Leland, J., Butcher, P. and Broadhurst, M., 2011. Patience makes a difference. Go Fishing, 32: 75–79.

Summary

Owing to their excellent eating qualities, mud crabs and eastern rock lobster are extensively targeted by recreational fishers throughout their distributions off northern and south-eastern Australia, respectively. Stocks of both species are managed by legal minimum sizes, bag limits and in some cases, gender restrictions; all of which result in varying proportions of catches being released. Two important questions concerning such release are: how many individuals survive and, for those that do, are they negatively impacted in any way?

We aimed to answer these questions for both species released after capture by common recreational fishing gears and methods during two experiments near Coffs Harbour. In the first experiment, mud crabs were targeted using hoop nets and three types of traps; all repeatedly set for three, six and 24 hours. Crabs were removed from the gears, assessed for damage and then individually released into cages for monitoring (along with undamaged ‘controls’) over three days. Some crabs were also sampled for blood to assess their stress.

In total, 690 crabs (54–132 mm carapace length; CL) were caught and caged. All individuals survived with no apparent stress, and only 18% were damaged; which typically involved lost swimmers and claws during removal from those gears with mesh netting, and especially hoop nets set for 24 hours.

During the second experiment, eastern rock lobster were caught in two types of conventional traps set for 24 hours, and also hand collected by free divers over up to three hours. After capture, all lobsters were transferred to cages and tanks, where they were sampled for stress and monitored along with controls for three months.

Like the mud crabs, all of the released lobsters (total of 158 measuring 49–125 mm CL) survived. But, while very few of the trapped lobsters were damaged, more than half of the hand-collected individuals were missing up to four legs and either one, or both, antennae. Further, all of the hand-collected lobsters had elevated stress immediately after capture, and lost weight during the monitoring period.

The two experiments strongly support the release of mud crabs and eastern rock lobster as a means for regulating exploitation of their stocks. However, damage to both species (and possible impacts beyond those examined here) might be limited through careful handling, and especially avoiding the antennae and legs of lobsters during collection by hand. Setting and regularly checking hoop nets over short periods (e.g., three to six hours) would similarly limit damage to mud crabs.