New research into the handling practices of Blue Swimmer Crabs (Portunus armatus) will help fishers pursue higher-value, live markets for their catch.

By Catherine Norwood

With live crabs fetching up to double the price of green or cooked crabs at various times of the year, a new handling guide for Blue Swimmer Crabs aims to help fishers tap into this market and get the best possible returns from their catch.

The guide is the result of an FRDC-funded research project led by Paul Exley at the Queensland Department of Primary Industries.

Paul says catches of Blue Swimmer Crabs have been declining in NSW, and quotas have been tightened. As a result, fishers have been keen to explore higher-value markets to maintain their financial viability while easing fishing pressure and supporting environmental sustainability goals. 

“Some crabbers established a live supply chain prior to the COVID-19 pandemic, but the customised wet trucks used for transport ceased operating during the pandemic,” says Paul.

“So, fishers wanted to investigate how to optimise the dry transport of live crabs as an alternative. This would allow them to use regular road freight to transport live crabs to market.” 

Surviving post-harvest stress

Blue Swimmer Crabs are highly sensitive to accumulated stressors such as physical handling, air exposure, aggression and temperature fluctuations.

Paul explains that when crabs are first hauled out of the water, they are already under extreme stress, resulting in high levels of toxins in their bodies that can quickly become fatal.

“If you can get them out of the net without damage and return them straight back to water, they are able to purge the stress-related toxins through their gills. This recovery step is critical to their survival.” 

Laboratory trials also tested how long Blue Swimmer Crabs could survive out of water. 

“We found that when Blue Swimmer Crabs are appropriately de-stressed and kept under quiet, damp, dark and cool conditions (22 degrees Celsius), they can survive for at least six hours out of water,” Paul says. “However, at 12 hours out of water, there was 100 per cent mortality.”

Trials showed that the less time crabs spent out of water, the faster they recovered. Providing a de-stress treatment before transport – submerging them in aerated seawater for at least three hours —significantly – improved survival rates. Chilling crabs to pacify them before transport, however, did not improve outcomes.

Paul says these findings suggest that dry transport of live Blue Swimmer Crabs is a viable option, provided transit times are relatively short and optimal conditions are maintained before and during the process.

“There is a crucial five- to six-hour window to transport live crabs without relying on costly wet trucks. Our treatment reduced mortality rates dramatically, from 77 per cent to just three per cent.” 

“This approach allows fishers to command premium prices for live crabs, boosting profitability, reducing spoilage and waste, and maximising the value of each catch.” 

To help fishers adopt these best practices, the research team developed the Live Blue Swimmer Crab Handling Guide and delivered workshops in several NSW fishing communities to promote broader uptake of the live trade.

The handling guide is available for download from the FRDC website. 

Related FRDC Project:

2018-024 Investigation and improvement of live Blue Swimmer Crab handling in NSW