Fishery biological informations on daggertooth pike- conger eels, Muraenesox cinereus around Tokushima prefecture [Japan]
2008
Ueta, Y.(Tokushima-ken. Agriculture, Forestry and Fisheries Technology Support Center, Minami (Japan). Fisheries Research Inst.)
Sex ratio, reproductive ecology, condition factor, growth, life span, and age composition of daggertooth pike-conger eels, Muraenesox cinereus around Tokushima Prefecture were studied from the measurements of body length, body weight, gonad weight, egg number and number of otolith ring about 3,000 individuals landed by small-scale trawller and bottom longline during 1987-1988. The annual ratio of male was 59%. Daily sex ratio trend to lean to either male or female. This result suggests that both male populations and female ones separatelly distribute. Spawning season was estimated to be during August to September from monthly change of gonad somatic index. Condition factor trend to be the least in September after spawning, and to raise from October to December. The life span was about fifteen years by calculating the number of otolith ring; daggertooth pike-conger eels hatched out during July to September with the peak season of August and settlement after planktonic season (Leptocephalus) during about one year. Theoretical growth equations of Bertalanffy were applied to relationships age and body length by sex. It was estimated from age composition of market size that 3-5 age populations became main target of fishery.
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