During earlier trials involving wild cod in captivity, scientists at Nofima have experienced problems getting the cod to eat pellet feed. Nofima, in collaboration with the Institute of Marine Research and SINTEF Fisheries and Aquaculture, has now demonstrated that 40 % of wild cod start eating after four weeks in captivity. Efficient sorting makes these cod attractive for on-growing.
This project is part of a major initiative by the Norwegian Seafood Research Fund (FHF) in capture-based aquaculture. The overall goal of this project was to contribute to increased profitability for capture-based aquaculture, feed enhancement and processing of wild-caught cod.
The cod was divided into two groups, of which one was fed capelin and the other pellet feed. After an introductory three-week period without feed, weaning began. In the group that was fed pellets, interest was relatively stable from the first week of feeding, while in the group that was fed capelin the proportion that consumed capelin continued to increase over the following three weeks. Significantly more fish accepted the capelin feed than the pellet feed, consumption was higher and there were better growth rates than in the group offered formulated feed (pellets). However, the cod that received pellets showed considerable interest in feeding, with several feed attempts but this food was often rejected and spat out again.
The cod involved in this trial were generally in good condition and the mortality rate from receiving the cod to completion of the trial was just 1.7 %. Even in the group offered natural prey (capelin), around 20 % of the cod would not eat, whereas up to 60 % of the fish would not eat pellets. However, there is such a large difference in feed costs between capelin and pellets that feed enhancement of wild cod is more economically viable if it is possible to distinguish which fish are willing to eat pellets and continue the feed enhancement of these fish.
“In the end we were left with 40 % that wanted pellets, and these had a growth rate in line with the anticipated growth for farmed cod. The remaining 60 % will be produced as high quality fresh cod,” says Senior Scientist and Project Manager Bjørn-Steinar Sæther at Nofima.
It is now important to develop techniques and methods to sort the fish that are willing to eat pellets from those that are not in an efficient and sustainable manner. Such techniques would make it easier for the industry to concentrate on feed enhancement of cod that are willing to consume pellets and achieve good growth rates. It appears that cod are attracted by the smell and/or taste of the pellets, but possibly the pellet’s structure is the reason some cod reject it as food.
“Since the proportion that start eating the pellets does not change much after the first week of feeding, but the proportion of fish that eat capelin increases significantly over time, it appears that only the most motivated fish are willing to accept pellets,” says Sæther.
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