Aquatic Environment and Biodiversity Annual Review 2012

Total reported dredge tows
200,000
180,000
160,000
140,000
120,000
100,000
80,000
60,000
40,000
20,000
0
AEBAR 2012: Benthic impacts
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
177
Fishing Year
oysters
scallops
Figure 7.11: The number of dredge tows for scallop or oysters reported on Catch Effort and Landing Returns
(CELR) between the 1989/90 and 2007/08 fishing years (data from Baird et al. 2011 and MPI databases). Data for the
2011/12 year may be incomplete.
7.3.3. Overlap of Fishing and Predicted Habitat Classes
Baird and Wood (2010, project BEN200601) overlaid the 16-year trawl footprint up to 2004-05 on the
15-class BOMEC to estimate the proportion of each class that had been trawled (and reported on
TCEPRs). They found that the size of the footprint and the proportion of each class trawled varied
substantially between habitat classes (Figure 7.12, Table 7.3). Class O is the largest BOMEC class but
has almost no reported fishing effort. Conversely, class I is one of the smaller classes but has a larger
trawl footprint that overlaps about 70% of the total class area. Two contrasting classes, together with
their trawl footprints, are shown in Figure 7.13. The cumulative trawl footprint from Baird and
Wood’s analysis overlaps about 8% of the 4.1 million km 2 of seafloor within the New Zealand EEZ
boundary (i.e., including the Territorial Sea). However, this overlap and that for some individual
BOMEC classes (particularly coastal classes A–E) will be underestimated because of the omission of
CELR data from these analyses. This analysis is being updated for offshore (middle depth and
deepwater) trawl fisheries under project DAE2010/04, Monitoring the trawl footprint for deepwater
fisheries, and the results are expected to be available in early 2013. MPI project BEN2012/01, Spatial
overlap of mobile bottom fishing methods and coastal benthic habitats, will update the work in
BEN2006/01, particularly focussing on the overlap between fishing and habitats in the coastal zone.