The Net Effect? - Whale and Dolphin Conservation Society

56
The Net Effect?
A WDCS report for Greenpeace
6. Conclusions and
recommendations
6.1 Significance of
cetacean bycatch
Fisheries bycatch clearly represents a major
problem for populations of small cetaceans,
probably the major problem in many parts of
the world and in the north-east Atlantic in
particular. Numerous studies have investigated
the issue in the north-east Atlantic over the
past two decades, albeit in a mostly piecemeal
and small-scale fashion, resulting in probably
hundreds of publications over many thousands
of pages. These have been funded by
various national governments and in many
cases by the European Commission. Clear
indications of problems have emerged, both
from onboard observer monitoring and from
strandings records, and in some cases good
estimates of the scale of the problem have
been produced. What is astounding, therefore,
is the almost total lack of any policy or, more
importantly, practical response to the issue at
either national or EU level (beyond the
driftnet ban adopted in 1998).
The cetacean species that are most affected
by bycatch in the north-east Atlantic, in
terms of absolute numbers, are the common
dolphin and the harbour porpoise. Bycatch
of common dolphins has been recorded in
the greatest numbers in pelagic trawl fisheries,
and that of harbour porpoises in
bottom-set gillnet fisheries.
In the case of pelagic trawls, there has been
too little monitoring to date to be able to
assess total mortality levels. However, the
number and scale of pelagic trawl fisheries
operating in the Celtic Sea, Biscay and
Channel area, coupled with the number of
stranded bycaught common dolphins
recorded on surrounding coasts, indicate that
the total mortality figure is likely to be high
and probably unsustainable.
More monitoring has been conducted of
bottom-set gillnet fisheries, at least in some
areas, and this has clearly demonstrated large
and unsustainable levels of harbour porpoise
bycatch, particularly in the Celtic Sea and
North Sea. In areas where porpoise population
levels are very low, such as the Baltic Sea
and the southern North Sea/eastern Channel,
even a very low level of bycatch is extremely
serious in conservation terms.
For other species, although bycatches may be
lower in absolute numbers, the impact may
be equally or possibly even more significant.
For instance, bycatches in pelagic trawl fisheries
include Atlantic white-sided dolphins,
striped dolphins, long-finned pilot whales
and bottlenose dolphins, most of which are
considered to be far less numerous in the
region than common dolphins. As both population
and bycatch estimates for these
species are at best only partial, the significance
of these mortalities for local populations
is unknown, but they are a potential
major cause for concern. The bottlenose
dolphin, for instance, is only recorded in very
small isolated populations in the waters off
south-west England and is also at risk from
inshore gillnets. Any incidental capture of
this species would be highly significant.
It is important to recognise that populations
of many of these species are probably being
impacted by several different fisheries (as
well as other anthropogenic causes of mortality).
For instance, the populations of
common dolphins in the Celtic Sea, Biscay
and Channel area have already been subjected
over many years to bycatch in the pelagic
tuna driftnet fishery (which has recently been
terminated) at levels that were probably
unsustainable. The limited studies of pelagic
trawl fisheries to date, combined with
evidence from strandings data, suggest that
common dolphin mortalities in these fisheries
may well be unsustainable. In addition,
common dolphins are caught, if to a lesser
extent, in bottom-set gillnet fisheries (and
possibly others) in this area.
Equally, the harbour porpoise population in
the Celtic Sea is already known to have been