Early induced maturation in cod (Gadus morhua) using low energy light : effect on muscle quality

Abstract

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 in May. 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.