Successful fish culture requires an understanding of constraints imposed by a particular species' ecology to create protocols that maximize survival and development through embryonic and larval stages. The effects of light intensity, spectral composition, and photoperiod on development and hatching of haddock (Melanogrammus aeglefinus) embryos were assessed in a 2 x 3 x 3 factorial design. Aliquots of fertilized eggs were exposed to combinations of high (1.7-1.9 mumol s(-1), m(-2)) or low (0.3-0.4 mumol s(-1) m(-2)) intensity blue (470 nm), green (530 nm) or white (full-spectrum) light, under different photoperiods (24:0, 18:6, or 12:12 h light/dark), in addition to continuous darkness (0:24 h light/dark, 0 mumol s(-1) m(-2)) and continuous very high intensity white light (24:0 h light/dark, 18 mumol s(-1) m(-2)). There were no observable light effects on timing and survival to different development stages. Total hatch [87.53 (+/- 0.68)%, mean ( SE)], viable hatch [91.12 (+/- 1.21)%], and total mortality [20.23 (+/- 1.25)%] were not significantly different between light treatments. Embryos incubated under continuous light hatched earlier [11.60 (+/- 0.04) days] and produced larvae smaller in body area [1.22 (+/- 0.01) mm(2)] than those experiencing a diel cycle. Embryos in continuous darkness incubated significantly longer [12.20 (+/- 0.10) days] and were small [1.25 (+/- 0.05) mm(2)]. Embryos under continuous very high intensity white light hatched significantly earlier [11.53 (+/- 0.05) days], but were large [1.46 (+/- 0.03) mm(2)] at hatch. Yolk-sac area was significantly reduced under continuous very high intensity white light [0.30 (+/- 0,02) mm(2)]. These results may be explained with reference to ecological aspects of haddock early life history and the role of photosensitive organs, e.g., retina and pineal organ, during development. In general, assuming that larger size-at-age confers a competitive feeding advantage on cultured larvae, our results indicate that haddock embryos benefit from a diel cycle of light/dark exposure during incubation. This information serves as an advancement of culture techniques for haddock, a desirable aquaculture species in Atlantic waters. (C) 2002 Elsevier Science B.V. All rights reserved.
