EFFECT OF VARYING levels of macro nutrients and
continuous light on growth, energy deposits and maturation in farmed cod
(Gadus morhua L.).
O.
Karlsen, G.I. Hemre, A. Mangor-Jensen, K. Tveit, G. Rosenlund
The
Atlantic cod is a lean species storing surplus energy in the liver, the
liver contributes 10-12% of total weight, more than twice the size of wild
cod. Also, farmed cod usually matures less then two years old; with a mean
weight around 1.5 kg, which is smaller than desired market size.
The
effect of varying levels of macro-nutrients and light conditions on growth,
energy allocation and age of maturation were evaluated in juvenile farmed
cod (Gadus morhua L.) kept in net pens from August until June. Seven
different diets varying in protein (36-66%), lipid (8-26%) and starch
(4-20%) were evaluated in a mixture design. Each dietary regime was
evaluated under continuous light and in natural light conditions.
Dietary
treatment affected energy allocation, growth, and feed utilization. Also,
irrespective of dietary treatment, all cod under natural light regime
matured during spring, while no cod were mature under the continuous light
regimes until the end of the experiment. Until January the growth was not
influenced by light regime, while maturation with all consequences reduced
growth, and as a consequence those kept under continuous light were 700 g
larger in June. Dietary treatment did not influence age of puberty, but
influenced growth and energy allocation.
(Institute
of Marine Research, Austevoll, Norway)