Transplantation of plaice (Pleuronectes platessa) (Abstract)
Hoffmann, E. (1989). Transplantation of plaice (Pleuronectes platessa) (Abstract), in: De Pauw, N. et al. (Ed.) Aquaculture: a biotechnology in progress: volume 1. pp. 453 In: De Pauw, N. et al. (1989). Aquaculture: a biotechnology in progress: volume 1. European Aquaculture Society: Bredene. ISBN 90-71625-03-6. 1-592 pp., more |
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| Abstract | Transplantation of young plaice from an estuary to semiclosed fjords has been carried out. The aim is to encourage the production in these fjords which are only occasionally invaded by 0g plaice. The project was initiated by the Danish fishermen's organization. In the period 1892-1957 a total of 80 million plaice was transplanted in the area. The results from that period showed that the economic yield of the transplantations was about the same size whether the plaice were transplanted or not. Nevertheless the fishermen wanted to try again and in the years 1985 and 1986 a total of 4 000 young plaice was transplanted. All fish were caught with a commercial eel-trawl and placed in a container with running water aboard the ship. The fish were then sailed for about 4h to the inner fjords where they were tagged and released. The tags were Floy tags type FD-67. All experiments were carried out at temperatures below 8°C in order to avoid tagging mortality. The mean length of the tagged fish was 18.5cm. This length was the same as that used in the earlier experiments. Until now,(March '87) a total of 12.5% has been recaptured. The mean length of the period before recapture was 213 days. Only 2% of the recaptures are from areas outside the inner fjords. The mean growth of the tagged fish was approximately 7cm.yr-1. The conclusions of these experiments are that plaice is able to live and grow in the inner fjords and that only a few emigrate to the North Sea. The recapture is relatively small compared to earlier experiments where a recapture of 30% was normal. This can be due to a lower fishing intensity in the inner fjords today compared to that in earlier periods. Economic evaluation of such transplantations are difficult but one thing can be demonstrated; if transplantations have to be carried out the mean length of the transplanted fish has to be smaller (from 5 to 12cm, i.e. 0- and I group). Moreover, it will be necessary to establish some sort of traps from which the fishes can easily be fished and transported to the inner fjords. Problems with the local fishermen in the areas where the young fish are caught have to be solved before such programs can be realized. |
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