Warming temperatures and smaller body sizes: synchronous changes in growth of North Sea fishes

Abstract

Decreasing body size has been proposed as a universal response to increasing temperatures. The physiology behind the response is well established for ectotherms inhabiting aquatic environments: as higher temperatures decrease the aerobic capacity, individuals with smaller body sizes have a reduced risk of oxygen deprivation. However, empirical evidence of this response at the scale of communities and ecosystems is lacking for marine fish species. Here, we show that over a 40-year period six of eight commercial fish species in the North Sea examined underwent concomitant reductions in asymptotic body size with the synchronous component of the total variability coinciding with a 1-2 °C increase in water temperature. Smaller body sizes decreased the yield-per-recruit of these stocks by an average of 23%. Although it is not possible to ascribe these phenotypic changes unequivocally to temperature, four aspects support this interpretation: (i) the synchronous trend was detected across species varying in their life history and life style; (ii) the decrease coincided with the period of increasing temperature; (iii) the direction of the phenotypic change is consistent with physiological knowledge; and (iv) no cross-species synchrony was detected in other species-specific factors potentially impacting growth. Our findings support a recent model-derived prediction that fish size will shrink in response to climate-induced changes in temperature and oxygen. The smaller body sizes being projected for the future are already detectable in the North Sea.

Population Genomics of Marine Fishes: Next-Generation Prospects and Challenges

“…Several studies suggest that fishing pressure and climate change could act as drivers of evolutionary change on contemporary time scales in natural marine fish populations (Jørgensen et al, 2007;Baudron et al, 2014;Crozier and Hutchings, 2014). Consequently, evolutionary processes should ideally be incorporated into conservation and management practices to secure both the future evolutionary potential and sustainable exploitation of marine fishes (Hoffmann and Sgro, 2011;Heino et al, 2013).…”

Environmental Impacts—Marine Ecosystems

“…This may affect the productivity and reproduction of the stock. An extension of this analysis to include seven other North Sea fish species also showed an overall decline in asymptotic size (Baudron et al 2014), but half of the decline in asymptotic size took place prior to 1988, during a period when temperature declined, suggesting that other factors are at work such as food limitation (as previously mentioned for plaice and sole).…”

“…There have been particularly rapid changes in temperature and other climate-related variables since the early 1980s, with many well described effects on North Sea ecosystems. However the examples presented in this chapter also show that biological responses in terms of growth, survival, phenology and population shifts are often more complex than might be expected from thermal response models or bioclimate envelope models (Cheung et al 2011;Baudron et al 2014). For example, the growth response of juvenile cod to increasing temperature in the Skagerrak was positive during spring but negative in summer, with a detectable density effect, but only at stock levels that have not been observed for many decades.…”

Climate Change and Food In/Security: A Critical Nexus

“…It has also been postulated that rising temperatures in water bodies have led to smaller body sizes of fishes such as herring and haddock [24]. This is because warmer water conditions have increased the anabolic oxygen demand underwater while simultaneously reducing oxygen solubility necessary for survival [24].…”