2 Purse seine fishery catch effort data

Kahawai (Arripis trutta) is the most frequently targeted fish for the purse seine fishery. Kahawai is a pelagic schooling species and the fishery is mainly of value to the purse seine fleet. The kahawai purse seine fishery cannot be understood without taking into account the other species, which the vessels target. For approximately five months of the year (December to May) the northern fleet, based in Tauranga, tends to target exclusively for skipjack tuna (Katsuwonus pelamis) with very little bycatch. When skipjack are not available the fleet fish for a mix of species including kahawai, jack mackerels (Trachurus spp.), and blue mackerel (Scomber australasicus). These are caught 'on demand' as export orders are received (to reduce product storage costs). The southern fleet, based in Nelson, fished exclusively for the mackerels and kahawai when fishing in southern waters. Since the mackerels and Kahawai school together in some areas, attempts to target for either of the mackerels will often result in a bycatch of kahawai.

Apart from the main targeted species, minor amounts of other species regularly caught in the purse seine fishery include: barracouta (Thyrsites atun), trevally (Pseudocaranx dentex), blue warehou (Seriolella brama), spiny dogfish (Squalus acanthias), and kingfish (Seriola lalandi lalandi).

The purse seine fishery operates mainly in the Bay of Plenty and on the east Northland coast. A small purse seine fishery operates between the Clarence River mouth and the Kaikoura Peninsula, with at least 70% of the catch being the Peruvian Jack Mackerel (Trachurus murphyii). Minor amounts of purse seining also occur along the west coast of both islands in the main jack mackerel fishing ground (Horn, 1991a).

All commercial fishing catch and effort data for the purse seine fishery are recorded for the Quota Management System and are stored in the Ministry of Fisheries databases. The pseine database holds a research version of these data. These data are used to calculate biological reference points such the Maximum Sustainable Yield (MSY) in terms of Current Annual Yield (CAY) or Maximum Constant Yield (MCY).

The data in the pseine database are a copy of all purse seine fishery catch and effort data from the Ministry of Fisheries databases from 1989 to 1993 and are summarised in Jones (1995).