FRESH-WATER CRAYFISH

New Zealand Herald, Volume LXXII, Issue 22197, 26 August 1935, Page 8

FRESH-WATER CRAYFISH

SPAWNING HABITS WELLINGTON DISCOVERY jfhe discovery of the spawning ground ef thousands of fresh-water crayfish by Mrs. W. W. Samson above the bank of a stream on her property at Silverstream in tho Hutt Valley was the most interesting thing ho had heard about fishes since the discovery of the peculiar circumstances under which whitebait are propagated, said tho chief inspector of fisheries, Mr. A. E. Hefford, when asked in Wellington to comment upon Mrs. Samson's observations. "1 believe the normal habit of all Crustacea is for the female to carry eggs under the tail or abdomen and that th© etias incubate while they are carried about,''" said Mr. Hefford. "Tho young are usually liberated into the water to swim and drift about. "It seems obvious that the freshwater crayfish have evolved a special t.cheme by which they secure the greatest measure of safety for their young. There must be some hazards of life in New Zealand streams to which young are subjected, which explains the habit of the. maternal crayfish burrowing into the banks of the higher streams. 1 have ba'jn curious to know of the breeding habits of the fresh-water cnyfish because they form food for trout and in many waters the trout have cleaned them up pretty well. , , , "The discovery shows that tho freshwater crayfish has a similar habit to that of the inariga—the parent of the whitebait. It was not until 1920 that the spawning of whitebait was established.. The inanga has the curious habit of migrating iri shoals to tho_ tidal waters near tho mouths of rivers in the autumn in readiness for the high tides of April or May and depositing eggs high and dry among rushes, grass and clover on the margins of tho rivers as far as the spring tides extend. This pro- , vision by which tho parent fish deposit their spawn at places which are only covered with water at the highest tides practically ensured immunity from enemies under tho original natural conditions which obtained previous to the colonisation of New Zealand."