Size-dependent thermal preferences in a pelagic fish

• Published in: Oikos 2010-08, Vol.119 (8), p.1265-1272
• Main Authors: Morita, Kentaro, Fukuwaka, Masa-aki, Tanimata, Naoki, Yamamura, Orio
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Body size; Body temperature; Body weight; Catabolism; Ecology; Freshwater fishes; Fundamental and applied biological sciences. Psychology; General aspects; Marine fishes; Oceans; Oncorhynchus; Salmon; Sea surface temperature; Seas; Size; Temperature; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution
• ISSN: 0030-1299; 1600-0706
• DOI: 10.1111/j.1600-0706.2009.18125.x

Large fish often inhabit colder waters than small fish. Using a simple bioenergetic model, we found that the optimal temperature for growth should decrease with increasing body size. We predicted that this mechanism would produce an ontogenetic change in thermal preference and then tested our predictions with Pacific salmon, Oncorhynchus spp. In a laboratory experiment, the slope of a regression of growth increment on initial size became steeper with increasing temperature, so that the optimal temperature for growth decreased with increasing body size. In field observations, larger and older salmon inhabited cooler areas, whereas smaller and younger salmon inhabited warmer areas. These patterns were consistent with a size-dependent effect of temperature on condition factor, a parameter shown experimentally to be a measure of the most recent growth performance. Temperatures for maximising condition factor were lower for larger fish. Thus, an ontogenetic change in individual thermal preference toward cooler areas maximises the growth performance of fish, and the negative effects of climate warming on growth are hypothesised to be more severe for larger fish.