Background

The Eastern Zone orange roughy fishery is based on the largest spawning aggregation found in  Australian waters since commercial fishing began in 1988.   

A joint CSIRO/industry acoustic survey of the St Helens and St Patricks Head spawning aggregations in  1999 found the biomass to be between 7-13% of that estimated for 1990. At this estimated level of  depletion it was recommended that scientific advice for management of the fishery should move towards  a full management strategy evaluation. In the mean time it was recommended that a suitable  management performance criterion would be to manage the fishery such that a measurable increase in  biomass could be obtained. It was agreed that this required extensive monitoring of the winter spawning  aggregations through a time series of quantitative acoustic surveys.    

In 2003 a monitoring program for the Eastern Zone was outlined by the industry in conjunction with the  Deepwater Assessment Group. The three year (2003-2005) monitoring plan undertook to temporarily  close the St. Helens spawning ground and conduct annual acoustic surveys of both St Patricks and St  Helens fishing grounds during the winter spawning aggregations using industry vessels with  hull-mounted 38kHz echosounder. These annual surveys were to highlight whether major changes in  spawning time, dynamics or school size were occuring.   

During 2006, a multi-frequency towed body survey was undertaken to provide a more quantitative  assessment of the status of the stock with an associated full stock assessment involving new age data.  The last quantitative assessment occurred in 1999 leaving 7 years to detect if rebuilding had taken place  with the best known quantitative surveying method available.  This is expected to provide the best  estimate of the current biomass of this roughy stock.

Need
Regardless of the outcomes of the 2006 assessment incorporating the MUFTI survey results, there  needs to be ongoing monitoring of the Eastern Zone orange roughy stocks.  Even if the current biomass  is estimated not to have rebuilt to more than 20%, thereby causing a zero targeted TAC under the  current Harvest Control Rules, industry members stress that they are committed to the long term  rebuilding and sustainable harvest of the stocks.  A critical part of this goal is that ongoing reliable information is continued to be collected.  This prevents  situations such as exists in the eastern gemfish stocks where monitoring and the time series of CPUE  data has stopped and currently prevents knowing the status of the stocks.  

One of the most cost-effective ways of continuing the collection of biological and acoustic biomass  information is to maintain the industry survey of the spawning aggregations.  This proposal is designed  to continue this time-series of information during 2007 and 2008.  The Eastern Zone orange roughy stock is theoretically in a recovery phase where stocks should be  building rather than declining. The deep-water assessment group has identified the need to carry out low  level, low cost monitoring of the eastern zone stock to:

i.                  guard against unexpected collapse of the stock in case the recovery projections are wrong.

ii.                to build up a long enough time-series to enable changes in stock to be detected.

iii.               provide a baseline of information upon which a high precision deep-water towed body acoustic  survey can be based.

Objectives

1            Carry out an acoustic survey of St Helens Hill  to provide a quantitative snapshot biomass estimate  of the main spawning aggregation based on 38kHz hull mounted echo-sounder data and established  echo-integration techniques. These are a repeat of the CSIRO 1990–1999 time-series survey lines.  

2            Provide a quantitative snapshot biomass estimate (including an estimate of error) of the main  spawning aggregation on St Patrick's Head based on 38kHz hull mounted echo-sounder data and established echo-integration techniques.  

3            Investigate the distribution of orange roughy over the greater St Helens / Patricks Head region  

4            Study school dynamics of main spawning aggregation throughout the survey period.  

5            Collect biological measures of length, sex, stage and otoliths on both St Helens and St Patrick's  Head