The biggest commercial scallop fishery in Western Australia is the Shark Bay Scallop Managed Fishery. We manage it by limiting entry, and through seasonal and area openings and closures, gear controls and limits on crew numbers. There is also a daily catch-rate level at which fishing for scallops must stop.
These controls are designed to keep commercial fishing ‘effort’ (the amount of fishing) at levels that will maintain sufficient spawning stock and achieve optimal yields.
The latest assessments show that scallop breeding stock levels are adequate and the amount of fishing is acceptable.
In 2011 a catch-share arrangement between prawn and scallop boats was also introduced. In Shark Bay, prawn boats can take 30 per cent of the scallop catch.
We work with the industry to monitor recruitment (addition of young scallops to the population) and other factors so we can predict where and when to catch scallops.
In recent years, the focus has been on fishing pre-spawning scallops when the meat size and quality is at its best and fishing to a specified catch-rate level.
In Shark Bay we also close the scallop fishery for the key spawning period. We then determine the amount of stock that can be harvested after the closure to retain carry-over of some scallop stock for the next year as a buffer against low recruitment. Although this was done in 2011, abnormal environmental conditions in Shark Bay in 2011 and into 2012 have resulted in very low scallop numbers throughout Shark Bay.
For more information, see Shark Bay Prawn and Scallop Fisheries Management Paper No. 235.
Research and monitoring
Scallop stocks can be variable depending on environmental factors such as the strength of the warm Leeuwin Current, which flows south.
Researchers are aiming for a better understanding of the variations in recruitment and influencing factors. Collection of satellite data on the Leeuwin Current is continuing, and water temperature data for Shark Bay is being collated to further investigate these influences on stocks.
To manage the fishery, we monitor stock status. Skippers complete daily log books, and these, with pre-season recruitment surveys and in-season surveys of size composition, provide the information needed.
Status of commercial scallop fisheries 2011
Abrolhos Islands and Mid West Trawl Managed Fishery
Shark Bay Scallop Managed Fishery
South Coast Trawl Fishery
We also obtain information on the quality of scallop meat to optimise the value of the scallops harvested.
Our Research Division carries out daily monitoring (real-time management) of the scallop fleet’s catch and effort to provide advice on when to close areas based on catch-rate levels.
In addition, an annual survey is carried out in November, which, together with existing detailed biological knowledge, enables an annual catch forecast to be made.
The data is also used as the basis for management arrangements in the following year.
A Fisheries Research and Development Corporation project on research into prawn/scallop gear interactions, scallop and prawn larval movement patterns in Shark Bay and potential effects of area closures in scallop/prawn management was completed in 2012.