Assessing the potential impact of salmon fisheries management on the conservation status of harbour seals (Phoca vitulina) in north‐east Scotland

Abstract

Conservation efforts are often constrained by uncertainty over the factors driving declines in marine mammal populations. In Scotland, there is concern over the potential impact of unrecorded shooting of seals, particularly where this occurs near Special Areas of Conservation. Here, we show that the abundance of harbour seals Phoca vitulina in the Moray Firth, north-east Scotland, declined by 2-5% per annum between 1993 and 2004. Records from local salmon fisheries and aquaculture sites indicated that 66-327 harbour seals were shot each year between 1994 and 2002. Matrix models and estimates of potential biological removal indicate that this level of shooting is sufficient to explain observed declines. Nevertheless, uncertainty over the number and identity of seals shot means that other factors such as changes in food availability may be contributing. Recent conservation measures markedly reduced the recorded levels of shooting in 2003 and 2004. In 2005, a coordinated management plan was developed to protect salmon fisheries interests while minimizing impacts on local seal populations. Comprehensive monitoring of future population trends and improved regulation of culls are now required to provide more robust assessments of the impact of human persecution on harbour seal populations in the Moray Firth and in other parts of the UK.

Detecting Density Dependence in Recovering Seal Populations

“…a, c Show cases of low environmental variability whereas b and d show cases of high environmental variability Whether population size or age structure should be used to look for changes in trends depends on the amount of error in both estimates. For example, externally imposed mortality, such as hunting, can give biased age ratios, unless the hunt is performed during times of the year when the population composition on land is representative of the population, or when the expected population composition is known (Kokko et al 1997;Thompson et al 2007). Determining age structure from censuses can be difficult because of differences in haul-out behavior among age groups and seasons, except for species where the age-and sex-specific behavior is known (Harkonen and Harding 2001;Carlens et al 2006).…”

Less government intervention in biodiversity management: risks and opportunities

“…Declining numbers of harbour seals, potentially caused by intensive shooting of seals by local District Salmon Fishery Boards (DSFBs) (Thompson et al 2007), combined with the risk of a Phocine Distemper Virus outbreak, led to the introduction of a Conservation Order by the Scottish Government in 2002 that prohibited the killing, injuring or taking of harbour seals. Faced with declining catches of salmon, and the imperative to protect salmon SACs, salmon fishery stakeholders sought to find a compromise between protecting salmon from seal predation while maintaining the favourable conservation status of the harbour seal SAC.…”

Status of J stock minke whales (Balaenoptera acutorostrata)

“…The PBR concept is widely used internationally to guide conservation of marine mammals (e.g. Gales 1995;Taylor et al 2000;Marsh et al 2004;Thompson et al 2007;Underwood et al 2008), and has been used by the European Union (ASCO-BANS 2000) and by New Zealand (Slooten and Dawson 2008) to evaluate bycatch of cetaceans. Japan's National Research Institute of Far Seas Fisheries has proposed a PBR-type method to set quotas on Dall's porpoises (Phocoenoides dalli) hunted in Japan, and a simulation study on how to apply this method is described in Okamura et al (2008).…”