Here is some information on another mortality event - this time with sealions. Anyone with ideas or comments should direct them to Mike Donahue.
Don Anderson date: Jan. 31 1998
NEW ZEALAND SEA LION MASS MORTALITIES
A serious mass mortality event is currently sweeping through the
two main breeding colonies of the New Zealand (Hooker's) sea lion
(Phocarcto shookeri), with 30-40% of this year's pups already
dead, and indications of increasing mortalities amongst adult
females.
The New Zealand sea lion is found only in New Zealand waters and
is one of the world's rarest seal species. In 1997, based on
pup production estimates, the population was estimated at between
11,000 and 15,000 animals.
Once distributed throughout New Zealand, from the tip of the North
Island to Campbell Island, deep in the subantarctic, the species
was taken to the brink of extinction by commercial sealers of
the early nineteenth century. The major concern in recent times
has been the impact of accidental catches in the trawl fishery
for squid around the Auckland Islands, which is one of New Zealand's
most important deepwater fisheries. For each of the past four
years Ministers of Conservation and Fisheries have set a catch
limit for sea lions. The squid fishery was closed early last
year, because the sea lion catch limit was exceeded.
Over the past ten years, the Department of Conservation (DOC)
has been monitoring the main breeding colonies of Dundas and Enderby
Island, part of the Auckland Islands group located some 420km
south of New Zealand's South Island. These two colonies (which
collectively occupy an area roughly the size of six football pitches)
account for some 95% of the sea lion breeding population. Annual
pup production in recent years has been approximately 2,500 animals.
Dundas Island is responsible for 80% of all pup production ,
but is surrounded by rocky reefs and is much harder to access
than Enderby, where DOC has a research station.
DOC scientists arrived at Enderby Island in mid-January, and everything
seemed to be normal. However, when weather conditions permitted
a visit to Dundas on 26 January, the team discovered some 700
recently-dead pups. Symptoms included puffy eyes, ulcerated anuses
and vaginas and lesions on the head. Dying pups often showed
spasms and paralysis. Fewer adults than usual were on the beach,
but at that time there were no signs that the older animals had
been affected. Returning to Enderby, the team soon found that
pups were beginning to die there also. In addition, adult females
started showing signs of paralysis. Afflicted animals also had
small raised lesions on the belly and neck. Post-mortems have
shown pus-filled swellings around the salivary gland in the neck.
The most recent estimate on the day of this posting is that 111
pups have died on Enderby, and a further 150 are unaccounted for.
20% of the adult females on the breeding beach are dead or afflicted
with lesions or paralysis. The numbers of adult females on the
beach are considerably lower than normal. An unknown number of
females (and males) may have died at sea, and some pups are consequently
starving to death.
Samples from autopsied pups and females and six pup carcasses
were flown back to the mainland by helicopter on 29 January.
Pathologists from Massey University Cetacean Investigation Centre
in Palmerston North will begin detailed examinations of the samples
on Monday 1 February.
Further updates will be posted with MARMAM on a weekly basis.
Any helpful advice or assistance will be warmly welcomed.
Please reply to:
mdonoghue@doc.govt.nz