6.3 METHODS FOR GROWING SMALL SPAT
6.3.1 Introduction
Constraints to growing spat to a large size under closely controlled conditions in a hatchery have been dealt with in general terms in 6.1. Space, the supply of treated, heated water and the large volumes of cultured algae required are major cost considerations.
Hatchery managers will know the production cost factors that need to be taken into account when fixing the price of seed. Prices will increase exponentially as size in terms of mean shell length increases and a point will be reached when growers are no longer prepared to pay for spat in the larger size categories. In developed countries with mature industries this point is generally reached when spat are 3 to 4 mm and very often when they are somewhat smaller.
Methods commonly used to handle and grow newly set scallop and clam spat were introduced in 5.4.3.2. Procedures for oysters are different but before describing what these differences are it is relevant to begin with the various tank system options for this part of the hatchery process, beginning with those used for spat set on cultch.