温暖化で魚が小さくなるのはなぜ?エラが原因ではないことがUMass Amherst主導の研究で判明(Why Are Fish Getting Smaller as Waters Warm? Not Because of Their Gills, Finds Study Led by UMass Amherst)

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2024-02-21 マサチューセッツ大学アマースト校

温暖化で魚が小さくなるのはなぜ?エラが原因ではないことがUMass Amherst主導の研究で判明(Why Are Fish Getting Smaller as Waters Warm? Not Because of Their Gills, Finds Study Led by UMass Amherst)
A brook trout’s oxygen consumption is measured to estimate its energy needs under different environmental temperatures.
Credit: Joshua Lonthair

マサチューセッツ大学アマースト校を中心とした科学者の共同チームが、気候変動による温かい水域で多くの魚が「縮小」しているという主要な理論の生理学的根拠がないことを最近発見した。これまで主要な理論とされてきたGill Oxygen Limitation(GOL)理論は、魚の大きさを説明する普遍的なメカニズムとして提案され、将来の世界の漁業収量の予測にも利用されてきた。しかし、研究者らは、水温の上昇が体サイズの有意な減少につながることを示した一方で、鰓の表面積が変化に対して説明できなかった。

<関連情報>

サケ科の冷水性魚類において、温暖化下で体が小さくなるのはエラ-酸素の制限によるものではない Smaller body size under warming is not due to gill-oxygen limitation in a cold-water salmonid

Joshua K. Lonthair,Nicholas C. Wegner,Brian S. Cheng,Nann A. Fangue,Matthew J. O’Donnell,Amy M. Regish,John D. Swenson,Estefany Argueta,Stephen D. McCormick,Benjamin H. Letcher,Lisa M. Komoroske
​​Journal of Experimental Biology  Published:21 February 2024
DOI:https://doi.org/10.1242/jeb.246477

ABSTRACT

Declining body size in fishes and other aquatic ectotherms associated with anthropogenic climate warming has significant implications for future fisheries yields, stock assessments and aquatic ecosystem stability. One proposed mechanism seeking to explain such body-size reductions, known as the gill oxygen limitation (GOL) hypothesis, has recently been used to model future impacts of climate warming on fisheries but has not been robustly empirically tested. We used brook trout (Salvelinus fontinalis), a fast-growing, cold-water salmonid species of broad economic, conservation and ecological value, to examine the GOL hypothesis in a long-term experiment quantifying effects of temperature on growth, resting metabolic rate (RMR), maximum metabolic rate (MMR) and gill surface area (GSA). Despite significantly reduced growth and body size at an elevated temperature, allometric slopes of GSA were not significantly different than 1.0 and were above those for RMR and MMR at both temperature treatments (15°C and 20°C), contrary to GOL expectations. We also found that the effect of temperature on RMR was time-dependent, contradicting the prediction that heightened temperatures increase metabolic rates and reinforcing the importance of longer-term exposures (e.g. >6 months) to fully understand the influence of acclimation on temperature–metabolic rate relationships. Our results indicate that although oxygen limitation may be important in some aspects of temperature–body size relationships and constraints on metabolic supply may contribute to reduced growth in some cases, it is unlikely that GOL is a universal mechanism explaining temperature–body size relationships in aquatic ectotherms. We suggest future research focus on alternative mechanisms underlying temperature–body size relationships, and that projections of climate change impacts on fisheries yields using models based on GOL assumptions be interpreted with caution.

生物環境工学
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