Shifts in a fish's resource holding power during a contact paired interaction: the influence of a copper-contaminated diet in rainbow trout.
The influence of sublethal chronic dietary copper (Cu) exposure on the dominant-subordinate relationship between pairs of juvenile rainbow trout (Oncorhynchus mykiss) was examined. Fish were fed either a normal (11 mg Cu kg(-1) food) or Cu-contaminated (721 mg Cu kg(-1) food) diet for 8 wk. Paired interactions were observed--control versus control, Cu-exposed versus Cu-exposed, and control versus Cu-exposed fish--using a computer-aided video tracking system to measure duration of interactions, total distance moved, and the number of encounters during each contest. In concurrence with game theory, each interaction became escalated with a lesser size disparity between contestants. However, in Cu-exposed versus Cu-exposed fish interactions, the dominant-subordinate relationship was decided sooner and with less aggression than a control versus control fish interaction with fish of a similar relative body mass disparity. During control versus Cu-exposed fish interactions, control fish would normally dominate interactions (12 out of 16 bouts) unless the Cu-exposed fish had a 15% body mass advantage. Muscle glycogen and lactate levels after each contest reflected the duration of bouts and winners of the contests, irrespective of Cu exposure. We conclude that Cu-contaminated fish are less able to compete and have lower resource holding power than controls and will withdraw from a contest at a lower level of interaction, unless a size advantage in the Cu-exposed fish increases the probability of winning.
Campbell
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Department of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, United Kingdom. h.a.campbell@bham.ac.uk
Handy
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Sims
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D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001835:Body Weight; D003300:Copper / Q000633:toxicity*; D004032:Diet; D006003:Glycogen / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D016015:Logistic Models; D018482:Muscle, Skeletal / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism / Q000502:physiology*; D012930:Social Dominance; D014741:Video Recording
D019344:Lactic Acid; D003300:Copper; D006003:Glycogen