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First published online June 26, 2009
Journal of Experimental Biology 212, 2296-2302 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.027102

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The behavioural, digestive and metabolic characteristics of fishes with different foraging strategies

Shi-Jian Fu^1,*, Ling-Qing Zeng¹, Xiu-Ming Li¹, Xu Pang¹, Zhen-Dong Cao¹, Jiang-Lan Peng¹ and Yu-Xiang Wang^1,2

¹ Laboratory of Evolutionary Physiology and Behavior, Chongqing Key Laboratory of Animal Biology, Chongqing Normal University, Chongqing 400047, China
² Department of Biology, Queen's University, Kingston, Ontario, Canada, K7L 3N6

^* Author for correspondence (e-mail: shijianfu9{at}hotmail.com)

Accepted 20 April 2009

To test the hypothesis that digestion has a more notable physiological effect on ambush foragers than on active foragers, we investigated the behavioural, digestive and metabolic characteristics, as well as the postprandial locomotory capacity, of four species of juvenile fish distributed along the Yangtze River, China, with distinct foraging strategies. The ambush foraging southern catfish (Silurus meridionlis) had the fewest movements per minute (MPM), lowest per cent time spent moving (PTM), slowest critical swimming speed (U_crit), lowest maintenance metabolism (_O2rest) and lowest maximum locomotory metabolism (_O2max). However, the southern catfish had the highest feeding level and maximum feeding metabolism (_O2peak) and the greatest decrease in U_crit after consumption of a large meal. Thus, this fish is highly adapted to its ambush behavioural strategy and sedentary life style. In the herbivorous grass carp (Ctenopharyngodon idellus), a low digestive capacity led to little change in postprandial locomotory performance, which benefits its frequent grazing behaviour. In this species, the greater amount of energy spent on routine activity and avoiding predators versus U_crit might be related to its herbivorous life style and high predation risk. The active foraging crucian carp (Carassius auratus) adopts a unique high energy cost strategy that allows for high capacity in both routine activity and digestion, and the great flexibility of its cardio-respiratory capacity (increased _O2max after feeding) guarantees a small decrease in U_crit even after maximum feeding. Finally, the sluggish foraging darkbarbel catfish (Pelteobagrus vachelli) has low digestive and locomotory capacity, but its energy-efficient venomous defence strategy may be related to its abundance. These results show that the digestive, behavioural and metabolic strategies differ among these fish species. The locomotory capacity in the sedentary fishes decreased profoundly after feeding, whereas it decreased little or not at all in the active fishes. The maintenance of high locomotory capacity after eating in the active fishes is probably related to a large metabolic capacity, a lower digestive capacity or an improvement in cardio-respiratory capacity after feeding.

Key words: ambush and active foragers, energy expenditure, feeding metabolism, foraging mode, locomotory capacity, metabolic ceiling

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