Measures of an organism's weight at a given length are often considered reliable indicators of energy reserves or ‘condition’, which can be related to fecundity and risk of mortality. Understanding the impact of environmental change on fish condition may therefore inform sustainable management of human activities in marine ecosystems. We investigated how changes in Canadian Pacific waters may be influencing the average condition of 35 commercially, culturally, and/or ecologically important demersal fish species. Because the condition of mature male and female, and immature individuals differs in its implications for population dynamics, ecological drivers, and measurement variability, we analysed these three maturity groups separately. We estimated density distributions, calculated Le Cren's relative body condition deviations, modelled spatiotemporal change in these deviations, and generated density-weighted annual indices of body condition. We used Bayesian Dynamic Factor Analysis to identify common trends across species and tested for correlations with environmental variables. For most species, warmer sea surface temperature and lagged North Pacific Gyre Oscillation appeared neutrally or positively correlated with condition. Only the immature condition was also strongly correlated with primary production, but this effect was equally likely to be negative (e.g., Pacific Spiny Dogfish, Lingcod, and Sablefish) as positive (e.g., Quillback Rockfish, Southern Rock Sole, and Spotted Ratfish). Our approach propagates uncertainty from condition estimation through to environmental correlations to provide both ecosystem-level and species-specific inference. Robust estimates of relationships between condition and environmental variables can inform ecosystem approaches to fisheries management, including short-term forecasts of weight-at-age or recruitment.

Abstract Nutrient‐rich waters along the Pacific coast of North America support diverse fish communities that have helped sustain coastal peoples for millennia. Five Nuu‐chah‐nulth First Nations on the west coast of what is now known as Vancouver Island, Canada, hold constitutional Indigenous rights to conduct a multispecies community fishery, which includes Pacific Halibut (Hippoglossus stenolepis). A 2009 court decision defined the extent of these Indigenous rights to be within 9 nm of the coast, thereby not fully recognizing the knowledge and authority of the traditional leadership and raising concerns about the potential for an increase in rockfish bycatch. Yelloweye Rockfish (Sebastes ruberrimus) are a potential ‘choke’ species for this fishery because the two species occupy similar depth ranges. A choke species is one that is caught incidentally while targeting other species and, if caught in excess of its quota limits, can trigger a halt to fishing on the target species. Guided by the insights of local Indigenous peoples and using both fishery‐independent survey and commercial longline catch data, we investigated the effects of fishing depth and spatial restriction on the relative catch weights of these two species using spatiotemporal models. We find evidence that a confined fishing area can limit opportunities for avoiding choke species. Specifically, fishing at depths deeper than 175 m, which occur outside the court defined area (CDA), would provide more opportunities for catching halibut while avoiding Yelloweye Rockfish than are currently available within the CDA. This Indigenous‐informed, analytical approach to a management problem is just one example of how Western scientists can engage in coproduction of knowledge with Indigenous peoples to transition from the ‘status quo’ towards a practice of ‘Two‐Eyed Seeing’ that more effectively balances Indigenous rights and species conservation. Policy implications: Our study highlights (1) the importance of considering choke species distributions and opportunities for their avoidance when implementing spatial harvest restrictions and (2) how related analytical and management decisions can benefit from being guided by the advice of Indigenous knowledge holders. Read the free Plain Language Summary for this article on the Journal blog.

Although most fisheries assessment and management focuses on the status of individual stocks, and regulations are commonly established as single-species total allowable catch limits (TACs), much of the catch from global fisheries comes from mixed-stock fisheries where species cannot be harvested separately. We show that in some fisheries where TAC and catch of demersal fish stocks are tracked, the average fraction of TAC harvested ranges from 21% to 68% overall and is declining. This is, in part, related to efforts to protect all species from overfishing, leading to 'choke species', which limit fishing pressure on other target species. While some choke species arise from a mix of low and high-productivity species, others result from allocation processes, which can be aggravated by shifting distributions due to climate change. Underutilization of TACs can also result from market limitations, low value of individual species, undercapacity or management measures. Proposed methods for increasing long-term yield require species to be managed in stock groups, or allowing the abundance of some stocks to fall below target reference points. We suggest that the observed low and declining aggregate harvests are due, primarily, to the focus on single-stock sustainability measures, rather than performance of the fisheries in relation to potential overall yield. While there is a growing consensus that single-species management should be replaced by an ecosystem-based approach, this will require clear legislative directives regarding management of the trade-offs involved. Time series considered in this analysis do not extend beyond 2019.

A limit reference point (LRP) is defined as a level of biomass to be avoided with high probability, which should be selected to protect fish stocks from “serious harm”. We present an evidence-based approach for diagnosing serious harm and apply it to the selection of LRPs for five Pacific herring ( Clupea pallasii) stocks in British Columbia (BC). Natural mortality ( M) is estimated to be time varying and has increased more than it declined over the past three decades, which presents a challenge for estimation of equilibrium reference points based on maximum sustainable yield. We present a semi-empirical approach for developing LRPs, which examines surplus production in relation to spawning biomass to determine whether there is evidence for low productivity, low biomass (LP-LB) states consistent with serious harm. Three stocks showed evidence of persistent LP-LB states that resulted in periods of fishery closures. Based on these results, an LRP of 30% of unfished spawning biomass (0.3 B 0 ) was recommended and adopted for management of all five major stocks of BC Pacific herring.

Fisheries science uses quantitative methods to inform management decisions that reflect cultural preferences which, in turn, indirectly influence the states of ecosystems. To date, it has largely supported Eurocentric preferences for the commodification of marine organisms under the tenets of maximum sustainable yield, whereby abundances are intentionally maintained far below their historical baselines despite broader socio-ecological trade-offs. In contrast, Indigenous Knowledge Systems (IKS) adhere to the principle of "take only what you need and leave lots for the ecosystem," implementing lower fishery removals to support socio-ecological resilience. Despite the power imbalance favouring Eurocentric preferences in decision-making, fisheries scientists increasingly recognize that the pairing of IKS and Western science, or Two-Eyed Seeing, would lead to more holistic management goals. For recognition to transcend tokenism, meaningful collaborations and co-governance structures underlying knowledge co-production must carry through to legislated policy changes. Using recent co-governance developments for fisheries management and spatial protections involving federal, provincial and Indigenous governments in Pacific Canada, we illustrate how the precautionary approach, including reference points and harvest control rules broadly applied in international fisheries, could be revised to make collaborative fisheries management compatible with IKS and improve biodiversity and fisheries protections. Our recommendations may create socio-economic trade-offs at different timescales for commercial fishers. Pre-empting that challenge, we discuss IKS-compatible economic approaches for addressing shorter term costs arising from reduced exploitation rates. Although our case study derives from Pacific Canada, the insights provided here are broadly applicable elsewhere in the world.

Species responses to climate change are often measured at broad spatiotemporal scales, which can miss the fine-scale changes that are most relevant to conservation and fisheries management. We develop a scaleable geostatistical approach to assess how juvenile and adult fish distributions have been shaped by changes in bottom temperature and dissolved oxygen over a recent decade of warming in the northeast Pacific. Across 38 demersal fishes, biomass trends were associated negatively with warming and positively with dissolved oxygen, but when trends in both biomass and climate were converted to velocities-the speed and direction a population would have to move to maintain consistent conditions-the effect of temperature change differed depending on local conditions. In the warmest locations, warming velocities were associated with negative biotic velocities for 19 of 69 species-maturity combinations, and yet were almost always associated with stable or positive biotic velocities in the coolest locations (64 of 69). These spatially consistent biomass declines (negative biotic velocities) in the warmest locations and increases in cooler locations suggest a redistribution of species with the potential for new ecological and fisheries interactions. After controlling for temperature, the more spatially consistent effects of dissolved oxygen were often negative, suggesting a mechanism other than hypoxia avoidance-potentially changes in primary production. Our approach identifies the species and locations that are most sensitive to observed changes in the environment at any scale, thus facilitating future vulnerability assessments.

To protect cold-water corals and sponges from fishing damage, management changes were made in 2012 to the groundfish bottom trawl fishery British Columbia, Canada. The Groundfish Trawl Habitat Agreement restricted the spatial footprint of the fishery and introduced a cold-water coral and sponge bycatch quota, which was among the world’s first. Using 12 years of catch records from the fishery, we found a 31% decrease in overall frequency of encounters of cold-water coral and sponge, a 76% decrease in mean catch weight, and an 89% decrease in total annual catch. We tracked changes in the relative utilization of fine-scale fishing grounds (“fishing opportunities”) and found evidence of active avoidance of areas with high cold-water coral and sponge density. The habitat agreement appears overall to have been successful at reducing impacts to cold-water coral and sponge, although we identified several areas of potential conservation concern where effort and catch have not decreased. Nonspatial management measures in a complex multispecies fishery can result in spatial changes in fishing behaviour, with positive conservation outcomes for bycatch species.

We assembled estimated biomass (B) time series from stock assessments for 24 Pacific Canadian groundfish stocks and modelled average and stock status through 2020 based on biomass relative to each stock’s (1) Limit Reference Point (B/LRP), (2) Upper Stock Reference (B/USR), and (3) biomass at maximum sustainable yield (B/B MSY ). The overall mean B/LRP in 2020 was 3.2 (95% credible interval [CI]: 2.6–3.9). The overall mean B/USR and B/B MSY in 2020 was 1.5 (95% CI: 1.3–1.9) and 1.4 (95% CI: 1.1–1.7), respectively. Average stock status declined from 1950 to around 2000 and has remained relatively stable since then. The change around 2000 followed the implementation of ITQs (individual transferable quotas) for the trawl fleet and the commencement of the synoptic trawl surveys. As of their last assessment, four stocks (Strait of Georgia Lingcod [Area 4B], coastwide Bocaccio, and inside and outside Quillback Rockfish) had a greater than 5% probability of being below their LRP (i.e., in the “ critical zone”); Pacific Cod in Area 3CD had a 4.6% probability. Roughly one-third of stocks had a greater than 1 in 4 chance of being below their USR (i.e., in the “ cautious zone”). Conversely, two-thirds of assessed groundfish stocks had a high (>75%) probability of being above the USR (i.e., in the “ healthy zone”).

The British Columbia longline fishery for Pacific halibut (Hippoglossus stenolepis) has experienced important recent management changes, including the introduction of comprehensive electronic catch monitoring on all vessels; an integrated transferable quota system; a reduction in Pacific halibut quotas; and, beginning in 2016, sharp decreases in quota for yelloweye rockfish (Sebastes ruberrimus, an incidentally caught species). We describe this fishery before integration, after integration, and after the yelloweye rockfish quota reduction using spatial clustering methods to define discrete fishing opportunities. We calculate the relative utilization of these fishing opportunities and their overlap with areas with high encounter rates of yelloweye rockfish during each of the three periods. The spatial footprint (area fished) increased before integration, then decreased after integration. Each period showed shifts in utilization among four large fishing areas. Immediately after the reductions in yelloweye rockfish quota, fishing opportunities with high encounter rates of yelloweye rockfish had significantly lower utilization than areas with low encounter rates, implying rapid avoidance behaviour.

Stock assessments are often used to provide management advice, such as a total allowable catch (TAC), to fishery managers. Many stocks are not assessed annually, and the TAC from the previous assessment is often maintained in years between assessments. We developed two interim management procedures (MPs) that update the estimate of current vulnerable biomass from a surveyed index of abundance to adjust the TAC from a previous assessment. These MPs differ in how they handle uncertainty in observed indices. Using closed-loop simulation, we evaluated the two interim MPs (with 10- and 5-year assessment intervals) against several "status quo" approaches: (1) an annual assessment, and (2) a stock assessment every 5 or 10 years with (a) fixed TACs or (b) projections between assessments. We evaluated performance across three life-history types and six operating model scenarios. The interim MPs performed similarly to annual assessments in terms of trends in biomass and yield, regardless of the assessment interval of the interim MPs. The interim MPs often produced more yield than the Fixed TAC MP with 10-year assessment intervals, for example, in depleted scenarios. The Fixed TAC MP performed more similarly to interim MPs when the assessment interval for the Fixed TAC MP was decreased to five years. The interim MPs can also perform well when circumstances arise that are not accounted for in the Projection MP. Our results show that interim MPs should be considered for infrequently assessed stocks or rebuilding stocks, and highlight potential cost savings of interim MPs over annual assessments.

In the context of ecosystem-based fisheries management, which should consider changing and uncertain environmental conditions, the development of ecosystem-based biological reference points (EBRPs) to account for important multi-species (MS) interactions, fishery operations, and climate change, is of paramount importance for sustainable fisheries management. However, EBRPs under varying plankton productivity states and fisheries management strategies are seldom developed, and the ecosystem effects of these changes are still largely unknown. In this study, ecosystem-based F-MSY (fishing mortality rate at MSY) values were estimated within an end-to-end ecosystem model (OSMOSE) for three focused fish species (Pacific Herring, Clupea pallasii; Pacific Cod, Gadus macrocephalus; Lingcod, Ophiodon elongatus) under three plankton productivity states of differing plankton biomass at high, current, and low levels. In addition, ecosystem effects were compared across different plankton productivity and fisheries management strategies with the latter consisting of two fishery scenarios (i.e. single-species-focused (SS) and MS-focused), various fishing mortality rates, and two harvest policies (with and without harvest control rules, HCRs). Main findings of this study include: (i) plankton productivity change affected the values of ecosystem-based F-MSY, which increased as plankton productivity states changed from low to high plankton biomass; (ii) ecosystem-based F-MSY for Pacific Herring and Pacific Cod stocks increased when fishery scenarios shifted from SS-focused to MS-focused; (iii) fisheries management incorporating HCR yielded more stable system catch and system biomass; and (iv) high plankton biomass combined with fisheries management using HCR could maintain stable ecosystem production and sustainable fisheries. Based on our findings, we highlight possible adaptive fisheries management strategies in the face of future climate and ocean changes. Overall, EBRPs complement SS stock assessments by incorporating key ecological processes and ecosystem properties, thus providing supporting evidence for better incorporation of ecosystem considerations into scientific advice for sustainable fisheries management.

Determining how fish respond to variation in biotic and abiotic conditions is a crucial prerequisite to forecasting changes in productivity and spatial distribution of fish stocks and designing sustainable marine resource management strategies. In the present study, we investigated the physical and biological drivers of the spatio-temporal dynamics of Pacific Herring (Clupea pallasi), which is a marine forage fish species important for commercial fisheries and First Nations in the northeastern Pacific. We fit multivariate spatio-temporal models to fisheries-independent trawl- and acoustics-based data collected off the West Coast of Vancouver Island (WCVI), Canada, during summers over the period 2006-2014. We evaluated the effects of the main ocean environmental drivers of WCVI lower trophic level productivity, including sea surface temperature (SST), chlorophyll a, fluorescence, salinity, oxygen, transmissivity and zooplankton density on variation in Pacific Herring biomass. Models were also used to measure spatio-temporal covariation with other pelagic, semi-pelagic, and bottom-associated fish species occurring off the WCVI to address potential competitive and predation interactions. Through application of these spatio-temporal models we found: (i) Pacific Herring biomass off the WCVI increased during 2006-2014; the highest Pacific Herring biomass was repeatedly found on the continental shelf (depths < 185 m) while low densities were usually observed along the shelf break (depths > 185 m), where Euphausiids, Pacific Hake, Sablefish and Arrowtooth Flounder were more abundant, which could reflect predation avoidance behaviour; (ii), the local biomass of Pacific Herring was related quadratically to the average SST in May; (iii) a positive covariation in spatio-temporal densities between Pacific Herring and its common zooplankton prey, supporting a potential bottom-up control hypothesis; (iv) a negative covariation in spatio-temporal densities between Pacific Herring and both Pacific Hake and Pacific Sardine, which could reflect predation and competitive interactions, respectively; and (v) a positive covariation in spatio-temporal densities between Pacific Herring and several groundfish species (i.e., Arrowtooth Flounder, Sablefish, Pacific Halibut, Pacific Cod), which highlights the need for an accurate assessment of the relative contribution of those species to the total summer predation pressure experienced by Pacific Herring off the WCVI. The findings of this study contribute to a better understanding of the WCVI marine ecosystem.

Harvest control rules (HCRs) are used in fisheries management to reduce fishing mortality as the level of perceived risk to the fish stock increases. This is typically done by adjusting fishing mortality rates based on estimated stock status relative to operational control points (OCPs). OCPs represent the stock status level at which management responses are taken. OCPs differ from biological reference points (BRPs), which represent biomass targets to be achieved, or low biomass thresholds to avoid. Both BRPs and OCPs can be based on theoretical quantities such as Maximum Sustainable Yield (MSY), Spawning Potential Ratio (SPR), or unfished spawning biomass (B-0). However, they can also be based on quantities such as the estimated average spawning biomass and fishing mortality during a productive period. Formal evaluation of the performance of HCRs that account for potential biases in estimated model parameters and stock status relative to OCPs can help managers and stakeholders select HCRs expected to provide acceptable outcomes and trade-offs. We use closed-loop simulation to evaluate the performance of five HCRs for two British Columbian groundfish stocks for which there is considerable uncertainty in underlying productivity: Hecate Strait Pacific Cod (Gallus macrocephalus) and Hecate Strait Rock Sole (Lepidopsetta spp.). Performance metrics representing ecological and economic fishery objectives are reported for two alternative productivity scenarios for each stock, including depensatory mortality for Pacific Cod, and alternative levels of natural mortality (M) for Rock Sole. We present an algorithm for calculating equilibrium M in the presence of density-dependence, and show general effects of uncertainty in Mon reference point calculations. Mechanisms for differences in performance among alternative HCRs are explored, and we show that even when model parameters or OCPs are very biased, some HCRs can still produce desirable management outcomes. We show that trade-off considerations are important because differential sources of stock assessment bias between the two species, and between scenarios within a given species, meant that no single HCR performed consistently. We suggest that prospective evaluation of alternative harvest policies using closed-loop simulation could be conducted routinely on a stock-specific basis, and can facilitate choice of HCRs, with a focus on outcomes rather than uncertainty per se.

A key component of ecosystem-based fisheries management (EBFM) is explicit consideration of trade-offs. Ecosystem models can be used to quantify trade-offs and focus discussion around objectives. Given large structural uncertainties inherent in ecosystem models, however, comparative approaches are recommended to identify results that are robust to model formulation. We developed ecosystem models of the continental shelf and slope of New South Wales, Australia, using two ecosystem modelling frameworks, Atlantis and Ecopath with Ecosim. The models were calibrated to emulate large-scale changes in ecosystem structure between 1976 and 1996, as predicted by data from fishery-independent trawl surveys. Calibrated models were projected forward under a range of “optimal” fishing efforts designed to achieve economic, conservation or biodiversity objectives. While there were large differences in model predictions for individual species, the models gave very similar qualitative results when ranking fishing policies and describing trade-offs. Our results illustrate the importance of identifying fishery objectives before build-up of fleet capacity, and the need to consider trade-offs when simultaneously stating multiple ecosystem-level goals. Our finding that structurally-distinct ecosystem models can provide consistent qualitative advice highlights the capacity of ecosystem models for informing strategic management questions, even in the presence of considerable uncertainty in ecosystem-level processes.

Density-dependent mortality of juvenile fishes is a key population regulation mechanism that is usually assumed to occur before fish recruit to fisheries. When density-dependent mortality occurs simultaneously with bycatch of juvenile fish but is not accounted for in stock assessments, estimates of population size and fishery reference points may be biased as a result. This paper develops an instantaneous, age-structured model accounting for simultaneous density-dependent mortality and bycatch in age-0 red snapper (Lutjanus campechanus), using equations derived from the Beverton-Holt stock-recruit function. Model equations are first presented and deterministic equilibrium properties of the model are explored. Two simplified Bayesian models (with and without post-recruitment density-dependent mortality) are then fitted to data from the 2009 Gulf of Mexico red snapper stock assessment to illustrate the effects of post-recruitment density-dependent mortality on estimates of stock size, stock status and recovery potential. Finally, the Bayesian models are re-run using simulated indices of abundance and age composition data to explore the estimability of model parameters under different amounts of process and observation error; and also to illustrate policy implications of model mis-specification in terms of timing of density-dependent processes. All analyses show that failure to account for post-recruitment density-dependent mortality in stock assessments can lead to overestimation of true abundance and recovery potential. Equilibrium analyses show that fishery reference points MSY and B-MSY may be overestimated if true post-recruitment density-dependent mortality is not accounted for. These analyses also illustrate the problematic nature of defining and calculating reference points in the presence of numerous sources of mortality that affect different demographic components of the population. We note that when population dynamics were simulated without density-dependent age-0 mortality simultaneous with bycatch, estimates of stock size and productivity obtained from an assessment model that assumed density-dependent age-0 mortality had relatively little bias. This was because the density-dependence parameter was correctly estimated to be close to zero. This suggests that it may be advisable to use the density-dependence model if there is a possibility that post-recruitment density-dependent mortality is a factor governing population dynamics. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.

We provide a perspective on steepness, reference points for fishery management, and stock assessment. We first review published data and give new results showing that key reference points are fixed when steepness and other life history parameters are fixed in stock assessments using a Beverton–Holt stock–recruitment relationship. We use both production and age-structured models to explore these patterns. For the production model, we derive explicit relationships for steepness and life history parameters and then for steepness and major reference points. For the age-structured model, we are required to generally use numerical computation, and so we provide an example that complements the analytical results of the production model. We discuss what it means to set steepness equal to 1 and how to construct a prior for steepness. Ways out of the difficult situation raised by fixing steepness and life history parameters include not fixing them, using a more complicated stock–recruitment relationship, and being more explicit about the information content of the data and what that means for policy makers. We discuss the strengths and limitations of each approach.

The New South Wales Offshore Trawl Fishery began to expand in 1976, following a large exploratory trawl survey carried out on the fishing grounds of the upper continental slope. This survey was repeated 20 years later with the same vessel and using similar protocols. Comparison of the survey results suggested that the overall fish biomass in the survey area had substantially decreased after 20 years. We have implemented an ecosystem model using the Atlantis framework to (1) emulate the evolution of the shelf ecosystems from 1976 to 1996 and (2) explore the effects of alternative fishing pressures on those ecosystems. We have been able to emulate the observed decline of most of the commercial groups of fish species in the Offshore Trawl Fishery, including sharks, and our results confirmed that fishing pressure was the most important cause of these observed changes. Fourteen fishing scenarios highlight the competing nature of some of the ecosystem-based sustainable fishing objectives.

Climate change is altering the rate and distribution of primary production in the world's oceans. Primary production is critical to maintaining biodiversity and supporting fishery catches, but predicting the response of populations to primary production change is complicated by predation and competition interactions. We simulated the effects of change in primary production on diverse marine ecosystems across a wide latitudinal range in Australia using the marine food web model Ecosim. We link models of primary production of lower trophic levels (phytoplankton and benthic producers) under climate change with Ecosim to predict changes in fishery catch, fishery value, biomass of animals of conservation interest, and indicators of community composition. Under a plausible climate change scenario, primary production will increase around Australia and generally this benefits fisheries catch and value and leads to increased biomass of threatened marine animals such as turtles and sharks. However, community composition is not strongly affected. Sensitivity analyses indicate overall positive linear responses of functional groups to primary production change. Responses are robust to the ecosystem type and the complexity of the model used. However, model formulations with more complex predation and competition interactions can reverse the expected responses for some species, resulting in catch declines for some fished species and localized declines of turtle and marine mammal populations under primary productivity increases. We conclude that climate-driven primary production change needs to be considered by marine ecosystem managers and more specifically, that production increases can simultaneously benefit fisheries and conservation. Greater focus on incorporating predation and competition interactions into models will significantly improve the ability to identify species and industries most at risk from climate change.