Growth and mortality param eters of Penaeus indicus
from Sit. Lanka (Negorabo and Chilaw) caught between September 1982 and June 1986 are analysed on annual
basis , based on length frequency data. The yield
is opleths were then drawn.
The asym ptotic length fo r d iffe re n t periods and areas v a rie d from 20.5 - 24 cm ( to ta l length) and
growth constant of the von B e rtalan ffy growth formula was found to be between 1,5 - 1 .8 . The to ta l m o rtality
v aried from 2.89 - 4«49» The mean n a tu ra l m o rta litie s
fo r the whole period of study were 2.7 and 2.6 fo r
Negorabo and Chilaw re sp e c tiv e ly , whereas fish in g
m o rta lity v aried between 0,39 - 0.97 in Negombo and
0.30 - 1.86 in Chilaw.
From there la tiv e y ie ld iso p le th s drawn, an in crease
of fishing effort which results in a value of fishing
mortality of 2.6 can be suggested with an inorease
of the minimum mesh size . As this is a multispecies
fishery the optimum mesh size should be determ ined
after findin a balance between the other commercially
im portant shrimp species.