FISHERY, BIOLOGY AND POPULATION DYNAMICS OF Epinephelus diacanthus (Valenciennes, 1828) LANDED AT VERAVAL, GUJARAT 3015
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Date
2019-09
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JAU, JUNAGADH
Abstract
August to November months i.e., the post monsoon and winter seasons were the most
productive periods in terms of catch and catch rate of E. diacanthus at Veraval. The
length of the species during the study period ranged from 121 mm (in March, April
and October) to 506 mm. The present study establishes that the slope of regression
equation for E. diacanthus was significantly (5%) different from the isometric value
of 3, indicating a negatively allometric growth for the species. The overall sex ratio
for E. diacanthus was 1: 2.06. Females dominated in all size classes up to 45 cm and
their percentage varied from 54.55 to 76.64%, while males became dominant after 45
cm. E. diacanthus spawned throughout the year with the peak in August-December.
The size at 50% of E. diacanthus matured in the population was 262 mm. Absolute
fecundity of E. diacanthus ranged from 58,806 during April to 2,24,640 in August.
The average fecundit y determined for the study period of one year was 1,25,253. The
estimated ova size of E. diacanthus ranged from 252 to 384 µm. Month wise GSI was
calculated and it was found to be higher in September, October, November and
December. The diet of E. diacanthus included Ambassis sp., Bregmaceros sp.,
Leiognathus sp., Prawns, Crab, Sepia, Squilla, Gastropods, Octopus, Copepods,
Bivalve, Lucifer Sp., Eggs and Larva of fishes, digested fish and shrimp. The
asymptotic length, growth coefficient, and age at zero length were respectively, 526
mm, 0.36 and - 0.0729 years. The growth performance index was 5.0. Recruitment ii
pattern was trimodal with its peak during May to June and August to September. The
total, natural and fishing mortality were 2.20, 0.41 and 1.80, respectively. The
exploitation ratio and rate of exploitation was 0.82 and 0.869, respectively. The
annual total stock, biomass and MSY were 32446 t, 26583 t and 29241 t, respectively.
The yield and yield per recruit at the present fishing effort was 22031.92 t and 65.13
g, respectively. The exploitation of the species at Veraval is above the sustainable
level. The fishing pressure has to be decreased by 20% from the present condition for
the sustainable fishery.