title: 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.
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, Scotland, UK.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Baudron
authors.forename: Coby L
authors.initials: CL
authors.lastname: Needle
authors.forename: Adriaan D
authors.initials: AD
authors.lastname: Rijnsdorp
authors.forename: C Tara
authors.initials: CT
authors.lastname: Marshall
mesh_terms: D000367:Age Factors; D000818:Animals; D049628:Body Size; D057231:Climate Change; D005399:Fishes / Q000254:growth & development / Q000502:physiology*; D008954:Models, Biological; D009659:North Sea; D012623:Seawater; D013696:Temperature
keywords: climate change; dynamic Factor Analysis; ectotherms; fish growth; fisheries; temperature size rule; von Bertalanffy