New Zealand Journal of Marine and Freshwater Research abstracts
Diet of southern Buller's albatross (Diomedea bulleri bulleri) and
the importance of fishery discards during chick rearing
GAVIN D. JAMES
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 8602
Christchurch, New Zealand
email: g.james@niwa.cri.nz
JEAN-CLAUDE STAHL
Museum of New Zealand, Te Papa Tongarewa
P. O. Box 467
Wellington, New Zealand
email: jeans@tepapa.govt.nz
Abstract Southern Buller's albatrosses (
Diomedea bulleri
bulleri Rothschild) are frequently associated with fishing vessels off
southern New Zealand, and may depend substantially on discards from fishing
vessels, particularly trawlers, during chick rearing. To test this hypothesis,
the diet was determined from 188 chick regurgitations collected at The Snares
(May 1996, July 1996 and 1997) and Solander Island (May and July 1997). Fish
(mostly discards but also some small species obtained naturally) was the
dominant prey category, occurring in 92% of samples, and forming 65% by weight
of solid food consumed. Salps (
Pyrosoma sp. and
Iasis zonaria)
were the most abundant prey items (44% of all items), and second most important
by frequency of occurrence (78%) and weight (24%). Cephalopod remains (mostly
arrow squid (
Nototodarus spp.) and
Histioteuthis atlantica)
occurred in 53% of samples, but contributed only 17% by number and 7% by
weight. Other dietary items included crustaceans (chiefly
Munida
gregaria,
Nectocarcinus antarctica,
and
Lepas
anatifera), bird feathers, and flotsam. Fishery discards were present in
70% of samples, constituted 60% of the diet by weight, and comprised 91% of the
weight of all fish consumed. Discard composition was dominated by Gadiformes
(mostly hoki (
Macruronus novaezelandiae)
and macrourids) in 1996,
and by jack mackerel (
Trachurus sp.) in 1997. Breeders at The Snares
took more discards in July 1997 (68 g per sample) than May or July 1996
(31 and 28 g respectively), those at Solander Island took more in May
(56 g) than July 1997 (29 g). In May 1996, the diet of birds at The
Snares tended to be biased towards fish (both discards and natural prey) after
long foraging trips, but towards cephalopods after short trips. Sexual
differences in diet and discard consumption tended to be more pronounced
amongst samples from The Snares. The high, and apparently increased proportion
of fish in the diet, strongly suggest that discards from fishing operations
have a beneficial effect on the population of southern Buller's albatrosses
breeding on The Snares.
Keywords Buller's albatross; Diomedea bulleri; diet;
discards; fisheries; The Snares; Solander Island; Trachurus sp.;
Macruronus novaezelandiae; Nototodarus sp.; Pyrosoma sp.;
Iasis zonaria; Munida gregaria
M99027
Received 10 May 1999; Accepted 7 February 2000
PDF file of entire paper: medium quality (1645K); (scanned from paper original: notes about this process)
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