Aquatic Environment and Biodiversity Annual Review 2012

AEBAR 2012: Non-protected bycatch
6.3.8. Scampi trawl fishery
In the most recent study, covering the period 1990–91 to 2009–10, the ratio estimator used to
calculate bycatch and discard rates in the scampi fishery was based on the number of trawls. Linear
mixed-effect models (LMEs) identified fishery area as the key variable influencing bycatch rates and
discard rates.
The key categories of catch/discards examined were; all QMS species combined, all non-QMS
species combined, all invertebrate species combined, javelinfish, and all other rattail species
combined.
Observer coverage in the scampi fishery has been relatively low compared with most of the other
fisheries assessed. The long-term level of observer coverage in the orange roughy, oreo, arrow squid,
southern blue whiting, and ling longline fisheries is greater than 18% of the target fishery catch (and
over 40% for southern blue whiting) whereas in the scampi fishery (and also in the jack mackerel
fishery) long-term coverage has only been about 11–12%. However, annual coverage in the scampi
fishery was greater than 10% in most years and fell below 5% only once (in 2000–01).
The annual number of observed trawls in the fishery ranged from 142 to 797, but has been over 300
trawls in most years. The number of vessels observed in each year ranged from 3 to 8 (equivalent to
33–66% of the fleet) and was very constant—5 or 6 vessels in most years. Analysis of the spread of
observer effort compared with that of the scampi fishery as a whole, across a range of variables,
indicated that this coverage was reasonably well spread. Although some less important regions of the
fishery received little or no coverage (e.g. the central Chatham Rise, where commercial scampi
fishing has only recently developed, and west coast South Island), the main scampi fisheries were
consistently sampled throughout the period examined. Vessels were mostly of a similar size, and the
small amount of effort by larger vessels was adequately covered, as was the full depth range of the
fishery and (despite highly intermittent sampling in several years) all periods of the year.
Over 450 bycatch species or species groups were observed in the scampi target fishery catch, most
being non-commercial species, including invertebrate species, caught in low numbers. Scampi
accounted for only about 17% of the total estimated catch from all observed trawls targeting scampi
since 1 October 1990. The main bycatch species or species groups were javelinfish (16%), other
(unidentified) rattails (13%), sea perch (Helicolenus spp., 8.4%), ling (7.5%), and hoki (6.1%). The
first three of these bycatch groups were mostly discarded (Figure 6.17). Of the other invertebrate
groups, unidentified crabs (1.1%) and unidentified starfish (0.8%) were caught in the greatest
amounts. When combined into broader taxonomic groups, bony fish (excluding rattails) contributed
the most to total bycatch (40%), followed by rattails (29%), rays and skates (3.5%), sharks and
dogfish (2.3%), crustaceans (2.2%), chimaeras (2.0%), echinoderms (1.6%), and cnidarians (0.6%). A
large percentage of the bycatch in these groups was discarded, and was less than 85% only for bony
fish (excluding rattails) (33%), rays and skates (67%), and chimaeras (28%).
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