Effects of light intensity,
spectral composition and photoperiod on development and hatching of haddock
(Melanogrammus aeglefinus) embryos
G.
Downing, M.K. Litvak-2002
Aquaculture,
213(1-4): 265-278
Abstract:
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 2×3×3 factorial design. Aliquots of fertilized
eggs were exposed to combinations of high (1.7–1.9 µmol s-1 m-2)
or low (0.3–0.4 µmol 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 µmol s-1 m-2) and
continuous very high intensity white light (24:0 h light/dark, 18 µmol 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) mm2] 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) mm2].
Embryos under continuous very high intensity white light hatched
significantly earlier [11.53 (±0.05) days], but were large [1.46 (±0.03)
mm2] at hatch. Yolk-sac area was significantly reduced under
continuous very high intensity white light [0.30 (±0.02) mm2].
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.