Capelin Egg Predation

Predation in the field
This study confirms that invasive red king crab fed on both capelin eggs and capelin off the coast of Finnmark, Norway. Capelin was found in 81.6% and 21.7% of the analysed red king crab stomachs in 2005 and 2006, respectively, while capelin eggs were found in 23.2% and 10.0% of crabs in 2005 and 2006, respectively. These results are in accordance with a previous study where 19% of the analysed red king crab stomachs were reported to contain capelin eggs (Anisimova et al. 2005). However, as some capelin eggs were hatching at the time of the survey in 2006, it is possible that egg density and the occurrence of eggs in crab stomachs were underestimated during that year.
The occurrence of egg predation by the red king crab

Such saturation of predators have been observed previously in fish (Kempf et al. 2008) and ctenophore (Majaneva et al. 2013). In Canadian waters, sea urchins (Strongylocentrotus droebachiensis) aggregate around dead capelin, but not at spawning beds with high capelin egg density (Crook & Davoren 2016). Assuming that dead capelin release more odour than capelin eggs, and because prey odour is considered to be an essential factor for foraging in red king crabs, these crabs may be attracted to dead capelin by olfactory stimuli (Zhou & Shirley 1997), just as crabs are efficiently attracted to bait in pot fisheries (Stiansen et al. 2010). Because the invasive red king crab feeds on dead post-spawned capelin on the seabed, the native haddock may compete with the red king crab for capelin, which is the most important prey for haddock during the spring season (Bogetveit et al. 2008). As haddock may feed on both dead post-spawn capelin and capelin eggs (Huse & Toresen 1996, Gjøsæter 1998), we speculate that this competition may indirectly enhance egg predation by

(2005) for the Barents Sea capelin in 2001. This implies that the red king crab may influence capelin egg mortality by feeding, but that the impact is unlikely to hamper recruitment of the Barents Sea capelin. However, the total egg loss is probably higher than the consumption estimates because of damage to eggs during feeding. In support of this, damage of prey that leads to higher mortality than that resulting from consumption alone has also been reported in experimental studies (Jørgensen 2005, Pavlova 2009, Michelsen