Stock assessment of stargazer in STA 7

Project: Stock assessment of stargazer in STA 7
Project Code: STA2004/01
Start Date: 1 October 2004
Completion Date: 28 February 2006
Vessel Use: Nil

Overall Objective:

1. Stock assessment of stargazer (Kathetostoma giganteum) in STA 7

Specific Objectives:

1. To conduct sampling in fish processing sheds and determine the length and age structure of the commercial catch of stargazer in STA 7. The target coefficient of variation (c.v.) for the catch at age is 30% (mean weighted c.v. across all age classes).
2. To age stargazer otoliths collected during the 2005 trawl survey.
3. To develop a stock assessment model for STA 7, including estimating abundance

Rationale:

General

Giant stargazer comprises an important component of the catch made by inshore trawlers on the west coast of the South Island. STA 7 is managed in the adaptive management programme (AMP). The TACC was increased to 997 t under a new AMP. In 2001/2002 the landings in QMA 7 for stargazer totalled about 800 t (TAC 702 t) out of a New Zealand total of 3238 t.

The R.V. Kaharoa has conducted trawl surveys off the west coast of the South Island (WCSI) since 1992 providing a time series of relative abundance and biological data for red cod, red gurnard, stargazer and tarakihi.

The relative biomass index for STA 7 from the recently completed WCSI trawl survey is 827 tonnes (CV of 15%). This index represents a 41% decrease from the 1992 to 1997 average of 1413 tonnes. As such, the decision rule for the STA 7 fishery was triggered and the fishery was referred to the 2003 Fisheries Assessment Plenary for evaluation. The Plenary recommended no management intervention was required at this time, except to provide for more information on stock status through:

1. The development of a full stock assessment model incorporating a review of existing and new trawl survey data, and
2. Obtaining another relative biomass estimate by bringing the WCSI trawl survey forward one year, and undertaking the survey every two years after this.

Objective 1

A commercial catch sampling programme is proposed to provide information on the size composition of stargazer taken by the commercial fishery in STAR7. This will be compared with that obtained by the proposed 2005 West Coast, South Island Trawl Survey, to estimate selectivity of commercial gear. Given that stargazer are landed head-off, it will not be possible to measure total length. It is therefore necessary to derive a relationship between total length and the alternative measurement taken in sheds (e.g. Pectoral origin to caudal fin), to make the necessary comparisons. Age structure will then be derived from the agelength-key developed from specimens collected during the trawl survey. The proposed research would be cost-effective as stargazer could be added to the existing catch sampling programme for john dory, gurnard and snapper (as well as that proposed for TAR7).

Objective 2

Otoliths for the earlier surveys have already been read. Owing to the difficulty in reading stargazer otoliths, it would be prudent to use the previous reader of the survey otoliths for this objective.

Objective 3

The initial aim of this objective is to produce an estimate of stock status, based on West Coast South Island Trawl surveys up to and including 2003, in time for the Fisheries Assessment Plenary in 2005. Having developed the model, the assessment will be revised towards the end of 2005, incorporating the results (age composition and relative biomass) from the 2005 survey (March 2005), and estimates of selectivity based on commercial shed sampling.

Strategic Relevance

The objective of this project is consistent with Strategic Objectives iii and v of 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:

• STA 7

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