ESTIMATES OF SUSTAINABLE YIELD FOR 50 DATA-POOR STOCKS IN THE PACIFIC COAST GROUNDFISH FISHERY MANAGEMENT PLAN (original) (raw)
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North American Journal of Fisheries Management, 2002
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North American Journal of Fisheries Management, 2002
In this paper, I explore how patterns of compensatory mortality, as assessed through stock-recruitment relationships, may influence optimal harvest rates and relative yields for several West Coast groundfish stocks. To do this, I revisited Clark's (1991) groundfish life history model and maximin (i.e., maximize the minimum) yield approach to evaluate target harvest rates for five stocks (Dover sole Microstomus pacificus, lingcod Ophiodon elongatus, sablefish Anoplopoma fimbria, Pacific hake Merluccius productus, and widow rockfish Sebastes entomelas) using recent estimates of fishery and life history parameters and stock-recruitment data. I found that a spawningstock-per-recruit target of roughly 35% of its unfished amount would be reasonable for these stocks if Clark's assumed stock-recruitment parameters are representative and the policy goal is a maximin yield. In contrast, use of estimated stock-recruitment parameters suggested more conservative percentages of the unfished spawning stock per recruit and more conservative harvest rate targets for most stocks. A key implication of this work is that Clark's groundfish life history model is sensitive to the stock-recruitment shape parameters. As a result, these parameters should be estimated where possible or imputed using results from meta-analyses. Overall, a conservation target of roughly 35% of the unfished spawning stock per recruit is very likely too low for lingcod, sablefish, and widow rockfish stocks under current environmental conditions, but it may be adequate for Dover sole and Pacific hake stocks.
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Failure to eliminate overfishing and attain optimum yield in the New England groundfish fishery
ICES Journal of Marine Science, 2014
Under US law, fishery management is required to eliminate overfishing and attain optimum yield (OY). In New England, many groundfish stocks continue to be overfished, and the fishery continues to harvest less than OY. The reasons for the shortfalls are rooted in the socioeconomic structure of the management regime, and technical and scientific issues that constrain the management system. The most recent change in the management regime (days-at-sea to catch shares) and performance relative to OY and the prevention of overfishing are analyzed along with metrics used to gauge performance. The commonly used age-based production model gives a problematic perception of stock abundance. Structural issues that seem to impair achieving OY are the adherence to the single-species interpretation of multiplespecies yield and the use of the F x% proxy. Simpler approaches to stock assessment are discussed. A management system that creates feasible goals and uses improved and simpler metrics to measure performance is needed to facilitate attainment of management goals.
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Canadian Journal of Fisheries and Aquatic Sciences, 2016
Projections are used to explore scenarios for catch advice and rebuilding and are an important tool for sustainably managing fisheries. We tested each projection specification for 12 groundfish stocks in the Northwest Atlantic to identify sources of bias and evaluate techniques for reducing bias. Projections were made from assessments using virtual population analysis (VPA) with 1–7 years of recent data removed from the full time series and were then compared with results from a VPA assessment on the full time series of data. The main source of bias in projections was the assessment model estimates of the numbers at age in the terminal model year + 1 (Na,T+1). Recruitment was responsible for more bias in projections beyond 3 years, when population numbers begin to be dominated by cohorts that were statistically generated. Retrospective analysis was performed and several adjustment factors to reduce bias were tested. Even after adjusting for bias, the remaining bias in projections wa...
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Fisheries Research, 2008
Monte Carlo simulations and equilibrium analyses are used to explore the behavior of threshold management strategies. The analyses explore the medium-to long-term implications of uncertainty about the steepness of the stock-recruitment relationship, variation as well as possible temporal autocorrelation in recruitment, and estimation and implementation uncertainty. The results highlight the trade-offs among various management strategies, in particular the trade-offs between average catch, inter-annual variation in catch, and the risk of dropping below the Pacific Fishery Management Council (PFMC) overfished threshold of 25% of the average unfished spawning biomass. Uncertainty regarding steepness is the major source of variation in the final size of the resource and whether it is below the overfished threshold, although the extent of recruitment variability also impacts these quantities. The extent of inter-annual variation in catches is determined primarily by the amount of implementation error. Although the values for the various performance measures depend on all of the factors examined to some extent, the impact of interactions among these factors is generally small.
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Fisheries Research, 2014
The majority of global fish stocks lack adequate data to evaluate stock status using conventional stock assessment methods. This poses a challenge for the sustainable management of these stocks. Recent requirements to set scientifically based catch limits in several countries, and growing consumer demand for sustainably managed fish have spurred an emerging field of methods for estimating overfishing thresholds and setting catch limits for stocks with limited data. Using a management strategy evaluation framework we quantified the performance of a number of data-limited methods. For most life-histories, we found that methods that made use of only historical catches often performed worse than maintaining current fishing levels. Only those methods that dynamically accounted for changes in abundance and/or depletion performed well at low stock sizes. Stock assessments that make use of historical catch and effort data did not necessarily out-perform simpler data-limited methods that made use of fewer data. There is a high value of additional information regarding stock depletion, historical fishing effort and current abundance when only catch data are available. We discuss the implications of our results for other data-limited methods and identify future research priorities.
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Journal of Bioeconomics, 2013
A recent highly cited paper from this journal develops a model predicting maximum sustainable yield (MSY ) of a fishery using the historical maximum catch (MaxCatch). The model is parameterized with a small sample of fisheries from the United States, and is subsequently applied to all of the world's fisheries to estimate the benefits of fishery recovery. That empirical relationship has been adopted for many subsequent high-profile analyses. Unfortunately, the analysis suffers from two important oversights: (1) because the model is non-linear, it suffers from "retransformation bias" and therefore the results significantly understate MSY and (2) the analysis is parameterized from of a very limited data set and so generalizability of the fitted empirical relationship between MSY and MaxCatch to global fisheries is questionable. In this note, we rectify both oversights and provide an updated estimate of the relationship between MSY and MaxCatch.
Trade-offs for data-limited fisheries when using harvest strategies based on catch-only models
Fish and Fisheries, 2018
Many of the world's fisheries are unassessed, with little information about population status or risk of overfishing. Unassessed fisheries are particularly predominant in developing countries and in small-scale fisheries, where they are important for food security. Several catch-only methods based on time series of fishery catch and commonly available life-history traits have been developed to estimate stock status (defined as biomass relative to biomass at maximum sustainable yield: B/B MSY). While their stock status performance has been extensively studied, performance of catch-only models as a management tool is unknown. We evaluated the extent to which a superensemble of three prominent catch-only models can provide a reliable basis for fisheries management and how | 1131 WALSH et AL. 1 INTRODUCTION 1131 2 METHODS 1134 2.1 Step 1: Develop operating models to simulate stocks 1134 2.2 Step 2: Stock assessment using a catch-only superensemble 1135 2.3 Step 3: Fine-tune and apply harvest control rules 1136 2.3.1 Effort-based 40-10 HCR 1136 2.3.2 Effort-based step HCR 1136 2.3.3 Catch-based 40-10 and step HCRs 1137 2.3.4 Setting precautionary buffers for HCRs 1137 2.4 Step 4: Simulate the implementation of harvest control rules 1137 2.5 Step 5: Evaluate performance 1137 3 RESULTS 1138 3.1 Reaching maximum sustainable yield and avoiding overfished stocks 1138 3.2 Avoiding overfishing and maximizing yield 1139 3.3 Trade-offs between objectives 1140 3.4 Performance compared to management assuming perfect information 1141 3.5 Sensitivity analysis with underreported catch 1142 4 DISCUSSION 1142 4.1 Performance of catch-only harvest strategies 1143 4.2 Using catch-only methods within a stepping stone approach 1143 4.3 Limitations of catch-only harvest strategies for implementation 1144 5 CONCLUSION 1145