Monitoring the Consequences of the Northwestern North Sea Sandeel Fishery Closure
Scottish Marine and Freshwater Science Volume 1 No 6
By 1997 sandeel abundance on the Wee Bankie was already depressed as a result of fishing activities, and continuation of the fishery up to 1999 caused further declines. As a precautionary measure to safeguard marine top predators, particularly seabirds at internationally important colonies in and around the Firth of Forth, an area off the east coast of Scotland, from Rattray Head to St Abbs, was closed to industrial fishing for sandeels in 2000. High levels of recruitment in 1999 and 2000, combined with a lack of any significant fishing activity in 1999, resulted in an immediate and substantial increase in the biomass of sandeels on the Wee Bankie grounds in 2000; the first year of the sandeel closure. Since 2001, sandeel biomass has steadily declined to levels in 2007 that were similar to those observed in 1997 and 1998 when the sandeel fishery in the area was active. In the absence of sustained recruitment, consumption by marine top predators, along with other causes of natural mortality, have exceeded growth production in the population. Closing the area to fishing has not been sufficient to ensure high abundances of sandeels in the area. Recruitment of young sandeels, at or above long-term average levels, is also necessary, and since this is primarily governed by natural process, this may be beyond the capacity of fisheries management alone to achieve. Variation in the abundance and feeding ecology of gadoid predators in the study area was unrelated to variation in sandeel abundance and so remained unaffected by closure of the fishery. Numbers of guillemots, razorbills, puffins and kittiwakes recorded at sea in the study area all appeared to increase with closure of the fishery, and then subsequently to decline again as local sandeel abundance declined. The increase in auk abundance at sea may well have resulted from an influx of non-breeding birds. Only the breeding performance of kittiwakes at the Isle of May appeared related to variation in local sandeel abundance. Simply closing offshore areas close to top predator colonies may not be sufficient to guarantee the long term prospects of predators at these locations.