NURSERIES FOR FISH.

Auckland Star, Volume LXVI, Issue 236, 5 October 1935, Page 8 (Supplement)

NURSERIES FOR FISH.

The study of the eggs of fish and also of the early stages of hatching ie carried on mainly by means of fine silk nets, known as “Hansen” nets; and at the later stages by means of the Peterson young-fish trawl. The spawning grounds of the plaice have been discovered, and it hae been found that the young larval fish are borne on certain currents towards the shallow waters off the coasts from Holland northward to Denmark. This concentration of millions of young fish into restricted areas has an inevitable effect on the fish themselves. The food supply is limited and the severe competition for it means that the growth rate in these waters is slow. Accordingly experiments have been made in transplanting young plaice to the rich food grounds of the Dogger Bank, and these have had remarkable results. It has been found that, while plaice in the nursery grounds grow at a rate of about two inches a year, those transmitted to the Dogger will grow as much as five inches. When a plaice is to be transplanted, it is first captured and then marked with a small numbered disc in the form of a cuff link, which is inserted under the fin. A record of the number of the disc is kept, together witli the time and place at which the fish was released. Fishermen are rewarded if they return the captured fish to tho Laboratory at Lowestoft, where it is possible to trace from the records all the relevant details. Approximately 30 per cent of the marked fish are returned within a year.