Early life history traits of the gold-eye rockfish, Sebastes thompsoni, in relation to successful utilization of drifting seaweed |
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Authors: | T Kokita M Omori |
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Institution: | (1) Department of Applied Bio-Science, Faculty of Agriculture, Tohoku University, 1-1 Tsutsumi-dori, Amamiya-machi, Aoba-ku, Sendai 981-0914, Japan, JP |
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Abstract: | The gold-eye rockfish Sebastes thompsoni lives in association with drifting seaweed during the early developmental period. Early life history traits of the gold-eye
rockfish were studied by means of otolith analysis of larvae and juveniles associated and unassociated with drifting seaweed
in the waters off southern Sanriku, Tohoku, northern Japan, from 1993 to 1995.␣Daily growth increments and the existence of
an extrusion check were confirmed by both a series of tetracycline marking experiments and an analysis of the relation between
the number of increments and the number of days after extrusion. Larvae and juveniles associated with drifting seaweed occurred
from late May to late July, with a peak in late June, showing the same seasonal fluctuation in abundance as drifting seaweed.
Larvae seemed to associate with drifting seaweed after aggregation to surface slick areas. Body size at the commencement and
the end of the seaweed-associated period was estimated at 18 and 50 mm total length, respectively. Growth rates were low until
the beginning of the association with seaweed; thereafter they became high but declined towards the end of seaweed-associated
life. Larvae and juveniles born later grew faster than those born earlier. This tendency was detected both before and during
the association with drifting seaweed. Although the season of abundant drifting seaweed was about 2␣months shorter, and occurred
2 months later, than the extrusion season of the gold-eye rockfish from early February to early June, this seemed to be compensated
by the growth variation dependent on birth month. Early life history traits of the gold-eye rockfish are discussed in relation
to the successful utilization of drifting seaweed.
Received: 3 August 1997 / Accepted: 24 March 1998 |
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