The Net Effect? - Whale and Dolphin Conservation Society

subjected to bycatch rates that far exceed
what could be considered sustainable (over
6% per annum) in English and Irish bottomset
gillnets alone, for probably more than a
decade. Other gillnet fleets in the Celtic Sea
have yet to be investigated. Plus, there is now
evidence from stranded animals in the UK
that this species may also be being impacted
by the pelagic trawl fisheries in this area.
Therefore, judgement of whether any individual
interaction is ‘sustainable’ must be made
in the context of total known or suspected
mortality across the range of fisheries (and
other causes of mortality) operating in an
area. It must also take account of the cumulative
depletion of populations that will be
caused by unsustainable mortality levels. In
principle, if an unsustainable level of bycatch
continues unchecked, the significance of that
mortality will become more acute year on
year as the population is gradually depleted.
Current bycatch levels for several species are
being judged against abundance estimates
that may now be significantly above the true
population levels, given the mortality rates
that are assumed to have occurred in the
years since population surveys were last conducted.
Current cetacean abundance estimates
in the north-east Atlantic are at best
speculative, as the only major survey was
conducted in the early 1990s, covering the
North Sea (and eastwards), but only the
Celtic Sea to the west of Britain and
mainland Europe. For most populations
there has been no assessment of trends or
conservation status. In this respect, the largescale
cetacean abundance survey (SCANS II)
planned to cover the North Sea and northeast
Atlantic, broadly out to EU fisheries
limits, in 2005 and 2006 is welcome.
However, more continuous surveillance of
population trends is also required.
Given all the major areas of uncertainty, it is
vital that extreme precaution is applied in
assessing the significance of cetacean bycatch
and, in particular, in defining conservation
and management objectives. It is recommended
that the intermediate precautionary
objective identified by ASCOBANS, to
reduce bycatches to less than 1% of the best
available population estimate, be the
absolute maximum threshold that should be
applied, and that targets and timeframes to
reduce bycatch to below this level, and ultimately
towards zero, should be adopted.
6.2 Assessment and
monitoring of fisheries
The collection of data on fisheries, including
effort, gear and location, must be improved,
and these data must be comparable between
fleets, in order to allow the extrapolation of
bycatch rates to individual fisheries and the
estimation of total mortality levels within an
area or population. Also, the accessibility of
these data, much of which are currently only
available for enforcement purposes, needs to
be extended to allow proper assessment of
the impacts of fisheries.
Routine and ongoing monitoring of fisheries
for cetacean bycatch is clearly essential in
order to assess the nature and scale of the
problem and also to acquire the information
needed to be able to devise appropriate mitigation
strategies. This can only be achieved
reliably through independent onboard
observers, with alternative monitoring strategies
only in the extreme circumstances where
an observer physically cannot be carried on a
vessel. Given the reluctance of many governments
to introduce routine monitoring of
incidental capture (despite an obligation to
do this under the Habitats Directive), and
the refusal of some skippers and even whole
fleets to carry observers where this has been
proposed, compulsory observer schemes are
the only way to ensure effective and equitable
monitoring.
Monitoring of fisheries must continue after the
introduction of mitigation measures in order to
assess the adequacy of their implementation,
The Net Effect?
A WDCS report for Greenpeace
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