Ethological Function of the Parr Marks in a Japnese Trout, Oncorhyncus masou f. ishikawai

概要

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The land-locked from (forma ishikawai) of the Japanese trout, Oncorhyncus masou, retains its dark oval markings on its lateral sides (parr marks) throughout life when living in narrow waters. The fish develops marked territoriality, and fighting is frequently observed between a resident and intruder. Aggressive behaviour consists of five patterns: approach, attack, lateral display, open-mouth display and chasing. The intruder is usually driven away by an approach and/or open-mouth display but sometimes other aggressive behaviour (lateral display, attack) follows. All aggressive behaviour patterns lead to the dispersal of the fish and the maintenance of territory. It was revealed by presenting various models with and without lateral markings, that the parr marks play an important role in releasing aggressive behaviour. This agrees well with the presence and retention of parr marks in the land-locked form living in narrow waters, which is extremely territorial.
社団法人日本動物学会の論文
1979-03-25