New Zealand Journal of Marine and Freshwater Research abstracts
Quantifying the relative intensity of fishing on New Zealand seamounts
Richard L. O’Driscoll
Malcolm R. Clark
National Institute of Water and Atmospheric
Research Limited
Private Bag 14 901, Kilbirnie
Wellington, New Zealand
email: r.odriscoll@niwa.co.nz
Abstract New Zealand seamounts support major fisheries
for several deepwater fish species, including orange roughy (Hoplostethus
atlanticus) and smooth oreo (Pseudocyttus maculatus). Although
a high proportion of features in the depth range 500-1000 m have been fished,
very little is known about the ecological impacts of bottom trawling on seamounts.
The potential impact is likely to be influenced by the spatial extent and
frequency of fishing. A new index is presented to assess the relative intensity
of trawling on New Zealand seamounts. The fishing effects index (FEI) incorporates
information on the density of fishing on the seamount as a proportion of
the seabed area and also on tow direction. Detailed fisheries data from more
than 250 000 tows were examined to calculate FEI for New Zealand seamounts.
The most intensively fished seamounts were on the south Chatham Rise, an
area characterised by a large number of relatively small features which were
fished serially for orange roughy in the 1980s and 1990s. Other seamounts
with high FEI were on the north Chatham Rise, Challenger Plateau, and off
the east coast of the North Island. A range of sensitivity analyses indicated
that the general rankings of seamounts were relatively robust to the choice
of arbitrary thresholds used to assign tows to seamounts.
Keywords impacts of trawling; deepwater fisheries; seamounts;
fishing effort distribution; orange roughy
M04141; Online publication date 17 June 2005 Received 8 October 2004;
accepted 24 December 2004
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39:
839-850
0028-8330/05/3904-0839 © The Royal Society of New Zealand 2005
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