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PHILIPPINES
Feeding treatments: Wild S. olivacea
Grow-out mangrove pen systems
suitable for coastal communities have been developed by AQD
over the years. Dependence on "trash fish" or fish
biomass, used as food by low income groups, remains a problem
in farming mud crabs. To reduce if not completely eliminate
such dependence, a low cost, incomplete pellet was formulated.
Wild S. olivacea (30-70 g BW) were stocked in pens with
feeding treatments as follows: A) no feeding (natural
productivity), B) no feeding for 1 month followed by
supplementary feeding with cow/carabao hide, C) fish biomass, and D) incomplete pellets. Growth rates peaked after three months then stabilized therafter, suggesting at this point selective harvest can be started. Crabs fed fish and cowhide had significantly larger sizes after 3 months. They also showed the highest total production, number of berried females and survival rates, although the latter was not significantly different among treatments. Crabs with supplementary feeding survived on natural food in the mangroves for the first month, indicating that artificial feeding of wild-sourced juveniles is not necessary during this period. Pellet stability and crab retrieval need improvement.
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Grow-out mangrove pen system for mudcrab |
Varieties of S. olivacea
Two varieties of wild S. olivacea juveniles tentatively identified as 'morongsod' and 'sinaw' were stocked separately in pens. 'Morongsod' are smaller, darker red and more aggressive than
'sinaw'. After four months, body size and weight were generally higher for 'sinaw' than 'morongsod'. However, the number of mature, berried and spawned females was higher for 'morongsod' compared to 'sinaw'. Genetic profile of the two
S. olivacea varieties needs to be confirmed.
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Two varieties of
Scylla olivacea juveniles-'sinaw' (left) and 'morongsod' (right) |
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