Summary of the capture of seabirds, marine mammals, and turtles in New Zealand commercial fisheries, 1998–99 to 2008–09

Citation

Abraham, E. R., & Thompson, F. N. (2011). Summary of the capture of seabirds, marine mammals, and turtles in New Zealand commercial fisheries, 1998–99 to 2008–09. New Zealand Aquatic Environment and Biodiversity Report No. 80. 155 p.

Summary

A summary is presented of all captures of seabirds, marine mammals, and turtles during trawl, longline, and setnet fishing within the outer boundary of the New Zealand Exclusive Economic Zone (EEZ), between 1 October 1998 and 30 September 2009. Ministry of Fisheries observers record captures of seabirds, marine mammals, and turtles, and these data, along with information on fishing effort, are used for estimating total captures. Protected species captures reported by fishers are also summarised. In 2008—09, the Ministry of Fisheries observer programme introduced a project to increase observer coverage of inshore fishing, including setnet and trawl fisheries. Captures reported from this project were included, greatly increasing observer coverage for inshore trawl and setnet fisheries.

Within this report, captures are divided into the following groups: sooty shearwater (Puffinus griseus), white-chinned petrel (Procellaria aequinoctialis), white-capped albatross (Thalassarche steadi), other al- batrosses, other birds, New Zealand sea lion (Phocarctos hookeri), New Zealand fur seal (Arctocephalus forsteri), dolphins, whales, and turtles. Captures are also reported by fishery, based on method (trawl, bottom longline, surface longline, and setnet), target species, and vessel size for bottom longline vessels. The report contains time series and maps of the observed and estimated captures.

In the 2008—09 fishing year, there were 465, 66, 34, and 21 seabirds observed caught in trawl, surface longline, bottom longline, and setnet fisheries, respectively. Observed captures in trawl fisheries, surface longline fisheries, and setnet fisheries increased compared to the 2007—08 year, and observed captures in bottom longline fisheries decreased. The most frequently caught seabird species were sooty shearwater, white-chinned petrel, and white-capped albatross, with 132, 90, and 81 observed caught, respectively. In addition to seabirds, 92 New Zealand fur seals, 3 New Zealand sea lions, 20 common dolphins (Delphinus delphis), 2 pilot whales (Globicephalus mela), 2 leatherback turtles (Dermochelys coriacea), 1 Hector's dolphin (Cephalorhynchus hectori), and 1 green turtle (Chelonia mydas) were observed caught during 2008—09.

Estimates of captures made using statistical modelling were available for some species groups and fisheries. These estimates were able to account for some non-representivity of observer coverge. Model estimates were avaliable for seabirds in trawl, surface longline, large vessel (over 34 m in length) bottom longline fisheries, and snapper bottom longline fisheries in north-eastern New Zealand. Model-based estimates were also available for common dolphin captures in the North Island jack mackerel fishery, fur seal captures in trawl fisheries, and sea lion captures in trawl fisheries. In fisheries, areas, and years where model based estimates had not been made, and where there was sufficient observer coverage, a simpler ratio-estimation method was used to estimate total captures.

The estimated captures of seabirds in trawl fisheries increased to 1601 (95% c.i.: 1351 to 1949, based on 43.2% of effort) in 2008—09 from 1111 (95% c.i.: 887 to 1431, based on 44.1% of effort) in 2007—08. During 2008—09, the estimated total seabird captures in surface longline fisheries was 591 (95% c.i.: 351 to 987, based on 100.0% of effort), and the estimated seabird captures in bottom longline fisheries was 1320 (95% c.i.: 778 to 2414, based on 69.6% of effort). In both surface and bottom longline fisheries, estimated captures of seabirds in 2008—09 were similar to the estimated number of captures in 2007—08. In both cases, there were increases in the mean number of estimated captures, but the increases were not significant.

The estimated number of New Zealand sea lion interactions in all trawl fisheries for 2007—08 was 74 (95% c.i.: 31 to 147, based on 41.0% of effort); the lowest estimated number of interactions since 2002—03. In the Auckland Islands squid fishery, sea lion exclusion devices (SLEDs) are used. These devices prevent sea lions from entering the cod end, and are designed to allow them to escape from the net. The estimated number of interactions is an estimate of the number of sea lions that would have been caught if no SLEDs had been fitted. Model estimated captures of fur seals in trawl fisheries were 550 (95% c.i.: 338 to 826, based on 42.8% of effort), the second lowest estimated number of captures in the eleven year period covered by the summary.

Data from setnet fisheries were included in the report. In 2008—09, there were increased observations of setnet fishing as part of the inshore coverage programme. Observer coverage reached 13%, with 2008—09 being the first year that coverage of setnet fishing exceeded 1%. Observed captures in setnet fisheries in 2008—09 included 8 Cape petrels, 5 sooty shearwaters, 5 yellow-eyed penguins, 1 Hector's dolphin, and 1 fur seal. The Hector's dolphin was caught in a setnet targeting tarakihi, south of Kaikoura. A 3.5 m white-pointer shark was also caught in a setnet targeting butterfish, to the south-east of Stewart Island.