FISHERY BULLETIN: VOL. 83, NO. 1 



over a 2-wk starvation period. Evidently con- 

 tinued otolith growth in starved fish resulted from 

 the metabolism of stored energy reserves. 



Estimates of food consumption indicated that 

 fish held under diel cyclic temperatures and fed 89c 

 B.W./24 h consumed significantly more food per 

 gram of fish when the food was offered during the 

 warm period (^-test, P < 0.01). No differences in 

 food consumption were noted in fish receiving a 4% 

 B.W./24 h ration on either the warm or cool portion 

 of the diel water-temperature regime (^-test, P > 

 0.05). It is likely that fish were not satiated at this 

 ration under either water- temperature regime. 

 Under the high ration, fish were satiated even 

 when the food was offered during the cool period of 

 the water-temperature cycle. Additional con- 

 sumption occurred only if food was offered during 

 the warm portion of the diel temperature cycle. 

 The additional food consumption was associated 

 with increased growth rates. It is not clear 

 whether the increased growth was simply a re- 

 sponse to differences in food consumption or also 

 reflected enhanced efficiency of food utilization in 

 fish exposed to cyclic temperatures similar to that 

 described by Brett (1979) and Biette and Geen 

 (1980). Differences in growth rate of fish fed 4% 

 B.W./24 h strongly suggest more efficient food 

 utilization in fish exposed to a cyclic temperature 

 regime. Food consumption did not differ although 

 growth rates (and increment widths) are signifi- 

 cantly greater 



Given that water temperature and food con- 

 sumption are considered the most important fea- 

 tures of fishes' environment affecting their growth 

 (Paloheimo and Dickie 1966), it is not surprising 

 that water-temperature regimes and ration levels 

 influence otolith growth increment production. 

 Our findings and those of English (1981) suggest 

 that interpretation of prey abundance and feeding 

 success from otolith microstructure data may be 

 masked by relatively small changes in water 

 temperature. Workers attempting to quantify fish 

 growth with respect to ration size through exami- 

 nation of otolith microstructure should be aware 

 of the effects of water temperature documented 

 here and design studies accordingly. 



ACKNOWLEDGMENTS 



We thank Eldon Stone of the Canada Depart- 

 ment of Fisheries and Oceans Capilano Hatchery 

 for providing the fish used in this study Tracey 

 Crawford and Jeff Johansen assisted with otolith 

 preparation. Ron Long, Department of Biological 



100 



Sciences, Simon Eraser University, prepared the 

 photographs. The critical review of an earlier draft 

 of this manuscript by S. Campana and M. Healey 

 is particularly appreciated. This work was sup- 

 ported by grants from Canada Department of 

 Fisheries and Oceans and the Natural Sciences 

 and Engineering Research Council to Glen H. 

 Geen. 



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