Orange Roughy is a long lived deep water species found in many places around the world, including in waters off southern Australia. The species was heavily fished in the late 1980’s and early 1990’s and is now managed in accordance with the Orange Roughy Conservation Program.
At the moment, commercial fishing for Orange Roughy can only take place on the Cascade Plateau where stocks are at healthy levels. Stock health and recovery rates in other areas have been monitored using two different methods: the stock assessment and the acoustic survey. Each of these methods has been producing different estimates of stock recovery.
AFMA and industry need accurate data to manage fish stocks effectively, so the South Eastern Trawl Fishing Industry Association, in conjunction with CSIRO, undertook futher Acoustic Optical Survey in the St. Helen’s Hill area (off eastern Tasmania) in 2013. This survey is a continuation of efforts to:
- Establish an acoustic estimate of spawning stock in the eastern Orange Roughy zone; and
- Assess changes in the biology of the species, including age, length, weight and spawning potential.
In these surveys an echo sounder transducer, similar to that used by a lot of recreational boats, is attached to a commercial trawl net and echo soundings are made of the fish school below the net. Different species of fish have different reflective characteristics and fish species can be identified by the strength of the soundings. The soundings are analysed to establish the type of fish species in the area and an estimate of how many fish there are.
Orange Roughy are captured in conjunction with taking the soundings to confirm the species and provide biological samples used to estimate sex composition, age and length of the fish in that school. Some initial results from the study have shown that the average age and length of Orange Roughy within the eastern zone stock has decreased, and estimates of spawning stock size indicate that the population is increasing.
We are planning more work to continue to improve the way in which we estimate the population size and recovery rate of Orange Roughy, but based on the most recent data it does appear that Orange Roughy is bouncing back.
For more information contact Marcus Finn, Manager Trawl fishery on 6225 5433 or marcus.finn@afma.gov.au.