Effects of wave action on the growth and survival of the scallops Euvola ziczac and Lyropecten nodosus in suspended culture

We examined the impact of wave induced movement on two species of scallops in suspended culture in the Golfo of Cariaco, Venezuela, by comparing growt h of juveniles in cages suspended at 6.5 m in depth using two methods. In o ne case movement from wave action was transmitted to the cages from support ing buoys at the surface, and in the other the supporting buoys were in dee per water, just above the cages, so that the cages were only slightly affec ted by wave action. For the scallop Euvola ziczac, which is normally found on sandy bottoms, the suspension methods markedly affected growth. After a 31-day growout period, all measured body parameters were markedly smaller f or the scallops strongly affected by wave action than for those less expose d to wave action. The differences were 27.0% for muscle mass, 28.7% for dig estive gland mass, 24.6% for the mass of remaining somatic tissues, 29.4% f or gonadal mass, 13.1% for shell mass and 8.4% for shell height. Survival w as 72-75% for the scallops more strongly affected by wave action compared t o 94-100% for those less affected by wave action. In contrast, parallel obs ervations on Lyropecten nodosus, which is normally found on rock and coral bottoms, showed no evidence of an effect of wave action on either growth or survival. L. nodosus was probably less affected by wave action than E. zic zac because its movement in the cages was likely reduced by its byssal atta chment and by its rugose and more flattened valves. For species such as E. ziczac, wave induced movement of culture enclosures should be minimized eit her by choosing protected sites or by using techniques that reduce the impa ct of waves. (C) 1999 Elsevier Science B.V. All rights reserved.