Aquatic Environment and Biodiversity Annual Review 2012

7.3.2. Distribution of Fishing
AEBAR 2012: Benthic impacts
Since 1989/90, mobile bottom fishing has been reported on one of three standardised reporting forms
(Table 7.2). Trawl Catch Effort and Processing Returns (TCEPRs) contain detailed spatial and other
information for each trawl tow, whereas Catch Effort and Landing Returns (CELRs) include only
summarised information for each day’s fishing, with very limited spatial resolution. Since 2007/08,
Trawl Catch and Effort Returns (TCERs) have been available for smaller, predominantly inshore
trawlers. These include spatial and other information for each trawl tow but in less detail than on
TCEPRs. Between 1989/90 and 2004/05, only about 25% of all mobile bottom fishing events were
reported on TCEPRs. Another 25% were bottom trawls reported on CELRs, and the remaining 50%
were dredge tows for shellfish reported on CELRs. The distribution of trawling reported on CELRs is
not the same as that reported on TCEPRs (Figure 7.8); the smaller trawlers using CELRs are much
more likely than the larger boats to fish close to the coast and target inshore species such as flatfish,
red cod, tarakihi, and red gurnard (collectively 73% of all trawl tows reported on CELRs). MPI
project BEN2012/01will update the work in BEN2006/01 producing maps of swept area and footprint
for more recent years.
Table 7.2: Attributes, usage, and resolution of spatial reporting required on Trawl Catch Effort and Processing
Returns (TCEPRs) Trawl Catch and Effort Returns (TCERs) and Catch Effort and Landing Returns (CELRs).
Year of introduction
Trawl catch and effort reporting forms
TCEPR TCER CELR
1988/89 2007/08 1988/89
Vessels using All trawlers >28 m
Other vessels as directed
Other vessels optional
Trawl tow reporting Tow by tow, start and finish
locations, speed, depth, gear
All trawlers 6–28 m unless
exempted
Tow by tow, start location,
speed, depth, gear
172
Trawlers not using TCER or
TCEPR
Shellfish dredgers
Daily summary, number of
tows, effort, gear
Spatial resolution 1 minute (lat/long) 1 minute (lat/long) Statistical reporting area
(optionally lat/long)
Baird et al. (2002) and Baird et al. (2001) described the distribution and frequency of reported fishing
by mobile bottom fishing gear (dredge, Danish seine, bottom trawl, bottom pair trawl, and mid-water
trawl in contact with the bottom) in New Zealand’s TS and EEZ during the 1990s and up to 2004/05,
respectively. They showed that fishing was highly heterogeneous (spatially), but had considerable
consistency among years; sites that were fished heavily in one year were likely to be fished heavily in
other years and vice versa. A similar but more detailed analysis was conducted for the Chatham Rise
and SubAntarctic areas by Baird et al. (2006). Tows reported on TCEPRs were included in the main
spatial analysis but some additional analysis was possible using tows reported on CELRs. Until
2006/07, many inshore vessels used CELRs and these comprised a substantial proportion of reported
trawling, even for some “deepwater” species. For instance, Cryer and Hartill (2002) estimated that, in
the Bay of Plenty, 78%, 75%, and 39% of trawl tows for tarakihi, gemfish, and hoki, respectively,
were reported on CELR forms in the 1990s. Since 2007/08, almost all trawling effort has been
reported on TCEPR or TCER forms.
Baird et al. (2011) calculated three annual measures of fishing effort: the number of tows, the
aggregate swept area (using assumed door spreads, see Figure 7.7), and the coverage (“footprint”) of
the total trawl contact. Trawls were represented spatially as tracklines between the reported start and