Fishery By-products: Squid, Bugs, Cuttlefish And Scallops

“Byproduct is the term used for harvested species that are not the main target of a fishery, but nevertheless are commercially valuable,” says CSIRO Marine and Atmospheric Research scientist, Dr David Milton.

“These byproduct species need to be managed sustainably along with prawns, which are the main target species in the fishery,” Dr Milton says.

“Little research has been done on byproduct in the NPF or other tropical prawn trawl fisheries. We therefore lack sufficient data for population assessments, or to evaluate options for their management.”

The two-year study involves a research partnership between CSIRO, the Australian Fisheries Management Authority and commercial fishers in the NPF. It will draw on data from historical studies in the NPF, fisheries observer and bycatch monitoring programs and voyages of the Marine National Facility RV Southern Surveyor.

Computer models will be developed to examine the response of byproduct populations to different prawn management scenarios and to guide the management of fishing effort on each byproduct group, while ensuring optimum catches of prawns.

For example, most of the squid catch in the NPF is thought to occur during winter in the south-western Gulf of Carpentaria when they aggregate to breed. The squid lay their egg cases on the seabed, making them particularly vulnerable to trawling. A management response might seek to avoid catching too may squid at this critical time, or to avoid key areas used by squid.

“Management strategies may include controls on fishing of byproduct species guided by species-specific stock assessments, or spatial and temporal closures guided by the identification of key areas and seasons and when these byproduct groups are most vulnerable,” Dr Milton says.

“We will also identify information gaps – such as spawning times and locations, and ecology – and options for dealing with data-poor situations, including research priorities and the feasibility of using fishery logbooks records to estimate annual catches of individual byproduct species.”

New approaches developed in the study will be of value to other Australian trawl fisheries including the Torres Strait prawn trawl, east coast prawn trawl and WA prawn trawl fisheries. The study is being funded by the Australian Government through the Fisheries Research and Development Corporation.