Petersenet al.(2005c) developed settlement tile units ofa relatively small size. Depending on the scale, several hundred to thousands of these tiles can be placed togetherusing egg crate to create large surfaces for settlement. Aftersettlement, the coral–tile units can be placed further apartas the juveniles develop and need more space. Once thespecies-specific settlement conditions have been investigated on a small experimental scale, large quantities of tilesand larvae can be applied. Water quality is an essential factor during the whole process of sexual reproduction.Besides water quality, water movement and light conditionsmay play an additional role during the settlement process.We typically use moderate water movement through simpleairlifters, which increases the chances for larvae–substratecontact, thus enhancing settlement and preventing damageof larvae. To reduce the initial competitive pressure, settlement commonly occurs on more sheltered, less lightexposed substrate from which the settler grows towardsmore light-exposed areas when it increases in size (Harrison & Wallace 1990). We usually use low-to-moderate lightlevels for any settlement set-up (<150lEm2s1). However, the role of water movement and light has been poorlystudied in relation to settlement under aquaculture conditions and needs further investigation to possibly enhancesettlement rates.
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