Recreational Catches
Yellowfin were a major species caught by North Island New Zealand recreational fishers in Northland, Bay of Plenty, and as far south as Hawkes Bay on the east coast, and Kawhia on the west. This species was predominantly caught by trolling, but they were also captured using spinning and jigging when fishing on aggregations of tuna feeding on bait balls. Numbers of Yellowfin weighed in at sport fishing clubs in New Zealand dropped from over 1,000 fish per year in the 1990s to an average of 30 fish per year between 2011-2015. This raises the question of what happened to them?
Commercial catches
A natural possibility to consider is that they were overfished by the New Zealand commercial operators. Yellowfin are taken commercially using Fish Aggregation Devices (or FADs), longline, purse seine, pole and line and trolling, and are also taken in recreational fishing. In New Zealand waters, after 1990, Yellowfin started to be taken in larger numbers. They were mainly taken as bycatch in the surface longline fishery targeting Bigeye tuna. About 68% of the commercial catch of Yellowfin comes from the Bigeye fishery, but Yellowfin only make up 2% of the catch. However, commercial catches in New Zealand waters are tiny fraction (0.07% in 2000-2011) of the Western and Central Pacific Ocean stock. Catches from New Zealand flagged and licensed vessels both inside and beyond the Exclusive Economic Zone (EEZ) were on the order of a couple of hundred tonnes. In contrast, catches of Yellowfin in the Western & Central Pacific were approximately 735,000 tonnes in 2020 and 778,000 in 2021.
The obvious implication is that reductions in Yellowfin in New Zealand waters were not due to the New Zealand commercial take. Yellowfin are highly migratory, so although commercial fishing in NZ waters is very small, the much larger Western and Central Pacific take could have a major impact, even in New Zealand. I’ll examine this more in another blog.
References
New Zealand Quota Management System summary for Yellowfin tuna.
Holdsworth, J. 2012. Yellowfin Tuna Fisheries in New Zealand and the Southwest Pacific Ocean. Blue Water Marine Research Ltd.
Hare S.R., et al. 2022. The western and central Pacific tuna fishery: 2021 overview and status of stocks. Fisheries Assessment Report no. 22. Noumea, New Caledonia: Pacific Community. 63 p.