Foraging, growth and
survival of Atlantic cod larvae reared in different light intensities and
photoperiods
Velmurugu Puvanendran, J.A. Brown-2002
Aquaculture, 214(1-4) : 131-151
Abstract:
Studies have shown that most marine fish larvae are
visual feeders and their feeding incidence increases with light intensity.
Although laboratory studies on photoperiod showed variable results, evidence
from the field suggest that larvae exposed to a continuous light may grow
better than larvae exposed to reduced photoperiods. We set up experiments to
investigate the foraging, growth and survival of Atlantic cod larvae (Gadus
morhua; Grand Banks origin) at different light intensities and
photoperiods. Behavioural observations were also carried out in an attempt
to explain any differences in the performance of cod larvae under varying
light intensities. Larval cod were reared at four light intensities (300,
600, 1200 and 2400 lx or 4.93, 10.96, 19.89 and 37.32 µE m-2,
respectively) and three photoperiods (24 L:0 D, 18 L:06 D and 12 L:12 D)
from hatching to metamorphosis (42 days post-hatch; dph). Cod larvae grew
and survived better in higher light intensity (2400 lx) and 24 L:0 D
photoperiod. Examination of the foraging indicated that cod larvae reared in
higher light intensity captured prey more efficiently than larvae reared in
low light. Results also showed that the mortality rates of larval cod from
2400 lx and 24 h photoperiod were significantly lower than the larvae from
other light intensity and photoperiod treatments until 28 dph. This
indicates that photoperiod and light levels could be reduced beyond 28 dph.
(Ocean Sciences Centre, Memorial University of
Newfoundland, St. John's, Newfoundland, Canada A1C 5S7, e-mail: puvy@mun.ca)