Bottom Fishery Impact Assessment Standard Draft April 2009 Contents



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6.Mapping of Bottom Fishing Effort


SPRFMO bottom fishing interim measure 2 requires participants to constrain fishing to within areas where fishing is ‘currently occurring’:


Bottom fisheries: In respect of bottom fisheries, Participants resolve to:

2. Not expand bottom fishing activities into new regions of the Area where such fishing is not currently occurring.

(SPRFMO 2007a)


At the 4th SWG meeting, areas where fishing is ‘currently occurring’ was defined as any area fished by at least one tow or set over the calendar years 2002 - 2006. In adopting the interim Benthic Assessment Framework in 2007 (SPRFMO 2007c), it was agreed that these areas are to be mapped as a historical bottom fishing footprint comprising all 20 minute latitude x longitude grid blocks (Lat/Lon, chart datum WGS84, unprojected) fished by at least one bottom fishing tow or set over the years 2002 - 2006.

Bottom fishing footprint maps are to be prepared using individual tow-by-tow data submitted by Participants for all historic bottom fishing operations. These data should be submitted to the Secretariat in accordance with the SPRFMO Data Standards for these fishing methods (SPRFMO 2007b), including start and end positions of individual tows or sets at a minimum resolution of 1/10th degree. Confidentiality of these data are protected under the SPRFMO standards for data exchange.

The SPRFMO Secretariat, in cooperation with the SWG, will develop and maintain electronic geospatial maps of joint bottom fishing effort for all Participants in bottom fisheries in the SPRFMO area over 2002 - 2006. Blocks will be standardized to begin on whole degrees of latitude and longitude. An example of such a map is shown in Figure 2, based on New Zealand bottom trawl tow positions.

Different bottom fishing methods have different levels of expected impact (Chuenpagdee et al. 2003), with mobile gears such as bottom trawling (benthic or bentho-pelagic trawling) or dredging ranked as having the highest impact, and stationary gears (such as bottom lining) having lower impact (see Section 4.6 - Hierarchy of Bottom Fishing Impacts). Bottom fishing effort and footprint maps should therefore be prepared separately for each of the main bottom fishing methods: trawling, dredging, lining, stationery netting, potting and trap fishing.

Geospatial databases used to prepare bottom fishing effort maps for each of the bottom fishing methods should include the following data for each individual fishing event:


  • Flag of the vessel which conducted the fishing event.

  • Year of the fishing event.

  • Start and end lat / lon for each individual set or tow.

  • An appropriate index of effort for each event (such as: trawls - length or duration of tow; bottom longline lines - line length and number of hooks; drop lines - number of hooks).


Figure 2. Example of a portion of the SPRFMO area bottom fishing footprint over the period 2002 - 2006 based on New Zealand bottom trawl data showing presence or absence of bottom trawling in 20-minute blocks (small boxes) within eight larger fishing regions (large boxes). Bathymetric contours between 200 m and 2,000 m within the SPRFMO convention area are shown.


Individual fishing position data should be submitted for all historical fishing events, including prior to 2002, and for all future bottom fishing events as part of the annual data submission process. In addition to preparing the ‘currently fished areas’ bottom footprint maps by method for the 2002 - 2006 reference period, this will enable maps to be prepared as and when required to evaluate fishing effort distribution and impact levels for other historical periods, or for fishing which occurs after 2006.

7.Mapping of Vulnerable Marine Ecosystems


Assessments prepared under this standard are required to determine whether proposed bottom fishing activities will have significant adverse impacts on “areas where vulnerable marine ecosystems are known to occur or are likely to occur based on the best available scientific information.” (bottom fishing IM 6, SPRFMO 2007a). This requires mapping of available data on the known or likely distribution of VMEs in the SPRFMO area. There a number of steps towards mapping VMEs in the SPRFMO area:

  • Mapping of known or predicted underwater topographic features, particularly seamounts, which may support vulnerable benthic species and ecosystems.

  • Mapping of fishing positions observed to contain ‘evidence of VMEs’, as defined in the rapid VME evidence assessment protocol in this standard, and of scientific observer data on benthic bycatches.

  • Mapping of seabed biodiversity data from research surveys, underwater visual images or scientific sampling programmes.

  • Analysis of the above information to identify, designate and map areas which are known or likely to contain VMEs, and which require protection from fishing impacts.

7.1Mapping of Underwater Topographic Features


UNGA Resolution 61/105 and the SPRFMO interim measure both identify seamounts as areas of particular concern regarding potential impact of fishing on VMEs which may occur on such features. The FAO deep-sea guidelines extend this to list a number of underwater topographic features or habitats which may contain VMEs, including summits and flanks of seamounts, submerged edges and slopes, guyots, banks, knolls, hills, canyons, trenches, hydrothermal vents and cold seeps (FAO 2008, Annex 1).

The SPRFMO SWG has requested the Secretariat to include data on such features in the SPRFMO Geospatial Database. Primary sources of such data include:



  • The global database of predicted seamount features produced by Kitchingman & Lai (2004).

  • The database of validated and cross-checked seamount features occurring in the SPRFMO Area produced by Allain et al. (2008).

  • Available bathymetric grid data for the South Pacific region from the General Bathymetric Chart of the Oceans (GEBCO), and for the Tasman Sea area from GeoScience Australia.

  • High resolution bathymetric data which may be collected by industry during fishing operations in the SPRFMO Area.

The bathymetric data sets should be used in geostatistical analyses coordinated by the SWG to detect and delineate seabed features with particular profile, slope, depth and elevation which characterise features which are likely to support VMEs. Such features should then be added into the SPRFMO geospatial database of underwater topographic features which may support VMEs.


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