Incubation of sablefish ( Anoplopama fimbria) in a system designed for culture of fragile marine teleost eggs

Abstract

An incubation system is presented that appears to overcome a number of problems associated with the culture of fragile marine teleost eggs. The system was developed during the experimental incubation of sablefish eggs, which are pelagic, incubate in deep water, have a small perivitelline space and a low bursting pressure, and are easily injured in culture. The system consists of a number of 11-l incubation modules (8-1 useful volume). We have used them at a density of 2600 egg/l of useful volume, but optimum density — not yet known — will depend on the total system volume, rate of water exchange in each module, and egg and larval metabolic rates. Each module is a cylinder mounted on a ball joint; the cylinder is offset from the vertical axis and is held in position by a sweep arm attached to an upper gearmotor. In operation the modules sweep through a cone-shaped area at 2 rpm. Each module drains to a common sump from which water is pumped through filters and a UV sterilizing unit to a headbox, thence back to each module by gravity flow (50–100 ml/min) through flowmeters. The total system was housed in a temperature-controlled room (5.5–6.0°C). Maximum rate of survival of fertilized eggs to hatching was 24%. Substantial effort is required to obtain mature gametes from wild sablefish spawners. Hence, while developing the system, a preliminary evaluation of some ancillary variables was undertaken with a view to ultimate optimization of the system. These include data on viability of stored gametes, fertilization technique, and timing of introduction of larvae to exogenous feeding. In addition, preliminary evidence suggests that the high fragility of sablefish eggs in culture may result primarily from their high sensitivity to mechanical shock associated with egg motion in the incubators prior to yolk plug closure.