Early growth and mortality of the Caribbean king crab Mithrax spinosissimus reared in the laboratory

The berried females of the Caribbean king crab Mithrax spinosissimus (Lamarck) used in this study were collected from canals on Big Pine Key, Sugarloaf Key and Lower Matecumbe Key (south Florida, USA) on 9 August, 8 October and 15 November 1986. Viable spawns hatched as first zoeae and molted to second zoeae within ca. 10 to 12 h. Most of the larvae reached the megalopa stage 1 d later, and molted to first crab 4 to 8 d after hatching (water temperature: 27.2° to 28.8°C). Low water temperature and/or early lack of food had a negative effect not only on stage duration, but also on the size of the early crab stages. Successful molt to first crabs occurred, however, in the absence of food. The growth rate (carapace length) between molts in early crab stages varied between ca. 20 and 30%. When provided with good water exchange, stocking density could be very high (>22 500 individuals m^-2), with no increase in mortality. The highest mortality rate was recorded when the larvae molted to first crab, and the highest rates of survival were always recorded when feeding was not initiated until after 5 to 8 d after hatching. No cannibalism was observed among larvae, and cannibalism was low in early crab stages. The study indicates that to achieve viable hatches and high larval survival in rearing M. spinosissimus, a continuous and adequate supply of high-quality seawater is a prerequisite both in larviculture and in maintaining brooding females.Contribution No. 93, Department of Oceanography and Ocean Engineering, Florida Institute of Technology