Morphometric
model and laboratory analysis of intracohort cannibalism in giant grouper Epinephelus
lanceolatus fry
J.-R. Hseu, P.-P. Hwang, Y.-Y. Ting-2004
Fisheries
Science, 70(3):
482-486
Abstract:
During larviculture of giant grouper, Epinephelus
lanceolatus, intracohort cannibalism usually results in mass mortality.
Thus, in the present study, we attempted to develop a cannibal-prey length
relationship from morphometric measurements for giant grouper fry and to
verify it with pairwise predation experiments. Based on measurements of
morphometric characteristics (i.e. mouth width, body depth, and total
length), a model of prey length (mm) to cannibal length was constructed: TLprey = 0.83 TLcannibal
- 2.48.
According to the equation, approximately 30% is a threshold in total length
differences to use for grading giant grouper fry. The threshold was
supported by our pairwise experiments using 136 pairs; we found that 33 out
of 36 cannibalism incidents occurred only when the prey was of equal or
smaller size than that predicted by the equation. In aquaculture practice of
this species, we thus suggest that when the length of larger fry exceeded
that of smaller fry by more than 30%, the potential cannibals should be
removed.
(Mariculture Research Center, Fisheries Research
Institute, Chiku, Tainan 724, Taiwan, Tel: 886-6-7880461 ext. 229. Fax:
886-6-7881597. Email: jrhseutfri@pchome.com.tw)