Optimal effort controls for the multispecies groundfish complex in New England: what might have been

2003 ◽  
Vol 60 (2) ◽  
pp. 159-170 ◽  
Author(s):  
Daniel S Holland ◽  
Jean-Jacques Maguire
Keyword(s):  
New England ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Fishing Mortality ◽  
Alternative Control ◽  
Control Rules ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Age Structured ◽  
Groundfish Fishery

Age-structured models are used to calculate catches and revenues of the principal stocks in the northeast multispecies groundfish fishery over the 1982–1997 period assuming alternative control rules on fishing effort had been employed. Various static levels of nominal effort are compared with controls that maintain fishing mortality below overfishing thresholds for all stocks. An unambiguous result from this analysis is that substantial reductions in fishing effort would have increased the value of the fishery even if resulting increases in spawning stock biomass (SSB) had not increased recruitment. Simple controls on nominal effort designed to maximize revenues would have provided nearly equivalent revenues to those achieved by maintaining fishing mortality for each stock at its individual maximum sustainable yield (FMSY) but would have led to overfishing of some stocks. Without the ability to tune the relative catches across stocks, strict controls on effort designed to prevent overfishing on individual stocks would likely have resulted in significantly lower and more variable revenues. Achieving SSB targets for three stocks would not have been possible given the observed recruitment.

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

2009 ◽  
Vol 67 (2) ◽  
pp. 258-269 ◽  
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.

scholarly journals An assessment of longnose trevally (Carangoides chrysophrys) (Cuvier, 1833) fishery in the Arabian Sea, Oman

2016 ◽  
Vol 21 ◽  
pp. 19
Author(s):  
Issam H. Al-Rasady ◽  
Anesh Govender
Keyword(s):  
Arabian Sea ◽  
Maximum Yield ◽  
Total Mortality ◽  
Fishing Effort ◽  
Fishing Mortality ◽  
North West ◽  
The North ◽  
Key Population ◽  
Stock Biomass ◽  
Spawning Stock

The Present study assessed the fishery state of longnose trevally (Carangoides chrysophrys) in the North West Arabian Sea. Key population parameters were estimated, and yield and spawning stock biomass per recruit analyses were conducted. The equation presented by Alagaraja (1984) for estimating natural mortality resulted in M = 0.29 year-1 and lead to the best estimate of longevity. Hence this value was used in the yield and spawning stock biomass per recruit analyses. The total mortality (Z) was estimated as 0.39 year-1, based on a catch curve analysis. Length-at- and age-at-50% captures were 38.21cm and 4 years respectively. The yield and spawning biomass per recruit analyses indicate that the current fishing mortality rate (Fcurr) was lower than the fishing mortality corresponding to the maximum yield per recruit (Fmax) and was also higher than the target reference point (F0.1) , suggesting that overfishing, currently, does not occur. However, any increase in the fishing effort in the future may lead to overfishing. 

scholarly journals Biased stock assessment when using multiple, hardly overlapping, tuning series if fishing trends vary spatially

2009 ◽  
Vol 66 (10) ◽  
pp. 2272-2277 ◽  
Author(s):  
Sarah B. M. Kraak ◽  
Niels Daan ◽  
Martin A. Pastoors
Keyword(s):  
Stock Assessment ◽  
Fishing Effort ◽  
Assessment Procedure ◽  
Moderate Degree ◽  
Fishing Mortality ◽  
Stock Biomass ◽  
Spatial Coverage ◽  
Spawning Stock ◽  
Age Model ◽  
Biased Perception

Abstract Kraak, S. B. M., Daan, N., and Pastoors, M. A. 2009. Biased stock assessment when using multiple, hardly overlapping, tuning series if fishing trends vary spatially. – ICES Journal of Marine Science, 66: 2272–2277. Fishing-effort distributions are subject to change, for autonomous reasons and in response to management regulations. Ignoring such changes in a stock-assessment procedure may lead to a biased perception. We simulated a stock distributed over two regions with inter-regional migration and different trends in exploitation and tested the performance of extended survivors analysis (XSA) and a statistical catch-at-age model in terms of bias, when spatially restricted tuning series were applied. If we used a single tuning index that covered only the more heavily fished region, estimates of fishing mortality and spawning-stock biomass were seriously biased. If two tuning series each exclusively covering one region were used (without overlap but together covering the whole area), estimates were also biased. Surprisingly, a moderate degree of overlap of spatial coverage of the two tuning indices was sufficient to reduce bias of the XSA assessment substantially. However, performance was best when one tuning series covered the entire stock area.

scholarly journals Fishing for MSY: using “pretty good yield” ranges without impairing recruitment

2016 ◽  
Vol 74 (2) ◽  
pp. 525-534 ◽  
Author(s):  
Anna Rindorf ◽  
Massimiliano Cardinale ◽  
Samuel Shephard ◽  
José A. A. De Oliveira ◽  
Einar Hjorleifsson ◽  
...  
Keyword(s):  
Good Yield ◽  
Maximum Sustainable Yield ◽  
Fishing Mortality ◽  
Fish Yield ◽  
Fish Stocks ◽  
Northern European ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Average Catch

Pretty good yield (PGY) is a sustainable fish yield corresponding to obtaining no less than a specified large percentage of the maximum sustainable yield (MSY). We investigated 19 European fish stocks to test the hypothesis that the 95% PGY yield range is inherently precautionary with respect to impairing recruitment. An FMSY range was calculated for each stock as the range of fishing mortalities (F) that lead to an average catch of at least 95% of MSY in long-term simulations. Further, a precautionary reference point for each stock (FP.05) was defined as the F resulting in a 5% probability of the spawning-stock biomass falling below an agreed biomass limit below which recruitment is impaired (Blim) in long-term simulations. For the majority of the stocks analysed, the upper bound of the FMSY range exceeded the estimated FP.05. However, larger fish species had higher precautionary limits to fishing mortality, and species with larger asymptotic length were less likely to have FMSY ranges impairing recruitment. Our study shows that fishing at FMSY generally is precautionary with respect to impairing recruitment for highly exploited teleost species in northern European waters, whereas the upper part of the range providing 95% of MSY is not necessarily precautionary for small- and medium-sized teleosts.

A bioeconomic model of marine sanctuaries on Georges Bank

2000 ◽  
Vol 57 (6) ◽  
pp. 1307-1319 ◽  
Author(s):  
Daniel S Holland
Keyword(s):  
New England ◽  
Gulf Of Maine ◽  
Georges Bank ◽  
Bioeconomic Model ◽  
Seasonal Movement ◽  
Southern New England ◽  
Modeling Methodology ◽  
Spawning Stock ◽  
Age Structured ◽  
Groundfish Fishery

An empirically estimated fleet dynamics model for New England trawlers is integrated with spatial, age-structured models of primary groundfish species on Georges Banks, southern New England, and the Gulf of Maine. This bioeconomic model is used to explore how permanent marine sanctuaries on Georges Bank might affect catches, revenues, and spawning stock of principal groundfish species in New England. The simulations explore how the location of sanctuaries relative to major ports and their orientation relative to seasonal movement patterns of fish stocks impact their effectiveness and the distribution of benefits across groups of fishers from different ports. The simulation results also demonstrate that the impacts of sanctuaries can vary greatly across species, sometimes increasing yields for some while decreasing yields for others. While the specific results from the simulations reflect the characteristics of the New England groundfish fishery, the modeling methodology and some general conclusions are applicable to other fisheries.

scholarly journals Evaluating the parameters of a MSY control rule for the Bristol Bay, Alaska, stock of red king crabs

2007 ◽  
Vol 64 (5) ◽  
pp. 995-1005 ◽  
Author(s):  
M. S. M. Siddeek ◽  
J. Zheng
Keyword(s):  
Maximum Sustainable Yield ◽  
Reference Points ◽  
Stochastic Simulations ◽  
Bristol Bay ◽  
Control Rule ◽  
Single Sex ◽  
Control Rules ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Spawning Potential Ratio

Abstract Siddeek, M. S. M. and Zheng, J. 2007. Evaluating the parameters of a MSY control rule for the Bristol Bay, Alaska, stock of red king crabs. – ICES Journal of Marine Science, 64: 995–1005. A maximum sustainable yield (MSY) control rule, which defines the level of overfishing, and determines the control rule parameters based on an age-, sex-, and size-structured assessment for Bristol Bay red king crabs (Paralithodes camtschaticus) is developed. Fx% (F corresponding to x% spawning potential ratio) is used as a proxy for FMSY and a minimum spawning-stock biomass (to open the fishery) for incorporation into the MSY control rule. The performance of the selected MSY control rule and the associated target control rule is evaluated using stochastic simulations. F50% is a reasonable proxy for FMSY when effective spawning biomass is used as the stock biomass in the stock-recruitment relationship. This method with appropriate modifications might be used for determining biological reference points and developing control rules for any crustacean stock with discrete growth, complex reproductive dynamics, and single sex exploitation.

When do marine reserves increase fishery yield?

2006 ◽  
Vol 63 (7) ◽  
pp. 1445-1449 ◽  
Author(s):  
Deborah R Hart
Keyword(s):  
Marine Reserves ◽  
Fishing Mortality ◽  
Placopecten Magellanicus ◽  
Sea Scallop ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Stock Recruitment ◽  
Age Structured ◽  
Age Structured Model

An age-structured model is developed for analyzing the effects of marine reserves and other long-term closures on fishery yield, assuming larvae are well-mixed and that exchange of adults between the open and closed areas is negligible. A number of analytic results are derived, including a formula for the gradient of yield with respect to fishing mortality and closure fraction. Increasing the closure fraction at equilibrium spawning stock biomass (SSB), B, will increase yield if and only if s′(B) > 1/b0(0), where s′(B) is the slope of the stock–recruitment curve at B and b0(0) is SSB per recruit at zero fishing mortality. Conditions for the level of closure required to prevent stock collapse are also derived. Applications of the theory to canary rockfish (Sebastes pinniger) and Georges Bank sea scallop (Placopecten magellanicus) illustrate that long-term closures increase yield only at low SSB associated with fishing mortalities greater than FMSY and with low closure fractions. The theory presented here gives simple analytic and graphical techniques for predicting the effects of long-term closures on yield and stock persistence.

scholarly journals A two-stage biomass model to assess the English Channel cuttlefish (Sepia officinalis L.) stock

2014 ◽  
Vol 71 (9) ◽  
pp. 2457-2468 ◽  
Author(s):  
Michaël Gras ◽  
Beatriz A. Roel ◽  
Franck Coppin ◽  
Eric Foucher ◽  
Jean-Paul Robin
Keyword(s):  
Reference Points ◽  
Sea Surface ◽  
Sepia Officinalis ◽  
Sustainable Utilization ◽  
English Channel ◽  
Two Stage ◽  
Stock Biomass ◽  
Exploitation Rate ◽  
Spawning Stock ◽  
Age Structured

Abstract The English Channel cuttlefish (Sepia officinalis) is the most abundant cephalopod resource in the Northeast Atlantic and one of the three most valuable resources for English Channel fishers. Depletion methods and age-structured models have been used to assess the stock, though they have shown limitations related to the model assumptions and data demand. A two-stage biomass model is, therefore, proposed here using, as input data, four abundance indices derived from survey and commercial trawl data collected by Ifremer and Cefas. The model suggests great interannual variability in abundance during the 17 years of the period considered and a decreasing trend in recent years. Model results suggest that recruitment strength is independent of spawning–stock biomass, but appears to be influenced by environmental conditions such as sea surface temperature at the start of the life cycle. Trends in exploitation rate do not reveal evidence of overexploitation. Reference points are proposed and suggestions for management of the sustainable utilization of cuttlefish in the English Channel are advanced.

Spatial variation in fishing intensity and its effect on yield

2008 ◽  
Vol 65 (4) ◽  
pp. 588-599 ◽  
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.

scholarly journals Prerecruit survival and recruitment of northern Gulf of St Lawrence Atlantic cod

2008 ◽  
Vol 65 (6) ◽  
pp. 946-952 ◽  
Author(s):  
Daniel E. Duplisea ◽  
Dominique Robert
Keyword(s):  
Linear Models ◽  
Atlantic Cod ◽  
Information Criterion ◽  
Factors Affecting ◽  
Control Rules ◽  
Strategy Evaluation ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Long Time ◽  
Parsimonious Model

Abstract Duplisea, D. E., and Robert, D. 2008. Prerecruit survival and recruitment of northern Gulf of St Lawrence Atlantic cod. – ICES Journal of Marine Science, 65: 946–952. Recruitment (R) of exploited marine fish populations is usually modelled exclusively as a function of spawning-stock biomass (SSB). A problem arising when modelling over long time-series is that the nature of the R–SSB relationship is unlikely to be stationary. Changes are often interpreted as productivity regime shifts and are linked to alterations in prerecruit survival rate. We examine the role of environment and predation by fish and harp seals as factors affecting the R–SSB relationship in the northern Gulf of St Lawrence cod, by fitting linear models using combinations of covariates to explain cod prerecruit survival. The most parsimonious model (based on a Bayesian Information Criterion, BIC) included cod, mackerel, and temperature, whereas redfish and seals did not appear in any of the best-fit models. Recruitment models derived from this analysis could be used in operating models for management strategy evaluation simulations for northern Gulf cod, so one could develop harvest control rules that are robust to changes in recruitment productivity regimes.

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