Capture of protected species in New Zealand trawl and longline fisheries, 1998–99 to 2006–07

Citation

Abraham, E. R., & Thompson, F. N. (2009). Capture of protected species in New Zealand trawl and longline fisheries, 1998–99 to 2006–07. New Zealand Aquatic Environment and Biodiversity Report No. 32. 197 p.

Summary

Seabirds, marine mammals, and turtles are caught in New Zealand commercial fisheries. These captures are reported by Ministry of Fisheries observers when they are onboard fishing vessels. In this report, summaries of the captures are presented for all observed trawl and longline fishing events within the New Zealand Exclusive Economic Zone between 1 October 1998, and 30 September 2007. Where there was sufficient observer coverage within a stratum, a ratio method was used to estimate the total captures with bootstrap confidence intervals.

Captures are summarised into the following species groups: white-capped albatross (Thalassarche steadi); white-chinned petrel (Procellaris aequinocalis); sooty shearwater (Puffinus griseus); other albatross; other birds; New Zealand fur seal (Arctocephalus forsteri); New Zealand sea lion (Phocarctos hookeri); Hector's and Maui's dolphin (Cephalorhynchus hectori, Cephalorhynchus hectori maui); pilot whale (Globicephala melas); other dolphin; other seals; other marine mammals; and turtles. The captures are reported by fishery, which is based on the method (trawl, bottom longline, and surface longline) and the target species. The report contains time series and maps of the captures.

In the 2006—07 fishing year there were 212, 187, and 58 birds observed caught in trawl, surface longline and bottom longline fisheries, respectively. The birds most frequently caught were sooty shearwater, white-capped albatross, and Buller's albatross (Thalassarche bulleri), with 86, 84, and 56 individuals being observed caught, respectively. Other captures included 12 of the critically endangered Chatham albatross (Thalassarche eremita) caught in bottom longline fisheries; 30 wandering-type albatross caught in surface longline fisheries; and 1 black petrel (Procellaria parkinsoni) caught during an inshore trawl.

Estimated captures of seabirds in trawl fisheries decreased from 1930 (95% c.i.: 1563 to 2340, based on 27.7% of effort) in 2005—06 to 1272 (95% c.i.: 962 to 1641, based on 42.4% of effort) in 2006—07. This decrease was particularly marked in the squid fishery, which was well observed, where estimated catches reduced from 1251 (95% c.i.: 939 to 1627, based on 81.1% of effort) in 2005—06 to 427 (95% c.i.: 364 to 496, based on 72.6% of effort) in 2006—2007. In surface longline fisheries there were 715 birds estimated to have been caught during 2006—07 (95% c.i.: 565 to 885, based on 99.8% of effort). While this was similar to previous years, there was a large increase in birds caught in the charter surface longline fisheries, from 17 (95% c.i.: 16 to 18, based on 100.0% of effort) in 2005—06 to 176 (95% c.i.: 154 to 201, based on 100.0% of effort) in 2006—07. In bottom longline fisheries 1120 birds were estimated caught in 2006—07 (95% c.i.: 581 to 1796, based on 49.6% of effort). The high uncertainty in seabird captures in bottom longline fisheries reflects the low observer coverage of 6.1%.

In addition to the seabirds, in 2006—07, 12 New Zealand sea lions, 82 New Zealand fur seals, 11 dolphins, and 2 leatherback turtles (Dermochelys coriacea) were observed caught. There were no other seals, Hector's or Maui's dolphin, pilot whales, or other marine mammals observed caught. The estimated catch of fur seals in trawl fisheries during 2006—07 was 419 (95% c.i.: 319 to 528, based on 42.4% of effort), the lowest estimated catch during the nine years of data.

Observer coverage in inshore trawl fisheries remains low. In 2006—07 only 292 inshore trawls were observed, 0.5% of the fishery. Ten birds were observed caught during these trawls, leading to an estimated capture of 243 birds (95% c.i.: 10 to 554) from the 16.4% of the inshore fishery with sufficient observer coverage to attempt an estimate.