Spawning characteristics of
the South African mudcrab Scylla serrata (Forskal) in captivity
J.A. Davis, G.J. Churchill, T. Hecht, P.
Sorgeloos-2004
Journal of the World Aquaculture Society, 65(2):
121-133 (from ISI Current
Contents)
Abstract:
Scylla serrata is a potential aquaculture species in Southern Africa.
Information about its reproductive biology is required as a prerequisite to
establishing hatchery technology. Adult female S. serrata were caught in the
Umlalazi estuary on the subtropical east coast of South Africa and kept in
captivity to observe and record spawning characteristics. Data collected
included crab size and mass, time in captivity prior to spawning, fecundity
per batch, relative fecundity, individual egg mass and size, size of zoea 1
larvae, incubation time, and hatch success rate. Of the 119 crabs kept in
captivity 83% spawned in the maturation system-most within 40 d of capture.
The crabs were highly fecund (mean relative fecundity per batch = 10,655 +/-
4,069 eggs/g female) and the majority of the batches hatched within 288 h
(12 d) at 27 C. Spawning in captivity occurred throughout the year, with a
peak in late winter/early spring. This differs slightly from records of
ovarian maturity stages of the crabs in the wild. A pattern of synchronous
spawning was recorded where the females were observed to extrude their eggs
in groups, commonly within 3 d of one another, separated by long periods of
inactivity, suggesting an exogenous spawning cue. A total of 1,374,488 zoea
larvae were obtained per kg of female per month. This means that if
sufficient mature females can be caught from the wild, these could be used
for stocking hatchery operations. The crabs were easy to maintain, mature,
and spawn in captivity. This will facilitate future domestication which will
eventually reduce the need for wild caught broodstock. The spawning
characteristics of South African S. serrata fit in well with those observed
for the genus throughout its distribution implying that ecological and
fisheries management could be similar.
(Ghet University, Lab Aquaculture & Artemia Ref.
Ctr., Rozier 44, B-9000 Ghent, Belgium, e-mail of P. Sorgeloos: Patrick.sorgeloos@Ugent.be)