Downing, G., Litvak, M.K.
Abstract:
Recent attention has focused on sustainability and diversification of the Atlantic Canadian aquaculture industry through the development of methods for the commercialization of non-salmonid fish species. Diminishing fishing quotas and high market values have attracted interest towards haddock (Melanogrammus aeglefinus). Haddock larvae primarily rely on vision to capture food. In nature the larvae are adapted to a light regime that is influenced by the attenuative and absorptive properties of their aquatic environment. These environmental conditions should be considered when transferring the larvae to the aquaculture hatchery mesocosm. Light conditions that maximize the contrast between prey and the environment facilitate the detection and capture of food by larvae, particularly during the critical switch from endogenous to exogenous feeding. Enhanced feeding should result in improved growth rates and reduced mortality. The objective of this study was to determine the impact of light, in particular light intensity on the growth and survival of larval haddock.
Haddock were stocked at a density of 20 larvae/L in 10 white plastic tanks of 100 litres each. Larvae were exposed to a treatment of white incandescent light at either high (100 lux) or low (5 lux) illuminance (5 tanks per treatment). Water temperature was maintained at 8 +/-
1 C; flow rates ranged from 200 - 300 ml/min. Larvae were fed algae (T-ISO), rotifers, and Artemia. The experiment ran for 33 days.
There were no significant differences in mean standard length between the two treatments. However, the largest mean body area (2.07 mm2) and highest survival rate (2.5 %) were obtained under the high light intensity (ANOVA, P < 0.05).
The results of this experiment confirm the importance of light in the aquaculture mesocosm. Determination of the best photic environment in which to raise haddock larvae is an important step towards the eventual commercialization of this species.
(Department of Biology, University of New Brunswick - Saint John (UNB-SJ), PO Box 5050, Saint John, New Brunswick, Canada E2L 4L5)
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