Food abundance and territory size in juvenile coho salmon (Oncorhynchus kisutch)

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Abstract
Feeding territory size and potential food abundance were measured simultaneously in a field population of junvenile (40-50 mm) coho salmon. Territory size was inversely related to the density of benthic food on the territory, as predicted from an energy-based model of territoriality. The relationship between the abundance of drift food and territory size was in the predicted direction, but was not significant. Territories were smaller where intruder pressure was higher, but intrusion rate and food abundance were not directly correlated. The effect of food abundance on territory size was not caused indirectly by attraction of nonterritorial fish to areas where food was abundant. In the laboratory the distance from which a resident coho attacked an approaching model intruder increased asymptotically with hunger. The fish appear to possess an appropriate behavioral mechanism (tactic) to adjust territory size to local food abundance.