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Sablefish (Anoplopoma fimbria) are a highly mobile species that support important commercial fisheries in the North Pacific Ocean. Information on the genetic stock structure of sablefish is vital for constructing management strategies that ensure the long-term viability of the species. Most previous genetic studies on sablefish have found panmixia throughout the majority of their range, but a recent study suggested that a population structure may exist. Here, we use low-coverage whole genome resequencing to investigate genetic structure in the northern end of the species' range (from Washington State, USA to the Bering Sea and Aleutian Islands, AK, USA). Additionally, we reanalyzed an existing genomic dataset containing 2661 markers to test specific hypotheses about genetic structure by sex. Genome resequencing data from 119 individuals screened at 7 110 228 markers revealed no evidence of population structure, and reanalysis of the existing genomic dataset supported the same conclusion. Differentiation across the genome was largely driven by variation at two putative inversions located ∼1 megabase apart, which did not display any signals of geographic differentiation. Our study further supports the conclusion of genetic panmixia in sablefish throughout its northern range. [ABSTRACT FROM AUTHOR]

The greater argentine is a benthopelagic fish with a northern amphi-Atlantic and southern Arctic distribution. Landings of this species have been steadily increasing since the early 2000s, mainly for ultra-processed fish food. The rising economic importance of this species begs for an accurate delineation of the management units needed to ensure the sustainability of the fishery. The alignment between management and biological units was investigated on three of the ICES stocks in the NE Atlantic (123a4, 5a14, and 5b6a) by genotyping 88 ad hoc- developed SNPs on 1299 individuals sampled along the Norwegian coast, north of Shetland, around the Faroe Islands, and in the Denmark Strait within Icelandic waters. Candidate loci to positive selection were particularly crucial for units' delineation and supported the current ICES 5b6a and 5a14 stocks around the Faroe Islands and Iceland, respectively. However, within the third stock investigated, 123a4, which corresponded mainly to the Norwegian coast, the sample from area 3a (Skagerrak) was significantly different from all the remaining in the same stock. This differentiation advocates for reconsideration of the present policy and suggests considering ICES Area 3a (Skagerrak) as an independent management unit. The environmental conditions in the Skagerrak area have left a genetic print on other marine taxa, which could putatively be the case in the greater argentine. [ABSTRACT FROM AUTHOR]

I recount my personal history, beginning as a young fisherman, becoming an academic fisheries biologist, and ultimately a leader of institutions dedicated to marine and polar research, higher education, and advising policymakers. After my dissertation in the early 1990s, I embarked on an active research career at the Institute of Marine Research (IMR) in Bergen, Norway, developing a sonar method to estimate the abundance of schooling, pelagic fish. My career then transitioned to middle leadership—15 years as Section Leader and Research Director at IMR—followed by >10 years as a top leader for The University Centre in Svalbard, the National Institute of Nutrition and Seafood Research, and finally the Norwegian Polar Institute. I describe the major challenges, opportunities, and processes these leadership roles have entailed. I hope to send a positive message about the influential role of science, and the necessity of clear communication of results and advice at a time when there is a sense of urgency. [ABSTRACT FROM AUTHOR]

Fishing behavior is an important link between management decisions and bioeconomic outcomes. The diversity in fishers' behavior, motivations, and abilities should inform incentive structures if management aims to consider heterogeneous impacts on and by communities. Modeling human behavior in resource management is important for successful fisheries, especially for fisheries undergoing rapid transformation, such as the Alaskan snow crab fishery. This study modeled how snow crabbers choose where to fish in the eastern Bering Sea and examined the diversity of strategies among individuals by fitting a random utility model to data on fishing locations using a variety of potential drivers of behavior as covariates. The overall fishing strategy of the snow crab fleet prioritizes revenue and shared information, while avoiding risk, poor weather, and cost. Diversity of fishing strategies was driven by differences in spatial footprint, vessel size, and ports of landing. Larger vessels ventured farther north, where weather conditions are more extreme. Despite differences in vessel size, crabbers were spatially adaptive and switched fishing regions depending on the abundance and distribution of crab. These findings on the patterns of fishing strategies can inform better management of the Alaskan snow crab fishery as it undergoes rebuilding. [ABSTRACT FROM AUTHOR]

Bycatch rates are essential to estimating fishery impacts and making management decisions, but data on bycatch are often limited. Tropical tuna purse seine (PS) fisheries catch numerous bycatch species, including vulnerable silky sharks. Even if bycatch proportion is relatively low, impacts on pelagic ecosystems may be important due to the large size of these fisheries. Partial observer coverage of bycatch is a major impediment to assessing impacts. Here we develop a generic Δ modeling approach for predicting catch of four major bycatch species, including silky sharks, in floating object-associated fishing sets of the French Indian Ocean PS fleet from 2011 to 2018 based on logbook and observer data. Cross-validation and variable selection are used to identify optimal models consisting of a random forest model for presence–absence and a negative binomial general-additive model for abundance when present. Though models explain small to moderate amounts of variance (5–15%), they outperform a simpler approach commonly used for reporting, and they allow us to estimate total annual bycatch for the four species with robust estimates of uncertainty. Interestingly, uncertainty relative to mean catch is lower for top predators than forage species, consistent with these species having similar behavior and ecological niches to tunas. [ABSTRACT FROM AUTHOR]

Addressing diverse and complex socio-ecological challenges is crucial for achieving ocean sustainability. This is especially true for effective fishery management, which is vital for the sustainability of marine resources. One way of overcoming barriers to fisheries reform is through interdisciplinary collaboration and innovative management and policy approaches. One such approach is market incentives offered by eco-certification against sustainability standards, such as those set by the Marine Stewardship Council (MSC). Complementary interventions that support sustainability improvements are fishery improvement projects (FIPs) and MSC pathway projects. These interventions have clear intermediary and final objectives, and monitoring impact throughout the implementation process remains important. We interviewed participants of a pathway project from five fisheries in South Africa and Mexico using semistructured interviews designed to capture the nonmonetary impacts of these projects as they progress. Our results show that interventions can play a role in facilitating broader collaboration within a fishery and across stakeholder groups, increasing sustainability awareness. Emphasizing the importance of stakeholder engagement and collaboration, we highlight how the project implementation process can lead to communication changes that lead to improved understanding and collaboration. Importantly, we reflect on the suitability of the survey in monitoring progress in such projects. [ABSTRACT FROM AUTHOR]

Open data that can be easily incorporated into analyses are essential for developing ecosystem approaches to marine ecological management: a common goal in fisheries policy in many countries. Although it is not always clear what constitutes an ecosystem approach, it always involves scientists working with a large variety of data and information, including data from physical and oceanographic sampling, multispecies surveys, and other sources describing human pressures. This can be problematic for analysts because these data, even when available, are often held in disparate datasets that do not necessarily correspond at appropriate temporal and spatial scales. Data can often only be obtained by specific requests to individuals in governmental agencies who are delivering on an increasing number of data requests as interest grows in practical ecosystem approach implementation. This data access model is not sustainable and hinders the momentum for ecosystem approach development. We describe a data bundling R package that makes data and climate projections available at appropriate scales to facilitate development of an ecosystem approach for the Gulf of St. Lawrence, Canada. This approach integrates closely with the present workflow of most government analysts, academics in fisheries, and scientists in private industry. The approach conforms with open data initiatives and makes data easily available globally while relieving some of the burden of data provision that can fall to some individuals in government laboratories. The structure and approach are generic, adaptable, and transferable to other regions and jurisdictions. [ABSTRACT FROM AUTHOR]

Diversification within and outside of small-scale fisheries (SSF) is a common strategy to stabilize revenues and increase resilience following disturbances. Using SSF in Virginia, USA as a case study, Herfindahl–Hirschman Indices (HHIs) were used to characterize individual and fleet levels of income diversification, while generalized linear mixed models were used to examine drivers of diversification behavior. HHI income values indicate that fishers tended to exhibit specialized behavior. More diversified fishers tended to have less interannual revenue variability and higher annual incomes. Decisions to increase or decrease diversification were associated with various factors, including total years of participation, annual income, the type of licenses held, landings levels, participation in marine-related business outside of SSF, and market prices. An understanding of diversification levels and associated drivers of behavior can help fishery managers and governing entities predict how fishers will react to perturbations. Environmental changes that alter species distributions and increase the potential for invasive species, as well as shifting sociodemographics within the fishing industry, will likely continue to influence diversification behavior in the future. Developing strategies to reduce the impact of these events on fishers and fishing communities will help to increase resilience and reduce vulnerability in SSF. [ABSTRACT FROM AUTHOR]

Large marine predators feeding on fish caught on fishing gear, referred to as 'depredation', occur in a wide range of fisheries worldwide. Depredation can result in negative ecological and socio-economic impacts, leading to conflict between fishers and depredating species. However, depredation remains understudied in many fisheries, and this hampers the development of effective mitigation solutions. In this study, 21 years of fishing data (2002–2022) were used to assess shark and odontocete depredation in the pelagic tuna longline fishery of New Caledonia. Using generalized linear models, the year, season, effort, soaking time, and vessel were identified as variables significantly influencing the probability of depredation to occur. Results showed that while shark depredation occurred more frequently than odontocete depredation (58.5% vs. 9.2% of the longline sets), they damaged a lower proportion of fish (3.9% vs. 12.3%) over the study period. Unlike sharks, odontocetes selectively depredate tuna, with their highest occurrence during periods of high tuna catch rates, suggesting a co-occurrence with fishing activities. Together, these results indicate that depredation in the New Caledonian fishery is high compared to other regions and provide essential information on the dynamics and impacts of the issue as a basis for considering management and mitigation options. [ABSTRACT FROM AUTHOR]

Ecosystem models, such as Ecopath with Ecosim (EwE), provide a platform to simulate intricate policy scenarios where multiple species, pressures, and ecosystem services interact. Complex questions often return complex answers, necessitating evidence and advice to be communicated in terms of trade-offs, risks, and uncertainty. Calibration procedures for EwE, which can act as a source of uncertainty and bias in model results, have yet to be explored in a comprehensive way that communicates how sensitive model outputs are to different calibration approaches. As the EwE community has grown, multiple divergent approaches have been applied to calibrate models through the estimation of vulnerability multipliers: parameters that augment the consumption rate limits of predators. Here we explore the underlying principles of vulnerability multipliers as well as existing calibration approaches and their justification. Two case studies are presented: the first explores how vulnerability multipliers emerge based on the chosen calibration approach using simulated data, while the second takes two operational EwE models (Irish Sea and Northwest Atlantic Continental Shelf) and compares their outputs when calibrated following alternate calibration approaches. We show how calibration approaches can impact model-derived advice and provide a list of best practice recommendations for EwE calibration. [ABSTRACT FROM AUTHOR]

Age data are crucial for understanding and managing target species in commercial and recreational fisheries. Octopus catches are increasing worldwide, yet ageing methods are still in their infancy. Octopus age is estimated by counting growth increments in stylets and beaks. These increments have been validated as daily in some species or assumed to be daily in other species. Here, we conducted an age validation study on both the stylets and beaks of a commercial octopus species (Octopus berrima). Subsequently, we compared and assessed the readability of growth increments in beaks and stylets of wild-caught O. berrima. We found that increment periodicity was nondaily for both structures, with increment periodicity also varying between structures (0.75 increments per day for stylets and 0.53 increments per day for beak). This study highlights the importance of validating increment periodicity for different octopus species and for both stylets and beaks to obtain accurate age and growth data. Without accurate age data, a species may be incorrectly managed with the potential for negative effects on the sustainability of wild populations. [ABSTRACT FROM AUTHOR]

This decade represents a critical period to profoundly rethink human–nature interactions in order to address the interwoven climate and biodiversity crises. Marine Protected Areas (MPAs) demonstrate promise for increasing ecosystem resilience and reversing habitat and population declines, but outcomes vary considerably from context to context. Partially protected areas offer a compromise between ecological recovery and the social needs of local communities, but their success is contingent on an array of factors. This in-depth review summarizes 15 years of marine conservation research and impact in Lyme Bay (southwest UK), to serve as a model for the future adoption of partially protected MPAs. The findings from the UK's longest integrated socioecological monitoring MPA study are presented and supplemented by an evaluation of the whole-site management approach as a core element of Lyme Bay's achievements. The journey from research to improved monitoring and ambitious policy is illustrated within and interspersed with stories of novel discoveries, ongoing challenges, and method developments. What started as a dedicated group of community members has grown into an immense collaboration between fishers, scientists, NGOs, and regulators, and their combined efforts have sent ripple effects of positive change across the globe. [ABSTRACT FROM AUTHOR]

Managing fishing operations' threat to marine mammal populations hinges on accurate bycatch estimates, often derived from fishery observer or monitoring programmes. Much global marine mammal bycatch occurs in gillnets, and observer protocols that do not include watching the haulback of gillnets may miss animals that drop out of the net. We investigated whether trips using a fish-focused observer protocol (no requirement to watch the haulback) in US northwestern Atlantic gillnet fisheries from 1994 to 2019 had different observed bycatch rates from trips under a mammal-focused observer protocol (watching the haulbacks) for grey seals (Halichoerus grypus atlantica), harbour seals (Phoca vitulina vitulina), and harbour porpoise (Phocoena phocoena phocoena). We found that observer protocol was likely to affect observed drop-out and bycatch rates. Under the fish-focused protocol, the ratio of animals removed from the net to those that fell from the net was generally higher than under the mammal-focused protocol, suggesting fish-focused observers missed bycatch that fell. Bycatch rates of animals removed from the net by fishers differed significantly between observer protocols for seals, but not for harbour porpoise, perhaps because of differences in entanglement and manner of decomposition. We estimate bycatch was underreported by 3–25% because of unobserved drop-outs on fish-focused observer protocols. [ABSTRACT FROM AUTHOR]

Fisheries face unprecedented environmental change. An important aspect of resilience to this change is the adaptive capacity of managers and stakeholders to respond to new conditions. A growing academic literature has demonstrated the value of fostering this adaptive capacity and highlighted key elements of fisheries social-ecological systems that can promote it. However, it is unclear to what extent these abstract academic ideas around adaptive capacity are relevant and valuable to on-the-ground resource managers, and if so, whether there are aspects of the literature that particularly resonate with their needs. Here, we compare academic concepts of adaptive capacity to the ways that management practitioners conceptualize and implement these ideas in practice, elicited through interviews with key professionals in United States federal fishery management bodies. Practitioners overwhelmingly cited flexibility to respond to change as the most consistently important element of adaptive capacity. Yet, they also detailed how the U.S. fishery management system routinely limits and constrains the flexibility of managers and stakeholders. Seeking out opportunities that enhance flexibility without jeopardizing other key aspects of adaptive capacity could increase management's adaptive capacity to global change in the USA and elsewhere. [ABSTRACT FROM AUTHOR]

Each year thousands of farmed Atlantic salmon escape from seawater net pens, and introgression has been documented in a range of wild populations. Due to greater experience in the wild, escapees that have been on the run for a longer period, and successfully transitioned to a wild diet (classified: "early escapees"), could potentially have a higher spawning success and contribute more to introgression than those that have been on the run for a shorter period and/or have not transitioned to a wild diet (classified: "recent escapees"). This is the first study to examine how the escape history of farmed Atlantic salmon captured in multiple rivers and coastal fisheries, varies in time and space. During 2011–2021, adult farmed escaped salmon were captured in four rivers and at six coastal sites in Norway. The level of linoleic acid, a terrestrial fatty acid high in commercial salmon feeds but low in the natural diet of wild salmon, was used to classify the farmed salmon as early or recent escapees. We observed temporal declines in the relative proportions of escaped vs. wild salmon in the catches, and the relative proportion of early vs. recent escapees in the most southern river (driven by samples from 2011 to 2015). Overall, 14% of the escaped salmon caught in the period were classified as early escapees. The relative proportion of early escapees was lower in the two southernmost rivers (21.2% and 6.30%), as compared to the coastal fisheries (40.9%) and the northernmost river (77.6%). Both aquaculture–management regulations and production strategies have likely influenced these observations. [ABSTRACT FROM AUTHOR]

South eastern Australia is a global warming hotspot, and is also home to ~70% of Australia's population and one of Australia's largest fisheries—the South East Scalefish and Shark Fishery. This fishery spans shelf to deep waters, subtropical to temperate waters, employs many gears, and interacts with over 100 species. Despite following best practice fisheries management principles, including taking an ecosystem perspective to overall fisheries interactions, management interventions have failed to arrest or recover the decline of some focal species. Using an Atlantis ecosystem model developed for the fishery over the past 20 years, this paper presents simulations that suggest climate change may be a major contributor to the trajectories seen for a number of species—such as jackass morwong (Nemadactylus macropterus), blue warehou (Seriolella brama), and gemfish (Rexea solandri). This kind of climate influence poses many challenges for fisheries management into the future, raising questions about what to do when climate change undermines or overrides fisheries management actions and objectives. [ABSTRACT FROM AUTHOR]

In many low-valued fisheries, the quantity and types of data that might be available to support fisheries management are often limited. Generally, information on the economic performance of the fishery is low in priority in these fisheries. Basic catch and effort information, however, may contain implicit information about economic performance of the vessels. From these data, technical efficiency scores and measures of capacity utilization can be derived. The technical efficiency score can provide a proxy measure of the distribution of economic performance, while changes in capacity utilization theoretically reflect changes in the economic conditions in the fishery. Given this, changes in these measures over time should also reflect changes in economic outcomes and performance. To test this, we use data from a data-rich fishery, including catch and effort information as well as detailed economic information (i.e. vessel-level profitability). Key technical performance measures are estimated using data envelopment analysis and compared with the economic performance measures. We show that these technical performance measures can provide useful indicators of changes in economic performance when economic information is not available. [ABSTRACT FROM AUTHOR]

For the Blue Foods economy—those sectors that gain value from the biological productivity of the oceans such as fisheries and aquaculture—climate shocks pose an existential threat. Species range shifts, harmful algal blooms, marine heatwaves, low oxygen events, coral bleaching, and hurricanes all present a serious economic risk to these industries, and yet there exist few financial tools for managing these risks. This contrasts with agriculture, where financial tools such as insurance are widely available for managing numerous weather-related shocks. Designing financial tools to aid risk management, such as insurance, for equitable resilience against marine climate shocks will give coastal communities access to the necessary means for reducing their sensitivity to climate shocks and improving their long-term adaptive capacity. We suggest that a convergence of the insurance industry and marine sectors, fostered through collaboration with governments, academics, and NGOs will help usher in new forms of insurance, such as ocean-index or parametric insurance. These new risk-management tools have the potential to help incentivize sustainable use of living marine resources, as well as strengthening the economic resilience of coastal communities to climate change. [ABSTRACT FROM AUTHOR]

Many years after the publication of Beverton and Holt's on the Dynamics of Exploited Fish Populations in 1957, many of the problems that they highlighted remain unsolved. For example, accurately estimating critical biological and fishing processes such as growth, natural mortality, recruitment, and selectivity continues to be challenging. Despite the lack of progress in some areas, there have been advances in our understanding of other areas of fisheries modelling and analysis, including the development of integrative studies of marine resources for the application of an ecosystem-based fisheries management. In this context, ICES Journal of Marine Science solicited contributions to the themed article set (TS) " Advances and challenges in the modelling and assessment of fishery resources ". Here, we summarize the contributions included in this TS that provide examples of emerging tools that are able to account for different issues of a stocks' assessments and integrated analyses. [ABSTRACT FROM AUTHOR]

Climate change-induced variabilities in the environment and fishing pressure affect the distribution and abundance of bigeye tuna in the Pacific Ocean. Understanding the causal relationships among these factors is complicated and challenging. We constructed a multi-output neural network model based on data from four types of bigeye tuna fisheries (longline and purse seine in the west-central and eastern Pacific Ocean, respectively) and marine environmental data, aiming to analyse the response of bigeye tuna to natural and anthropogenic factors from 1995 to 2019 in the Pacific Ocean. The input layer weights were used to explore the importance of environmental variable, while the output layer weights evaluated the contribution of fishing operations. These factors determined the final spatiotemporal distribution and abundance dynamics for bigeye tuna. The optimal model predicted a strong correlation between the locations of major habitats and El Niño southern Oscillation (ENSO) events, indicating that bigeye tuna abundance dynamics respond to the intensity of climate variability. During El Niño events, suitable conditions lead to an expansion of the main habitats east of 170°W, while during La Niña events, the strengthening of the westward advection leads to the contraction of major habitats west of 170°W. Furthermore, the resource abundance of bigeye tuna is predicted to be higher during moderate to weak El Niño events than during strong El Niño events. The abundances in purse seine and longline-dependent fisheries demonstrate significant different distribution patterns under different ENSO events, reflecting the unique environmental preferences at different life stages of bigeye tuna. Given the increasing frequency of climate variability and escalating fishing pressures, our findings provide beneficial insights for the sustainable development of bigeye tuna resource in the Pacific Ocean. [ABSTRACT FROM AUTHOR]

Species Distribution Models are pivotal for fisheries management. There has been an increasing number of fishery data sources available, making data integration an attractive way to improve model predictions. A wide range of methods have been applied to integrate different datasets in different disciplines. We focus on the use of Integrated Species Distribution Models (ISDMs) due to their capacity to formally accommodate different types of data and scale proportional gear efficiencies. ISDMs use joint modelling to integrate information from different data sources to improve parameter estimation by fitting shared environmental, temporal and spatial effects. We illustrate this method first using a simulated example, and then apply it to a case study that combines data coming from a fishery-independent trawl survey and a fishery-dependent trammel net observations on Solea solea. We explore the sensitivity of model outputs to several weightings for the commercial data and also compare integrated model results with ensemble modelling to combine population trends in the case study. We obtain similar results but discuss that ensemble modelling requires both response variables and link functions to be the same across models. We conclude by discussing the flexibility and requirements of ISDMs to formally combine different fishery datasets. [ABSTRACT FROM AUTHOR]

Recently, various state-space implementations of surplus production models (SPMs) have been developed for data-limited stocks. Often, catches and fishing effort are underestimated and discards are ignored. This results in biased estimates of stock status and reference points. Therefore, we conduct a sensitivity analysis for different under-reporting scenarios (due to non-declared landings, by-catch, and discards) on model estimates and thus advice for the black hake species in northwest Africa. Two modelling frameworks were used, namely a stochastic SPM in continuous time (SPiCT) and Just Another Bayesian Biomass Assessment (JABBA). A common set of diagnostics was developed to allow comparison across modelling frameworks. Scenarios correspond to hypotheses about misreporting and assumptions and priors that were kept consistent. The ratio of current fishing mortality over the fishing pressure that gives the maximum sustainable yield, F/FMSY , is most affected by under-reporting. Results are sensitive to the prior assumed for the initial depletion level, B0/K , and research is needed. If the misreporting is changing over time, relative quantities (e.g. F/FMSY) and trends are biased, while if misreporting (or at least a part of misreporting) is constant, relative quantities are unbiased. Therefore, the nature of any trend in misreporting should be investigated. [ABSTRACT FROM AUTHOR]

Less variable than life history parameters (LHPs), it is life history ratios (LHRs) that define how taxa allocate energy between growth, maintenance and reproduction, and respond to fishing pressure. Limited by small samples, variable data quality, and a focus on LHP estimation, previous meta-analyses have failed to settle debate about the extent to which LHRs are relatively invariant across all taxa or characteristic of specific taxa. We collected de novo 1335 published studies and applying rigorous standardization and quality control procedures developed, and make available, a database of high-quality M / K and L m/ L ∞ estimates. We describe two parallel but independent meta-analyses: a cross-validation study of the predictability of M / K by taxonomic category and an evaluation of alternative relationships between the LHRs using Akaike information criteria. These analyses demonstrate that the LHRs are correlated and vary predictably by taxa, with aggregation to the level of family and genera having the most predictive power in our database. We postulate that the LHRs of taxa may relate to their stoichiometric niches, which could open up interesting lines for ecological research and provide new tools for predicting the LHRs of poorly studied taxa. [ABSTRACT FROM AUTHOR]

Knowledge of fisheries impacts, past and present, is essential for understanding the ecology and conservation of seabirds, but in a rapidly changing world, knowledge and research directions require updating. In this Introduction and in the articles in this Themed Set "Impacts of fishing on seabirds", we update our understanding of how fishing impacts seabird communities and identify areas for future research. Despite awareness of the problems and mitigation efforts for >20 years, fisheries still negatively impact seabirds via the effects of bycatch, competition, and discards. Bycatch continues to kill hundreds of thousands of seabirds annually, with negative population-level consequences. Fisheries for forage fish (e.g. anchovy, sandeel, and krill) negatively impact seabirds by competing for the same stocks. Historically, discards supplemented seabird diets, benefitting some species but also increasing bycatch rates and altering seabird community composition. However, declining discard production has led to potentially deleterious diet switches, but reduced bycatch rates. To improve research into these problems, we make the following recommendations: (1) improve data collection on seabird–vessel interaction and bycatch rates, on fishing effort and vessel movements (especially small-scale fleets), and on mitigation compliance, (2) counter the current bias towards temperate and high-latitude ecosystems, larger-bodied species and particular life stages or times of year (e.g. adults during breeding), and (3) advance our currently poor understanding of combined effects of fisheries and other threats (e.g. climate change, offshore renewables). In addition, research is required on under-studied aspects of fishing impacts: consequences for depleted sub-surface predators, impacts of illegal, unreported and unregulated fishing, artisanal and emerging fisheries, such as those targeting mesopelagic fish, have received insufficient research attention. Some of these shortfalls can be overcome with new tools (e.g. electronic monitoring, remote sensing, artificial intelligence, and big data) but quantifying and addressing fishing impacts on seabirds requires greater research investment at appropriate spatio-temporal scales, and more inclusive dialogue from grassroots to national and international levels to improve governance as fishing industries continue to evolve. [ABSTRACT FROM AUTHOR]

Climate change is increasingly impacting marine fisheries worldwide. Concurrently, scientific interest has grown to understand how these systems can cope and adapt, with research shifting from examining vulnerability to assessing risks to focusing on determining and operationalizing resilience. As fisheries-climate-resilience researchers and practitioners navigating a sea of frameworks, toolkits, strategies, policy goals, and management desires, we take stock to ask: what does resilience mean to us? Drawing on our experiences in the northeast United States, we discuss the challenges and ambiguity we encounter in concepts of social-ecological resilience and explore implications for research and implementation. We bring together perspectives to discuss various approaches to resilience, highlighting shared and unique challenges we face. We outline three key considerations as we move forward in resilience research and practice: (1) the need for greater transparency and reflexivity among researchers regarding how they frame and approach resilience; (2) the value of increasing coordination and communication among fisheries groups working on these topics; and (3) the use of co-developed and co-produced resilience research and strategies. We urge for greater centring of communities in these discussions and to explicitly consider how resilience interacts with equity outcomes. [ABSTRACT FROM AUTHOR]

Causes of population collapse and failed recovery often remain enigmatic in marine forage fish like Pacific herring (Clupea pallasii) that experience dramatic population oscillations. Diseases such as ichthyophoniasis are hypothesized to contribute to these declines, but lack of long-term datasets frequently prevents inference. Analysis of pathogen surveillance and population assessment datasets spanning 2007–2019 indicate that the age-based prevalence estimate of Ichthyophonus infection was, on average, 54% greater among a collapsed population of Pacific herring (Prince William Sound, Alaska, USA) as compared to a nearby population (Sitka Sound, Alaska, USA) that is relatively robust. During the study years, the age-based infection prevalence ranged from 14 to 44% in Prince William Sound and 5 to 33% in Sitka Sound. At both sites, the age-based infection prevalence declined over time, with an average decrease of 7% per year. Statistical analyses indicated that infection prevalence between the two populations was reduced by regional factors affecting both sites, and that these factors were independent of herring density. Infection prevalence in both populations was positively correlated with herring age and negatively correlated with the Pacific Decadal Oscillation. This study demonstrates how synthesis of environmental, stock assessment, and disease assessment data can be leveraged to elucidate epidemiological trends in diseases of wild fish. [ABSTRACT FROM AUTHOR]

The coastal waters off Peru are among the world's most productive, thanks to the Humboldt Current and its strong coastal upwelling. Fisheries and an ever-expanding mariculture sector provide millions of Peruvians livelihoods, income, and nutrition. Coastal communities engaging with these sectors face a volatile environment they have historically adapted to. But when the COVID-19 pandemic unfolded in 2020, affecting all aspects of life, challenges for the fisheries and mariculture sectors emerged to a yet unprecedented extent. This work applies a mixed-method approach for documenting and analysing the effects of the pandemic on the Peruvian seafood sector and seafood worker's economy in particular. Mobility restrictions and market closures disrupted seafood supply chains, altering access to nutrition and income for many people involved. Interviewees aimed to diversify livelihood strategies and use personal networks to withstand the crisis, while some established adaptation strategies, such as migration towards other fishing grounds, were largely impeded. Our results highlight the vulnerability of seafood value chains—mainly artisanal and small-scale fisheries—in the face of such a global crisis. The implications of the pandemic for the long-term sustainability of Peruvian coastal–marine activities are discussed and set into the context of previously experienced crises in the region. [ABSTRACT FROM AUTHOR]

Understanding how fisheries influence seabird distribution is critical in the development of sustainable fisheries management. Species distribution models were applied to analyse the influence of the fishing footprint, discards, and oceanographic factors on seabird attendance patterns to trawlers in the Gulf of Cádiz. More than 30 species of seabirds were attracted to trawlers, although only seven were registered with relatively high frequency and abundance. For these species, fishery footprint was a good predictor for the distribution of four out of seven (yellow-legged gull, lesser black-backed gull, northern gannet, and Cory's shearwater). Yellow-legged and lesser black-backed gull flocked in large numbers to trawlers, mostly in shallow areas where they were also attracted by purse seines. Northern gannets and Cory's shearwaters appeared with relatively high frequency and their distributions correlated with trawler effort and abundance of potential prey discards. Balearic shearwaters were attracted in low numbers and concentrated in shallow areas, where potential prey discards were also more abundant. For these three species, discards as surrogate of natural prey distribution were good predictors of trawler attendance. Our research revealed that, at a local scale, the degree of interaction of seabirds on fishing discards varies by species. Therefore, fine-scale studies are essential in identifying interactions between seabirds and fisheries, and thus assessing conservation issues such as bycatch or the consequences of discard bans. [ABSTRACT FROM AUTHOR]

Fishery bycatch is a serious threat to several protected, endangered, and threatened species (PETs), requiring urgent action to develop and implement conservation measures. This study performs an Ecological Risk Assessment for the Effects of Fishing (ERAEF) using a spatially and temporally Productivity–Susceptibility Analysis (PSA) to calculate the potential risk to great shearwaters (Ardenna gravis) from direct interaction with the metiers of the artisanal tuna fishing fleet at the Bay of Biscay (baitboats and trollers). The PSA incorporates productivity attributes based on the Fecundity Factor Index; and susceptibility attributes calculated from the species spatio-temporal abundance patterns obtained developing density surface models and distribution and intensity of fishing activity based on pooled Vessel Monitoring System and logbook data. The PSA shows an overall moderate risk to great shearwaters by the artisanal tuna fishery also revealing that baitboats are less risky than trollers (risk score of 3.12 ± 0.09 and 2.70 ± 0.05, respectively). Spatially, the likelihood of presence of high potential risk areas was associated with prey availability for both the PET and the commercial fish species. The systematic, repeatable, and standardized ERAEF followed in this study can be used to advice for ecosystem-based fisheries management to improve management measures for reducing bycatch of PETs around the world. [ABSTRACT FROM AUTHOR]

Fishery discards supplement food for many seabirds, but the impacts of declining discards are poorly understood. Discards may be beneficial for some populations but have negative impacts by increasing bycatch risk or because they are junk-food. The Falkland Islands support > 70% of global black-browed albatross Thalassarche melanophris populations, which feed on discards. However, the effect of discards on population demographics, and implications of fishery management changes, are unknown. We analysed stomach contents of black-browed albatross chicks across eight breeding seasons (2004–2020) from New Island, Falkland Islands, to assess variation in discard consumption and how this relates to foraging conditions and breeding success. Across years, 68%–98% of samples contained natural prey, whilst 23%–88% of samples contained fishery discards. Discard consumption was positively related to fishery catches of hoki Macruronus magellanicus and sea surface temperature anomalies SSTA (°C), and negatively related to breeding success. These results suggest a diet-switching behaviour for Falkland Islands albatrosses, whereby birds switch from preferred natural prey to suboptimal discards when environmental conditions, and hence natural feeding opportunities, are unfavourable. Crucially, this study highlights that fishery discards do not compensate for poor natural foraging conditions for breeding albatrosses in the long term. [ABSTRACT FROM AUTHOR]

The "blue economy" idea promotes the responsible and sustainable use of coastal and marine resources. The need to balance the exploitation and economic use of these resources has moved to the top of the research agenda and management priorities for small island developing states (SIDS). SIDS face unique challenges due to their geographic, economic, and environmental characteristics. While the specific challenges can vary based on the individual SIDS, some common future challenges include (i) climate change and sea-level rise resulting from the increased frequency and intensity of storms and coastal erosion; (ii) natural disasters such as hurricanes, cyclones, tsunamis, and earthquakes, resulting in extensive damage, disruption of essential services, and lead to loss of lives and livelihoods; (iii) lack of sustainable development and economic diversification leading to reliance on few key sectors, such as tourism and agriculture, which are vulnerable to market fluctuations; (iv) energy security and renewable energy transition; as there is dependency on imported fossil fuels for their energy needs, price fluctuations and supply disruptions occurs; (v) biodiversity conservation and marine resource management; they host unique ecosystems and rich biodiversity, including coral reefs, mangroves, and marine species; and (vi) access to finance and technology; there are direct opportunities, for accessing funds to support technology development under sustainable finance projects. This themed article set attracted 14 submissions, 7 of which were accepted for publication. The topics covered fisheries, climate change effects, marine litter, and development of new technologies and finance mechanisms to support the SIDS. Overall, these contributions have emphasized the remarkable role that SIDS play in the protection and management of coastal and marine ecosystems, but also highlighted several needs and key priorities. [ABSTRACT FROM AUTHOR]

Increasingly, mixed-effect fishery stock assessment models are being developed where deviations about functional forms of different processes are modelled as random effects and the extent of variance is estimated internal to the model. Concurrently, sampling variance parameters associated with likelihoods for fitting composition data within fisheries assessments are more often being estimated internal to the model as well. We examine the performance of stock assessment models when multiple process variance and sampling variance terms are simultaneously estimated within assessment models. We specifically examine how assessment performance is affected by the choice of composition likelihood, the degree of overdispersion in composition data, overparameterization, and modelling variation on the wrong process. In doing so, we build a simulation containing overdispersion and correlations in composition data, directional variation in catchability and/or selectivity, and estimation models which include random effects and composition likelihoods with theoretically estimable variances. Results suggest that with standard data available in fisheries assessments, process variance parameters associated with some commonly employed methods and sampling variance parameters can be simultaneously estimated internal to an assessment, and performance greatly improves with increased composition data. Our results also suggest little downside to overparameterization of selectivity and catchability when the true process is not time-varying, which largely agrees with previous research. However, when a process is truly time-varying and the assessment models time-variation on a different process, namely when selectivity is time-varying and instead natural mortality is modelled as potentially time-varying, we find a risk of severe increases in bias and decreases in confidence interval coverage for assessed quantities. This bias and decrease in coverage could, however, be partially mitigated by also modelling time-variation on the correct process. [ABSTRACT FROM AUTHOR]

The benefits of individual vessel quota (IVQ) management in terms of improved harvest strategy and profitability are well recognized, but there is less focus on how different components of a quota portfolio can influence decisions underlying the effort allocation and profit-maximizing behaviour of fishers. Variations in the components of the quota portfolio may create economic incentives that alter the optimal harvest strategy and profitability. Thus, we study the potential impact of different components of quota portfolio on the intra-annual harvest strategy and profitability in two segments of the Norwegian bottom trawl fleet. By developing a vessel-based spatio-temporal bioeconomic framework, we demonstrate and compare adopted harvest strategies and accrued profits for small and large trawl vessels under three scenarios regarding restrictive quotas in codfish fishery. Our analysis confirms that alternations in the components of the quota portfolio influence the spatio-temporal dynamics of the fishing effort for small and large trawl vessels in different ways, probably due to the differences in vessel-specific characteristics. We also demonstrate that the differences in profit between small and large vessels in part depend on the overall size of the quota portfolio. The economies of scale in the trawl industry are being eroded as the shares of higher-priced species in the quota portfolio decreases. The benefits of economies of scale cannot be reaped as trawlers respond to the reduction in profit by redirecting effort from offshore areas of the Arctic to nearshore waters or staying ashore. Likewise, having small quotas of high-priced species reduces the effectiveness of the IVQ system in meeting management objectives, and could in some cases undermine sustainability outcomes. Our results also demonstrate that both the intensity with which fishers react to the fluctuations in market price levels and fishers' perceptions of location attractiveness are influenced by the components of the quota portfolio. [ABSTRACT FROM AUTHOR]

The Maine Department of Marine Resources (MEDMR) is a state agency tasked with developing, conserving, researching, and promoting commercial and recreational marine fisheries across Maine's vast coastline. Close collaborations with industry members in each of the 30 or more fisheries that support Maine's coastal economy are central to MEDMR's efforts to address this suite of tasks. Here we reflect on recent decades of MEDMR's work and demonstrate how MEDMR fisheries research programmes are preparing for an uncertain future through the lens of three broadly applicable climate-driven challenges: (1) a rapidly changing marine ecosystem; (2) recommendations driven by state and federal climate initiatives; and (3) the need to share institutional knowledge with a new generation of marine resource scientists. We do this by highlighting our scientific and co-management approach to coastal Maine fisheries that have prospered, declined, or followed a unique trend over the last 25+ years. We use these examples to illustrate our lessons learned when studying a diverse array of fisheries, highlight the importance of collaborations with academia and the commercial fishing industry, and share our recommendations to marine resource scientists for addressing the climate-driven challenges that motivated this work. [ABSTRACT FROM AUTHOR]

The marine habitats within the Kep Archipelago, Cambodia, support species of conservation importance and commercial value. Despite the area being designated a Marine Fisheries Management Area (equivalent to a Marine Protected Area locally), illegal trawling has continued to damage vulnerable habitats within the region. To augment the protection of the designated area, Conservation and Anti Trawl Structures (CATS) have been deployed locally. These structures can snare the nets of illegal trawlers and provide a hard substratum for coral colonization. A sidescan sonar survey and ground truthing campaign was used to precisely locate the 40 CATS deployed and produce maps of the important benthic habitats in the area. Due to the challenging coastal environment and minimal available infrastructure, this study used small, rechargeable or low-power (12 V), and low-cost habitat mapping equipment to map the approximate extent of several benthic habitats of conservation interest. The area and type of habitat protected by CATS has been estimated by combining the marine habitat map with the precise locations of the deployed CATS. It is hoped that this information will help inform local management decisions, such as optimizing the placement of future CATS. [ABSTRACT FROM AUTHOR]

One of the main drivers of marine ecosystem change is fishing activity, bottom trawling being the most intensive fishing practice affecting benthic ecosystems worldwide. In the western Mediterranean Sea, Norway lobster stocks present signs of overexploitation due to trawling pressure, as their biomass and abundance have decreased abruptly during the last few years. No-take fishery reserves, a type of marine protected area where fishing is prohibited, could be efficient management measures to recover Norway lobster overexploited populations and coexisting demersal megafauna. Adopting a BACI (before–after control–impact) approach, we performed experimental fishing surveys before and after 4 years of the implementation of a deep-sea no-take reserve in the northwestern Mediterranean. After 4 years of closure, the Norway lobster population increased in abundance, biomass, body size, and trophic level in the no-take reserve. Our approach also revealed an increase in Norway lobster biomass beyond its boundaries, suggesting a spillover effect. Other demersal fish species also increased in biomass and abundance in the no-take reserve. Based on the results of this study, we suggest that no-take reserves might be an effective measure for recovering the Norway lobster stock and some species present in the same habitat. [ABSTRACT FROM AUTHOR]

The neritic-oceanic squid Illex argentinus supports one of the largest fisheries in the Southwest Atlantic. It is characterized by extensive migrations across the Patagonian Shelf and complex population structure comprising distinct seasonal spawning groups. To address uncertainty as to the demographic independence of these groups that may compromise sustainable management, a multidisciplinary approach was applied integrating statolith ageing with genome-wide single-nucleotide polymorphism (SNP) analysis. To obtain complete coverage of the spawning groups, sampling was carried out at multiple times during the 2020 fishing season and covered a large proportion of the species' range across the Patagonian Shelf. Statolith and microstructure analysis revealed three distinct seasonal spawning groups of winter-, spring-, and summer-hatched individuals. Subgroups were identified within each seasonal group, with statolith microstructure indicating differences in environmental conditions during ontogeny. Analysis of >10 000 SNPs reported no evidence of neutral or non-neutral genetic structure among the various groups. These findings indicate that I. argentinus across the Patagonian Shelf belong to one genetic population and a collaborative management strategy involving international stakeholders is required. The connectivity among spawning groups may represent a "bet-hedging" mechanism important for population resilience. [ABSTRACT FROM AUTHOR]

In many situations, species distribution models need to make use of multiple data sources to address their objectives. We developed a spatio-temporal modelling framework that integrates research survey data and data collected by observers onboard fishing vessels while accounting for physical barriers (islands, convoluted coastlines). We demonstrated our framework for two bycatch species in New Zealand deepwater fisheries: spiny dogfish (Squalus acanthias) and javelinfish (Lepidorhynchus denticulatus). Results indicated that employing observer-only data or integrated data is necessary to map fish biomass at the scale of the New Zealand exclusive economic zone, and to interpolate local biomass indices (e.g. for the east coast of the South Island) in years with no survey but available observer data. Results also showed that, if enough survey data are available, fisheries analysts should: (1) develop both an integrated model and a model relying on survey-only data; and (2) for a given geographic area, ultimately choose the index produced with integrated data or the index produced with survey-only data based on the reliability of the interannual variability of the index. We also conducted a simulation experiment, which indicated that the predictions of our spatio-temporal models are virtually insensitive to the consideration of physical barriers. [ABSTRACT FROM AUTHOR]

Small-scale fisheries are cornerstones of wealth, food, and tradition for people throughout the Pacific region. Yet, their governance is plagued by a lack of relevant data. Using data collected from household income and expenditure surveys carried out in 13 Pacific Island Countries and Territories over the last decade, we bring enhanced resolution to these fisheries by describing how households engage in small-scale fishing and accounting the income generated from these activities. We find most households do not actively participate in fishing, and most that do, fish only for subsistence. Over time, however, the rates at which households participate in fishing may be declining. Further, the total income generated through aquatic foods caught for subsistence is nearly double that of foods caught for sale, but on a per household basis fishing for commercial purposes is more lucrative. Differences point to important distinctions in how households engage with and generate income from commercial and subsistence fishing, including where activities are often conducted, and the types of aquatic foods targeted. These distinctions have implications for how livelihoods-focused policies and programmes can be developed to ensure aquatic food systems continue to support Pacific Island communities as the deadline for the Sustainable Development Goals approaches. [ABSTRACT FROM AUTHOR]

We investigated the movements of European seabass, Dicentrarchus labrax , to understand habitat use and connectivity to evaluate how individual seabass are protected by the spatiotemporal fisheries restrictions in place. We tagged seabass with acoustic transmitters in a study area in the Port of Zeebrugge (Belgium) in the southern North Sea. The 370,200 detections of 57 seabass in the study area revealed high residency in the period from late March–May to September–November, as well as high site fidelity (70.7%). Whereas the majority of seabass left the area in winter, 13 seabass stayed in the harbour experiencing temperatures as low as 2.8°C. Two groups of seabass were identified having different core movement areas in the inner and outer harbours, although movement between the two areas was possible. The distinct differences in habitat use between these groups resulted in a significantly different level of exposure to fisheries under the same policy framework. By quantifying the level of protection of seabass, based on the spatiotemporal fisheries management in place, our study underlines the importance of taking into account movement behaviour when evaluating conservation measures. [ABSTRACT FROM AUTHOR]

Sustainable management of aquatic resources requires efficient acquisition and processing of vast amounts of information to check the compliance of fishing activities with the regulations. Recent implementation of the European Common Fisheries Policy Landing Obligation implies the declaration of all listed species and sizes at the harbour. To comply with such regulation, fishers need to collect and store all discards onboard the vessel, which results in additional processing time, labour demands, and costs. In this study, we presented a system that allowed image-based documentation of discards on the conveyor belt. We presented a novel integrated end-to-end simultaneous detection and weight prediction pipeline based on the state-of-the-art deep convolutional neural network. The performance of the network was evaluated per species and under different occlusion levels. The resulting model was able to detect discards with a macro F1-score of |$94.10\%$| and a weighted F1-score of |$93.88\%$|⁠. Weight of the fish could be predicted with mean absolute error, mean absolute percentage error, and root squared error of 29.74 (g), |$23.78\%$|⁠ , and 44.69 (g), respectively. Additionally, we presented a new dataset containing images of fish, which, unlike common object detection datasets, also contains weight measurements and occlusion level per individual fish. [ABSTRACT FROM AUTHOR]

The Bering Sea is a productive large marine ecosystem that supports numerous commercial fisheries, while climate change is introducing rapid warming and freshening, especially in coastal water. The success of early life stages of marine fish can impact adult abundance levels; little is known about how behavioural or physiological plasticity in relation to environmental changes at one stage (e.g. spawning) may affect survival during subsequent stages (e.g. larvae), nor whether trade-offs exist that affect how a species demonstrates such plasticity. We utilized a statistical approach to examine phenological and geographical flexibility in spawning behaviour for four species of groundfish. In situ sea surface temperature (SST) and salinity (SSS) associations were also estimated by statistical models for six species of groundfish larvae. All species exhibited greater spawning geography flexibility than phenological flexibility during the egg stage. All larval stages exhibited specific temperature and salinity associations across unique combinations of SST and SSS. These species-specific patterns, in the context of potential climate change impacts, suggest that flexibility in spawning behaviour may not adequately compensate for the presence of unfavourable habitats at the larval stage. [ABSTRACT FROM AUTHOR]

Space is a critical component of fisheries management. Despite this, very few of the world's fish and shellfish stocks are currently assessed using methods that are spatially structured. In the Northeast Atlantic, northern shrimp in the North Sea and Skagerrak, is currently assessed using a spatially structured assessment model. This metapopulation model includes two spatial units (the Norwegian Deep and the Skagerrak), however, in the recent past, the fishery on northern shrimp in the North Sea also occurred in a third neighbouring fishing area, the Fladen Ground. Here, we have reconstructed the dynamics of northern shrimp in the Fladen Ground using historic landings, a standardized commercial index of abundance and fragmented survey data and integrated this third spatial unit into the assessment model of the stock. In doing so, we find evidence of sequential spatial depletion, whereby high rates of fishing mortality have successively eroded stock components in a west to east pattern of overexploitation and produced cryptic collapses. This finding is the first documented case of sequential spatial depletion in the Northeast Atlantic, a phenomenon that could be common and largely overlooked by stock assessment methods that are inherently non-spatial. [ABSTRACT FROM AUTHOR]

Antarctic krill (Euphausia superba) and Ice krill (Euphausia crystallorophias) are key species within Southern Ocean marine ecosystems. Given their importance in regional food webs, coupled with the uncertain impacts of climate change, the on-going recovery of krill-eating marine mammals, and the expanding commercial fishery for Antarctic krill, there is an increasing need to improve current estimates of their circumpolar habitat distribution. Here, we provide an estimate of the austral summer circumpolar habitat distribution of both species using an ensemble of habitat models and updated environmental covariates. Our models were able to resolve the segregated habitats of both species. We find that extensive potential habitat for Antarctic krill is mainly situated in the open ocean and concentrated in the Atlantic sector of the Southern Ocean, while Ice krill habitat was concentrated more evenly around the continent, largely over the continental shelf. Ice krill habitat was mainly predicted by surface oxygen concentration and water column temperature, while Antarctic krill was additionally characterized by mixed layer depth, distance to the continental shelf edge, and surface salinity. Our results further improve understanding about these key species, helping inform sustainable circumpolar management practices. [ABSTRACT FROM AUTHOR]

Diel vertical migration (DVM) in marine organisms is an evolved response to maximize foraging opportunities and minimize predation risk. This pattern in vertical distribution is a widely observed phenomenon and common in pelagic forage fish species. Modelling these dynamics has important relevance to understanding marine ecosystem dynamics, predator–prey interactions, and marine food webs. We examine DVM in sand lance—an ecologically important taxa of forage fishes throughout northern hemisphere marine systems and target of commercial fisheries. Much remains unknown about their diurnal emergence from sediments. We apply data from autonomous stereo-camera deployments and tank observations to provide new insight to DVM patterns in Pacific sand lance (Ammodytes personatus). We model emergence curves using beta regression models with random effects, depicting important differences in the shape of ascent and descent. Our observations and analyses document crepuscular movement patterns, suggesting pelagic foraging occurs primarily at dawn and dusk. Results suggest critical light thresholds are necessary to initiate and maintain pelagic foraging. Results also suggest the importance of seasonality and life stage, such that adult fish exhibit reduced pelagic foraging in the fall relative to juvenile fish. These results constitute a comprehensive evaluation of DVM in this species, better define the physical drivers, and mathematically depict the pattern and shape of emergence timing. [ABSTRACT FROM AUTHOR]

Recent efforts in ocean mapping of seafloor habitat have made data increasingly available. For bottom-dwelling and/or sessile species, there is often a strong relationship between population productivity and habitat, and stock assessment models are likely to be improved by the inclusion of habitat. Here, we extend a recently developed spatio-temporal biomass dynamics model to allow habitat to inform probabilities of non-zero tows and catchability. Simulation experiments demonstrate the ability of this new approach to reliably capture population trends over time and space, with the applicability of the method further demonstrated using data from the Canadian Maritimes Inshore Sea Scallop Fishery in the Bay of Fundy. This habitat-informed spatio-temporal biomass dynamics model better captures underlying processes, reduces uncertainty, thereby improving our understanding of stock status from which fisheries management decisions can be based. [ABSTRACT FROM AUTHOR]

Blue marlin (Makaira nigricans) and sailfish (Istiophorus platypterus) are ecologically important predators and valuable species throughout the world's recreational, commercial, and subsistence fisheries. Comparing multi-species vertical habitat use can inform ecological uncertainties such as inter-species competition, as well as relative vulnerabilities to fishing activities. In this study, we identified key differences in both depth use and which environmental variables drive these selections, which highlights the variability in the catchability both as target species in recreational fisheries and bycatch in commercial fisheries. To understand these two species' vertical habitat use, we examined depth profiles from 26 sailfish and 48 blue marlin tagged with pop-up satellite archival tags deployed in the Eastern Tropical Pacific Ocean. While both species are surface-oriented, we found evidence of vertical niche partitioning where sailfish spend more time at deeper depths than blue marlin. Blue marlin recorded an average mean depth of 18.5 m (±10.8 m) during daytime and 5.2 m (±5.5 m) at nighttime (Figure 31a), while sailfish recorded an average mean depth of 23.6 m (±11.1 m) during daytime and 6.45 m (±4.64 m) at nighttime. Generalized additive mixed models fitted to predict mean and max depth revealed sea level anomaly (SLA), oxygen, sea surface temperature, and mixed layer depth as significant predictors of vertical habitat use for both species. We also examined catch logs from three recreational fishing lodges in Central America to understand the influence of environmental conditions on billfish sightings per unit effort. For blue marlin and sailfish, SLA was a significant predictor in each of the four depth models (mean day, mean night, max day, max night). SLA was the variable with highest percent deviance explained for all four sailfish depth models and three of the four blue marlin depth models and had a positive relationship with all response variables for all four blue marlin depth models and three sailfish depth models (mean daytime, max daytime, max nighttime), where higher positive SLA values were associated with deeper depth responses. [ABSTRACT FROM AUTHOR]

Predicting recruitment in a reliable fashion is a great challenge within operational fisheries advice. Here, we consulted the unique but undercommunicated IMR Cod Larva Project (1975–1990), its spin-offs, placed in an international era of advancements over the last 50 years to glance into the future. Few initiatives of this kind have applied such extensive research approaches, spanning from laboratory, mesocosm, tank, and field studies to process modelling. The "critical period" concept appeared misleading, covering months rather than days of the early life history stages (ELHS) of Northeast Arctic cod. Larval feeding success was strongly modified by improved encounter rates from wind-induced turbulence. In addition, the following maternal effect studies evidenced that the dynamics of stock demography prior to spawning should be upheld to promote recruitment success. Although we now have lower-trophic level models as well as ELHS individual-based models, such models are still insufficiently reflecting the needed spatiotemporal resolution. The same problem applies to climate/circulation models. Nevertheless, this long-lasting research has significantly improved the mechanistic understanding of ELHS dynamics but also of the more predictable adult reproductive parameters. Based on a "to-list list," we suggest research avenues that should be pursued to further improve our ability predicting recruitment strength in marine fish stocks. [ABSTRACT FROM AUTHOR]

Estuaries worldwide provide critical habitat to many ecologically and socioeconomically important fish species. However, the high turbidity and strong environmental gradients inherent to many estuaries make the monitoring of fish populations a challenging task. To assess the health and diversity of local fish populations, resource managers often employ fisheries-independent sampling methods, which result in valuable population assessments, but suffer from low-temporal resolution and high rates of mortality. Passive acoustic monitoring (PAM) provides a near-continuous, non-invasive means for monitoring soniferous fish activity over extended periods, but its utility for quantifying entire fish communities is largely untested, especially in turbid estuaries. Here, we use synchronized acoustic and gillnet sampling at 51 locations in the Mission-Aransas Estuary (TX), across two sampling seasons to test correlations between acoustic indices and gillnet catch. Positive correlations were observed between gillnet catch and sound pressure levels in both broadband (50–22050 Hz) and low-frequency (50–2500 Hz) bands. Additionally, sciaenid calling activity was positively correlated with sciaenid catch during the spring, when most spawning activity occurs. Our results indicate that PAM can be used to monitor the relative abundances of fish in Gulf of Mexico estuaries and beyond, although this is subject to species identity and seasonal dynamics. [ABSTRACT FROM AUTHOR]

An organism's body condition describes its mass given its length and is often positively associated with fitness. The condition of Atlantic cod (Gadus morhua) in the Baltic Sea has declined dramatically since the early 1990s, possibly due to increased competition for food and hypoxia. However, the effects of biotic and abiotic variables on body condition have not been evaluated at local scales, which is important given spatial heterogeneity. We evaluate changes in distribution, experienced environmental conditions, and individual-level condition of cod in relation to covariates at different spatial scales using geostatistical models with spatial and spatiotemporal random effects. Sprat, Saduria entomon , temperature and oxygen were positively associated with condition, and depth was negatively associated. However, the effects of explanatory variables were small—spatial and spatiotemporal latent variables explained 5.7 times more variation than all covariates together (year excluded). Weighting environmental oxygen with local biomass densities revealed steeper declining trends compared to the unweighted oxygen in the environment, while the effect of weighting was less clear for condition. Understanding the drivers of spatiotemporal variation in body condition is critical for predicting responses to environmental change and to effective fishery management; yet low explanatory power of covariates on individual condition constitutes a major challenge. [ABSTRACT FROM AUTHOR]