The consequences of size‐selective fishing mortality for larval production and sustainable yield in species with obligate male care

AbstractSize-based harvest limits or gear regulations are often used to manage fishing mortality and ensure the spawning biomass of females is sufficiently protected. Yet, management interactions with species’ mating systems that affect fishery sustainability and yield are rarely considered. For species with obligate male care, it is possible that size-specific harvest of males will decrease larval production. In order to examine how size-based management practices interact with mating systems, we modeled fisheries of two species with obligate care of nests, corkwing wrasse (Symphodus melops, Labridae) and lingcod (Ophiodon elongatus, Hexigrammidae) under two management scenarios, a minimum size limit and a harvest slot limit. We simulated the population dynamics, larval production, and yield to the fishery under a range of fishing mortalities. We also modeled size-dependent male care to determine its interaction with management. In both species, the slot limit decreased yield by less than 12% (relative to minimum size limits) at low fishing mortalities; at higher mortalities, individuals rarely survived to outgrow the slot and spawning potential decreased substantially relative to unfished levels, similar to minimum size limits. Spawning potential decreased less when managed with a slot limit if we included a positive feedback between male size, care, and hatching success, but the benefit of implementing the slot depended both on the relative proportions of each sex selected by the fishery, and on our assumptions regarding male size and care. This work highlights that the effects of size- and sex-selective fisheries management can be nuanced and produce counter-intuitive results.

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Can stock–recruitment points determine which spawning potential ratio is the best proxy for maximum sustainable yield reference points?

ICES Journal of Marine Science ◽

10.1093/icesjms/fst105 ◽

2013 ◽

Vol 70 (6) ◽

pp. 1075-1080 ◽

Cited By ~ 6

Author(s):

Christopher M. Legault ◽

Elizabeth N. Brooks

Keyword(s):

Life History ◽

Mortality Rate ◽

Maximum Sustainable Yield ◽

Reference Points ◽

Sustainable Yield ◽

Marine Science ◽

Fishing Mortality ◽

Scatter Plots ◽

Stock Recruitment ◽

Spawning Potential Ratio

Abstract Legault, C. M., and Brooks, E. N. 2013. Can stock–recruitment points determine which spawning potential ratio is the best proxy for maximum sustainable yield reference points? – ICES Journal of Marine Science, 70: 1075–1080. The approach of examining scatter plots of stock–recruitment (S–R) estimates to determine appropriate spawning potential ratio (SPR)-based proxies for FMSY was investigated through simulation. As originally proposed, the approach assumed that points above a replacement line indicate year classes that produced a surplus of spawners, while points below that line failed to achieve replacement. In practice, this has been implemented by determining Fmed, the fishing mortality rate that produces a replacement line with 50% of the points above and 50% below the line. A new variation on this approach suggests FMSY proxies can be determined by examining the distribution of S–R points that are above or below replacement lines associated with specific SPRs. Through both analytical calculations and stochastic results, we demonstrate that this approach is fundamentally flawed and that in some cases the inference is diametrically opposed to the method's intended purpose. We reject this approach as a tool for determining FMSY proxies. We recommend that the current proxy of F40% be maintained as appropriate for a typical groundfish life history.

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Spatial variation in fishing intensity and its effect on yield

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f07-174 ◽

2008 ◽

Vol 65 (4) ◽

pp. 588-599 ◽

Cited By ~ 31

Author(s):

Stephen Ralston ◽

Michael R O’Farrell

Keyword(s):

Spatial Variation ◽

Local Density ◽

Life Stage ◽

Maximum Sustainable Yield ◽

Recruitment Rate ◽

Sustainable Yield ◽

Fishing Mortality ◽

Density Dependent ◽

Age Structured ◽

Effect On Yield

Fishing mortality is rarely, if ever, evenly distributed over space, yet this is a common assumption of many fisheries models. To evaluate the effect of spatial heterogeneity in fishing mortality on yield, we constructed age-structured models that allowed for differing levels of fishing in three regions within the boundaries of a stock and explored alternative assumptions about the life stage in which density-dependent compensation operates. If the fishing mortality rate (F) is not excessive (i.e., F ≤ FMSY defined for the spatially homogeneous case; MSY, maximum sustainable yield), simulations demonstrated that minor to moderate spatial variation in fishing intensity does not impact sustainable yield. However, if fishing mortality is excessive (F > FMSY), spatial variation in fishing intensity often improves yield and can actually produce yields in excess of MSY when compensation occurs after dispersal, and the density-dependent recruitment rate is a function of the local density of adults. The yield premium generated in these simulations by postdispersal density dependence is due to a low level of compensatory mortality in heavily fished areas coupled with dispersal of propagules into these areas from lightly fished adjacent regions.

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Evaluating management strategies to implement the recovery plan for Iberian hake (Merluccius merluccius); the impact of censored catch information

ICES Journal of Marine Science ◽

10.1093/icesjms/fsp233 ◽

2009 ◽

Vol 67 (2) ◽

pp. 258-269 ◽

Cited By ~ 7

Author(s):

Ernesto Jardim ◽

Santiago Cerviño ◽

Manuela Azevedo

Keyword(s):

Management Strategies ◽

Maximum Sustainable Yield ◽

Sustainable Yield ◽

Fishing Mortality ◽

Merluccius Merluccius ◽

Total Allowable Catch ◽

Recovery Plan ◽

Stock Biomass ◽

Spawning Stock ◽

The Impact

Abstract Jardim, E., Cerviño, S., and Azevedo, M. 2010. Evaluating management strategies to implement the recovery plan for Iberian hake (Merluccius merluccius); the impact of censored catch information. – ICES Journal of Marine Science, 67: 258–269. Iberian hake assessment revealed an increase in fishing mortality (F) despite enforcement of a recovery plan. Recent landings exceeded the total allowable catch and discarding rates were high. Alternative management strategies based on F control were evaluated with respect to the probability of recovering spawning-stock biomass (SSB), expected profits, and robustness to uncertainty on catch information and stock dynamics. Results showed that the use of censored catch data, i.e. excluding the Gulf of Cádiz or discards, may lead to inappropriate conclusions. Reducing fishing mortality was necessary for SSB to recover. An Fmax strategy with discard reduction showed the highest probability of rebuilding SSB and led the fishery to sustainable exploitation, with an expected %SPR of 30–40% in 2025, mean individual weight in the landings of 450 g in 2015, and yield increasing by >20%. Because of uncertainty in the estimates of maximum sustainable yield, management strategies based on FMSY were least robust, but all strategies were robust to alternative stock–recruit models.

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Relationship of Fishing Mortality to Natural Mortality and Growth at the Level of Maximum Sustainable Yield

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f82-141 ◽

1982 ◽

Vol 39 (7) ◽

pp. 1054-1058 ◽

Cited By ~ 15

Author(s):

R. B. Deriso

Keyword(s):

Logistic Model ◽

Mortality Rates ◽

Maximum Sustainable Yield ◽

Sustainable Yield ◽

Natural Mortality ◽

Fishing Mortality ◽

Difference Model ◽

Relationship Of ◽

Yield Per Recruit ◽

Delay Difference

Fishing mortality constraints are derived for fishes harvested at the maximum sustainable yield (MSY) determined by a delay-difference population model. Those constraints depend upon rates of natural mortality and growth as well as a simple constraint placed on abundance of the exploited population. The results are generalized for a wider class of population models where it is shown that MSY fishing mortality is constrained often to be less than the fishing mortality which maximizes yield per recruit. Fishing mortality rates are lower in the delay difference model in comparison to MSY fishing rates in the logistic model, when a quadratic spawner–recruit curve is applied.Key words: delay-difference model, logistic model, fishing mortality, maximum sustainable yield, yield per recruit

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Will depleted populations of Pacific salmon recover under persistent reductions in survival and catastrophic mortality events?

ICES Journal of Marine Science ◽

10.1093/icesjms/fsq117 ◽

2010 ◽

Vol 67 (9) ◽

pp. 2018-2026 ◽

Cited By ~ 7

Author(s):

Carrie A. Holt

Keyword(s):

Pacific Salmon ◽

Survival Rates ◽

Simulation Models ◽

Time Frame ◽

Maximum Sustainable Yield ◽

Sustainable Yield ◽

Fishing Mortality ◽

Replacement Level ◽

Case Examples ◽

Green Zone

Abstract Holt, C. A. 2010. Will depleted populations of Pacific salmon recover under persistent reductions in survival and catastrophic mortality events? – ICES Journal of Marine Science, 67: 2018–2026. Under Canada's Wild Salmon Policy, benchmarks between zones of biological status are required to distinguish populations requiring conservation attention (Red and Amber zones) from those that can be managed for production (Green zone). The recovery of depleted populations (i.e. from Red to Green) will depend in part on the choice of the lower benchmark. At a minimum, that benchmark should be set high enough to allow recovery within an acceptable time-frame in the absence of targeted fishing. Currently, benchmarks are evaluated and selected using simulation models that assess the probability of recovery to spawner abundance associated with the maximum sustainable yield within a specified time-frame. Guided by case examples, the evaluation is extended to include two scenarios of future conditions: persistent reductions in survival rates below the replacement level; and increased frequency of catastrophic mortality (die-off) events. Probabilities of recovery appear to be more sensitive to persistent reductions in survival than to increased probability of die-off events. The current lower benchmarks on spawner abundance and fishing mortality might not be sufficiently precautionary to allow recovery under those conditions.

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The estimation of potential yield and stock status using life–history parameters

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2004.1582 ◽

2005 ◽

Vol 360 (1453) ◽

pp. 163-170 ◽

Cited By ~ 58

Author(s):

J. R. Beddington ◽

G. P. Kirkwood

Keyword(s):

Life History ◽

Growth Parameters ◽

Maximum Yield ◽

Maximum Sustainable Yield ◽

Sustainable Yield ◽

Fishing Mortality ◽

Potential Yield ◽

Stock Status ◽

Fishing Capacity ◽

Stock Recruitment

Using life–history invariants, this paper develops techniques that allow the estimation of maximum sustainable yield and the fishing mortality rate that produces the maximum yield from estimates of the growth parameters, the length at first capture and the steepness of the stock recruitment relationship. This allows sustainable yields and fishing capacity to be estimated from sparse data, such as those available for developing country fisheries.

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An evaluation of the collapse and recovery of the yellowtail flounder (Limanda ferruginea) stock on the Grand Bank

ICES Journal of Marine Science ◽

10.1093/icesjms/fsq121 ◽

2010 ◽

Vol 67 (9) ◽

pp. 1887-1895 ◽

Cited By ~ 5

Author(s):

William B. Brodie ◽

Stephen J. Walsh ◽

Dawn Maddock Parsons

Keyword(s):

Key Management ◽

Management Strategies ◽

Maximum Sustainable Yield ◽

Climatic Conditions ◽

Sustainable Yield ◽

Fishing Mortality ◽

Precautionary Approach ◽

Yellowtail Flounder ◽

Limanda Ferruginea ◽

Management Measures

Abstract Brodie, W. B., Walsh, S. J., and Maddock Parsons, D. 2010. An evaluation of the collapse and recovery of the yellowtail flounder (Limanda ferruginea) stock on the Grand Bank. – ICES Journal of Marine Science, 67: 1887–1895. In 1994, the biomass of yellowtail flounder on the Grand Bank had declined to 20% of the biomass associated with the maximum sustainable yield (Bmsy) because of overfishing in the 1980s, and the Northwest Atlantic Fisheries Organization (NAFO) declared a moratorium on fishing of this stock (and several others in the area). After 4 years of moratorium, the biomass had quadrupled, the fishery was reopened, and the biomass is now well above Bmsy. Based on advice developed within a precautionary approach framework, total allowable catches were set corresponding to a fishing mortality of ≤0.67 × Fmsy. When the fishery was reopened in 1998, several measures to reduce the fishing mortality and ensure continued recovery were introduced. We review and evaluate the science and the management strategies developed during the decline, collapse, and recovery, noting that yellowtail flounder is the only groundfish stock on the Grand Bank that has fully recovered after its collapse. Key management measures included the elimination of fishing by non-NAFO vessels, protection of strong year classes, and keeping the fishing mortality below 0.67 × Fmsy. Although overfishing is viewed as causing the stock decline, productivity was strongly affected by climatic conditions during the collapse and recovery. Changes in water temperature coincided with major changes in the catch and fishing mortality.

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Consequences of a mismatch between biological and management units on our perception of Atlantic cod off New England

ICES Journal of Marine Science ◽

10.1093/icesjms/fsu113 ◽

2014 ◽

Vol 71 (6) ◽

pp. 1366-1381 ◽

Cited By ~ 35

Author(s):

Lisa A. Kerr ◽

Steven X. Cadrin ◽

Adrienne I. Kovach

Keyword(s):

Population Structure ◽

New England ◽

Atlantic Cod ◽

Management Unit ◽

Sustainable Yield ◽

Georges Bank ◽

Fishing Mortality ◽

Management Units ◽

Biological Unit ◽

Unit Model

A mismatch between the scale of fishery management units and biological population structure can potentially result in a misperception of the productivity and sustainable yield of fish stocks. We used simulation modelling as a tool to compare the perception of productivity, stability, and sustainability of Atlantic cod (Gadus morhua) off New England from an operating model based on the current US management units to a model that more closely reflects the biological complexity of the resource. Two age-structured models were compared: (i) the management unit model, wherein cod were grouped based on the current spatially defined US management areas (Gulf of Maine and Georges Bank), and (ii) the biological unit model, consisting of three genetically defined population components (northern spring spawning, southern winter/spring spawning, and eastern Georges Bank spring-spawning groups). Overall, the regional productivity and maximum sustainable yield of the biological unit model was lower compared with the management unit model. The biological unit model also provided insights on the distribution of productivity in the region, with southern and northern spawning groups being the dominant contributors to the regional spawning–stock biomass and yield and the eastern Georges Bank spawning group being the minority contributor at low to intermediate levels of fishing mortality. The comparison of models revealed that the perception of Atlantic cod derived from the management unit model was of a resource that is more resilient to fishing mortality and not as susceptible to “collapse” as indicated by the biological unit model. For Atlantic cod, one of the main risks of ignoring population structure appears the potential for overexploitation of segments of the population. Consideration of population structure of cod changed our perception of the magnitude and distribution of productivity in the region, suggesting that expectations of sustainable yield of cod in US waters should be reconsidered.

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Estimating biomass, fishing mortality, and “total allowable discards” for surveyed non-target fish

ICES Journal of Marine Science ◽

10.1093/icesjms/fsu146 ◽

2014 ◽

Vol 72 (2) ◽

pp. 458-466 ◽

Cited By ~ 6

Author(s):

Samuel Shephard ◽

David G. Reid ◽

Hans D. Gerritsen ◽

Keith D. Farnsworth

Keyword(s):

Demersal Fish ◽

Maximum Sustainable Yield ◽

Sustainable Yield ◽

Fishing Mortality ◽

Target Species ◽

Reference Levels ◽

Total Allowable Catch ◽

Target Fish ◽

The Impact ◽

Study Species

Abstract Demersal fisheries targeting a few high-value species often catch and discard other “non-target” species. It is difficult to quantify the impact of this incidental mortality when population biomass of a non-target species is unknown. We calculate biomass for 14 demersal fish species in ICES Area VIIg (Celtic Sea) by applying species- and length-based catchability corrections to catch records from the Irish Groundfish Survey (IGFS). We then combine these biomass estimates with records of commercial discards (and landings for marketable non-target species) to calculate annual harvesting rates (HR) for each study species. Uncertainty is incorporated into estimates of both biomass and HR. Our survey-based HR estimates for cod and whiting compared well with HR-converted fishing mortality (F) estimates from analytical assessments for these two stocks. Of the non-target species tested, red gurnard (Chelidonichthys cuculus) recorded some annual HRs greater than those for cod or whiting; challenging “Pope’s postulate” that F on non-target stocks in an assemblage will not exceed that on target stocks. We relate HR for each species to two corresponding maximum sustainable yield (MSY) reference levels; six non-target species (including three ray species) show annual HRs ≥ HRMSY. This result suggests that it may not be possible to conserve vulnerable non-target species when F is coupled to that of target species. Based on biomass, HR, and HRMSY, we estimate “total allowable catch” for each non-target species.

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