Estimation of snapper year class strength in SNA 1

Project: Estimation of snapper year class strength in SNA 1
Project Code: SNA2004/02
Start Date: 1 October 2004
Completion Date: 31 May 2006
Vessel Use: None

Overall Objectives:

1. To estimate the year class strengths of snapper (Pagrus auratus) in SNA 1

Specific Objectives:

1. To carry out sampling and estimate the relative proportion at age and length of recruited snapper sampled from the commercial longline catch in SNA 1 throughout the fishing year 2004/05. The target coefficient of variation (c.v.) for the catch at age will be 20 % (mean weighted c.v. across all age classes).

Note:

The duration of this project will be 20 months, 1 October 2004 to 31 May 2006. This will allow the successful tenderer time to sample the fishery for 12 months and present the results to the Fishery Assessment Working Group meetings in 2006.

Rationale:

General

The snapper fishery is New Zealand’s largest inshore finfish fishery by value. SNA 1 is the largest snapper fishery with a current TACC of 4500 t out of the total snapper TACC for all areas combined of 6494 t. Snapper also form important fisheries for Maori and recreational fishers, but the annual catch is not known reliably.

In the current stock assessment model, yearly recruitment indices are estimated using trawl survey indices and catch at age data sampled from the commercial fisheries. The catch at age data are collected annually but the trawl surveys are now planned to be carried out at irregular intervals; the plan is to survey 1+ snapper in the following year if the 0+ cohort has experienced extremely warm or cool conditions. The last Hauraki Gulf survey was in November 2000.

Objective 1

The aim of shed sampling is to estimate the age and length structure of the commercial landings of snapper. This provides catch-at-age information, which may be combined with estimates of selectivity-at-age to estimate stock age composition. This information on age and length composition is an important input into the age-structured models used for the assessment of snapper stocks and contributes to the estimation of productivity and sustainable yields.

In SNA 1 the East Northland, Hauraki Gulf and the Bay of Plenty fisheries will be sampled for longline catches throughout the whole year. Until 2002-03 these fisheries have been sampled only in spring and summer. As the fishery now operates all through the year samples will be taken from all seasons. These data will be used to update the snapper assessment for SNA1 in 2006.

Strategic Relevance

All the objectives in this project are consistent with the Fisheries Resources goal in the Ministry of Fisheries Strategic Research Directions document.

Cost Recovery Information:

The percentage allocation for this project will be attributed to the following Fishstock according to rule 9.1 of the Fisheries (Cost Recovery) Rules 2001:

• SNA 1

The project is estimated to cost between $200,000 — $250,000.