Feeding management on the growth and survival rate of mud crab (Scylla serrata)

Introduction

Mud crab (Scylla serrata) or red mud crab locallynamed as "alimango" is considered as one of the mostimportant food from the sea. This is a lucrative forbusiness because of its taste and high price commandin the market (Palattao, 2008). Scylla serrata can bedefined by the following physical characteristics. Thefront is cut into four lobes of about equal size andprominence. The anteriolateral border is cut into ninesharply acuminate teeth of approximately the samesize. The carapace is smooth, except for faint granularridges running from the last anteriolateral spinegoing obliquely onwards and is interrupted more orless at the cervical groove and a ridge on the region ofthe epibranchial. The chelipeds are smooth. Threestrong spines are present on the anterior border ofthe arm and followed proximally with one or twolarge tubercles. On the posterior border of the armare two spines, one distally located and the other ashort distance behind. The inner border of the wrist isarmed with a strong spine and its outer border with acomparatively smaller spine. The upper surface of thehand bears three spines which are sometimes reducedto mere tubercles. These spines are distributed asfollows: one of the wrist articulations and one each onthe inner and outer borders of the upper surface andare located distally. The penultimate segment of themale abdomen is broader than long and hasconvergent sides. The ultimate segment istriangularly rounded (Fernandez et al., 1996).

The environmental impact of marine fish-farmingdepends very much on species, culture method,stocking density, and feed type, hydrography of thesite and husbandry practices. There is concern thatrapid expansion of aquaculture may be constrained inthe future by dependence on low-value marine fish(trash fish) and fish meal which is used asaquaculture feed ingredients (Tidwell and Allan,2001). One of the most important issues in fisheriesall over the world is that of trash fish. Cai and Sun(2007) described that it is important to determine thecarrying capacity of an aquaculture area to effectivelymanage the mariculture environment. Similar studyof Cho et al. (1994) that the use of trash fish in marineaquaculture has always been associated withenvironmental degradation, over-exploitation of finitepelagic fish stocks and issues with pathogentransmission. Another type of feeds is the bread mealand grated coconut which has the greatercontribution in the growth and survival of differentfishery products. Breadmeal supplies a significantportion of the nutrients required for growth. It has8% to 13% protein content (Ambasankar et al., 2009). 

There has been a huge interest in the aquacultureof this species due to its high demand and price,high flesh content and rapid growth rates incaptivity. In addition, Marketman (2005)emphasize that mud crab usually has hightolerance to nitrate and ammonia which isbeneficial because ammonia-N is often the mostlimiting factor on closed aquaculture systems. Withthe aforementioned characteristics and importanceof mud crabs and the fact that Filipinos nowadaysreally have to find ways in order to support theneeds of the increasing number of populationsthrough aquaculture, the researchers chose tostudy mud crab and find out its growth by usingtrash fish, bread meal and grated coconut as theirsource of food.

Generally, this study aimed to determine the growthand survival rate of mudcrab fed with supplementalfeeds cultured in brackish water pond. Specifically,the study aimed to answer the following questions:What is the survival percentage and growth rate of themud crab fed with trash fish, grated coconut, andbread meal as supplemental feeds?; What is theenvironmental condition of the experimental set-up?Is there any significant difference of the growth ofmud crab fed with trash fish, grated coconut, andbread meal as supplemental feeds?; and What feedingmanagement program can be proposed.