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Influences of illumination intensity on the nearest neighbour distance in coho salmon Oncorhynchus kisutch
Author(s) -
Azuma T.,
Iwata M.
Publication year - 1994
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1994.tb01077.x
Subject(s) - photopic vision , fish <actinopterygii> , fish measurement , biology , oncorhynchus , scotopic vision , intensity (physics) , carassius auratus , light intensity , fishery , zoology , physics , optics , biochemistry , retinal
Effects of illumination intensity on the nearest neighbour distance (NND) of coho salmon in an experimental aquarium were studied under illumination intensities ranging from 0 to 4000 Ix. The NNDs in sighted (intact) fish were divided into three groups according to the illumination intensities; the largest [1.15 times fork length (f.l.)] at 0 1x, the medium (0.78 to 0.84 f.l.) at 0.01 to 0.4 1x, and the least (0.60 to 0.66 f.l.) at 4–4000 1x. The fact that NNDs under 4 1x or higher illumination conditions were significantly smaller than those under 0.01 to 0.4 1x conditions suggests a change from photopic to scotopic vision. Blinded fish exhibited constant NNDs irrespective of illumination intensity and the value was similar to that of sighted fish under the 0 1x condition. The NNDs of blinded fish and sighted fish exposed to 0 1x were larger than the simulated NND calculated by hypothesizing that fish distribute randomly in the experimental aquarium. These results indicate that NND in a coho school is maintained primarily by vision, however, the NND is not determined by vision alone but by integrated senses.