Estimation of the abundance of black oreo and smooth oreo in selected areas

Project: Estimation of the abundance of black oreo and smooth oreo in selected areas
Project Code: OEO2004/01
Start Date: 1 October 2004
Completion Date: 30 September 2006
Vessel Use: Subject to tender

Overall Objectives:

1. To estimate the abundance of black oreo (Allocyttus niger) and smooth oreo (Psuedocyttus maculatus) in selected areas.

Specific Objectives:

1. To estimate the abundance, with a target coefficient of variation (c.v.) of the estimate of 20-30% for smooth oreo in OEO 4 on the Chatham Rise.

Note:

The duration of this project will be 24 months, 1 October 2004 to 30 September 2006. This is to allow time for the successful tenderer to analyse the results from the abundance survey conducted late in 2004 and present them to the fishery assessment meetings during 2006.

Rationale:

General

The acoustic survey technique has been under development in New Zealand for orange roughy and oreos for a number of years. Issues that still need further work include:

• Determination of target strength of oreos and associated species
• Identification of acoustic targets
• Determination of the impact of the shadow zone on acoustic estimates
• Estimation of the absorption coefficient of sound in seawater
• Determination of the optimal survey design, particularly on hills
• Estimation of the apparently large proportion of oreos away from the main aggregations that is found in low background densities

These issues were addressed during work carried out during winter 1997 (DEOR02 and DEOE04) and November 1997 (OEO9701). An acoustic survey of OEO 3A and part of OEO 4 on the Chatham Rise was conducted during November - December 1997 (OEO9701) and of OEO 4 in September – October 1998 (OEO9801). Acoustic research conducted in 2000 and 2001 (OEO2000/01) focused on determination of target strength of oreos and associated species and species composition of oreo mark-types. An acoustic survey to estimate the abundance of smooth oreo in OEO 4 was carried out in October – November 2001 in project OEO2001/01. An acoustic survey to estimate the abundance of black oreo in OEO 3A was carried out in October – November 2002 in project OEO2002/01.

A study to investigate the feasibility of conducting an acoustic survey in OEO 1 or OEO 6 is proposed for 2003/04 in project OEO2003/01, with a pilot survey proposed for 2004/05 if the feasibility study is positive.

The following is a summary of the acoustic surveys that have provided estimates of abundance of black and smooth oreos and that have been used as inputs into the stock assessments for these species:

• 1997 – black oreo and smooth oreo in OEO 3A and 4
• 1998 – black oreo and smooth oreo in OEO 4
• 2001 – smooth oreo in OEO 4
• 2002 – black oreo in OEO 3A

The Deepwater Medium Term Research Plan discusses the need to estimate the abundance of oreos in each of the main fisheries on a regular basis. The main oreo fisheries are:

• the Southland area of OEO 1
• OEO 3A on the Chatham Rise
• OEO 4 on the Chatham Rise
• the major fisheries in the Bounty and Pukaki areas of OEO 6

The results of the 2003 stock assessment indicated that the stock of smooth oreo in OEO 4 was above BMSY, and that recent catches are sustainable, at least in the short to medium term. Based on the current stock assessments for the various oreo Fishstocks, smooth oreo in OEO 4 have the largest estimates of current biomass, the largest estimates of sustainable yield, and the largest stock size in relation to virgin biomass (and conversely the lowest level of depletion) of any of the oreo Fishstocks. Therefore, it appears that this fishery has the potential to produce the largest sustainable yield over the long term of any of the oreo Fishstocks. Moreover, based on biological and technical considerations, smooth oreo in OEO 4 appear more amenable to biomass estimation using acoustics than do oreos in the other Fishstocks.

The MFish Deepwater Medium Term Research Plan has a programme of updating the biomass indices for each of the main oreo fisheries in the New Zealand EEZ every 3 to 5 years. Two acoustic surveys have been carried out for smooth oreo in OEO 4 – in 1998 and 2001. In the early years of developing a time series of acoustic biomass indices it is important to update the indices more frequently, especially as new information is gained on the dynamics affecting the indices. Therefore, it is proposed to obtain an acoustic biomass estimate for smooth oreo in OEO 4 in 2004 – 3 years since the previous survey.

It is proposed to estimate the abundance, with a target coefficient of variation (c.v.) of the estimate of 20-30% for smooth oreo in OEO 4.

Strategic Relevance

All the objectives in this project are consistent with the Fisheries Resources goal in the Strategic Framework and Directions for Fisheries Research Contracted by the Ministry of Fisheries 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:

• OEO 4

The project is estimated to cost between $1 million - $1.5 million.