Estimation of snapper year class strength in SNA 8

Project: Estimation of snapper year class strength in SNA 8
Project Code: SNA2004/03
Start Date: 1 October 2004
Completion Date: 30 September 2005
Vessel Use: None

Overall Objectives:

1. To estimate the year class strengths of snapper (Pagrus auratus) in SNA 8.

Specific Objectives:

1. To carry out sampling and estimate the relative proportion at age and length of recruited snapper sampled from the commercial trawl catch in SNA 8 during spring and summer 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).

Rationale:

General

The snapper fishery is New Zealand’s largest inshore finfish fishery by value. SNA 8 is the second largest snapper fishery with a current TACC of 1500 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 less regular; the last west coast (SNA 8) survey was in 1999.

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 8 the trawl catches will be sampled, but only in the spring/summer period when most of the catch is taken. These data will be used to update the snapper assessment for SNA8 in 2005 (SNA2004/01).

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 8

The project is estimated to cost between $50,000 — $100,000.