Aquatic Environment and Biodiversity Annual Review 2012

AEBAR 2012: Non-protected bycatch
the full range of vessel sizes. The annual number of observed tows decreased from 3580 in 2000–01
to 1999 in 2006–07. Coverage has been spread over the geographical range of this fishery, with high
sampling throughout the west coast South Island (WCSI) and Chatham Rise fishing grounds and, less
frequently, in the Sub-Antarctic. Lower levels of sampling have been achieved in the Cook Strait and
Puysegur fisheries, and coverage was lower still around the North Island although this area accounts
for very little of the overall catch. Good observer coverage was achieved during the hoki spawning
season (July to early September), but coverage outside of this period was variable and underrepresentative
in some months in some years, especially in the Sub-Antarctic, Chatham Rise and
Puysegur fisheries.
Hoki, hake, and ling accounted for 87% (77%, 6%, and 4% respectively) of the total observed catch
from trawls targeting hoki, hake, and ling between 2000–01 and 2006–07. The remaining 13%
comprised a large range of species, especially javelinfish (2.1%), silver warehou (1.7%), rattails
(1.4%), and spiny dogfish (1.1%). In total, over 470 species or species groups have been identified by
observers, the majority of which are non-commercial species caught in low numbers.
Chondrichthyans in general, often unspecified but including spiny dogfish and basking shark, have
accounted for much of the non-commercial catch. Echinoderms, squids, crustaceans, and other
unidentified invertebrates were also well represented in the bycatch of this fishery.
Total bycatch in the hoki, hake, and ling fishery between 2000–01 and 2006–07 ranged from about 36
000 to 58 000 t per year (compared to the combined total landed catch of hoki, hake, and ling of 130
000 to 238 000 t). Estimates of total bycatch for 1990–91 to 1998–99 from earlier projects (for the
hoki target fishery alone), ranged from about 15 000 t to 60 000 t (Figure 6.7). Overall, total bycatch
increased during the 1990s to a peak in the early 2000s, and has since declined slowly. Annual
bycatch for the 1990–01 to 2006–07 period was also estimated for commercial species (QMS species
and species which were generally retained (>75%) and comprised 0.1% or more of the total observed
catch) and non-commercial species, rather than QMS and non-QMS species. Roughly similar amounts
of these two categories were caught overall, and each showed a similar pattern over time to total
bycatch.
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