Invasive red king crabs feed on both spawned-out capelin and their eggs

Abstract

The aim of the present study was to test the hypothesis that the invasive red king crab Paralithodes camtschaticus may hamper capelin (Mallotus villosus) recruitment through egg consumption. Field studies (2005, 2006), laboratory experiments (2011), and models of consumption were applied. To explore the response of the predator to prey density, crab abundance and capelin egg density were estimated in stratified study areas. Stomach evacuation rates of capelin eggs in red king crab stomachs were investigated experimentally, and the average evacuation time estimated to be 5.38 h at 2.9°C. The average evacuation time was applied to a consumption model where uncertainty in input values was assessed by Monte Carlo simulation. Estimated egg consumption values were 0.04% and 2.23% of the total number of eggs in studied spawning areas, in 2005 and 2006, respectively. The high variability in quantity of eggs in stomachs generated most of the uncertainty in consumption estimates. Red king crabs did not show an aggregative response to capelin egg density, nor was the magnitude of egg consumption correlated with egg density. Dead post-spawn capelin was a major and more important prey than eggs for red king crab. Our findings imply that semelparity in Barents Sea capelin may lead to predator swamping, thereby reducing capelin egg consumption by the invasive red king crab.

On the Atlantic blue crab ( Callinectes sapidus Rathbun 1896) in southern European coastal waters: Time to turn a threat into a resource?

“…trypanosome blood parasites by hosting the leech Johanssonia arctica: Hemmingsen et al, 2005Hemmingsen et al, , 2010;  designated as an aquatic nuisance species in the USA by the Aquatic Nuisance Species Task Force (ANSTF) since 1998;  in 2002 the ANSTF implemented a Green Crab Management Plan to assess the impacts and prevent, eradicate, and control the species;  negative impacts have been demonstrated on a number of benthic invertebrate taxa, including bivalves and other crustaceans (Floyd and Williams, 2004;Grosholz et al, 2000;Pickering and Quijón, 2011;Gehrels et al, 2016);  indirect negative effects have been suggested on physical characteristics of benthic habitats through bioturbation (Schratzberger and M. Warwick, 1999;Neira et al, 2006;Malyshev and Quijón, 2011;Lutz-Collins et al, 2016);  no parasite-related indirect effects have been emphasized to date; however, it has been suggested that the species may have a lower susceptibility to pathogens than other decapod crustaceans (e.g. Hematodinium infections: Hamilton et al, 2010); Economic Impact  negative effects have been indicated on the recruitment of valuable finfish species by feeding on egg-clutches (Mikkelsen and Pedersen, 2012; but see Dvoretsky, 2015 andPedersen, 2017);  non-univocal effects have been highlighted on the abundance of finfish and crustacean species of economic interest (Falk-Petersen et al, 2011;Jørgensen and Spiridonov, 2013;Dvoretsky and Dvoretsky, 2015);  negative impacts have been indicated on juvenile stages of fish and crustacean species of economic interest (Taylor, 2005;Rossong et al, 2006);  considerable economic impacts have been long acknowledged on native shellfish products; for example, in 2005 the Oregon Dungeness Crab Commission estimated the potential impact on the west coast dungeness crab (Metacarcinus magister Dana, 1852) fishery in $50 million, while Lovell et al (2007) showed that the estimated average annual losses to east coast  severe interference of bycatch with traditional fishing methods, as crabs feed on captured commercial species, and damage fishing gears; bycatch impels the abandon of historically important coastal fishing grounds (Godøy et al, 2003;Furevik et al, 2008;…”