THE NATURALIST

Otago Witness, Issue 3765, 11 May 1926, Page 78

THE NATURALIST

INLAND SHAGS AND SPORTING FISH.

r.y

Cryptos.

(Fob the Witness.) Shags are to be found throughout the >hole world, except in Polynesia, but 2s r ®w Zealand waters and rivers contain luore different kinds of shags than do •kose of any ether country in the world. In all, there are 15 species found in New ihwland and the surrounding islands, while there are only 12 in North and South Aweroa, seven in Asia, six in Africa, five X) Australia, and three iu jiurope. Most t»iu-u inhabit the coastal regions, nesting on rocky eminences and on islands, but some prefer rivers ad inland lakes, And these latter generally build their jiests in trees, considerable numbers consorting together.

Messrs Hutton and Drummond .n their book, “The Animals of New Zealand,” eay

“The large number of species in New Zealand is attributed to two causes. First, this qountiV was the meeting-place of two migrarory streams, one from the Malay [Archiiielago and New Caledonia, the other from Patagonia. Secondly, New Zealand has been broken up into a number of islands, lying at considerable distances apart, and these have been isolated for •. very long time.” That is to say, New Zealand wAs first populated by the junction of birds from avo sources of origin, iwbo, having migrated to New Zealand, “were then isolated by the cutting oft of ftfco routes which joined New Zealand to F;»rope on the one hand and South America on the other. To-da#, they are to be seen in numbers along all our coasts end rivers, the black shag, the pied shag, (the white throated shag, and the spotted being common to both islands Snags are greedy birds, and voracious feed ers, displaying remarkable dexterity in p a-suing and seizing fish. Si Julius von LCaast, writing of the pied shag, gives e good illustration of the diving and fishing capabilities of cormorants (shags) generally. He was standing near a spot ■where one of the northern spurs of Mount Nvurehison slopes down to the Buller River, which there forms small falls and xafkis. A cormorant was standing on an isjgSted rock, round which the foaming w.'rtprs dashed. By and by the bird sudIftwJy jumped into the white foam, to the surprise of the observer. “In the l*'it mstance," he says. “I thought he wou'd not get out again, but would be dashed to death by the whirling waters; but ®non he reappeared, swimming rapidly to'nuds the edge, and then flying on to his cAd observatory to continue his sport. It is probable that the snr ” fishes taken down by the falls, being stunned by the force of the water, are easily caught by th«; courageous bird.” (“Animals >f New Zealand,” page 300). la the open water ol lakes and sea they are none the less expert, catching the greater nart of their food while diving. Some people assert that the shag swallows the fish it has caught while still under water, but this fact is open to some doubt. Oe penguin certainly is able to swallow *ihi]e submerged, but it is more common, at least, for the shags o bring their catch to the surface They often *wim with their heads submerged while watching for their food, and dive from the surface, remaining under water up to a minute and a-half, and travelling in iliat time up to seventy yards Their activity in our fishing streams have caused them tc be outlawed by ajl fishermen Nearly every acclimatisation society will pay up to 3s per head for shags destroyed on rivers or lakes. Bangers have opened birds with up to 17 yearling trout in their stomachs, and the secretary of one society estimates that a shag will eat each day on the average six fish up to 21b in weight. A little simple arithmetic will show what an amount of damage a rookerv of these birds will do to a trout stream. The Otago Society has a specimen tif black shag which was captured with a trout of nearly three pounds weight stuck in its throat.

Before the advent of Furopeans in New Zealand, inland shags fed mainly upon the most abundant eels, which to-day still form a large part of the diet. However, 'it is an undisnutnble fact that since the introduction of sporting fish, sporting fish fiave also been devoured, and consequently cormorants have been doomed to attack by all Mr H Guthrie-Kmith. nevertheless, in “Mutton Birds and Other Birds,” is inclined to take a more moderate view. This is what he says:

“Except on my own lake at Tutira (Southland), I believe there is no part of Now Zealand where the destruction of fchags is not thought to be a righteous action. Everywhere be* unfortunate birds are persecuted as the destroyers ot fish, and fish thev do undoubtedly take. On our riveirs and fresh water lakes they Are believed to harm tho imported trout, and on onr sens to be a menace to the fisherman’s interest*, and it may indeed happen that in some districts, under certain conditions, and for - time, shags tare harmful. Those, however, who have 2no*t fJoeelv observed the conduct of feeding ihaga believe that the captures made 3n waters where both In rut and cels abound are cml’y of the latter “On the *nl »ion rivr.oi of Scotland the ifipper iu.nl to he shot down until he was “•ftaJ * piq ‘A'uioua in )oa poxoad

dian of the salmon ova. In Victoria, too, the destruction of shags has resulted, not in an increase, but very great decrease of fiah in the Murray River, its billabongs and lakes. “Anglers and fishermen, like the rest of mankind, are but too prone to rush to conclusions based on insufficient evidence. and both in Scotland and Victoria persistent observation and experiments have shown that the birds feed chiefly on the enemies of the fishes’ eggs “Mv local experience, too, goes to prove that the presence cf shags in considerable numbers is no bar to stocking suitable water. On Tutira the trout are increasing fast, aLhough on the lake and on the run I have allowed no shags to be molested in any way whatsoever; and it may yet prove in New Zealand that the indiscriminate slaughter of shags will turn out to be inimical to the very interests sought to be preserved. “In Stewart Island saleable fish is mostly obtained in the open sea, yet the shags of every species draw their main supply of food from the inlets. At any rate, it is quite unlikely that everv species of shag does equal harm, and i + may well happen that some of these persecuted breeds destroy Crustacea that take the eggs and f ry of the blue cod and other marketable fish.” Tn the light of this evidence it might perhaps be as well, were suitable experiments carried out in New Zealand, to ascertain just how much of a menace, if any, the much-reviled sha.g really is to the sporting and marketable fish of our waters.