Diatom production in the marine environment:
implications for larval fish growth and condition
M. A. St. John, C. Clemmesen, T.
Lund, T. Köster-2001
ICES Journal of Marine Science, 58(5):
1106-1113
Abstract:
To test the effects of diatom production
on larval fish growth and condition, laboratory experiments were
performed with larval North Sea cod reared on different
algal food chains. These food chains were based on
cultures of (a) the diatoms Skeletonema costatum and
Thalassiosira weissflogii; (b) the dinoflagellate Heterocapsa
triquetra; (c) the flagellate Rhodomonas baltica;
(d) a diet composed of both Skeletonema and Heterocapsa
food chains (1:1), and (e) a starvation group. These
algae were fed to cultures of adult Acartia tonsa.
Copepod eggs were collected, hatched, and the N1 nauplii
(200 l-1) were fed to post-yolk-sac larval cod. Results
indicate that larval growth rates are significantly influenced
by the content of essential fatty acids of the algal
food source: growth rates were positively correlated
with the content of DHA (C22:6 ω3) and negatively
with EPA (C20:5 ω3). The ratio of ω3/ ω6 fatty
acids in the algal source had no significant effect. The
highest and lowest growth rates were observed in food chains
based on H. triquetra and T. weissflogii, respectively
(means for days 14-16 of 4.0 and -4.7). The mixed
diatom/dinoflagellate diet resulted in intermediate
growth rates and condition. Regressions of growth
rates against EPA and DHA content indicated no inhibitory
effect of diatom production on growth in larval cod.
(Danish Institute for Fisheries Research, Department
of Marine and Coastal Ecology, Kavalergarden 6, DK-2920, Denmark,
e-mail : msj@dfu.min.dk)