Industry Concerned with Sea Lion Activity in Southern Ocean
5 September 2013
Industry Concerned with Increased Sea Lion Activity in Southern Ocean
The southern blue whiting fishing fleet is making every effort to avoid sea lion captures in the Southern Ocean, after unprecedented numbers of sea lions have arrived in the remote fishery this season to forage around trawl nets. These animals, mostly young males, are feeding opportunistically on or in the trawl nets when they come to the surface, placing themselves at risk of becoming caught.
Deepwater Group CEO George Clement says the numbers captured are both “unprecedented and very concerning” and that industry and the Ministry for Primary Industries (MPI) are doing everything possible to reduce these unwelcomed interactions.
“Last year the southern blue whiting fleet did not catch a single sea lion. We fish more than 100 kilometres from land and normally only a few adventurous males come this far out. This year we are seeing many more sea lions and these are taking greater risks around our gear. We are avoiding fishing where we they are most likely to be, based on previous years, but this year their behaviours’ are very different,” he says.
“To date this season, 20 sea lions have been caught in the fishery. Fortunately the vessel crews have managed to release four of them alive. Five sea lions were caught in one trawl, which is previously unheard of. Fishing in this remote region for southern blue whiting occurs only during August and September, so we get no notice of sea lion numbers until we turn up there.”
Industry and MPI are actively responding to these unfortunate events with a range of measures to prevent any further incidental captures of these Campbell Islands’ sea lions.
“We are trialling Sea Lion Exclusion Devices (SLEDs), which have proven to be extremely successful the Auckland Islands squid fishery where sea lion captures have been all but eliminated. The Government has asked us to extend this trial across the whole fleet and all vessel operators have agreed to do so.”
“The sea lion behaviour appears to be more aggressive in this season’s southern blue whiting fishery than we have seen before, certainly more so than in the squid fishery. This unprecedented and risky behaviour of the young males comes on the back of the second poorest squid year in the 27 year history of the fishery. MPI and DWG are working closely to establish the effectiveness of SLEDs in these new circumstances. MPI has observers on all vessels in the fishery”.
George Clement says other measures to prevent sea lion captures are important as well and, in the meantime, may prove to be more effective.
“We are minimising the time our fishing gear is on the surface to lessen the chance of the sea lions being attracted to the nets to feed. There is a 12 nautical mile exclusion zone for trawling around the Campbell Islands providing a sanctuary for feeding, proposed by industry and implemented by Government.
“We are also working closely with MPI to establish what might be causing these young males to be so far offshore in such numbers in order to identify further ways to avoid captures. Vessel crews, operators and MPI observers are providing a good flow of up to date information to both industry and government.
At times this season large numbers of sea lions have been attracted to the nets at the surface when they are hauled and when the sea lions know food is more readily available.
“Sea lions are smart animals feeding opportunistically around our vessels, unwittingly putting themselves in harm’s way as they do so. Our challenge is to outsmart them and so to prevent them from harm.”
All the captured sea lions are males, and are generally younger than full breeding age. The southern blue whiting grounds are 100-200 kilometres offshore, outside the normal foraging range of female sea lions from Campbell and Auckland Islands.
“While any loss of sea lions is most regrettable, these losses of males will not reduce the ability of the Campbell Islands’ sea lions to reproduce,” George Clement said.
“As New Zealand sea lions have a harem structure, with one bull servicing many females, there will always be replacement bulls to stand in for any losses. We seek to avoid any interactions with sea lions but note that loss of males is less of a risk to their population than losses of females could be.”
“Scientists assess that the Campbell Island population has been increasing in size for some years and that might be why we are seeing many more sea lions being attracted to our vessels this season.”
“Even with the very unusual number of captures this season, the losses are below the levels that have been calculated by scientists to have any effect on the population.”
“Nevertheless, we are working hard to ensure that we understand the drivers of these new behaviours and to deploy ways to minimise harm to these sea lion populations.”
About 21 per cent of New Zealand sea lions are born on the Campbell Islands, with New Zealand’s main rookeries further north on the Auckland Islands. Smaller numbers of sea lions are now breeding in Otago and on Stewart Island.