SHAGS

Forest and Bird, Issue 125, 1 August 1957, Page 6

SHAGS

By

R. NELSON

TN the annual publication of the Deer--1 stalkers’ Association “a certain shag” is said to be a noxious bird and it is argued by the writer (by inference) that because all species of shags are not declared noxious, neither should all species of deer. There are, of course, wide differences. In the first place the black shag is not officially classed as a noxious bird, but because it largely frequents rivers, which most shags do not, and is believed to take some trout, which it does, it is included in the fifth schedule of the Wild Life Act, and allowed to be shot. Next is the fact that the black shag is a native bird which was here long before we came, and it has its place in New Zealand’s balanced nature scheme. We brought in the trout, they are interlopers, not the shag, but the introduction of the sporting fish provided greater food supplies for the shag and therefore in the ordered .scheme of nature the possibility of higher populations of shags. Now to this extent there is probably a case for keeping the black shag population under control down to reasonable levels. There is, however, no justice whatever in exterminating a native bird in its own habitat by subsidised shooting and wholesale destruction of parents, chicks and eggs in the shagnurseries during the nesting season, as is done in New Zealand.

Moreover, the black shag is not entirely harmful—it does some good, possibly even more good than harm by removing the weakling fish, and by taking eels which destroy many trout fry. It is even possible that the shag makes no difference to the adult trout population, or if it does make a difference it would be a beneficial one by removing the surplus fish and thus permitting the survivors to develop into bigger, better fish. It is not generally recognised that any given area of water has its fish carryingcapacity which cannot be exceeded except by fertilisation. It does not matter how many fish fry are liberated, the survival figure will be rigidly limited by the carryingcapacity of the water concerned. The very first essential in carryingcapacity is that of food supply—then comes natural cover and protection from predators, but even with ample cover and protection from predators the survival figure will not be exceeded. On the other hand, if the number is reduced below survival figure the result will be bigger and better fish. It will be seen, therefore, that the interests of trout fishermen can be best served by joining us in an effort to prevent erosion by the retention of the natural vegetation on the hills and along the creeks, thus preserving food supplies and fish cover.

A further and growing need, of course, is to prevent water pollution by industrial wastes, sawdust, etc. Only after attending to these essential considerations can the shag be seen in its correct perspective.