LUNAR PERIODICITY IN CATCH RATE AND REPRODUCTIVE CONDITION OF ADULT EASTERN KING PRAWNS, PENAEUS-PLEBEJUS, IN COASTAL WATERS OF SOUTH-EASTERN QUEENSLAND, AUSTRALIA
Aj. Courtney et al., LUNAR PERIODICITY IN CATCH RATE AND REPRODUCTIVE CONDITION OF ADULT EASTERN KING PRAWNS, PENAEUS-PLEBEJUS, IN COASTAL WATERS OF SOUTH-EASTERN QUEENSLAND, AUSTRALIA, Marine and freshwater research, 47(1), 1996, pp. 67-76
This study examined the lunar and diel variation in catch rates and re
productive condition of adult eastern king prawns, Penaeus plebejus, i
n relatively deep (160 m) coastal waters off southeastern Queensland.
Females numerically dominated catches over most of the lunar cycle and
constituted 76% of the weight of the catch. Analysis of variance (ANO
VA) revealed an interaction between lunar phase and sex; catches peake
d during Lunar Phase 3 (full moon +/- 3 days) and were particularly ma
rked for males. This was the only period during the lunar cycle when t
he sex ratio approached 1:1. There was also an interaction between tra
wl-time and sex; male catch rates were at a minimum early in the eveni
ng, whereas female catch rates were at a maximum then and declined thr
oughout the night. Trawler logbook catch rate data from the same area
over a similar period indicated an interaction between lunar cycle and
lunar phase. ANOVA revealed an effect of the interaction between phas
e and sex on the incidence of soft prawns; the incidence of soft males
increased during Phase 4 (half moon waning to new moon +/- 3 days). O
vary weight also varied between phases and was higher during Phases 2
(half moon waxing to full moon +/- 3 days) and 4 (half moon waning to
new moon +/- 3 days). Trends in the ovary weight and the incidence of
histologically mature and ripe females suggested there are two periods
of increased spawning activity during each lunar cycle. A cyclic regr
ession fitted to the data explained 93% of the variation in the incide
nce of ripe females between samples. The influence of these cyclic tre
nds in catch rate and reproductive condition should be considered when
monitoring the spawning stock in the fishery and when planning sampli
ng strategies in any future reproductive studies.