Fisheries Infosite

Highly Migratory Species


Highly migratory species vary in their biology, value, and harvest method. Each presents its own challenges with respect to ensuring it remains sustainable and is utilised within acceptable environmental limits. The highly migratory nature of these fisheries presents an additional challenge - New Zealand is at the outer limit of the distribution of most HMS, and our catches are only a tiny fraction of the total. The abundance of HMS in New Zealand waters is seasonal, and varies from year to year. If a stock declines globally, its availability will likely reduce in New Zealand waters too (sometimes more abruptly than in its core habitat e.g. in Tropical fisheries). 

New Zealand manages most of its important commercial fisheries using catch limits. Information on the catch limits in place, as well as recent catches, can be found in the species section

 General information on New Zealand’s quota management system (PDF | 2.4mb)

The main methods used to commercially harvest highly migratory species are associated with specific issues that can require careful management (both domestically and internationally).

Large Pelagic Fisheries 

Large pelagic species are caught commercially by the method of surface longlining. 

The environmental impacts of pelagic longline fisheries relate mainly to the bycatch of non-target fish species, and incidental catches of other species such as seabirds and turtles. 

Many vulnerable seabird species – particularly petrels and albatrosses – overlap with pelagic longline fisheries. Seabirds may attempt to take the bait from longline hooks, and can become entangled and drown. Mitigation measures include setting at night, when fewer birds are present, using streamer or tori lines, which may frighten birds away from the baited hooks while they are being set, and weighting lines to ensure they sink out of reach of the birds more rapidly. Measures aimed at minimising interactions with seabirds are outlined in the Annual Operational Plan 2013-14 for HMS fisheries, and are based on achieving the objectives in New Zealand’s National Plan of Action for Seabirds.

Sea turtles may also become hooked on or entangled in longlines. Such incidents are rare in New Zealand fisheries waters, but the Department of Conservation, in conjunction with the Ministry for Primary Industries, has supplied surface longline vessels with equipment to safely release any turtles that do become caught up in fishing gear.

Bycatch of sharks in HMS fisheries is managed in line with objectives in the National Plan of Action for the Conservation and Management of Sharks (NPOA-Sharks 2013).

Surface longline fishers have developed a code of practice that documents the steps they will take to help mitigate their environmental impacts.

Purse Seine Fisheries for Skipjack

The New Zealand purse seine fishery for skipjack tuna is based on ‘free’ or ‘unassociated’ fish and has very little bycatch of other species. Elsewhere in the Pacific however, much purse seine fishing for skipjack is carried out on ‘associated’ sets, generally using what are known as Fish Aggregating Devices (or FADs). A FAD can be anything from a log to a complex structure of webbing, rope, and buoys, which are designed to attract tuna. Use of FADs can be an efficient way of catching large volumes of tuna, but may also lead to the bycatch of non-target or less desirable species, including those for which sustainability concerns exist (for example bigeye and yellowfin tunas). 

WCPFC has adopted conservation and management measures to manage the skipjack fishery and its bycatch of bigeye and yellowfin tuna. 

Albacore Troll Fishery 

The albacore troll fishery in New Zealand is not associated with any major bycatch or environmental issues, and has achieved independent certification from the Marine Stewardship Council. New Zealand is however working actively with our Pacific neighbours to develop appropriate controls on the catch of albacore, both within the zones of Pacific countries (including New Zealand), and on the high seas – where catches have been expanding, although they remain below the maximum sustainable level.

Contact us about this page    Last updated 24/01/2017