Aggressive distance in juvenile coho salmon (Oncorhynchus kisutch)

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Abstract
The distances from which resident coho salmon approached, charged, or gave lateral displays to intruders were recorded, as were the approach and charge velocities. Each of five residents was tested while under three feeding regimes, and in response to three sizes of intruder 120 mm smaller, 10 mm smaller, and of the same size as the resident). Larger intruders were approached and displayed to from greater distances, and charge distance also tended to increase with intruder size. Feeding regime had no effects on aggressive distance. Neither approach nor charge velocity was influenced by intruder size, but charge velocity was highest in the least well fed fish. These results are discussed with reference to the economic defendabilily theory of territoriality.