Pen Culture of the Mud Crab Scylla serrata in Mtwapa Mangrove System, Kenya

Abstract

A pen culture system of the mud crab, Scylla serrata was introduced in Mtwapa mangrove creek with the aim of finding an alternative source of income and food for the local communities, who practice artisanal fishery in the creek. Other objectives were to motivate the interaction between scientists and the community through technology transfer, and to collect scientific data necessary for maintenance and management of the culture system. Pen construction took place from October 2000 – January 2001. The pen was located in the intertidal area and measured 800 m2. It was constructed and fenced using uzio (fish trap) material made of mangrove poles and wood. Stocking of the pen with seed crabs occurred from February–May 2001. Local sources was used to obtain a total of 1697 crab seeds which were measured (carapace length and width), weighed and sexed before stocking. The crabs were fed with trash fish obtained from a local fish processing plant. Feeding was conducted once daily, preferably at high tide. Salinity of the pond ranged from 12.8 to 35 ‰; temperature between 25 and 36 ºC, pH from 7.95–8.25 and dissolved oxygen (DO) from 2.65–4.00 mg/l. Harvesting of the crabs started after 4 months from date of stocking. Additional activities that occurred in the pen were planting of suitable mangrove seeds (Rhizophora mucronata and Avicennia marina) in the bare areas of the pen. These provided canopies for the crab as well as reforesting the area.