Management strategies
associating batch-graded and size-graded postlarvae can reduce heterogeneous
individual growth in Macrobrachium rosenbergii (de Man)
K. Ranjeet, B. Madhusoodana Kurup-2002
Aquaculture
Research, 33(15):
1221-1228
Abstract:
Two sets of adaptive trials were performed to
determine the effects of size grading and batch grading on size
heterogeneity in cultured Macrobrachium rosenbergii raised in the
Coconut Garden channels of Kuttanad, Southern India. In the first set of
trials, postlarvae were batch graded on the basis of their hatching order,
segregated and grown separately as first-hatched and second-hatched groups.
In the second set of trials, postlarvae were size graded as jumpers and
laggards and were grown in separate channels. The average weight attained by
prawns after 10 months of culture was highest for jumpers (83.11 g)
and lowest for the prawns from the first-hatched group (43.76 g). The
percentage of males was highest in the population of jumpers (58.23%).
Highest production was recorded in the channel stocked with postlarvae from
the second-hatched group (103.4 kg ha-1) and lowest
production was obtained from the first-hatched group (63.74 kg ha-1).
The proportions of undesirable small males were highest among laggards and
the first-hatched group: 24.8% and 15.1% respectively. The level of
heterozygosity within morphotypes was also high in these groups. Jumpers
attained good growth by the end of culture but, because of their low
survival rate, this approach was not economically feasible. However, higher
production and survival in the second-hatched group improved economic
viability. Thus, for better results, stocking with later-hatched groups
would be more appropriate than stocking with the first-hatched group.
(School of Industrial Fisheries, Cochin University of
Science and Technology, Fine Arts Avenue, Kochi-682 016, India. E-mail of
Madhusoodana Kurup: madhukurup@hotmail.com)