MATURATION IN THE FEMALE EASTERN KING PRAWN PENAEUS-PLEBEJUS FROM COASTAL WATERS OF EASTERN AUSTRALIA, AND CONSIDERATIONS FOR QUANTIFYING EGG-PRODUCTION IN PENAEID PRAWNS
Aj. Courtney et al., MATURATION IN THE FEMALE EASTERN KING PRAWN PENAEUS-PLEBEJUS FROM COASTAL WATERS OF EASTERN AUSTRALIA, AND CONSIDERATIONS FOR QUANTIFYING EGG-PRODUCTION IN PENAEID PRAWNS, Marine Biology, 122(4), 1995, pp. 547-556
The trawl fishery for eastern king prawns, Penaeus plebejus, is of maj
or commercial significance on the east coast of Australia. This paper
describes the reproductive biology of female P. plebejus and presents
new information relevant to quantifying egg production in penaeid praw
n populations. The study concluded that the gonosomatic index (GSI) co
varied with prawn size and was, therefore, likely to be a poor indicat
or of reproductive activity for penaeid prawn populations. GSI was als
o found to be not independent of ovary histological stage, moult stage
, insemination status and parasitisation by bopyrid isopods. An histol
ogical description of ovarian development and the incidence of each st
age of development is provided. This includes a description of the ovu
lation stage, which has not been previously recorded in naturally-occu
rring populations. Fifty percent of female P. plebejus were classed as
mature at 42 mm CL. The relationships between GSI, percent mature, an
d percent inseminated with size suggest that there is a decline in the
capacity of large (> 60 mm CL) females to produce and fertilise eggs.
The declines in both GSI and percent mature is indicative of ovarian
senescence in large(old) females, which has not been recorded previous
ly in penaeid prawns. An index which considers the relationships betwe
en the percent mature, fecundity and the percent inseminated with size
, as well as the influence of mortality on the population, is put forw
ard to determine the relative contribution of different size classes o
f females to egg production. The index suggests that females > 50 mm C
L contribute little to egg production, and that the bulk of eggs are p
roduced by 35 to 48 mm CL females.