The implications of warming climate for the management of North Sea demersal fisheries

Abstract

Since the 1950s, records from the North Sea show a gradual increase in temperature. Using temperature as a proxy indexing the state of the environment, relationships between recruitment, spawning-stock biomass, and temperature are investigated for major North Sea stocks. Cod, plaice, and sole exhibit significant negative relationships between temperature and recruitment, while there is evidence of a positive effect for saithe and whiting. Stock-recruitment models that incorporate temperature are developed and used to examine implications for the management of these stocks with small increases in mean winter sea surface temperature. These suggest that for cod, minimum safe biomass reference points are unlikely to be achieved even at fishing mortality rates that are considered safe. The same analysis suggests that sustainable fishing for cod is still possible with higher yields than have been experienced in recent years. Crow

Forage fish abundance is a predictor of timing of breeding and hatching brood size in a coastal seabird

“…Moreover, the abundance of 1 yr old saithe was positively correlated with wNAO and in both colonies the shags bred earlier when more 1 yr old saithe were available. Saithe in the North Sea has responded positively to increasing SSTs (Cook & Heath 2005), and an earlier spawning has also been observed for saithe in Faroese waters (Homrum et al 2012). There were no correlations between SSTs and the abundance indices of young saithe in our analysis (Table 2), nor when we back-lagged the saithe data an extra year to account for possible effects on first-year fish (r = 0.08, p = 0.736).…”

“…Cook & Heath (2005) demonstrated a close positive correlation between recruitment, spawning-stock biomass and SST for saithe Pollachius virens in the North Sea. Although no such correlations have been published for the Northeast Arctic saithe in the Norwegian Sea, SSTs have been increasing there since 1990 (e.g.…”

Socio-economic Impacts—Fisheries

“…Empirical data on exploited populations often show strong relationships between recruitment success, fisheries catches and climatic variables. These strong relationships have been demonstrated, for example, for cod (O'Brien et al 2000;Brander and Mohn 2004;Cook and Heath 2005), plaice (Brunel and Boucher 2007), herring (Nash and Dickey-Collas 2005), mackerel (Jansen and Gislason 2011) and seabass (Pawson 1992). Correlations have been found between fish recruitment and various climate variables, including sea surface temperature, the NAO and even offshore winds (Table 12.2).…”

Changes in size at maturity of European hake Atlantic populations in relation with stock structure and environmental regimes

“…Althoug temperature was not used in the multiple regression analysis, it is known that it impacts on age and size at maturity (Armstrong et al, 2004;Drinkwater, 2005), although the responses of fish to this factor varies between species (Cook and Heath, 2005). Rose (2005) suggests that small pelagics respond quickly and strongly to climate changes because of their physiological limits and fast potential growth.…”

“…In spite of the several technical measures taken to recover the stock status, most have failed. This has raised again the debate (Anon., 2004) as to whether fishing is the main factor causing the decline of stocks, or whether environmental factors are the main cause (Cook and Heath, 2005). To demonstrate that environment plays important role on population dynamics is a hard task, firstly because its effect is often mixed with those produced by fishing and the inherent difficulty to discern between them; but, secondly due to lack of good quality data that can produce robust statistical results.…”