Unidentified Fish in Wanganui River

Manawatu Times, Volume LIV, Issue 7099, 23 December 1929, Page 2

Unidentified Fish in Wanganui River

POSSIBLY HYBRID.

CHARACTERISTICS OF BOTH TROUT AND SALMON.

Since steps were taken to stock the Wanganui River with Atlantic salmon, efforts have been made by the Wanganui Acclimatising Society to ascertain whether endeavours to introduce this fish had been successful. So far no catches have been recorded. Several strange fish have been landed at various times, however, and one specimen was recently forwarded to Mr. A. E. Hefford, inspector of fisheries, for identification.

In his report on the fish Mr. Hefford sa y S; —"The characteristics of the fish taken together are typical neither of the Atlantic salmon nor of the trout species. It partakes of the character of both, but it more resembles a trout than a salmon. Its scales are smaller than those of the salmon.” Mr. Hefford describes in detail the characteristics of the specimen in respect to scales, gill, rakers and fins. He stated that there are 19 gill rakers on both left and right arches, this characteristic bringing the fish within the definition of a salmon. On the other hand, an examination of the fins supports the trout classification. • In summing up Mr. Hefford says: “This specimen inclines to trout in most of the points which are usually but not invariably diagnostic characters, but its gill rakers are those of the salmon. The quostion is: “Where can we place it ? I confess that I am unable to place it definitely either under one or the other species. It might be a hybrid. The question then arises as to how such hybridism could occur. Does it mean that adult salmon have run into the Wanganui, though unpereeived by human observers, and mated with trout of opposite sex? It has-been known to happen, not infrequently, that a precociously milting salmon parr may fertilise ova shed by fa female salmon. It seems to me quite possible that this may have happened in the case of some of the salmon planted in the Wanganui Biver. “This, at least, seems to be the only satisfactory way at present of accounting for the character of this particular fish, though one must also recognise that none of these characters is absolutely invariable. It has been found that-the scale count is not constant for either species; also that the gill rakers vary from 16 to 18 in the trout and from 18 to 22 in the salmon. It may easily prove on further investigation of larger numbers of specimens that there are occasional trout with more than IS gill rakers. I have myself found an undoubted Te Anau salmon with only 17 on one side and 20 on the other. It all points to the head to further systematic observation and study of these questions.”