Large scale, synchronous variability of marine fish populations driven by commercial exploitation

Synchronous variations in the abundance of geographically distinct marine fish populations are known to occur across spatial scales on the order of 1,000 km and greater. The prevailing assumption is that this large-scale coherent variability is a response to coupled atmosphere–ocean dynamics, commonly represented by climate indexes, such as the Atlantic Multidecadal Oscillation and North Atlantic Oscillation. On the other hand, it has been suggested that exploitation might contribute to this coherent variability. This possibility has been generally ignored or dismissed on the grounds that exploitation is unlikely to operate synchronously at such large spatial scales. Our analysis of adult fishing mortality and spawning stock biomass of 22 North Atlantic cod (Gadus morhua) stocks revealed that both the temporal and spatial scales in fishing mortality and spawning stock biomass were equivalent to those of the climate drivers. From these results, we conclude that greater consideration must be given to the potential of exploitation as a driving force behind broad, coherent variability of heavily exploited fish species.

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Salinity and Recruitment of Atlantic Cod (Gadus morhua) in the Newfoundland Region

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f93-181 ◽

1993 ◽

Vol 50 (8) ◽

pp. 1599-1609 ◽

Cited By ~ 25

Author(s):

Ransom A. Myers ◽

Kenneth F. Drinkwater ◽

Nicholas J. Barrowman ◽

James W. Baird

Keyword(s):

North Atlantic ◽

Gadus Morhua ◽

Atlantic Cod ◽

Population Analysis ◽

Grand Banks ◽

The North ◽

Virtual Population ◽

Stock Biomass ◽

Spawning Stock ◽

Recruitment Time

Recruitment predictions for Atlantic cod (Gadus morhua) in the North Atlantic, based upon a previously published regression with salinity, are found to be well correlated with recent recruitment estimates from both virtual population analysis and those derived from research surveys. The addition of spawning stock biomass in the regression significantly increased the percentage of the variance accounted for in the recruitment time series. A similar relationship between recruitment and salinity was found for two nearby stocks (southern Grand Banks and St. Pierre Bank). Oceanographic and food chain mechanisms that might be responsible for a link between salinity and recruitment are discussed.

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Cod recruitment is strongly affected by climate when stock biomass is low

ICES Journal of Marine Science ◽

10.1016/j.icesjms.2004.07.029 ◽

2005 ◽

Vol 62 (3) ◽

pp. 339-343 ◽

Cited By ~ 93

Author(s):

Keith M. Brander

Keyword(s):

North Atlantic ◽

Gadus Morhua ◽

Environmental Variability ◽

Atlantic Cod ◽

Management Strategies ◽

Pooled Analysis ◽

The North ◽

Stock Biomass ◽

Spawning Stock ◽

The North Atlantic

Abstract Stocks of Atlantic cod (Gadus morhua) have been declining over much of the North Atlantic for the past 30 years, owing to a combination of overfishing and adverse changes in their environment. In a previous study, environmental effects were introduced as an extra parameter in the stock-recruit relationship, where they act as a multiplier, independent of the level of spawning-stock biomass (SSB). Using a non-parametric pooled analysis of all cod stocks on the European Shelf south of 62°N, it is shown here that environmental variability (as represented by the North Atlantic Oscillation) only has a significant effect on recruitment when the spawning stock is low. This has implications for fisheries management strategies, and for rates of stock recovery, which will be very dependent on environmental conditions.

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Spatial scales of variability in cod recruitment in the North Atlantic

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f95-778 ◽

1995 ◽

Vol 52 (9) ◽

pp. 1849-1862 ◽

Cited By ~ 30

Author(s):

R. A. Myers ◽

G. Mertz ◽

N. J. Barrowman

Keyword(s):

North Atlantic ◽

Large Scale ◽

Gadus Morhua ◽

Atlantic Cod ◽

Spatial Scales ◽

Population Analysis ◽

Estimation Error ◽

Commercial Catch ◽

The North ◽

The North Atlantic

We reexamine the hypothesis that there are large-scale (thousands of kilometres) patterns of recruitment of Atlantic cod (Gadus morhua) in the North Atlantic. Previous analyses have used sequential population analysis to reconstruct population histories; however, these methods are subject to a variety of biases and rely on the accuracy of commercial catch-at-age data. Several different studies have arrived at conflicting interpretations using virtually the same data. Here we analyze alternative data from research surveys using statistical methods that explicitly account for estimation error and we also employ detrended sequential population analysis. We conclude that the spatial scale of recruitment correlations generally does not exceed 500 km.

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

ICES Journal of Marine Science ◽

10.1093/icesjms/fsn081 ◽

2008 ◽

Vol 65 (6) ◽

pp. 946-952 ◽

Cited By ~ 5

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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The influence of spatially variable and connected recruitment on complex stock dynamics and its ecological and management implications

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2018-0151 ◽

2019 ◽

Vol 76 (6) ◽

pp. 937-949 ◽

Cited By ~ 1

Author(s):

Lisha Guan ◽

Yong Chen ◽

James A. Wilson ◽

Timothy Waring ◽

Lisa A. Kerr ◽

...

Keyword(s):

Gadus Morhua ◽

Gulf Of Maine ◽

Atlantic Cod ◽

Temporal Trends ◽

Substantial Reduction ◽

Management Implications ◽

Agent Based ◽

Stock Biomass ◽

Spawning Stock ◽

The Individual

To evaluate the influence of spatially variable and connected recruitments at spawning component scale on complex stock dynamics, a typical agent-based complex stock was modeled based on the Atlantic cod (Gadus morhua) stock in the Gulf of Maine. We simulated three scenarios with different degrees of connectivity (i.e., individual exchange) between the spatially variable recruitments of 36 spawning components within four subpopulations under the stock. Subsequently, the temporal trends were compared for different scenarios in age-1 recruitment, spawning stock biomass, and local depletion proportion of the overall complex stock and the individual subpopulations. Results show that increased recruitment connectivity from 0.1–0.2 to 0.6–0.8 between various components tends to increase the productivity and stability of a complex stock at local and global scales and reduce the proportion of depleted components due to overfishing. Moreover, depletions of less productive components may occur without a substantial reduction in the overall complex stock biomass and recruitment.

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

ICES Journal of Marine Science ◽

10.1093/icesjms/fsm024 ◽

2007 ◽

Vol 64 (4) ◽

pp. 761-767 ◽

Cited By ~ 34

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.

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Simulation of the Arctic—North Atlantic Ocean Circulation with a Two-Equation K-Omega Turbulence Parameterization

Journal of Marine Science and Engineering ◽

10.3390/jmse6030095 ◽

2018 ◽

Vol 6 (3) ◽

pp. 95 ◽

Cited By ~ 1

Author(s):

Sergey Moshonkin ◽

Vladimir Zalesny ◽

Anatoly Gusev

Keyword(s):

Prandtl Number ◽

Ocean Circulation ◽

North Atlantic ◽

Large Scale ◽

Mixed Layer Depth ◽

Ocean Dynamics ◽

Dynamics Simulation ◽

The Arctic ◽

Buoyancy Frequency ◽

Physical Factors

The results of large-scale ocean dynamics simulation taking into account the parameterization of vertical turbulent exchange are considered. Numerical experiments were carried out using k − ω turbulence model embedded to the Institute of Numerical Mathematics Ocean general circulation Model (INMOM). Both the circulation and turbulence models are solved using the splitting method with respect to physical processes. We split k − ω equations into the two stages describing transport-diffusion and generation-dissipation processes. At the generation-dissipation stage, the equation for ω does not depend on k. It allows us to solve both turbulence equations analytically that ensure high computational efficiency. The coupled model is used to simulate the hydrophysical fields of the North Atlantic and Arctic Oceans for 1948–2009. The model has a horizontal resolution of 0.25 ∘ and 40 σ -levels along the vertical. The numerical results show the model’s satisfactory performance in simulating large-scale ocean circulation and upper layer dynamics. The sensitivity of the solution to the change in the coefficients entering into the analytical solution of the k − ω model which describe the influence of some physical factors is studied. These factors are the climatic annual mean buoyancy frequency (AMBF) and Prandtl number as a function of the Richardson number. The experiments demonstrate that taking into account the AMBF improves the reproduction of large-scale ocean characteristics. Prandtl number variations improve the upper mixed layer depth simulation.

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Island in the Stream: Oceanography and Fisheries of the Charleston Bump

Island in the Stream: Oceanography and Fisheries of the Charleston Bump ◽

10.47886/9781888569230.ch6 ◽

2001 ◽

Keyword(s):

North Atlantic ◽

Fishery Management ◽

Population Analysis ◽

Mortality Rates ◽

Fishing Mortality ◽

Stock Biomass ◽

The Status ◽

Eastern North Atlantic ◽

Charleston Bump ◽

Definition Of

<em> Abstract.</em>—The status of the wreckfish <em> Polyprion americanus </em>stock caught on the Blake Plateau in the southeastern United States Atlantic was analyzed by calibrated virtual population analysis (VPA) to estimate trends in fishing mortality and population (or stock) biomass. Calibration of the FADAPT VPA program was to fishery-dependent catch-per-unit effort (CPUE) for a range in assumed values for natural mortality (M). Age-length keys were developed from two aging studies of wreckfish (1988– 1992 and 1995–1998). Keys were developed annually (pooled across seasons to create three “annual” age-length keys to represent 1988–1990, 1991–1993, and 1994–1998) and seasonally (pooled across years to create three seasonal age-length keys to represent April–June, July–September, and October to end of fishing year on 15 January). Analyses based on both annual and seasonal catch matrices showed similar patterns and values, with the seasonal catch matrix producing slightly lower estimates of fishing mortality rates (F) and higher estimates of biological reference points based on F. Fishing mortality rates peaked in 1989, as did the maximum annual U.S. landings (4.2 million pounds). Subsequently, both landings and fishing mortality rates have generally declined. Although stock biomass has generally declined over the study period, recruitment at age 7 has risen since about 1994. Meanwhile, annual estimates of static spawning potential ratio (SPR), which are inversely related to F, have risen since 1994. Fishing mortality rates from recent low landings are at or near the South Atlantic Fishery Management Council’s threshold definition of overfishing (static SPR of 30%), while the process of rebuilding with improving recruitment appears to be underway. Concern persists because the assessment is based on the underlying assumption that wreckfish from the Blake Plateau form a single stock separate from the eastern North Atlantic and genetic evidence suggests the stock encompasses the entire North Atlantic.

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