Selectivity, Unaccounted Mortality and Their Impact on the Resource

The landed catch is not the only source of fishing mortality associated with fishing activities.  The various other sources of unaccounted or collateral fishing mortality, include: illegal, unreported and mis-reported fishing (IUU); ghost fishing,  discarding of unmarketable by-catch; fish dying after escaping from fishing gear; increased risk of predation, etc.  Developing selective fishing gears to enable unwanted catch to escape is an effective way of reducing the size of any unmarketable by-catch and therefore potential discard mortality.  However, its efficacy in reducing unaccounted fishing mortality depends the assumption that those fish that escape do so unharmed.  Therefore, if escape mortality is sufficiently high, the assumed benefits of reducing fishing mortality through a reduction in discards may be substantially overestimated, or even negated.  This presentation will review unaccounted or collateral fishing mortality in context with selective fishing.   In particular, it will highlight recent and ongoing work addressing discard and escape mortality, and discus whether it is feasible to minimise them, or optimise the relationship between them, to ensure the efficiency and sustainability of selective fisheries.