Are there rogue harbor seals in Whatcom Creek? The potential impact of harbor seals on a local salmon hatchery

Conflicts often arise between humans and predators when there is perceived competition over a resource. In the Salish Sea, salmon are a socioeconomically important fish species and an important food source for harbor seals (Phoca vitulina). Currently, there is debate on the impact that harbor seals have on salmonid populations in the region. Rogue individuals are defined as those that have a greater per capita impact on fisheries than individuals in the general population. Rogue harbor seals have been identified in other estuarine systems and can have major implications for management purposes. Harbor seals come to Whatcom Creek in Bellingham, USA, every fall, coinciding with the annual salmon runs. Past studies indicate that seals come into the creek to forage and are viewed as competitors by the local fishers. Over a four-year period (2012-2015), we tracked the occurrence and foraging behavior of individual seals using photo identification and defined a successful hunt as a surfacing event in which a seal had possession of a salmon. We described the existence of rogue individuals by combining relative occurrence and foraging success, the latter of which we are currently analyzing. Thus far, we have identified 91 individual seals, which on average were observed 2.20 ± 2.51 SD times per year. The most frequently observed individuals have visited the creek 16 (n=2 seals) and 11 (n=1) times per year. Preliminary results indicate that certain individuals returned to the creek in successive seasons, however each year the majority of seals foraging in the creek were comprised of new individuals with an average of 22.75 ± 21.29 SD new individuals per year. It appears that if there are rogue seals at Whatcom Creek, they represent a small number of individuals.