Trawl surveys were conducted to provide an index of abundance and biological information for prawn species in northern Queensland.
Tiger and endeavour prawns are a major component of the catch from commercial prawn trawlers in North Queensland and Torres Strait coastal waters. From 1998-2009 these northern prawn stocks and bycatch were monitored using fishery independent recruitment surveys. Data from these surveys in combination with commercial fisher logbook data are being used to determine a sustainable harvest level for this sector of the trawl fishery.
All of the main commercial prawn species were monitored by the surveys. The six predominant species being:
- brown tiger prawn (Penaeus esculentus)
- grooved tiger prawn (Penaeus semisulcatus)
- blue endeavour prawn (Metapenaeus endeavouri)
- false or red endeavour (Metapenaeus ensis)
- red spot king prawn (Melicertus longistylus)
- western or blue-leg king prawn (Melicertus latisulcatus).
The surveys also collected information on bycatch, interactions with species of conservation interest and other commercial species - such as blue swimmer crabs and tropical rock lobster.
How are they monitored
A research trawler was used to conduct trawl surveys at the start of the North Queensland and Torres Strait prawn trawl seasons. These surveys provided information on the size, sex and abundance of commercial prawns for each species.
Two surveys were conducted each year:
- Cooktown to Papua New Guinea waters of the Torres Strait in February
- Cape Bowling Green (south of Townsville) to Port Douglas in March
The catch rates between surveys (years) were standardised by using the same fixed sites, vessel, trawl nets, time of the season and lunar phase. These surveys provided a relative index of prawn abundance (stock size) at the start of each fishing season.
How are the data used?
During 2010 data from the surveys were utilised to complement and support an update of the tiger prawn stock assessments conducted for the tiger prawn fishery. The data was also used to support the export accreditation of the East Coast Otter Trawl and Torres Strait Prawn Fisheries under the Environment Protection and Biodiversity Conservation (EPBC) Act 1999.