There are certainly some omissions in the article which had me concerned. The
full abstract is below. This gives a far better level of detail of how they
arrived at the total number of deaths.
" Crude extrapolation suggests that total mortality is c. 18 000 (8000-31 000)"
I must admit to being surprised by this. I spent some time on a trawler when I
worked at NSW Fisheries and never saw anything like this ever happening.
Cheers
Graham Turner
ABSTRACT
Many seabirds are killed or injured by fishing gear, contributing to the high
proportion of threatened seabirds. This study estimates the impact of the South
African deep-water hake Merluccius spp. trawl fishery on seabirds. At least 30
birds were killed in 190 h of dedicated observations of trawl warps during 2004
and 2005. Most were killed when their wings were entangled around the trawl
warp and they were dragged under by the force of the water passing over the
warp. Albatrosses were killed most frequently: shy albatrosses Thalassarche
cauta (43% of all birds killed) and black-browed albatrosses Thalassarche
melanophrys (37%), with smaller numbers of white-chinned petrels Procellaria
aequinoctialis (10%), Cape gannets Morus capensis (7%) and sooty shearwaters
Puffinus griseus (3%). Mortalities occurred mainly during dumping of fishery
wastes, and were more frequent in winter, when more birds attended fishing
vessels. Average mortality rates were 0.56 (95% confidence interval 0.32-0.82)
birds killed per hour during dumping in winter, 0.21 (0.07-0.38) during dumping
in summer and 0.09 (0.02-0.19) when not dumping in winter. No birds were killed
in the absence of dumping in summer. Albatrosses suffered a disproportionately
high mortality rate, with 15% of birds dragged under drowning, compared with 4%
of all other species. Deaths resulting from entanglement in fishing nets mainly
affected Cape gannets M. capensis, and occurred at an average rate of 3.0
(0.9-5.4) birds per 100 trawls (n=331 trawls). Serious warp incidents were
independent of age among albatrosses, but there was a tendency for immature
gannets to have a higher interaction rate than adults. Crude extrapolation
suggests that total mortality is c. 18 000 (8000-31 000) birds per year, of
which 85% are killed on warps and 15% entangled in nets. These estimates are of
the same order of magnitude as estimates of long-line bycatch in South African
waters. Mitigation measures have been implemented to reduce mortality in this
fishery.
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