A fisheries management strategy robust to ignorance: rotational harvest in the presence of indirect fishing mortality

2000 ◽  
Vol 57 (12) ◽  
pp. 2357-2362 ◽  
Author(s):  
Ransom A Myers ◽  
Susanna D Fuller ◽  
Daniel G Kehler
Keyword(s):  
Management Strategy ◽  
Narrow Range ◽  
Fishing Mortality ◽  
Placopecten Magellanicus ◽  
Sea Scallop ◽  
Simple Theoretical Model ◽  
Stock Biomass ◽  
Wide Range ◽  
Spawning Stock ◽  
Harvest Strategy

We develop a simple theoretical model of yield and spawning stock biomass per recruit for the American sea scallop (Placopecten magellanicus), which appears to have high indirect fishing mortality when harvested with dredges, i.e., mortality caused by the act of fishing that does not result in landings. The age at and degree to which individuals are affected by the indirect mortality are unknown, and it does not appear possible to develop a robust harvest strategy with yearly harvests unless indirect fishing mortality is well quantified. We show that there could be substantial benefits to a rotational harvest strategy for sessile species with high indirect fishing mortality. First, the strategy appears to be robust to ignorance about indirect fishing mortality and results in equal or better yields than a yearly harvest across a wide range of indirect fishing mortalities. Second, under most conditions, a higher spawning stock biomass is maintained. Third, rotational management is more easily enforced, as it does not require specifying a narrow range of fishing mortality in order to maximize yield.

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 Evaluation of the quality of the North Sea herring assessment

2009 ◽  
Vol 66 (8) ◽  
pp. 1814-1822 ◽  
Author(s):  
E. John Simmonds
Keyword(s):  
North Sea ◽  
Management Strategy ◽  
Fishing Mortality ◽  
The North ◽  
Stock Biomass ◽  
Spawning Stock ◽  
The North Sea ◽  
Acoustic Surveys ◽  
One Year

Abstract Simmonds, E. J. 2009. Evaluation of the quality of the North Sea herring assessment. – ICES Journal of Marine Science, 66: 1814–1822. The assessment of North Sea herring has been used to give advice on catch quota for more than 20 years. The data sources comprise acoustic surveys, International Bottom Trawl Surveys, Methot Isaacs–Kidd net post-larval surveys, larval surveys, and catch-at-age data. These sources and their uses are briefly reviewed, and the changes in the weighting attached to each index in the assessment over time are discussed. The performance of the assessment is examined both in historical and analytical retrospectives of spawning–stock biomass and fishing mortality, and in retrospective assessments of numbers by cohort. Increased length of the time-series, the use of a statistical model with appropriate weighting, and a more consistent management strategy have all contributed to the assessment becoming highly stable from one year to the next. The results presented lead to the conclusion that the assessments provide an excellent basis for the management of this stock.

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 Is a management framework based on spawning-stock biomass indicators sustainable? A viability approach

2007 ◽  
Vol 64 (4) ◽  
pp. 761-767 ◽  
Author(s):  
Michel De Lara ◽  
Luc Doyen ◽  
Thérèse Guilbaud ◽  
Marie-Joëlle Rochet
Keyword(s):  
Fisheries Management ◽  
Significant Contribution ◽  
Bay Of Biscay ◽  
Fishing Mortality ◽  
Precautionary Approach ◽  
Management Framework ◽  
Control Approach ◽  
Management Indicators ◽  
Stock Biomass ◽  
Spawning Stock

Abstract De Lara, M., Doyen, L., Guilbaud, Th., and Rochet, M-J. 2007. Is a management framework based on spawning-stock biomass indicators sustainable? A viability approach. – ICES Journal of Marine Science, 64: 761–767: 000–000. Fisheries management agencies have to drive resources on sustainable paths, i.e. within defined boundaries for an indefinite time. The viable-control approach is proposed as a relevant method to deal with sustainability. We analyse the ICES precautionary approach (PA) by means of the notion of viability domain, and provide a mathematical test for sustainability. It is found that the PA based on spawning-stock biomass (SSB) and fishing mortality (F) indicators is sustainable only when recruits make a significant contribution to SSB. In this case, advice based upon SSB, with an appropriate reference point, is sufficient to ensure sustainability. In all other cases, SSB is not a sufficient metric of stock productivity and must be complemented with other management indicators to ensure sustainability. The approach is illustrated with numerical applications to the northern hake and Bay of Biscay anchovy.

A length-based multispecies model for evaluating community responses to fishing

2006 ◽  
Vol 63 (6) ◽  
pp. 1344-1359 ◽  
Author(s):  
Stephen J Hall ◽  
Jeremy S Collie ◽  
Daniel E Duplisea ◽  
Simon Jennings ◽  
Mark Bravington ◽  
...  
Keyword(s):  
Fish Species ◽  
Single Species ◽  
Community Level ◽  
Fishing Mortality ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Multispecies Model ◽  
Species Declines ◽  
Ecosystem Based Fisheries Management ◽  
Biomass Spectra

Quantitative ecosystem indicators are needed to fulfill the mandate for ecosystem-based fisheries management. A variety of community metrics could potentially be used, but before reference levels for such indices can be established the sensitivity of candidate indices to fishing and other disturbances must be determined. One approach for obtaining such information is to test candidate indicators with models that mimic real ecosystems and can be manipulated experimentally. Here we construct a size-based multispecies model of a community of fish species that interact by predation. The model was parameterized for 21 fish species to obtain a predation-regulated community. Following an analysis of the sensitivity of the model to parameter uncertainty, we tested the sensitivity of community-level indicators to increasing levels of fishing mortality (F). Abundance and biomass spectra were sensitive to fishing mortality, with the slope decreasing with increasing F. Species diversity size spectra were also very sensitive to F, with diversity in the largest size classes declining rapidly. In contrast, k-dominance curves were less sensitive to fishing pressure. Importantly, however, although most community-level metrics showed clear trends in response to fishing, single-species declines in spawning stock biomass were the most sensitive indicators of fishing effects.

scholarly journals On the dynamics of Sardina pilchardus: orbits of stability and environmental forcing

2010 ◽  
Vol 67 (8) ◽  
pp. 1565-1573
Author(s):  
A. P. Solari ◽  
M. T. G. Santamaría ◽  
M. F. Borges ◽  
A. M. P. Santos ◽  
H. Mendes ◽  
...  
Keyword(s):  
Sea Surface ◽  
External Forcing ◽  
Fishing Mortality ◽  
Sardina Pilchardus ◽  
Environmental Forcing ◽  
Stock Biomass ◽  
External Variables ◽  
Multiresolution Decomposition ◽  
Spawning Stock ◽  
Upwelling Index

Abstract Solari, A. P., Santamaría, M. T. G., Borges, M. F., Santos, A. M. P., Mendes, H., Balguerías, E., Díaz Cordero, J. A., Castro, J. J., and Bas, C. 2010. On the dynamics of Sardina pilchardus: orbits of stability and environmental forcing. – ICES Journal of Marine Science, 67: 1565–1573. The dynamics of Sardina pilchardus in Iberian upwelling are examined. Spawning-stock biomass (SSB), recruitment (R), and production (R/SSB) data for the years 1978–2006 are analysed in relation to the upwelling index (UPW) and sea surface temperature (SST). The population oscillates in two relatively stable orbits (identified by multiresolution decomposition of the recruitment series) because the external forcing (UPW and SST) are the inverse of each other and the synchrony is lost between the two external variables, R and R/SSB as they shift towards steep, negative (depensatory) trends. Such mechanics may have induced recruitment failures and significant decreases in abundance of Iberian sardine. The relationships are assumed to validate a complex and dynamic continuum (multiple orbits of stability) and an alternative variable-carrying-capacity population model. Radial systems with two orbits of stability are proposed for the R/SSB and S/SSB (where S is the stock size) relationships. Results are discussed in relation to classical and alternative SR models to address stock rehabilitation and fishing mortality issues as the population shifts towards low recruitment and abundance, and critical factors to consider in developing exploitation strategies for systems with multiple orbits of stability are discussed.

scholarly journals An alternative reference point in the context of ecosystem-based fisheries management: maximum sustainable dead biomass

2015 ◽  
Vol 72 (8) ◽  
pp. 2257-2268 ◽  
Author(s):  
Hans-Joachim Rätz ◽  
John Casey ◽  
Steven J. Holmes ◽  
Josep Lloret ◽  
Hendrik Dörner ◽  
...  
Keyword(s):  
Fisheries Management ◽  
Reference Points ◽  
Production Model ◽  
Fish Stock ◽  
Compensatory Mechanism ◽  
Fishing Mortality ◽  
Dead Biomass ◽  
Selection Pattern ◽  
Stock Biomass ◽  
Spawning Stock

Abstract Under the 2013 Reform of the European Union's Common Fisheries Policy (CFP), fisheries management aims to ensure that, within a reasonable time frame, the exploitation of marine biological resources restores and maintains populations of harvested stocks above levels that can produce the maximum sustainable yield (MSY). The CFP also calls for the implementation of an ecosystem-based approach to fisheries management (EBFM). In this paper, we present the concept of maximum sustainable dead biomass (MSDB) and its associated management reference points for fishing mortality and spawning-stock biomass as alternatives to those associated with MSY. The concept of MSDB is illustrated by a dynamic pool production model of a virtual fish stock which takes into account variations in natural mortality (M), fishing mortality (F), and exploitation pattern. Our approach implies a compensatory mechanism whereby survivors may benefit from compensatory density dependence and is implemented through progressive substitution of M with F for varying rates of total mortality (Z). We demonstrate that the reference points for fishing mortality and spawning-stock biomass associated with MSDB are less sensitive to increasing compensation of M with F than those associated with MSY and more sensitive to changes in selection pattern. MSDB-based reference points, which are consistent with maximum stock productivity, are also associated with lower fishing mortality rates and higher stock biomasses than their MSY-based counterparts. Given that selection pattern can be influenced through fishery input measures (e.g. technical gear measures, decisions on areas, and/or times of fishing), whereas variations of M in response to F are not controllable (indeed poorly understood), that the results of many fish stock assessments are imprecise, that maximum stock productivity corresponds to MSDB and that MSY-based reference points may best be considered as limits, we propose that MSDB-based reference points provide a more appropriate basis for management under an EBFM.

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. 

Hexose Monophosphate Accumulation and Related Metabolic Changes in Unfrozen and Thawed Adductor Muscle of the Sea Scallop (Placopecten magellanicus)

1973 ◽  
Vol 30 (1) ◽  
pp. 45-52 ◽  
Author(s):  
Doris Fraser Hiltz ◽  
W. J. Dyer
Keyword(s):  
Adductor Muscle ◽  
Metabolic Changes ◽  
Hexose Monophosphate ◽  
Placopecten Magellanicus ◽  
Sea Scallop ◽  
Chill Storage ◽  
Quick Freezing ◽  
Wide Range ◽  
Maillard Browning ◽  
Index Of Quality

The hexose monophosphates (glucose-6-phosphate (G6P), fructose-6-phosphate, and glucose-1-phosphate) accumulate postmortem in scallop adductor muscle (meats) during chill storage, increasing from only traces at death to levels totalling about 10 μmole/g after 8–10 days. In both unfrozen and thawed meats, G6P accounted consistently for 80–85% of the total hexose monophosphate, over a wide range of actual concentrations. Quick freezing at any time postmortem did not affect the concentrations of hexose monophosphates or related metabolic constituents. Thawing of the prerigor-frozen muscle, however, either slowly or rapidly, resulted in considerable G6P formation, and accelerated markedly the subsequent rate and extent of G6P production. The exceptionally high levels (− 20 μmole/g) reached in the thawed meats after 1–2 days at 5 C are implicated in the development of burned flavors, odors, and discolorations (i.e. Maillard browning reactions) observed in these thawed meats when cooked. While thawing of the prerigor-frozen muscle led to some hypoxanthine (Hx) and octopine formation, the subsequent rate of Hx accumulation at 5 C was three times faster in the thawed meats than in unfrozen meats. In meats frozen postrigor, thawing resulted in negligible change in concentrations of the metabolites; subsequent patterns of change during storage differed little from those in unfrozen muscle, although Hx accumulation was more rapid. Hx content showed potential as an index of quality in thawed scallop muscle.

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.

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