Impacts of Fisheries
Discards and offal discharge
For years, some seabirds have benefited from
fisheries through food provided at sea by discharging offal and
discarding undersize fish. As a result, the abundance of scavenging
species (e.g. great skua, northern fulmar) may have been elevated
above levels that could be sustained by naturally occurring
food sources. The necessary introduction of measures to
conserve fish stocks has reduced the amount of discards, as
has the decline of some commercial fisheries, which has also
resulted in less offal being discharged. The reduction in food
provided by the fishing industry may have contributed to the
decline in population of fulmars and other offshore
surface-feeders since the mid-1990s. Another consequence of fewer
discards is that great skuas have had to rely increasingly on other
food sources, including the predation of other seabirds, which is
having a negative impact on their prey populations (e.g. Arctic
North Sea sandeel fishery
In the North Sea, an average of 880,000
tonnes of lesser sandeels (Ammodytes marinus) were caught
per year during1994-2003. Subsequently, catches fell to just
290,000 tonnes per year (ICES in litt.).
The part of the fishery that operated over the
Wee Bankie off southeast Scotland during the 1990s significantly
depressed adult survival and breeding success of black-legged
kittiwakes at adjacent colonies compared with years prior to the
fishery opening and after it was closed2. Since 2000 there
has been a ban on sandeel fishing off eastern Scotland
and north east England. If fishing is resumed in
this area to levels that significantly reduce local sandeel stock
size, it would probably exacerbate reductions in breeding success
and survival caused by increases in sea surface temperature as a
result of climate change 2.
Currently over 90% of sandeels caught
within the UK's European Economic Zone, are taken from
the Dogger Bank off eastern England (ICES in litt). The
extent of the pressure exerted on UK seabirds by the Dogger Bank
fishery is currently unknown. Much of the fishing goes on
beyond the foraging range of kittiwakes at most colonies;
however, it would be unwise to conclude that
sandeel fishing is having no impact since the impact this
fishing has on the number and quality of sandeels that are within
foraging range is unknown.
Data are currently lacking on the
numbers of seabirds caught by long-line and other fisheries in UK
waters, and additional information would contribute to efforts to
address the impact of bycatch on seabirds at a European
level. Northern fulmars appear to be particularly
susceptible to entanglement in offshore fishing nets and taking the
baited hooks of long-line fisheries3, whilst Auks
can become trapped in inshore salmon nets4.
1 Votier, S. C., Furness, R. W.,
Bearhop, S., Crane, J. E., Caldow, R. W. G., Catry, P., Ensor, K.,
Hamer, K. C., Hudson, A. V., Kalmbach, E., Klomp, N. I., Pfeiffer,
S., Phillips, R. A., Prieto, I. & Thompson, D. R. 2004. Changes
in fisheries discard rates and seabird communities. Nature 427:
M., Jenson, H., Daunt, F., Mavor, R. and Wanless, S. 2008.
Differential effects of a local industrial sand lance fishery on
seabird breeding performance. Ecological Applications, 18(3):
3 Dunn, E. K. and
C. Steel. 2001. The impact of long-line fishing on seabirds in the
north-east Atlantic: recommendations for reducing mortality.
RSPB/JNCC, Sandy, England
4 Murray, S., S. Wanless, and M. P. Harris.
1994. The effects of fixed salmon Salmo salar nets on guillemot
Uria aalge and razorbill Alca torda in northeast Scotland in 1992.
Biological Conservation 70: 251-256.