Stepwise function of natural growth forScylla serratain East Africa: a valuable tool for assessing growth of mud crabs in aquaculture

Abstract

Predicting growth is critical in aquaculture, but models of growth are largely missing for mud crab species. Here, we present the first model of natural growth in juvenile and adult mud crabs Scylla serrata from East Africa using a stepwise growth function based on data on intermoult periods and growth at moult from field mark-recapture, pond and laboratory studies. The results showed a sigmoid growth pattern in carapace width and suggest that S. serrata in East Africa will reach 300 g and sexual maturity~9.9 months after settlement, and a commercial size of 500 g after 12.4 months. Analyses of the literature identified several issues with the common praxis to compare standard growth measures between aquaculture studies with different initial size or growing periods. Using the new growth function to estimate the proportional difference between modelled and obtained growth as an alternative method, we show that growth rates of S. serrata cultured in cage systems, which are dominant in East Africa, was <40% of the estimated natural growth and growth obtained in pond systems. The analysis also indicated that growth rates of S. serrata in Southeast Asia was over 50% higher compared with similar culture systems in East Africa, and that different species of mud crabs had large differences in growth rates.This study shows that growth in the present mud crab aquaculture systems in East Africa is below their expected potential. Further work is needed to identify the factors behind this observation.

Growth, survival and intactness of green mud crab (Scylla Paramamosain) broodstock under different captive grow out protocols

“…While, a distinct difference in growth between sexes was noticed for S. Oceania and for S. serrata (Marichamy and Rajapachiam, 2001). However, daily weight gain of 1-4 g was reported for mud crab that varies with species and sex, with males having a faster growth than females (Christensen et al, 2004); size of experimental animal (Ehrhardt, 2008); and location of experiment (Moksnes et al, 2014). Thus growth and SGR values obtained in this experiment for S. paramamosain are supported by the above mentioned authors.…”

“…In crustaceans, moulting in juvenile stages is frequent and the moulting duration increases as the size grows bigger (Ehrhardt, 2008;Shelley and Lovatelli, 2011) and in many crustaceans, growth attainment rate per moult reduces with age, especially after pubertal moulting or maturity, resulted complex growth patterns (Ehrhardt, 2008). Meanwhile, a sigmoid growth pattern was modeled for S. serrata from mark-recapture methods, pond cultures and laboratory experiment (Moksnes et al,2014). The growth pattern observed from this experiment on S. paramamosain is thus supported by the theme of the above mentioned authors.…”

“…On the contrary, a higher growth of mud crab under drive-in cages set into mangrove than the pen culture was reported (David, 2009). Meanwhile, a 40% less growth of S. serrata in cage system than pond culture or natural growth was stated (Moksnes et al, 2014).…”

“…Concepts *Corresponding author email: latiful.bfri@gmail.com on growth and surivalare considered as useful tools in aquaculture for projecting culture cycle and deciding the optimum harvesting time and size; thus ultimately minimizes the production cost and maximizes the farm output in terms of yield and revenues (Agbayani, 2001;Moksnes et al, 2014). On the other hand, growth, age and size are considered as necessary basic elements in determining the level of maturity for breeding purposes.…”

Growth analysis, mortality and exploitation level of Mud Crab Scylla serrata, Forskål 1775, (Malacostraca : Portunidae) in Mangkang Wetan waters, Semarang, Central Java, Indonesia

“…Mud crabs (S. serrata) are widely distributed throughout the Indo-West-Pacific region (IWP) and are often associated with mangrove forests (Butcher et al, 2012;Hubatsch et al, 2015;Viswanathan et al, 2016). S. serrata has a high economic value in both domestic and international markets (Moksnes et al, 2014;Hubatsch et al, 2015). S. serrata can live out of the water area up to five days so, that, these crabs are suitable for long distant delivery (Atagholipour et al, 2013).…”