Reports

Development of industrialized cod farming: Control of growth and sexual maturation with advanced lighting equipment / Improved lighting technology for regulating sexual maturation of farmed cod

Published:

01/11/2009

Authors:

Rannveig Björnsdóttir, Jónína Þ Jóhannsdóttir, Jón Árnason, Þorleifur Eiríksson, Cristian Gallo, Böðvar Þórisson, Þorleifur Ágústsson, Björn Þrándur Björnsson, Guðbjörg Stella Árnadóttir

Supported by:

AVS Fisheries Research Fund

Development of industrialized cod farming: Control of growth and sexual maturation with advanced lighting equipment / Improved lighting technology for regulating sexual maturation of farmed cod

The overall goal of the project was to improve farming techniques in cod farming with the use of a new type of light in the goal of controlling the sexual maturity of cod. These are lights that emit a single wavelength that is better distributed over the aqueous phase compared to halogen lights that are traditionally used, and this new type of light has proven to be very effective in preliminary research. It was also investigated whether light control immediately at the juvenile stage could possibly contribute to this effect in the heifer fire. Continuous treatment with the lights at the juvenile stage did not affect the juveniles' growth, but there were indications of fewer growth defects in the juveniles. However, light control at the juvenile stage seemed to have a negative effect on the growth of the fish after transport to sea cages, in addition to which there were many unexplained declines in that group. Light control of fish in cages had a positive effect on the growth of the fish compared to fish kept during the natural light cycle in sea cage farming. The project also developed and standardized new methods for measuring the concentration of growth hormones in cod, and the method proved to be both sensitive and safe. The relationship between growth rate and concentration of growth hormone in the blood of the fish could not be demonstrated in this study, but the method offers great future potential in studies of, for example, the growth rate of wild cod. The project also carried out a detailed study of the effects of seaweed farming on the diversity and species composition of benthic fauna under pens. Extensive changes in the species composition of benthic animals were observed despite a small load associated with fire in the pens over a three-year period.

The overall aim of the project was to improve cod farming technology by delaying sexual maturation of cod by the use of a new lighting technology. The novel lights emit only one wavelength that is more effectively dispersed in water compared to the metal halogen lights traditionally used. Continuous manipulation using the novel light technology during the juvenile stage did not affect fish growth or survival. Indications of reduced frequency of deformities were however observed in this group. Light manipulation during the juvenile stage was further found to negatively affect fish growth following transfer to sea cages and significantly higher unexplained loss of fish was observed in this group. Continuous light manipulation during on growing in sea cages resulted in significantly improved growth of the fish compared with fish exposed to ambient light. New methods were furthermore developed for measuring the concentration of growth hormones in cod. A relationship between fish growth and the concentration of growth hormones could not be established. The method however provides an important tool for future studies of the growth of eg wild cod. Detailed studies of species diversity in bottom layers below the sea cages were also carried out, revealing extensive changes in species composition during the three-year study.

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