Foraging behaviour of
Atlantic cod (Gadus morhua) larvae in relation to prey concentration
V. Puvanendran, L.L. Leader, J.A. Brown-2002
Canadian Journal of Zoology, 80(4): 689-699
(from Current Contents)
Abstract :
In spite of a tremendous amount of research on
Atlantic cod (Gadus morhua) larvae, no information is available on the
development of foraging behaviour over an extended period. We investigated
the ontogeny of foraging behaviour of Atlantic cod larvae exposed to
different prey concentrations from hatching to metamorphosis. The objective
of this work was to determine if their foraging behaviour is influenced by
prey concentration. Rotifers and (or) Artemia sp. were used as prey at
concentrations of 0, 500, 1000, 2000, and 4000/L. During behavioural
observations, which were carried out twice a week, foraging behaviour and
activity of cod larvae were quantified. Larvae were sampled once a week and
standard length and gut fullness were recorded. Larvae reared at
concentrations of 1000 and 2000 prey/L swam significantly more but foraged
(quantified by capture success) significantly less than the larvae reared at
4000 prey/L. Larvae reared at 4000 prey/L performed more orientations
towards prey than larvae reared at all lower prey concentrations and the
time spent per orientation increased from day 2 at all prey concentrations
but declined as the larvae grew. However, this decline occurred earlier in
larvae reared at 4000 prey/L than in larvae reared at other prey
concentrations, and larvae reared at 4000 prey/L spent the shortest time per
orientation at day 27 compared with day 34. Larvae reared at 4000 prey/L
showed significantly higher success in capturing prey than larvae reared at
all lower prey concentrations. After day 13 post hatch, larvae reared at
4000 prey/L were significantly greater in length than larvae reared at all
other prey concentrations. Larvae reared at 0, 500, and 1000 prey/L did not
survive beyond 11, 15, and 32 days, respectively, indicating that fewer than
2000 prey/L may not be adequate to keep cod larvae alive during intensive
rearing. Our results suggest that the foraging behaviour of Atlantic cod
larvae is influenced by prey concentration.
(Mem Univ Newfoundland, Ctr Ocean Sci, St Johns, NF
A1C 5S7, Canada, e-mail: puvy@mun.ca)