Effects of a bio-invasion of the Pacific oyster, Crassostrea gigas (Thunberg, 1793) in five shallow water habitats in Scandinavia

Abstract

Experimental studies evaluating the effects of food availability on the movement of free-ranging animals generally involve food supplementation rather than suppression. Both approaches can yield similar insights, but we were interested in the potential for using food suppression for the management and control of invasive predators, in particular, the brown treesnake (Boiga irregularis) on Guam. However, understanding a species' response to food resources is critical before employing such a strategy. We studied the movements of 24 radio-tagged B. irregularis initially caught within four 4-ha unfenced plots in rodent-abundant (control) and rodent-suppressed (treatment) grassland habitats over a 40-day period. Because monitoring duration differed among snakes, we also analyzed short-term (16-day) activity areas. Over the 16 days, snakes associated with rodent-suppressed plots had 86% larger activity areas (ha), 94% greater dispersal distances (m), and 43% greater movement rates (m/h) than snakes associated with control plots. Boiga irregularis moved extensively, but these movements were not always reflected in the size of the snake's total activity area. Movement rates did not differ between sexes, but snakes in above-average body condition moved greater distances per hour than those in below-average condition irrespective of treatment. Our study indicates that a relatively small prey suppression effort can cause almost immediate and significant changes in B. irregularis movement. On Guam, prey suppression might enhance control efforts by either increasing trap capture success or discouraging snakes from entering areas of conservation or management concern. However, the outcome of using prey suppression as a control tool in areas threatened with the accidental introduction of the brown treesnake is more difficult to predict and might have negative consequences such as elevated dispersal rates.

Declining Populations of Mytilus spp. in North Atlantic Coastal Waters—A Swedish Perspective

“…The oyster herpesvirus-1 (OsHV-1) and variants have increasingly been recorded for causing high mortality rate in Pacific oyster cultures in Europe since 2008 (Segarra et al 2010, EFSA AHAW Panel 2015, Martenot et al 2015. After the warm summer of 2014, high mortalities of Crassostrea gigas occurred in a hatchery and in wild populations at the Swedish west coast and the nearby Norwegian south coast (Mortensen et al 2017). All size classes were affected, and the disease seemed to be a combined infection of OsHV-1 and pathogenic Vibrio species (mainly Vibrio aestuarianus) in combination with increased physiological stress (after spawning) and elevated temperature.…”

Umami synergy as the scientific principle behind taste-pairing champagne and oysters

“…The samples were collected in Limfjorden in the Northern part of Denmark, which is the largest remaining, natural terroir in the world for the European oysters. However, possibly due to climate changes, populations of Crassostrea gigas have since the mid-1990s massively invaded Limfjorden as well as other Nordic shallow water habitats 45 and since 2017 established a self-sustaining population. There are growing concerns regarding the future of the indigenous European oyster whose habitats become overgrown by Pacific oysters.…”

Reviewing Introduction Histories, Pathways, Invasiveness, and Impact of Non-Indigenous Species in Danish Marine Waters

“…However, we scored the species outside the expert assessment group with the highest score of all species (16). Furthermore, all scores would have had high or very high validity, i.e., they have been based on quantitative scientific information from Danish, Scandinavian, or North European populations [63][64][65]. There is no commercial culture of Pacific oysters in Danish waters, and commercial fishery is restricted.…”