Long‐term trends in fish recruitment in the north‐east Atlantic related to climate change

Abstract

This study investigates the temporal correspondence between the main patterns of recruitment variations among north-east Atlantic exploited fish populations and large-scale climate and temperature indices. It is of primary importance to know what changes in fish stock productivity can be expected in response to climate change, to design appropriate management strategies. The dominant patterns of recruitment variation were extracted using a standardized principal component analysis (PCA). The first principal component (PC) was a long-term decline, with a stepwise change occurring in 1987. A majority of Baltic Sea, North Sea, west of Scotland and Irish Sea populations, especially the gadoids, have followed this decreasing trend. On the contrary, some herring populations and the populations of boreal ecosystems have followed an opposite increasing trend. The dominant signal in north-east Atlantic sea surface temperature, also extracted by a PCA, was highly correlated with the increase in the Northern Hemisphere Temperature anomaly, which is considered to be an index of global warming. The first component of recruitment was inversely correlated with these changes in regional and global temperature. The second PC of recruitment was a decadal scale oscillation, which was not correlated with climate indicators. The analysis of correlations between population recruitment and local temperature also indicated that the dominant pattern of recruitment variation may be related to an effect of global warming. The influence of fishing on recruitment, via its effect on the spawning stock biomass (SSB), was also investigated by the analysis of correlations between fishing mortality, SSB and recruitment. Results indicate that fishing can be another factor explaining recruitment trends, probably acting in combination with the effect of climate, but cannot explain alone the patterns of recruitment variation found here.

Exploring plasticity in the wild: laying date–temperature reaction norms in the common gull Larus canus

“…This in turn determines when the study area becomes available for nest building. In addition, local temperature affects the availability of fish (herring and sprat) through local sea surface temperature (Brunel & Boucher 2007), and is likely to affect the availability of terrestrial invertebrates (mainly earthworms) that the common gulls feed on.…”

Temporal shifts in recruitment dynamics of North Atlantic fish stocks: effects of spawning stock and temperature

“…Actually, the importance of the environment for fluctuations in fish stocks was already acknowledged as early as the 1870s (Kendall & Duker 1998). Since then, recruitment has been correlated with temperature in numerous studies on single stocks and fewer covering many stocks (examples of the latter are in Planque & Fredou 1999, Fox et al 2000, and Brunel & Boucher 2007. Unfortunately, many such correlations tend to weaken or disappear when retested with extended data series (Myers 1998).…”

Responses of Marine Organisms to Climate Change across Oceans

“…In the north-east Atlantic, investigation of climate-driven recruitment variation across 40 fish stocks belonging to nine species showed a general long-term decline in recruitment correlated with warming sea surface temperatures (Brunel and Boucher, 2007). While it is likely that fishing also played a role in observed trends in recruitment for some populations through depletion of spawning stock, for many such as cod, Gadus morhua, in the Irish Sea, the decline in recruitment commenced while stocks were still at high levels, implying a deterioration in favorable environmental conditions for early life stages.…”