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

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 300g and sexual maturity similar to 9.9months after settlement, and a commercial size of 500g after 12.4months. 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.

[1]  H. Daouda.  Using the DRASTIC method to study the vulnerability of groundwater in the aquifer of the Continental terminal of the town of Abomey-Calavi in Benin , 2015 .

[2]  P. Moksnes,et al.  Cannibalistic interactions of juvenile mud crabs Scylla serrata: the effect of shelter and crab size , 2013 .

[3]  O. Mirera.  Trends in exploitation, development and management of artisanal mud crab (Scylla serrata-Forsskal-1775) fishery and small-scale culture in Kenya: An overview , 2011 .

[4]  A. Lovatelli,et al.  Mud Crab Aquaculture: A Practical Manual , 2011 .

[5]  B. Paterson,et al.  Mud Crab Aquaculture , 2011 .

[6]  M. David.  Mud Crab (Scylla serrata) Culture: Understanding the Technology in a Silvofisheries Perspective , 2010 .

[7]  D. Mirera,et al.  A preliminary study on the response of mangrove mud crab (Scylla serrata) to different feed types under drive-in cage culture system , 2009 .

[8]  N. Ehrhardt.  Estimating growth of the Florida spiny lobster, Panulirus argus, from molt frequency and size increment data derived from tag and recapture experiments , 2008 .

[9]  E. Quinitio,et al.  Extension of nursery culture of Scylla serrata (Forsskål) juveniles in net cages and ponds , 2007 .

[10]  M. Walton,et al.  Comparative performance of hatchery-reared and wild Scylla paramamosain (Estampador, 1949) in pond culture , 2007 .

[11]  M. Walton,et al.  Population ecology of the mud crab Scylla paramamosain (Estampador) in an estuarine mangrove system; a mark-recapture study , 2007 .

[12]  P. Southgate,et al.  The effects of supplemental dietary cholesterol on growth, development and survival of mud crab, Scylla serrata, megalopa fed semi-purified diets , 2006 .

[13]  S. Christensen,et al.  Pond production of the mud crabs Scylla paramamosain (Estampador) and S. olivacea (Herbst) in the Mekong Delta, Vietnam, using two different supplementary diets , 2004 .

[14]  G. Williams,et al.  The combined effects of temperature and salinity on growth and survival of juvenile mud crabs (Scylla serrata Forskål) , 2004 .

[15]  E. Rodriguez,et al.  Pen culture of mud crab Scylla serrata in tidal flats reforested with mangrove trees , 2002 .

[16]  S. Sheen.  Dietary cholesterol requirement of juvenile mud crab Scylla serrata , 2000 .

[17]  S. Sheen,et al.  The effects of dietary lipid levels on the growth response of juvenile mud crab Scylla serrata , 1999 .

[18]  O. Millamena,et al.  Commercial evaluation of monosex pond culture of the mud crab Scylla species at three stocking densities in the Philippines. , 1999 .

[19]  Kevin D. Hopkins,et al.  Reporting Fish Growth: A Review of the Basics , 1992 .

[20]  R. Agbayani,et al.  Economic feasibility analysis of the monoculture of mudcrab (Scylla serrata) Forsskal , 1990 .

[21]  C. Ryer,et al.  Use of microwire tags for tagging juvenile blue crabs(callinectes sapidus Rathbun) , 1986 .

[22]  M. Heasman.  Aspects of the general biology and fishery of the mud crab Scylla serrata (forskal) in Moreton Bay, Queensland , 1980 .

[23]  B. Hill.  Abundance, breeding and growth of the crab Scylla serrata in two South African estuaries , 1975 .

[24]  D. Mirera.  Capture-based mud crab (Scylla serrata) aquaculture and artisanal fishery in East Africa- Practical and ecological perspectives : Mud crab ecology and aquaculture , 2013 .

[25]  D. Nyqvist.  Impact of crab-seed collection for aquaculture on juvenile mud-crab ( Scylla serrata ) populations at Mafia Island , Tanzania , 2011 .

[26]  S. Cannicci,et al.  Stock structure and demographic history of the Indo-West Pacific mud crab Scylla serrata , 2010 .

[27]  G. Begg,et al.  Tropical fish otoliths : information for assessment, management and ecology , 2009 .

[28]  D. Fielder.  Mud crab aquaculture in Australia and Southeast Asia - Proceedings of the ACIAR Crab Aquaculture Scoping Study and Workshop 28–29 April 2003, Joondooburri Conference Centre, Bribie Island , 2004 .

[29]  T. Brey.  Growth Performance and Mortality in Aquatic Macrobenthic Invertebrates , 1999 .

[30]  W. Say,et al.  Pen culture of mud crabs, genus Scylla in the mangrove ecosystems of Sarawak, east Malaysia , 1999 .

[31]  C. Keenan.  Aquaculture of the mud crab, genus Scylla: past, present and future , 1999 .

[32]  Austin B. Williams,et al.  Synopsis of biological data on the blue crab, callinectes sapidus Rathbun , 1984 .

[33]  W. Macnae.  A General Account of the Fauna and Flora of Mangrove Swamps and Forests in the Indo-West-Pacific Region , 1969 .