ADVANCES IN THE SPAWNING OF THE Parvocalanus crassirostris COPEPOD REARED AT HIGH DENSITIES

The copepods are considered as potential prey for the marine fish larvae, in favourable terms of nutritional quality and visual stimuli for the larvae. However, their use as livefeed has been limited for difficulties to attain a high density in culture. In herbivorous copepods the low density is related to the low fecundity as the rearing ages, but it is not yet known why this occurs.

This study was carried out in the Live Feed Laboratory at the University of Cordoba (Colombia), to evaluate fecundity and egg production against high rearing densities of the copepod Parvocalanus crassirostris. Six different ranges of rearing densities were evaluated from 6-15 up to 65-90 adults mL^-1. The spawn was realized in 3 L Erlenmeyer in a 500 mL volume without aeration. The Erlenmeyers (experimental units) were covered with aluminium foil, and the air between the water surface and the lid was replaced with pure oxygen. The fecundity began to decrease significantly at densities greater than 25 adults mL^-1; and the relative egg production (eggs mL^-1 day^-1) was higher in densities with a range from 26-35 to 36-55 adults mL^-1. In conclusion, P. crassirostris can spawn at high density without aeration (turbulence), with pure oxygen and low vessel depths.