Bottom Fishery Impact Assessment Standard Draft April 2009 Contents

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5.1Detection of ‘Evidence of VMEs’

SPRFMO bottom fishing interim measure 7 is intended to apply in cases of unexpected interactions with VMEs in areas where no other pre-determined management action has been implemented to prevent significant adverse impacts. IM 7 specifies an immediate 5 nautical mile move-on provision when ‘evidence of VMEs’ is encountered and is intended to be applied at sea during individual fishing operations. A number of key principles, constraints and requirements need to be considered when designing a protocol to detect evidence of a VME:

Key Principles for a Protocol to Identify ‘Evidence of a VME’

  • Evidence of a VME needs to be defined in a way which makes this measure implementable at sea. Such evidence must necessarily be defined in terms of benthic by-catch made during individual bottom fishing operations (e.g. trawl tows or line sets).

  • Evidence should be derived from species which possess the characteristics considered to make them vulnerable to deep-sea bottom fisheries, as defined in the FAO deep-sea guidelines. Emphasis should be placed on taxonomic groups which may contribute to forming VMEs (FAO 2008, Annex 1).

  • The protocol should be rapid to implement at the end of each tow or set, and should not require a high level of taxonomic identification expertise. Relatively few, higher order taxonomic groups should be used, rather than individual species or genera.

  • Some measure of quantity needs to be incorporated to allow the protocol to distinguish between a sporadic capture of a single organism which may not indicate evidence of a VME and a quantity of by-catch which is considered to constitute evidence of a vulnerable ecosystem.

  • Higher ranks / scores should be accorded to species considered more vulnerable to fishing impacts, or which are considered to be strong indicators of VMEs. The protocol should also incorporate some measure of biodiversity, to accord higher scores to bycatches of many species, as opposed to a single species.

Designation of Taxa Constituting Evidence of a VME

The FAO deep-sea guidelines (paragraph 42) identify characteristics of species or communities that should be considered to be vulnerable to impacts of bottom fishing. Annex 1 of the guidelines provides examples of taxonomic groups of organisms which have those characteristics, and which could contribute to forming VMEs (FAO 2008). From these guidelines, taxonomic groups selected for incorporation into a SPRFMO VME Evidence protocol should be those which are:

  • Functionally significant to the community or ecosystem, either by creating structural complexity that other species may utilize as habitat, or by providing some unique function that supports the community;

  • Low productivity species due to life history traits such as slow growth, high longevity, low fecundity, or unpredictable recruitment;

  • Unique, rare or endemic to a small area;

  • Fragile to bottom fishing gear;

  • Retained to some degree, and previously observed, in bottom fishing gear;

  • Quickly identifiable by scientific observers onboard without the aid of complex taxonomic identification guides or equipment.

Taxonomic groups which meet the above criteria, and which are proposed for inclusion in the SPRFMO VME Evidence protocol (Parker et al. in press) are listed in Table 1. Taxa such as bryozoans and feathery hydroids have been excluded from this list because they are generally not retained by bottom fishing gears.
Weight Thresholds Constituting Evidence of a VME

Bottom trawls are inefficient at sampling benthic organisms, with poor selectivity for some benthic species of concern such as fragile coldwater corals. Bottom trawl benthic bycatches are therefore likely to consist of low weights, even in areas of abundant VME taxa. However, bycatches of a single retained benthic organism may not constitute evidence of a VME. It is therefore necessary to determine appropriate bycatch weight thresholds which indicate likelihood of interaction with a actual VME, while avoiding triggering a move-on response, and unnecessary spread of fishing effort, in areas with sparse benthic organisms. Such threshold weights should be based on analysis of actual bottom fishing bycatch data for the method and region to be fished, to integrate some measure of gear selectivity for the chosen taxa.

Proposed threshold weights for SPRFMO Area bottom trawl fisheries were determined for each taxonomic group in Table 1 based on the cumulative distribution of bycatch weights observed in 19,000 bottom trawl tows in the New Zealand deep-sea trawl fishery from 1998 - 2002, an exploratory fishing period when VME encounters would be expected to have been most frequent (Parker 2008, Ministry of Fisheries 2008, Parker et al. in press). The median of the cumulative weight frequency distribution for by-catches of each taxonomic group is proposed as an appropriate threshold to distinguish between bycatches of isolated or spares benthic organisms, and bycatches which constitute evidence of an actual VME (see Parker et al. in press). The resulting bycatch threshold weights for the proposed VME evidence taxa are shown in Table 1.
VME Indicator / Vulnerability Rankings

In addition to threshold weights, a relative weighting score should be assigned to each taxonomic group based on understanding of the respective vulnerability of each taxon. Taxa that have life history characteristics making them vulnerable to fishing activities, or which are strongly indicative of VMEs, should be allocated a higher score. Other groups, less vulnerable themselves but which are indicators of habitats suitable for vulnerable species, could be included, but with a lower score.

Level of biodiversity is also an important measure of the vulnerability of VMEs, and of the importance of protecting such areas. In addition to evaluation of individual taxa, some measure of biodiversity should be included in the VME evidence protocol. This is achieved in Table 1 by allocating a score of 3 to taxa considered to be vulnerable and likely indicators of VMEs, while allocating a score of 1 to additional taxa which are less vulnerable, but which may indicate suitable VME habitats, and which contribute to biodiversity. The combined scoring process ensures that a single large catch of a vulnerable taxon will trigger the move-on rule, but that bycatch of several vulnerable groups, even if below the threshold weights, will also constitute evidence of a VME.

VME Evidence Protocol
The proposed taxonomic groups to be used for identifying evidence of interaction with a VME, proposed threshold weights for these taxa and proposed VME ranking scores are summarised in Table 1.
Table 1. List of taxonomic groups which should be used assessed to identify evidence of fishing on a VME in the South Pacific Ocean (Parker 2008, Ministry of Fisheries 2008, Parker et al. in press).

Taxonomic Group

Common Name

Bycatch Weight Threshold (kg)

VME Rank / Score

Phylum: Porifera




Phylum: Cnidaria

Class Anthozoa:

Order: Actiniaria





stony corals




black corals




soft corals




sea fans




sea pens



Class: Hydrozoa:

Order: Anthoathecatae

Family Stylasteridae




Unidentified corals




Phylum: Echinodermata

Class: Crinoidea

sea lilies



Order: Brisingida

armless stars



(Note: Taxa associated with seep and vent systems should be included in future revisions if bottom fisheries intend to fish in the vicinity of seep and vent systems.)

The taxa, threshold weights and VME scores in Table 1 are combined into a proposed rapid assessment protocol, as detailed on the VME Evidence Form, shown in Appendix A. This provides a simple, rapid procedure to determine if a particular benthic bycatch is likely to be from a VME, based on a few key taxonomic groups. In incorporating the vulnerability rankings and threshold weights into a real-time protocol for use at sea, available information is synthesized on the simple scoring form, incorporating the weights of each vulnerable group, presence of habitat indicators and an index of taxonomic diversity into a single score. Under this protocol, a score of 3 constitutes evidence of a VME, and should trigger a move-on.

Implementation of the Evidence of a VME Protocol
Effective implementation of a VME Evidence Protocol for each individual bottom fishing operation in the SPRFMO Area can best be achieved by 100% coverage by suitably trained and experienced observers, as is required by the SPRFMO interim measures (IM 9) for bottom fisheries.

To aid in accurately identifying specimens from these groups, a classification guide specific to the taxa to be monitored under the VME Evidence Protocol, utilizing non-technical and visually apparent characteristics to rapidly distinguish the groups (Tracey et al. 2008), is attached in Appendix B.

Vessels encountering evidence of a VME, as defined in the above protocol, must cease fishing within 5 nm of the fishing site, and report the position and details of VME evidence to the SPRFMO Secretariat. The fishing position should be defined as the location where hauling of the net commenced for that tow2.

The SPRFMO Secretariat should regularly inform all other participants of the positions of sites with evidence of VMEs. Participants will be expected to take such information into account during preparation or updating of bottom fishery impact assessments.

Participants must indicate in their assessments what action will be taken in relation to avoidance of sites showing evidence of a VME during subsequent fishing operations by their vessels.

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