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Fisheries can adversely affect threatened bycatch species and vulnerable marine ecosystems (VMEs). Thresholds are unique amongst bycatch management methods in providing flexibility in individual participants' approaches to avoid exceeding limits, and particularly for individual vessel quotas, in incentivizing the innovation of effective and commercially viable solutions. This study assessed bycatch thresholds for sharks and relatives, air-breathing marine species and macroinvertebrate indicators for identifying benthic VMEs of 21 intergovernmental organizations and arrangements (IGOs). Seven IGOs lacking bycatch thresholds, who tended to have fewer members, might rely on bycatch management by national authorities. Sharks were the predominant focus. IGOs did not know if thresholds were reached for almost half of measures, likely due to compliance monitoring deficits. Individual vessel limits may be more equitable and prevent a race for fish. However, risk pools and fleetwide thresholds may be more effective when mitigation approaches for individual vessels are limited. No IGO uses individual transferable bycatch quotas or risk pools, which would be challenging to implement regionally. No thresholds were reference points of a harvest strategy. There were limited incidences of thresholds being reached. Thresholds might be set too high to meet objectives. When reached, there was high variability in management responses being systematically implemented. Addressing deficits of thresholds being set too low, inadequate compliance monitoring and inconsistent management response implementation could improve performance. Thresholds have the potential to be an effective component of regional bycatch management strategies, incentivizing fishers to minimize their individual and collective bycatch fishing mortality and adverse effects on VMEs. [ABSTRACT FROM AUTHOR]

Marine population modeling, which underpins the scientific advice to support fisheries interventions, is an active research field with recent advancements to address modern challenges (e.g., climate change) and enduring issues (e.g., data limitations). Based on discussions during the 'Land of Plenty' session at the 2021 World Fisheries Congress, we synthesize current challenges, recent advances, and interdisciplinary developments in biological fisheries models (i.e., data-limited, stock assessment, spatial, ecosystem, and climate), management strategy evaluation, and the scientific advice that bridges the science-policy interface. Our review demonstrates that proliferation of interdisciplinary research teams and enhanced data collection protocols have enabled increased integration of spatiotemporal, ecosystem, and socioeconomic dimensions in many fisheries models. However, not all management systems have the resources to implement model-based advice, while protocols for sharing confidential data are lacking and impeding research advances. We recommend that management and modeling frameworks continue to adopt participatory co-management approaches that emphasize wider inclusion of local knowledge and stakeholder input to fill knowledge gaps and promote information sharing. Moreover, fisheries management, by which we mean the end-to-end process of data collection, scientific analysis, and implementation of evidence-informed management actions, must integrate improved communication, engagement, and capacity building, while incorporating feedback loops at each stage. Increasing application of management strategy evaluation is viewed as a critical unifying component, which will bridge fisheries modeling disciplines, aid management decision-making, and better incorporate the array of stakeholders, thereby leading to a more proactive, pragmatic, transparent, and inclusive management framework–ensuring better informed decisions in an uncertain world. [ABSTRACT FROM AUTHOR]

Policy decisions should be guided by the relative degree of risk of error and bias and strength of evidence of the efficacy of alternative management interventions. This study describes the benefits and limitations of applying a sequential evidence hierarchy to evaluate alternative fisheries bycatch management strategies. Fisheries bycatch is an obstacle to global food and livelihood security and is a main anthropogenic threat to several threatened species. Independent synthesis of all accumulated information is a fundamental principle for developing transparent, evidence-informed regional conservation policy. Meta-analytic syntheses produce the most robust and generalizable findings that are optimal for guiding regional bycatch management. Otherwise, given too few studies to support robust meta-syntheses, decisions should rely on qualitative syntheses of accumulated studies. Bycatch mitigation methods with findings only available from studies with relatively weak forms of evidence, or lacking any evidence, should only be considered as a precautionary approach when more certain alternatives are unavailable. Strictly applying a hierarchical approach on study evidence to make policy decisions, however, risks ignoring potentially important findings derived from studies using methods low on an evidence hierarchy. Instead, in making bycatch management policies, authorities should account for all accumulated evidence and the implications of different approaches for testing different hypotheses. Fisheries bycatch policy guided, but not bounded, by a sequential evidence hierarchy promises to achieve ecological and socioeconomic objectives. [ABSTRACT FROM AUTHOR]

Participatory decision tools enable stakeholders to reconcile conflicting natural resources management objectives. Fisheries targeting highly productive species can have profound impacts on co-occurring bycatch species with low fecundity and other life history traits that make them vulnerable to anthropogenic sources of mortality. This study developed a decision tool for integrated bycatch management for data-limited to data-rich fisheries, improving upon current piecemeal approaches. First, through a systematic literature review, participants compile a comprehensive database of methods to mitigate the catch and fishing mortality of threatened bycatch species. These mitigation methods are then categorized into tiers of a sequential mitigation hierarchy, where interventions that avoid capture are considered before those that minimize catchability, followed by methods that minimize fishing mortality, before approaches that offset residual impacts. The methods are also assembled within an evidence hierarchy, where findings from meta-analytic modelling studies are more robust and generalizable than from individual studies. The decision tool enables stakeholders to evaluate alternative bycatch management strategies' efficacy at meeting specific and measurable objectives for mitigating the catch and mortality of bycatch and for costs from multispecies conflicts, economic viability, practicality and safety, while accounting for the fishery-specific feasibility of compliance monitoring of alternative bycatch management measures. Ongoing adaptation of the bycatch management framework addresses findings from performance assessments, updated evidence, new mitigation methods and changes to governance systems. The proposed decision tool therefore enables stakeholders to develop bycatch management frameworks that provide precautionary protection for the most vulnerable populations with acceptable tradeoffs. [ABSTRACT FROM AUTHOR]

Bycatch in fisheries can have profound effects on the abundance of species with relatively low resilience to increased mortality, can alter the evolutionary characteristics and concomitant fitness of affected populations through heritable trait-based selective removals, and can alter ecosystem functions, structure and services through food web trophic links. We challenge current piecemeal bycatch management paradigms, which reduce the mortality of one taxon of conservation concern at the unintended expense of others. Bycatch mitigation measures may also reduce intraspecific genetic diversity. We drew examples of broadly prescribed 'best practice' methods to mitigate bycatch that result in unintended cross-taxa conflicts from pelagic longline, tuna purse seine, gillnet and trawl fisheries. We identified priority improvements in data quality and in understanding ecological effects of bycatch fishing mortality to support holistic ecological risk assessments of the effects of bycatch removals conducted through semi-quantitative and model-based approaches. A transition to integrated bycatch assessment and management that comprehensively consider biodiversity across its hierarchical manifestations is needed, where relative risks and conflicts from alternative bycatch management measures are evaluated and accounted for in fisheries decision-making processes. This would enable managers to select measures with intentional and acceptable tradeoffs to best meet objectives, when conflicts are unavoidable. [ABSTRACT FROM AUTHOR]

Monitoring and managing fisheries bycatch is increasingly recognized as a critical component of robust fisheries management frameworks. This review, addressing this subject, begins by defining bycatch and analyzing the reasons it happens, from accidental to intentional discarding. It identifies the most common species composing bycatch of the main tuna fisheries using purse seine and longline gear. Considerations of options available to estimate bycatch, their potential biases and uncertainties, and ways to address these issues are discussed. The formulas used to estimate bycatch also point to the options to reduce them, lowering bycatch per unit of effort or lowering effort itself. It shows that a mean can be reduced by reducing all its component figures, or by eliminating the high values at the extreme of the distribution (i.e., where a small proportion of events causes a large proportion of the problem), a common issue in bycatch. A generic strategy is described that can be applied to all gears and fisheries, and it is then described for the fisheries of interest, showing examples of its application. These cover many mitigation actions based on gear and operational changes. Management options aiming at reducing bycatch are also mentioned. A detailed description of the ways the strategy has been implemented for purse seiners and longliners is provided. Finally, market strategies, education and awareness of stakeholders, mainly fishers, and some potential future developments are briefly described. [ABSTRACT FROM AUTHOR]