The effects of population density on the rate of growth, maturation, and productivity of the stock of the northeast Arctic cod Gadus morhua morhua

Kovalev, Yu. A.

doi:10.1134/s003294520901007x

Cited by 5 publications

(3 citation statements)

References 21 publications

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“…Length at age of the younger fish was negatively associated with total stock size in the preceding years, whereas such an effect was only found in weight at age of older cod ( Fig. S4 and Table S2), as also found by Kovalev and Yaragina (38). …”

supporting

confidence: 61%

Synergies between climate and management for Atlantic cod fisheries at high latitudes

Kjesbu¹,

Bogstad²,

Devine³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

182

189

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The widespread depletion of commercially exploited marine living resources is often seen as a general failure of management and results in criticism of contemporary management procedures. When populations show dramatic and positive changes in population size, this invariably leads to questions about whether favorable climatic conditions or good management (or both) were responsible. The Barents Sea cod (Gadus morhua) stock has recently increased markedly and the spawning stock biomass is now at an unprecedented high. We identify the crucial social and environmental factors that made this unique growth possible. The relationship between vital rates of Barents Sea cod stock productivity (recruitment, growth, and mortality) and environment is investigated, followed by simulations of population size under different management scenarios. We show that the recent sustained reduction in fishing mortality, facilitated by the implementation of a "harvest control rule," was essential to the increase in population size. Simulations show that a drastic reduction in fishing mortality has resulted in a doubling of the total population biomass compared with that expected under the former management regime. However, management alone was not solely responsible. We document that prevailing climate, operating through several mechanistic links, positively reinforced management actions. Heightened temperature resulted in an increase in the extent of the suitable feeding area for Barents Sea cod, likely offering a release from density-dependent effects (for example, food competition and cannibalism) through prolonged overlap with prey and improved adult stock productivity. Management and climate may thus interact to give a positive outlook for exploited high-latitude marine resources.gadoids | population dynamics | quota | ocean warming | polar displacement

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supporting

confidence: 61%

Synergies between climate and management for Atlantic cod fisheries at high latitudes

Kjesbu¹,

Bogstad²,

Devine³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

182

189

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“…The spatial component of habitat size may be of particular importance in this context (Andersen et al, 2017). Although these findings suggest that density dependence early in life may dominate in marine fish, density-dependent body growth may still be relevant, as has been established by case studies in several populations of marine fish (Ivanov & Beverton, 1985;Kovalev & Yaragina, 2009;Olafsdottir et al, 2015;Rijnsdorp & Van Leeuwen, 1992;Rindorf, Jensen, & Schrum, 2008). However, there have been few attempts to systematically study the prevalence of density-dependent growth.…”

Section: Introductionmentioning

confidence: 98%

Density regulation in Northeast Atlantic fish populations: Density dependence is stronger in recruitment than in somatic growth

Zimmermann

Ricard

Heino

2018

Journal of Animal Ecology

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Population regulation is a central concept in ecology, yet in many cases its presence and the underlying mechanisms are difficult to demonstrate. The current paradigm maintains that marine fish populations are predominantly regulated by density-dependent recruitment. While it is known that density-dependent somatic growth can be present too, its general importance remains unknown and most practical applications neglect it. This study aimed to close this gap by for the first time quantifying and comparing density dependence in growth and recruitment over a large set of fish populations. We fitted density-dependent models to time-series data on population size, recruitment and age-specific weight from commercially exploited fish populations in the Northeast Atlantic Ocean and the Baltic Sea. Data were standardized to enable a direct comparison within and among populations, and estimated parameters were used to quantify the impact of density regulation on population biomass. Statistically significant density dependence in recruitment was detected in a large proportion of populations (70%), whereas for density dependence in somatic growth the prevalence of density dependence depended heavily on the method (26% and 69%). Despite age-dependent variability, the density dependence in recruitment was consistently stronger among age groups and between alternative approaches that use weight-at-age or weight increments to assess growth. Estimates of density-dependent reduction in biomass underlined these results: 97% of populations with statistically significant parameters for growth and recruitment showed a larger impact of density-dependent recruitment on population biomass. The results reaffirm the importance of density-dependent recruitment in marine fishes, yet they also show that density dependence in somatic growth is not uncommon. Furthermore, the results are important from an applied perspective because density dependence in somatic growth affects productivity and catch composition, and therefore the benefits of maintaining fish populations at specific densities.

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“…However, an analysis of the year classes suggested that both fisheries-induced evolution (FIE) and the compensatory phenotypic response (caused by faster individual growth) resulted in earlier sexual maturation . A decrease in F will increase the proportion of slowly growing and late-maturing individuals that transmit hereditary traits to the offspring (Kovalev and Yaragina 2009).…”

Section: Introductionmentioning

confidence: 99%

Long-term interplay between harvest regimes and biophysical conditions may lead to persistent changes in age at sexual maturity of Northeast Arctic cod (Gadus morhua)

Rørvik¹,

Bogstad

Ottersen

et al. 2022

Can. J. Fish. Aquat. Sci.

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This investigation commenced by constructing principal maturation schedule equations as a function of fishing mortality (F), key biophysical factors and a term attributed to fisheries-induced adaptive change (FIAC). Following the onset of industrial trawl fishery on the model stock, Northeast Arctic cod (NEAC) (1934-2020), F on immature age groups 5-8 years (F5-8) increased and mean age at 50% maturity (A50) decreased from ≈10 years in the late 1940s to ≈7 years today. Large annual fluctuations in total stock biomass (TSB), sea temperature (KolaT) and F5-8 were used to better understand A50 responses. In the model, the annual accumulation of F5-8 drives FIAC. The model includes the option that NEAC may sustain F5 8 up to a certain level (F_bal) before FIAC becomes statistically evident, with F_bal falling between 0.00 and 0.40 for A50. This dynamic range in F_bal indicates a sophisticated, underlying adaptive response. Independent of F_bal, our analysis clarifies that FIAC is necessary to explain the observed changes in A50.

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The effects of population density on the rate of growth, maturation, and productivity of the stock of the northeast Arctic cod Gadus morhua morhua

Cited by 5 publications

References 21 publications

Synergies between climate and management for Atlantic cod fisheries at high latitudes

Synergies between climate and management for Atlantic cod fisheries at high latitudes

Density regulation in Northeast Atlantic fish populations: Density dependence is stronger in recruitment than in somatic growth

Long-term interplay between harvest regimes and biophysical conditions may lead to persistent changes in age at sexual maturity of Northeast Arctic cod (Gadus morhua)

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