A review of the basis by which RFMOs have determined VME encounter thresholds by taxa and gear-types

The detection of a VME during fishing operations is typically based on the presence of an unusually high catch of VME indicator taxa in the catch that exceeds an agreed threshold level.

Different objectives, such as determining if a VME is present or determining whether a significant adverse impact has occurred, are likely to require quite different encounter thresholds.

Relative differences in thresholds are likely for evidence of the existence of a VME (low), evidence of a significant adverse impact at a local scale (medium) and evidence of a significant adverse impact at the scale of the total area of VME habitat (high).

Encounter thresholds are part of an overall management approach to VMEs, including closed areas and gear restrictions, this means that it is essential that the context and objectives of individual thresholds are clearly articulated.

An important challenge in setting thresholds is the management decision on the level of precaution that should be applied to protecting VMEs from significant adverse impacts compared to the need to obtain sufficient information to conclude that such an impact has occurred.

Thresholds for bottom trawl, agreed in NAFO, and for demersal longline, agreed by CCAMLR, have been widely incorporated by other RFMO/As.

When considering threshold values adopted by other RFMOS it may be more appropriate to leverage the science on determining the distribution and abundance of VMEs rather than inherit the negotiated outcomes that are reflected in the prevailing regulations.