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 skuas)1.

 

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.

 

Seabird bycatch

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: 727-730.

2 Frederiksen, 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): 701–710.

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.