Population variability under stressors is dependent on body mass growth and asymptotic body size.

Leonie Färber,Rob Van Gemert,Joël M Durant,Øystein Langangen,Ken H Andersen

doi:10.1098/rsos.192011

Leonie Färber, Rob Van Gemert + Show 3 more

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https://doi.org/10.1098/rsos.192011

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Abstract

The recruitment and biomass of a fish stock are influenced by their environmental conditions and anthropogenic pressures such as fishing. The variability in the environment often translates into fluctuations in recruitment, which then propagate throughout the stock biomass. In order to manage fish stocks sustainably, it is necessary to understand their dynamics. Here, we systematically explore the dynamics and sensitivity of fish stock recruitment and biomass to environmental noise. Using an age-structured and trait-based model, we explore random noise (white noise) and autocorrelated noise (red noise) in combination with low to high levels of harvesting. We determine the vital rates of stocks covering a wide range of possible body mass (size) growth rates and asymptotic size parameter combinations. Our study indicates that the variability of stock recruitment and biomass are probably correlated with the stock's asymptotic size and growth rate. We find that fast-growing and large-sized fish stocks are likely to be less vulnerable to disturbances than slow-growing and small-sized fish stocks. We show how the natural variability in fish stocks is amplified by fishing, not just for one stock but for a broad range of fish life histories.

Highlights

The natural environmental conditions, e.g. sea temperature, that a fish stock experiences fluctuate continuously
Our study indicates that the variability of stock recruitment and biomass are probably correlated with the stock’s asymptotic size and growth rate
We investigated a parameter space within the 80% most common asymptotic sizes and body mass growth rates of the species included in the FishBase database [25], available through the R [26] (v. 3.4.4) package ‘rfishbase’ (v. 3.0.4) [27]

Summary

Introduction

The natural environmental conditions, e.g. sea temperature, that a fish stock experiences fluctuate continuously. Hidalgo et al [4] showed in a simulation of population dynamics that, with exploitation, the importance of the contribution of recruitment to the total biomass increases; environmental effects (simulated by white and red noise) have a stronger effect on biomass dynamics. Owing to their longevity, large-sized and slow-growing fish often have many cohorts contributing to the overall recruitment. A study on North Atlantic cod (Gadus morhua) stocks showed that environmental effects (autocorrelated and non-correlated dynamics) that influence recruitment by modulating, for example, food availability and temperature lead to increased sensitivity to collapse among fished populations [14]. Species with high rates of body mass growth are more prone to collapse under fishing pressure and environmental variability [15]

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