Relations among environmental conditions and growth in the tropical scallop Euvola ( Pecten) ziczac (L.) in suspended culture in the Golfo de Cariaco, Venezuela

Abstract

Spat of zigzag scallops, Euvola ziczac, measuring 3 mm, were placed in suspended culture at Turpialito in the Golfo de Cariaco, Venezuela, in August 1989 and their growth followed until August 1990. Shell length increased rapidly to 40 mm during the first 4 months (August to November), corresponding to the period of highest temperatures (>24.5°C) and lowest abundance of phytoplankton, and thereafter increased slowly. In contrast, the growth of the muscle and other somatic tissues began in January and continued until August. In the latter period temperatures are generally lower (<24.5°C) and food more abundant. Gonadal growth also began in January. Sexual maturity is attained at ≈44 mm in shell length. Decreases in the gonadal mass in April–May and July–August probably reflected spawning. Scallop mortality was low from the beginning of this study until March 1990, in spite of manipulations of the scallops (changing of pearl nets) and fluctuations in environmental conditions; however, mortality occurred during April and again in July and August 1990. Large scallops may have a heightened sensitivity to high temperatures and low food availability, particularly when the gonads are large and mature.