Otago University sea lion study slammed by experts

Poor science deserves to be challenged and three sea lion scientists have done just that.

A study led by Dr Stefan Meyer from the University of Otago’s Anti-Commercial Fishing Department (not an official title) claimed to have “game-changing” evidence that allegedly showed commercial squid fishing posed a direct and major threat to the endangered New Zealand sea lion.

That was too much for a group of independent scientists – Dr Jim Roberts from the National Institute of Water and Atmospheric Research, Dr Simon Childerhouse from Blue Planet Marine and Prof Wendi Rose from Massey University - who have worked closely with sea lions and were moved to vigorously debunk the study published in the international journal PNAS and reported in the New Zealand Herald.

They were concerned such articles misinformed the public and policy makers about the cause of the sea lions’ decline, with potentially damaging consequences for their conservation.

The current population is estimated at being just under 12,000. The Auckland islands, 460km south of Bluff, are the main breeding ground.

Last summer the annual Department of Conservation survey recorded a healthy increase in pup numbers – up 14 percent on the previous year from 1727 to 1965 pups.

The pup counts appear to have stabilised between 1600 to 1700 pups per year since 2009, according to DoC and the Ministry for Primary Industries’ threat management plan 2017-22.

MPI’s 2016 Aquatic Environment and Biodiversity Annual review recognised “there is no single threat that is impacting on the sea lion population and recovery will require mitigation of multiple threats at the four main breeding sites."

Despite that, Meyer and co-author Associate Prof Bruce Robertson, also of Otago, claimed management of sea lion bycatch in the arrow squid fishery placed the population at risk of extinction and that the sea lion exclusion devices that allow the animals to escape from nets may be hiding deaths and injuries.

MPI emerged from its bunker to make the vague response that it was completing a technical review of the paper and could not comment on its conclusions.

Dearie me. It already has the evidence in its own threat management plan.

However, the three expert sea lion scientists were more forthright, saying the Otago study was deeply flawed and they were mystified as to how it had passed a peer review process.

“Even for the most pessimistic fisheries scenario where all sea lion interactions with commercial trawls resulted in death, fisheries-related mortality was not nearly sufficient to explain the 50 percent decline in the number of breeders,” scientists Roberts, Childerhouse and Rose said.

“Full investigations into the causes of pup deaths have been conducted since 2006.

“A total of 438 dead pups have been assessed, of which 55 percent were diagnosed to have died as a direct result of infection by the bacterium Klebsiella pneumoniae.

“The next most common cause of death was trauma or drowning in mud holes, killing 21 percent of pups.”

Why did Meyer et al dismiss these other threats?, they asked.

Why indeed?

Maybe because they did not fit with preconceived notions. If the truth is inconvenient, best to ignore it.

Will it be to the advantage of New Zealand sea lion conservation to dismiss threats other than fishing as unimportant, despite the weight of evidence to the contrary?, Roberts and his colleagues further asked.

“We don’t think so,” they answered.

“Good progress is being made to understand the root causes of the catastrophic decline at the Auckland Islands, including the roles of disease, nutrition and fisheries. But we still haven’t resolved the best management options for reversing the downward trend.

“It is essential that simplification and misinformation are not allowed to confuse our collective efforts to understand and conserve New Zealand’s own sea lion.”