Government Sea Lion proposal at odds with new DOC information: expert

A University of Otago expert on rare New Zealand Sea Lions says the Government’s proposed radical policy change which he is certain will endanger the species comes despite two of its own departments producing conflicting advice on the issue.

University of Otago Senior Lecturer in Zoology Dr Bruce Robertson says recent advice to the Government that by-catch of NZ sea lions from squid fishing is no longer a risk to the species runs counter to a just-published Department of Conservation (DOC) study on the role of disease outbreaks and fishing related deaths in the 50 per cent decline of the New Zealand sea lion population.

“The DOC study directly contradicts MAF’s assertion that by-catch of NZ sea lions in the squid fishery is no longer an issue contributing to the extinction risk of the species,” Dr Robertson says.

The research by DOC scientist Dr Louise Chilvers uses the modeling tool, Population Viability Analysis, which is used by conservation managers to resolve extinction risk and weigh management scenarios in threatened species recovery.

The study, just published online in the international science journal Polar Biology, concludes “sustained fisheries bycatch at current estimated levels… …could result in a population decline and possible functional extinction”.

The DOC study also found that while naturally occurring disease outbreaks “reduce the growth rate of the population; it does not cause a decline”. The study concludes that at the current rate, sea lion population decline “would result in this population being functionally extinct by 2035, (that is) 24 years from now”.

These findings support the conclusions of Dr Robertson’s own recently published study that concluded by-catch, and also resource competition with the squid fishery, is resulting in the decline of the Auckland Island breeding colonies of the sea lion. Dr Robertson’s study also noted that disease outbreaks were not behind the dramatic decline of the sea lion population.

The New Zealand Government fisheries managers (MAF), however, has concluded that by-catch of NZ sea lions in the squid fishery is no longer an issue contributing to the extinction risk of the species. MAF outlines in their discussion document (initial position paper, IPP) that the “direct effect of fishing-related mortality on the New Zealand sea lion population is minimal”.

The IPP is produced with the purpose of setting a limit (fishing related mortality limit, FRML) on the number of New Zealand sea lions drowned in the deepwater trawl nets of the squid fishery around the sub-Antarctic Auckland Islands in the coming 2011/2012 fishing season.

Dr Robertson says it is very concerning that two government departments are poles apart in their conclusions on the management of a Nationally Critical New Zealand species.

“On the one hand, we have the Department of Conservation using a conservation management tool and saying fishing effort will lead to the functional extinction of the sea lion population within 24 years. While on the other hand, MAF’s current fisheries model, designed to determine the number of sea lions that can be sustainably harvested each year, suggests that fishing effort is having “minimal” impact on sea lions,” he says.

“Serious concerns have been raised by scientists and modelers about MAF’s fisheries model, not the least being that it predicts sea lions will become extinct in the complete absence of squid fishing. Indeed, MAF’s own statements in the IPP highlight Government concerns that the fisheries model may not be reflecting reality.”

Dr Robertson says MAF’s conclusion that fishing effort is having “minimal” impact on sea lions also goes against MAF’s own science advice that fishing effort results in what the Government calls “unquantified cryptic mortality”.

“The only logical explanation for MAF’s statement that fishing impacts on sea lions are minimal is that MAF have produced a number for the “unquantified” cryptic mortality. Given the IPP acknowledges that there is no scientific evidence to quantify this type of mortality, this number must be a work of fiction.”

“As such, we have a level of sea lion mortality due to fishing that remains unknown at this time, which might be low or, of more concern, might be high. Clearly, it is premature to be stating fishing impacts are minimal.”

Dr Robertson says that given the conflicting conclusions made by the two Government Ministries there is an urgent need for an independent review of the Government’s proposed management of sea lions.