Aquatic Environment and Biodiversity Annual Review 2012

AEBAR 2012: Non-protected bycatch
Figure 6.11: Annual estimates of fish bycatch in the southern blue whiting trawl fishery, calculated for
QMS species, non-commercial species (OTH), and overall (TOT) for 2002–03 to 2006–07 (in black). Also
shown (in grey) are estimates of bycatch in each category (excluding QMS) for 1990–91 to 2001–02
(Anderson 2004a). Error bars show the 95% confidence intervals. Note: the 98–00 fishing year
encompasses the 18 months between September 1998 and March 2000, the transitional period between a
change from an Oct–Sep to Apr–Mar fishing year. The dark line in the bottom panel shows the total
annual estimated landings of SBW (Ministry of Fisheries 2009).
Total annual discard estimates between 2002–03 and 2006–07 ranged from about 90 t to 250 t per
year. Discard amounts sometimes exceeded bycatch due to the large contribution of the target species
(50–230 t per year) to total discards – the result usually of fish losses during recovery of the trawl.
Discarding of commercial species was virtually non-existent in most years and discards of noncommercial
species amounted to only 10–50 t per year. The main species discarded were southern
blue whiting, rattails and porbeagle sharks. Total annual discard estimates for 1990–91 to 2001–02,
from earlier reports, were mostly between about 140 t and 750 t but were about 1200 t in 1991–92
(Figure 6.12). Discards of southern blue whiting (and therefore total discards) decreased substantially
at the end of the 1990s and have remained at low levels, below 250 t per year, at least up until 2006–0
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