Identification of factors affecting growth and survival of the tropical scallop Euvola (Pecten) ziczac in the Golfo de Cariaco, Venezuela

We examined the effect of environmental variables on the growth and surviva l of the tropical scallop, Euvola ziczac (L.), in suspended culture at Turp ialito in the Golfo de Cariaco, northeastern Venezuela. Four growth trials were run, three using 10-mm spat produced from hatchery spawnings in August 1992, which were grown at 8, 21 and 34 m in depth, and a fourth using 10-m m wild spat from spawning in April 1993, which were grown at 21 m in depth. Monthly measurements of somatic and reproductive growth were related to co ncurrent measures of numerous environmental factors, including fouling on t he shells and pearl nets. Growth and survival varied markedly among treatme nts and the major factor explaining the differences appeared to be the nega tive effects of fouling (especially the effects of organisms colonizing the shells) and variations in when gonadal development began. Somatic growth w as markedly greater in treatments where gonadal development was delayed. Fo r the August 1992 cohort at 8 and 21 m in depth, low phytoplankton abundanc e and high temperatures, possibly coincident with physiological stress from spawning, probably caused decreased growth and survival in the period duri ng and just after spawning. Phytoplankton abundance (number of cells and ch lorophyll a concentration) was a good predictor of growth for the August 19 92 cohort grown at 34 m and the April 1993 cohort at 21 m, the treatments i n which the scallops attained the largest size. The growth of juveniles (pr ior to development of gonads) seemed to be little affected by temporal chan ges in environmental conditions in the Golfo do Cariaco. Suspended culture or E. ziczac is likely to be economically feasible during periods of low fo uling, but not when fouling is intensive. (C) 2000 Elsevier Science B.V. Al l rights reserved.