Metcalfe N B, Huntingford F A, Graham W D, Thorpe J E
Department of Zoology, Glasgow University, U.K.
Proc R Soc Lond B Biol Sci. 1989 Feb 22;236(1282):7-19. doi: 10.1098/rspb.1989.0009.
Atlantic salmon have a variable life cycle. In good growing conditions, underyearling fish may metamorphose into the migratory smolt phase during their second spring, or delay at least a further year. The strategy adopted by particular fish appears to become fixed during their first summer. This paper examines whether either feeding efficiency or dominance in mid-summer correlates with the life-history strategy adopted. Eighty fish were individually marked and their feeding efficiency (= mean handling time for food items) and dominance rank measured under laboratory conditions in mid-July. Growth rates of the fish were then monitored over the next three months, until developmental strategies became apparent. Discriminant and logistic regression analyses revealed that both dominance rank and size attained by July were independent, significant predictors of future developmental pattern (the age at metamorphosis being correctly predicted on the basis of rank and size in 84% of cases) whereas feeding efficiency had no effect. Thus fish that were dominant or larger two months after first feeding or both had a greater probability of migrating after only one year in freshwater than those more subordinate or smaller or both.
大西洋鲑鱼具有可变的生命周期。在良好的生长条件下，一龄鱼可能在第二个春季变态为洄游型的稚鱼阶段，或者至少再延迟一年。特定的鱼所采用的策略似乎在它们的第一个夏季就固定下来了。本文研究了仲夏时节的摄食效率或优势地位是否与所采用的生活史策略相关。80条鱼被单独标记，并在7月中旬的实验室条件下测量它们的摄食效率（=食物项目的平均处理时间）和优势等级。然后在接下来的三个月里监测这些鱼的生长速度，直到发育策略变得明显。判别分析和逻辑回归分析表明，7月时的优势等级和达到的体型都是未来发育模式的独立且显著的预测指标（根据等级和体型正确预测变态年龄的情况占84%），而摄食效率没有影响。因此，在首次摄食两个月后占主导地位或体型较大或两者兼具的鱼，在淡水中仅生活一年后洄游的可能性比那些地位较低或体型较小或两者皆是的鱼更大。
