Environmental drivers of mean weight-at-age variability in pelagic and benthic fish from the NW Iberian Peninsula

Abstract

The mean weight-at-age of fish species is an indicator of fish growth and physiological condition, as well as a basic parameter for assessing and managing fish stocks. Here, we investigate the temporal trends of the mean weight-at-age of four different commercial species with different life strategies: (i) the short-lived pelagic European sardine ( Sardina pilchardus ), (ii) the horse mackerel ( Trachurus trachurus ) and two medium-lived benthic, (iii) the megrim ( Lepidorhombus whiffiagonis ) and iv) the four-spotted megrim ( Lepidorhombus boscii ), in North Atlantic Iberian waters from 2000 to 2018. Generalised additive models were implemented to identify the main (density-dependent and density-independent) drivers of fish weight-at-age variability: abundance, sex, maturity, sea surface temperature, sea bottom temperature, North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation indices. In all four species, abundance had a negative effect on mean weight-at-age. Temperature affected mean weight-at-age in sardine and megrim, while NAO influenced it in horse mackerel and four-spotted megrim. In the case of the sardine, we observed a progressive decrease in the mean weight-at-age of adults in the series in contrast to the four-spotted megrim; however, there was no effect of year on either horse mackerel or megrim. We discuss the influence of life strategy on fish response to drivers.

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