Effect of mesh coverings on retention and growth of blacklip pearl oyster (Pinctada margaritifera) spat during early nursery culture

Abstract

-Hatchery produced pearl oyster spat are generally transferred to the ocean on spat collectors which may, or may not, be covered with fine mesh to prevent spat loss. This study examined the effectiveness of mesh bag covers on culture units for spat of the blacklip pearl oyster, Pinctada margaritifera. It assessed spat retention and growth in culture units without mesh bags (REMOVE) and in those where mesh bags were replaced weekly (REPLACE), washed weekly (WASH) or left unwashed (NO WASH) for the duration of the six-week experiment. Culture units in the REPLACE treatment had the greatest number of spat at the end of the experiment and 41% more spat than in the REMOVE treatment. Grading of the spat from each treatment at the end of the experiment showed that the REPLACE treatment had the highest number of spat in large and medium size classes with mean (± SE) dorso-ventral height of 23.9 ± 0.5 mm and 17.4 ± 0.5 mm, respectively. Mean wet weight of the mesh bags at the end of the experiment differed between treatments with bags from the WASH and NO WASH treatments having significantly greater mean wet weights than those from the REPLACE treatment. The results show that the presence of a mesh bag around spat culture units may improve retention of spat by between 18-41%. However, protective mesh bags may foul quickly and, to maximise retention and spat growth, weekly replacement of mesh bags should be undertaken.

Effect of Color and Mesh Size on Growth Performance and Net Fouling of Suspended Hatchery Trays for Crassostrea belcheri (Sowerby 1871) Oysters

“…A number of studies report on aspects of the nursery culture of oysters in suspended plastic trays (Holliday et al, 1991;Widman et al, 1991;Taylor et al, 1998;Beer and Southgate, 2008). The aims of this study were to determine the effects of aperture and color of plastic mesh on growth performance and net fouling rates during the nursery culture of hatchery-reared C. belcheri spat in suspended plastic mesh trays in southern Thailand.…”