N.Z. MARINE DEPARTMENT-FISHERIE,S BULLETIN No. .į

It will be observed from the foregoing records that the foocl of the large black
shag varies according to the food available u,here it chooses to feecl; cloubtless, a
wider range of foods would be shown if material was collected froll salt water. To
what extent it selects or shows preference for special foods of those available
where it chooses to feed is not known, except that generally fisli of one kind or
another comprise the bulk of its food. Present eviclence simply shows that it feeds
on such food as is available. There is no eviclence that it chooses certain areas
because of the abundance of any particular kincl of fish or that its distribution
is even principally governed by considerations of abunclance of food in general.
The bird is knor,vn to nest and roost especially on cliffs on the sea coast and
in trees overharging or near streams or lakes inlancl. Suitable cliffs are found
only on parts of the coast, for example, round Banks Peninsula, and suitable
inland sites vary in local abundance.
It is not known whethel there are seasonal changes in the feeding grouncls of
the coastal ancl inlancl colonies, to what extent inter:change and recruitment of one
stock from the other takes place, or, indeed, whetl-rer cólonies remain, throughout
the year, sufficiently distinct to vl'arrant separate consideration.
To sum up the eviclence as regarcls the l{orth Island and Marlborough and
Car-rterbury in the South Island, it is clear that a general condemnation of the black
shag is unwarrantecl. The bird is shown to feed largely on trout in inland waters
which contain trout, and largely on eels in shallow lakes and lagoons. A mixed
cliet in r,vhich trout, eels, flounders, and mullet are conspicuous is taken in some
tidal waters. The shag is not sho'rvn to be beneficial in any way to trout fisheries,
for the only eels consurled, which were specifrcally identified, were of the shortfinned
species (Falla and Stokell-Lake Ellesmere material). This species is
not known to attack trout. It is 'Lrsually of a more suitable size for shags to eat,
ancl is the numerically don-rinant eel at Lake Ellesmere and in the lower Waikato
basin ancl generally in coastal lagoons and sluggish ticlal reaches of rivers, u,here
shags have been reported most frec¡rcntly to take eels. The evideuce, so far as
it extends, suggests that, on inland waters in tl-re parts of ldew Zealancl uncler
discussion, the black shag is harmÍul rather than beneficial to trout fisheries.
Too little is known o{ tl-re total number of bircls freciuenting inland lvaters to enable
the significance of their depredations in lrlelv Zealand r¡iaters generally to be assessecl.
Falla ancl Stokell cliscuss numbers of bircls in the North lsland and in Marlborough
ancl Nelson. The numbers reported to ther-n lîay or may not be correct, ltut in the
aggregate they suggest that the black shag is greatly less abundant inland than
is suggested by annual reports of the Department of Internal Affairs. Reports
for the four years ended March , 1941, show that the mean annual number of shags
destroyecl in the Taupo and Rotorua districts was 1,311. Thereafter the total fell,
at a time when ammunition was difÊcult to procure and most able-bodied men
were in the armecl services. Reports from acclimatization societies do not usually
give clear statements of.the numbers of shags destroyed and places lvhere thel'
were killecl. More often they give the amount spent on bounties, sometimes without
speciflcation of the amounts for different predators and often without clear statements
as to numbers clestroyed by their staffs.
Evidence of the feeding habits and local abundance of the large black shag in
fresh waters in the southern half of the South Island is given by Williams (1945).
Fisheries bulletin (N.Z. Marine Dept.) no. 9 (1948)
ltze