Characterisation of New Zealand longline fisheries for highly migratory species

Trophia has been contracted by the New Zealand Ministry of Fisheries :

To characterise the New Zealand longline fisheries for highly migratory species with

SPECIFIC OBJECTIVES:

  1. To characterise spatial and temporal trends in catch and effort for target and bycatch species in the New Zealand fisheries for highly migratory species.

  2. To characterise the gear changes that have occurred in New Zealand fisheries for HMS species in the New Zealand fisheries waters and adjacent high-seas areas.

  3. To quantitatively estimate the effect of those gear changes on target species catchability through time.

  4. To characterise the reasons for changes in yellowfin fisheries in New Zealand fisheries waters.

  5. To analyses all existing commercial catch and effort data for the above fisheries to the end of 2009/10 fishing year and undertake a CPUE standardisations.

Tuna Fisheries in New Zealand waters were described for the fishing years 2002-03 and 2003-04 in detail, and in context of the six most recent fishing years from 1998-99 by Kendrick 2006. That report described a period during which the domestic fleet expanded rapidly to replace licensed foreign vessels fishing in the New Zealand Exclusive Economic Zone (EEZ), and tuna fisheries were the last significant free-entry fisheries left outside of the Quota Management System (QMS) in New Zealand waters. Tunas and swordfish, except for Southern bluefin tuna, were not subject to any catch restrictions or to compulsory reporting requirements up to October 2004, except that all retained catch from longlining, targeted at tuna species, was required to be reported on Tuna Longline Catch Effort Returns (TLCER), but the commercially valuable species that are the focus of this report were generally well reported. Swordfish were a valuable component of the catch but could not legally be targeted.

In October 2004, bigeye, Pacific bluefin, southern bluefin, and yelloweye tunas, and swordfish were introduced into the QMS, with swordfish becoming a legal target species. Several key bycatch species, namely mako, blue, and porbeagle sharks, moonfish, Ray’s bream, and swordfish were also introduced at this time.

By 2008 the number of longline vessels operating in New Zealand had declined to 35. Despite the fact that the domestic longline fleet mainly targets bigeye and southern bluefin tuna, the greatest part of the catch consists of albacore and swordfish. Blue shark is the most common non-tuna bycatch species in the longline fishery followed by Ray’s Bream.

From March 2003, a completely redesigned Tuna Longlining Form (TLCER) has been in use, and, along with clearer instructions to fishers, has markedly improved the quality of data available from longlining. Data verification standards administered by the MFish data management group have also greatly improved the quality of all catch effort data since about 2000.

It is timely for a comprehensive characterisation study to describe the operation of these fisheries particularly during the years since their introduction into the QMS.