i.e. dynamic closures) and conservation of biodiversity hotspots and migratory corridors. However, the sheer size of the oceans, lack of GPS capability, and aspects of marine fish life history traits (e.g., adult/offspring size ratios, high mortality rates) create challenges to obtaining this data. We address these challenges and forecast how they will be met in the next 10 years through increased use of drones and sensor networks, decreasing tag size with increased sensor capacity trends, the ICARUS initiative to increase satellite tracking capacity, and improved connectivity between marine and terrestrial movement researchers and databases.

Ecosystems say good management pays off

Abstract: Understanding the strengths and weaknesses of alternative assessment methods, harvest strategies and management approaches are an important part of operationalizing single‐species and ecosystem‐based fisheries management. Simulations run using two variants of a whole‐of‐ecosystem model for the Southern and Eastern Scalefish and Shark Fishery (SESSF) area shows that (a) data‐rich assessments outperform data‐poor assessments for target species and that this performance is reflected in the values of many system‐level ecosystem indicators; (b) ecosystem and multispecies management outperforms single‐species management applied over the same domain; (c) investment in robust science‐based fisheries management pays dividends even when there are multiple jurisdictions, some of which are not implementing effective management; and (d) that multispecies yield‐oriented strategies can deliver higher total catches without a notable decline in overall system performance, although the resulting system structure is different to that obtained with other forms of ecosystem‐based management.

A field effort to capture critically endangered vaquitas Phocoena sinus for protection from entanglement in illegal gillnets

Abstract: Author(s): Rojas-Bracho, L; Gulland, Frances M.; Smith, Cynthis R.; Taylor, Barbara; Wells, RS; Thomas, PO; Bauer, B; Heide-JA¸rgensen, MP; Teilmann, J; Dietz, R; Balle, JD; Jensen, MV; Sinding, MHS; Jaramillo-Legorreta, A; Abel, G; Read, AJ; Westgate, AJ; Colegrove, K; Gomez, F; Martz, K; Rebolledo, R; Ridgway, Sam H.; Rowles, T; van Elk, CE; Boehm, J; Cardenas-Hinojosa, G; Constandse, R; Nieto-Garcia, E; Phillips, W; Sabio, D; Sanchez, R; Sweeney, J; Townsend, F; Vivanco, J; Vivanco, JC; Walker, S

Estimating effective population size of large marine populations, is it feasible?

Abstract: Sustainable exploitation of marine populations is a challenging task relying on information about their current and past abundance. Fisheries‐related data can be scarce and unreliable making them unsuitable for quantitative modelling. One fishery independent method that has attracted attention in this context consists in estimating the effective population size (Nₑ), a concept founded in population genetics. We reviewed recent empirical studies on Nₑ and carried out a simulation study to evaluate the feasibility of estimating Nₑ in large fish populations with the currently available methods. The detailed review of 26 studies found that published empirical Nₑ values were very similar despite differences in species and total population sizes (N). Genetic simulations for an age‐structured fish population were carried out for a range of population and samples sizes, and Nₑ was estimated using the Linkage Disequilibrium method. The results showed that already for medium‐sized populations (1 million individuals) and common sample sizes (50 individuals), negative estimates were likely to occur which for real applications is commonly interpreted as indicating very large (infinite) Nₑ. Moreover, on average, Nₑ estimates were negatively biased. The simulations further indicated that around 1% of the total number of individuals might have to be sampled to ensure sufficiently precise estimates of Nₑ. For large marine populations, this implies rather large samples (several thousands to millions of individuals). If however such large samples were to be collected, many more population parameters than only Nₑ could be estimated.