Short‐term mortality of trapped and discarded Portunus armatus following ice‐slurry immersion.

Abstract: In southeastern Australia, some commercial fishers sort their catches of trapped Portunus armatus in ice slurries to pacify and facilitate discarding sub‐legal and ovigerous individuals, but with unknown mortality. To estimate mortality, during 90 trap lifts, 101 and 110 small P. armatus were sorted dry and in ice slurries, respectively (over 0.5–10.0 min). All discards were individually caged and monitored with 32 similar‐sized control animals (caught by benign methods) for 48 hr. Irrespective of handling, only eight discarded P. armatus were physically damaged. None of the controls died, compared with 1 and 13% of the dry‐ and ice‐slurry sorted conspecifics. The probability of mortality was estimated at 0.005 immediately after emptying the traps and remained temporally constant for dry‐sorted individuals, but was positively associated with time in the ice slurries, reaching 50% at 9 min. Minimising sorting in ice slurries to <2 min should cause minimal impact to P. armatus, although other unaccounted mortalities (e.g., predation) and sublethal effects warrant assessment. [ABSTRACT FROM AUTHOR]