Distribution of Larvae of Pinnixa rathbuni SAKAI (Decapoda : Pinnotheridae) in Ise Bay and its Neighbouring Coastal Waters,Central Japan-Ⅱ\n : Larval Aggregations,with Notes on their Dispersal Properties
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In deducing that abundant benthic populations of Pinnixa rathbuni have been always found in western parts of Ise Bay, it was thought that early larvae would appear first in the western parts of the bay. But past observations showed they were always found abundantly first in the eastern parts of the bay. So there remained to be inquired into the question why they occurred abundantly not in the west but in the eastern parts of the bay. Thus, it is necessary to know in detail the properties of aggregations of the larvae found in the eastern parts of the bay. This paper deals with investigating a small-scale distribution of the larvae in the eastern parts of the bay where numerous larvae, at early stages, appear. Zoea 1 - 5 larvae were found abundantly in a very narrow belt-shaped zone along the coast of Tita Peninsula , though the centre of their distribution was localized just off ゛Utumi" and ゛Yamami" . Patterns of the small-scale spatial distribution were almost the same through the zoeal stages. This indicates that dispersal would not be considerable through the zoeal larvae. Aggregated masses for zoea 1 - 4 stages, which were observed close to the coast of "Utumi" and "Yamami",showed an almost clear-cut margin and thus a trapezoid-shaped distribution,because the numbers of the larvae caught changed drastically in directions both toward the off-shore water and along the coasts of Tita Peninsula. Distributional features of the larvae indicated that dispersal of the larvae, forming the belt-shaped zone of aggregations along the coast of Tita Peninsula, would be strengthened only in the southern area along the coast, being negligible in the northern area. Characteristic water movements underlie the forming of the belt-shaped aggregations along the coast. However, aggregations of larvae must be caused by the larvae themselves, hydrographical and other biological features are not responsible for forming this much aggregated distribution. This is clearly understood by comparison with those copepod collected simultaneously. Aggregations of early larvae, found in the eastern part of Ise Bay, would be correlated with the presence of aggregated benthic adults, though we have not yet evidence for the presence of this hypothesized benthic population.
雑誌名
三重大学水産学部研究報告 = Bulletin of the Faculty of Fisheries, Mie University
Distribution of Larvae of Pinnixa rathbuni SAKAI (Decapoda : Pinnotheridae) in Ise Bay and its Neighbouring Coastal Waters,Central Japan-Ⅱ\n : Larval Aggregations,with Notes on their Dispersal Properties
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