Removal efficiency of prey in stomach contents of the Dolly Varden, Salvelinus malma malma by using a stomach pump in a river at Shiretoko Peninsula, northern Japan
2009
Yamamoto, A.(Tokyo Univ. of Agriculture, Abashiri, Hokkaido (Japan). Faculty of Bio-Industry) | Takami, T. | Kuwabara, R.
Feeding habits and removal efficiency of prey in stomach content (RE) of fluvial Dolly Varden of a standard length larger than 10 cm were investigated by a stomach pump in a stream located in Shiretoko Peninsula. Dominance taxa in the stomach contents were chironomid larva in May and October, gammarids in June, caddis larva (Goera spp.) in July and August, and salmonid eggs in September, 2004. RE by the pump showed over 65% during the study period. There were no significant differences in the prey-type compositions between samples by stomach pump and by operation. Sometimes, when the fish fed entirely on larger preys like cased caddis or salmonid eggs, RE of the pump was low. There were negative correlations between standard length or stomach fullness index and RE. Therefore, the stomach pump seemed to be effective for the feeding investigation of stream-dwelling salmonid fishes without killing. However, when the fish fed entirely on large preys and the fish was lager than 15 cm (standard length), the modification for the estimation of RE is required. It is a future task to clarify various conditions for this modification.
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