Fisheries and the New Zealand sea lion

Find out about sea lion deaths in trawl nets, and how Fisheries New Zealand is trying to stop this.

Sea lion captures

The most common way for sea lions to be affected by fishing is when they swim into trawl nets in search of food, get trapped, and drown. It is estimated that 6 sea lions die in trawl nets each year, mostly around subantarctic islands where they breed. Fisheries New Zealand has worked with the fishing industry to reduce sea lion deaths in these fisheries.

Data from the Squid 6T fishery shows that fishing is having a small impact on the sea lion population. It is estimated that fewer than 4 sea lions have been killed each year over the past 5 years. Modelling suggests the sea lion population will be no more than 1.5% smaller in 2025 due to the impacts of fishing.

Sea lion exclusion devices (SLEDs)

The fishing industry uses "sea lion exclusion devices" (SLEDs) in trawl nets in:

  • the Squid 6T fishery near the Auckland Islands
  • the southern blue whiting fishery near Campbell Island.

SLEDs were introduced in 2000. Their design has been adjusted over the years to improve them. They are considered to be effective at allowing most sea lions to escape from the trawl net and survive.

SLEDs are checked in the Squid 6T fishery

Vessels in the Squid 6T fishery carry at least 2 SLEDs, which are inspected at the start of every season to make sure they meet specifications. Fishery observers on vessels in this fishery also:

  • audit SLED specifications
  • ensure that SLEDs are in good working order
  • confirm that SLEDs are being used correctly.

SLED research shows the devices are working

Significantly fewer sea lions have been captured since SLED use began.

Fisheries New Zealand research in 2018 and 2019 looked into the effectiveness of SLEDs. This work showed that SLEDs allow most sea lions to escape and survive. 

How SLEDs work

How effective are SLEDs?

  • Midwater trawl nets: 88% of sea lions that enter a SLED net swim out. A small number of those (5% to 7%) drown before they reach the surface.
  • Bottom trawl nets: 57% of sea lions that that enter a SLED net swim out. Between 5% and 7% run out of air before they reach the surface, and drown.

The Squid 6T Operational Plan 2019–2023

New Zealand's largest sea lion breeding colonies are on the Auckland Islands. Commercial fishing vessels targeting squid and scampi operate 12 nautical miles offshore. Fisheries New Zealand keeps a close eye on the Squid 6T fishery. In 2020, on-board observers monitored 91% of all fishing effort.

Interactions between sea lions and squid fishing activity are managed through the Squid 6T Operational Plan. This sets out a range of measures to avoid, remedy, or mitigate the effect of fishing-related sea lion deaths.

The main regulatory measure in the plan is a limit of 52 fishing-related sea lion mortalities a year. If that limit is reached, the fishery will be closed immediately. 

Squid 6T Operational Plan 2019–2023 [PDF, 455 KB]

We need to continue to minimise sea lion deaths

There are signs sea lion populations are recovering.

The measures put in place to manage fishing activity appear to be reducing sea lion deaths. We need to make sure that continues.

Fisheries New Zealand would prefer if no sea lions were caught by fishing vessels. But all food production, whether on land or at sea, has an impact on the environment. We need to strike the right balance between producing food and minimising the impact fishing can have on sea lions. If we know fishing is having too big an impact on the population, the government will take action. This could include closing the fishery.

Who to contact

If you have questions about New Zealand sea lions and the threat management plan, email

Find out more

Operational plan to manage the incidental capture of New Zealand sea lions in the southern blue whiting fishery, Campbell Island (SBW6I) [PDF, 420 KB]

Spatial assessment of fisheries risk for New Zealand sea lions at the Auckland Islands [PDF, 4.6 MB]

Population effects of New Zealand sea lion mortality scenarios in squid fishery at the Auckland Islands [PDF, 1.2 MB]

Desktop estimation of New Zealand sea lion cryptic mortality in trawls using SLEDs [PDF, 593 KB]

Simulating sea lion dives to assess the probability of post-exit drowning for sea lions exiting SLEDs [PDF, 2.7 MB]

Threat Management Plan for New Zealand sea lions – DOC

Quantitative Risk Assessment of Threats to New Zealand Sea Lions – AEBR 166 [PDF, 6.6 MB]

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