Recruitment and Survival of Milkfish Chanos chanos Larvae in the Surf Zone.

概要

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The majority of <I>Chanos chanos</I> larvae collected from the surf zone at Villa and Tigbauan, Iloilo, Philippines, fell within a narrow range for total length (TL; 12.0-15, 0mm in 96% of 2, 386 larvae) and had otolith increment counts of 15-20 (78%). The increment counts showed serial increases representing 5-10 days in some samples, at increase rates of 0.5-0.6/day, but such increases were not accompanied by increases in total length. Based on the low frequency (7.3%) of surf-zone larvae possessing food items in the gut, milkfish larvae occurring in the surf zone were considered to be under deficient feeding conditions. Otolith increments were formed at a rate of 1/day in well-fed larvae and 0.4/day in starved, captive larvae, in which stagnation of TL growth was also observed. The retardation of otolith increment formation and overall body growth in the surf zone larvae were considered to have resulted from deficient feeding conditions of a larval group entering and remaining in the surf zone for a certain period and/or from the concurrent recruitment and disappearance of larvae in the surf zone. The maximum duration of stay of the larvae in the surf zone was estimated to be about 10 days, from about day 15 to day 25 after hatching. Consequently, it is necessary for the larvae to move to juvenile nursery grounds within this period.
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