Estimation of inshore fish abundance off the west coast South Island using trawl surveys

Project: Estimation of inshore fish abundance off the west coast South Island using trawl surveys
Project Code: INT2004/01
Start Date: 1 October 2004
Completion Date: 30 September 2005
Vessel Use: R.V. Kaharoa, February-March 2005

Overall Objectives:

1. To determine the relative abundance and distribution of inshore finfish species off the west coast of the South Island, and Tasman Bay and Golden Bay; focusing on red cod (Pseudophycis bachus), red gurnard (Chelidonichthys kumu), stargazer (Kathetostoma giganteum) and tarakihi (Nemadactylus macropterus).

Specific Objectives:

1. To determine the relative abundance and distribution of red cod, red gurnard, stargazer and tarakihi off the west coast of the South Island from Farewell Spit to the Haast River mouth, and within Tasman Bay and Golden Bay by carrying out a trawl survey. The target coefficients of variation (c.v.’s) of the biomass estimates for these species are as follows: red cod (20-25 %), red gurnard (20 %), giant stargazer (20 %) and tarakihi (20 %).
2. To collect the data and determine the length frequency, length-weight relationship and reproductive condition of red cod, red gurnard, giant stargazer, tarakihi.
3. To collect otoliths from red cod, red gurnard, giant stargazer, tarakihi.
4. To collect the data to determine the length frequencies of all other Quota Management System (QMS) species.
5. To identify benthic macro-invertebrates collected during the trawl survey.

Rationale:

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

The species covered by this survey time series include most of the major species in the inshore trawl fishery in QMA 7. In 1999/00 the combined landings in QMA 7 for all four target species totalled about 3142 t with RCO 7 accounting for 663 t out of a New Zealand total of 5590 t; GUR 7 - 331 t out of 2429 t; STA 7 - 1184 t out of 3472 t; and TAR 7 - 964 t out of 5719 t.

Objectives 1, 2, 3 and 4

A long-term time series of fishery- independent relative abundance indices is a useful tool to monitor fish stocks and interpret fluctuations in abundance. The proposed WCSI trawl survey will maintain the valuable time series of relative abundance indices for red cod, red gurnard, stargazer and tarakihi and provide data that can be used in stock assessments. For STA 7, the survey biomass index is the major criterion in the decision rule for the STA 7 AMP. The relative biomass index for STA 7 from the 2003 survey was 827 t. 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 that the next WCSI survey be brought forward to 2005.

Information on relative abundance, size structure and growth rates of Tarakihi and Stargazer will be used for the proposed stock assessments for these two species.

Objective 5

This objective will continue with the time series of information on the community structure of benthic invertebrates in the trawl survey area (initiated during the 2003 survey), as a means of monitoring the environmental effects of fishing.

Strategic Relevance

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

Cost Recovery Information:

The percentage allocation for this project will be attributed to the following Fishstocks according to rule 9.2 of the Fisheries (Cost Recovery) Rules 2001:

• STA 7
• TAR 7
• RCO 7
• GUR 7

The project is estimated to cost between $300,000 – $400,000.