|In this project, light emitting diodes (LED) where added to sea pens containing farmed cod in order
to investigate whether additional light influenced the timing of fish maturation, and/or the chemical,
biological, cellular and textural properties of the fish musculature. This project, which took place in
northern Norway, commenced November 1, 2005 and ended at the end of June 2006. After
analysis, the results showed that additional LED lights effected the timing of maturation in both
male and female cod. The cod subjected to additional lighting (L-group), matured approximately a
month earlier than the fish in the control (ambient) sea pen (C-group).
Light manipulation resulted in a peak in GSI values in the L-group female fish (35±11) in April,
one month earlier than the peak in the C-group females in May (45±12). The alteration in spawning
time for fish in the L-group fish resulted in lower protein values and a harder texture earlier in the
season in this fish, in comparison to fish in the C-group. The earlier spawning in the L-group led to
an earlier increase towards pre-spawning quality, in comparison to fish in the C-group. This is
shown by higher protein values in the female L-group (15.4±1.5) compared to 14,0±1.3 in the Cgroup
Undergoing maturation is a very energy consuming process, and cod stops growing for several
months during this period. In addition the fish degrade existing muscle mass and liver tissue.
There were marked differences between the sexes in relation to the spawning cycle in both the Land
C- groups. In both groups the female cod lost significantly more muscle protein than the male
fish, and had a harder texture (shear resistance). However, although the female fish lost more
protein than male fish, the results suggest that the female fish in the L-group had less muscle
protein loss than female cod in the C-group, thereby possible indicating that lights used to speed up
maturation can reduce energy loss in females during spawning.