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Publication year : 0
Thematic : Fisheries
Language : English
Note
This article describes the growth, mortality,
and selection patterns in early larval stage of
Japanese seabass Lateolabrax japonicus in Ariake
Bay, Kyushu, Japan. Japanese seabass larvae were
collected from the spawning ground in December
2007, and juveniles were collected from the nursery
ground in March 2008. Otoliths were analyzed to
produce back-calculated daily records of size-at-age
and growth rate. Back-calculated growth rates and
sizes were compared between larvae and juveniles to
determine whether selective mortality occurred. A
weight-specific growth coefficient (G) and instantaneous
mortality coefficient (M) were computed, and
the recruitment potential was evaluated from the ratio
of M:G. Selection for fast-growing and bigger larvae
was evident during the 5–14 days after hatching
(DAH). Selective mortality acted to preferentially
remove fish that were slow growing and/or relatively
small members of the cohort at least during the period
examined. Trends in the growth rate differences
between larvae and juveniles suggested that the
selection process continued beyond 14 DAH although
the exact duration over which selective mortality
occurred was unknown. Survivors of Japanese seabass
exhibited traits consistent with all aspects of the
‘growth–mortality’ hypothesis: faster growth, larger
size-at-age, and shorter larval stage duration (LSD),
i.e., larvae with faster growth, bigger size-at-age and a
shorter LSD selectively survived the larval period.
Larvae had higher M (0.323) than G (0.159), resulting
in the M:G ratio of[1.0 (M:G = 2.031), suggesting
that the larval cohort was rapidly losing biomass.
Future studies should look to determine the duration
over which selective mortality occurs and the timing
of transition between M and G (M = G) and accumulation
of cohort biomass.
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Keywords : Marine protected areas
Encoded by : Pauline Carmel Joy Eje
