Effects of low temperature exposure and acclimation on the behavioural responses of the green crab (Carcinus maenas) from Newfoundland, Canada.

The green shore crab (Carcinus maenas) is native to Western Europe but has spread around the globe and is described as one of the top 100 worst invasive species. On the east coast of North America, their northern-most limit is the island of Newfoundland, Canada, where they can experience water temperatures as low as -1 °C. We investigated the physiological responses of C. maenas to a temperature reduction regime as well as to long-term acclimation to temperatures representative of winter (2 °C) and summer (12 °C) in Newfoundland. Heart rate, oxygen consumption and estimated energy expenditure declined steadily with decreasing temperature, but a marked change was observed between 6 and 4 °C, with lowest levels recorded in 2 °C. After long-term acclimation to 2 °C there was a sustained reduction in physiological parameters. Even though these physiological parameters were very low in 2 °C, the crabs still exhibited intermittent activity. This supports the presence of a dormancy, rather than true torpor/hibernation below 5 °C, in which crabs will continue to actively move and feed, albeit much more slowly. The population in Newfoundland contains haplotypes from both the invasive northern and southern lineages, and they appear to retain a similar low temperature response compared with most other populations of green crab from both their native and expanded range.

Invasive green crab populations initially established in Canada within the Bay of Fundy, New Brunswick in the 1950s and were present in all five Atlantic provinces by 2007. Genetic evidence suggests that the Atlantic Canadian populations originated from two separate introductions with differences in time of establishment among regions and possible population-level behavioural differences. In this study, we examine intraspecific foraging behaviour among crabs from different populations, and interspecific foraging behaviour between genetically similar crabs and juvenile lobsters. Both sets of foraging experiments involved competition for a limited food source over a 1-h period. In intraspecific match-ups, recent invaders from Newfoundland (NL) were significantly superior foragers than long-established invaders from Nova Scotia (NS) and New Brunswick (NB) populations; however, we found no differences between NL and Prince Edward Island (PE) invaders. Crabs from PE were better competitors than those from NS and NB, but these differences were not significant. Interspecific competition experiments indicated that the feeding behaviour of recent invaders (NL) and genetically similar, but long-established invaders (NS), differed in the presence of juvenile lobsters. Our study documents striking behavioural differences among populations of green crab from a small geographic region, which may reflect a combination of both genetic differences and time since establishment. These differences may result in varying impacts on newly invaded habitats.

Temperature mediates non-competitive foraging in indigenous rock (Cancer irroratus Say) and recently introduced green (Carcinus maenas L.) crabs from Newfoundland and Labrador

The impact of human‐induced stressors, such as invasive species, is often measured at the organismal level, but is much less commonly scaled up to the population level. Interactions with invasive species represent an increasingly common source of stressor in many habitats. However, due to the increasing abundance of invasive species around the globe, invasive species now commonly cause stresses not only for native species in invaded areas, but also for other invasive species. I examine the European green crab Carcinus maenas, an invasive species along the northeast coast of North America, which is known to be negatively impacted in this invaded region by interactions with the invasive Asian shore crab Hemigrapsus sanguineus. Asian shore crabs are known to negatively impact green crabs via two mechanisms: by directly preying on green crab juveniles and by indirectly reducing green crab fecundity via interference (and potentially exploitative) competition that alters green crab diets. I used life‐table analyses to scale these two mechanistic stressors up to the population level in order to examine their relative impacts on green crab populations. I demonstrate that lost fecundity has larger impacts on per capita population growth rates, but that both predation and lost fecundity are capable of reducing population growth sufficiently to produce the declines in green crab populations that have been observed in areas where these two species overlap. By scaling up the impacts of one invader on a second invader, I have demonstrated that multiple documented interactions between these species are capable of having population‐level impacts and that both may be contributing to the decline of European green crabs in their invaded range on the east coast of North America.

The European green crab isn't too fussy about where it lives. Not content with its native range, which extends from Iceland to northern Africa, the green crab has also set up home in Japan, Australia, South Africa, Argentina and North America. These globe-trotting tendencies make the green crab an excellent model to study how animals cope with temperature changes, explains Carolyn Tepolt of Stanford University, USA. Enlisting the help of George Somero, Tepolt decided to explore the temperature tolerance – and ability to fine-tune that tolerance – of green crab populations around the world (p.1129).However, Tepolt realised that she wouldn't be able to bring crabs back to her lab – most countries are understandably reluctant to allow highly invasive species to cross their borders – so she would have to take the lab to them. Technician John Lee helped Tepolt transform cooler boxes into portable acclimation tanks by fitting them with aquarium heaters and chillers; but she also needed a simple method to measure the crabs' heart rate. ‘Heart function is a common measure of heat tolerance in cold-blooded animals’, Tepolt explains. ‘As temperatures rise, the animal's heart rate increases. When you reach the animal's maximum tolerated temperature – the critical temperature – the heart rate suddenly plummets.’ To let Tepolt measure crabs' heart rate in the field, Lee constructed a non-invasive portable monitor that could be attached to the crab's shell just over the heart. By measuring infrared light bouncing back from a crab's expanding or contracting heart, Tepolt was able to record heart rate.Taking her portable lab, Tepolt travelled to seven sites around the globe (Norway, Portugal, three sites along the east coast of North America and two sites along the west coast) to test the thermal limits of their green crab populations. At each site, she trapped green crabs and placed them in acclimation tanks for several weeks, keeping one group at 5°C and another group at 25°C. She then tested the heat tolerance of each group by attaching heart rate monitors to the crabs, ramping up the temperature in the tanks by 5°C an hour, and measuring the critical temperature at which the crabs' heart rate plummeted. To test the crabs' cold tolerance, she decreased the temperature to 0°C and measured their average heart rate. Tepolt expected that green crabs, as an invasive species, would have better heat tolerance than non-invasive species. Sure enough, she found that the average critical temperature for green crabs was 34.5–36.5°C, higher than the 30–35°C critical temperatures previously recorded for other crabs and lobsters living at the same sites. Green crabs were also remarkably cold tolerant; they all survived short-term exposure to 0°C.But the real key to green crabs' invasive success may lie in their ability to fine-tune their response to shifting temperatures. Tepolt saw that warm-acclimated crabs coped better with higher temperatures than their cold-acclimated counterparts: the critical temperature for 25°C-acclimated crabs was 1.8–2.4°C higher than that seen for 5°C-acclimated crabs. ‘This suggests that green crabs can shift their thermal limits through acclimation’, says Tepolt. However, even after they had acclimated to the same temperature, crabs found in Portuguese waters were better at coping with heat and fared worse at chillier temperatures than their Norwegian cousins. This is exciting, says Tepolt, because it suggests that crab populations are locally adapted to their environments – and that perhaps not all populations are equally suited to invading new regions. In the face of global warming, such variation may mean the difference between life and death.

The first report of Hematodinium perezi genotype I infection of Chinese mitten crab (Eriocheir sinensis) from the River Thames, UK.

The European green crab (Carcinus maenas) is a newly invasive species in Newfoundland, where it has likely been present for ≤15 years. The green crab has been found in stomach contents of American lobster (Homarus americanus) in New England and Nova Scotia, Canada, but predation on this species has not yet been quantified in Newfoundland. We conducted feeding experiments to determine whether lobsters from Newfoundland were as likely as those from Nova Scotia (which have coexisted with green crabs for >60 years) to recognize and prey upon this new species. We also performed experiments to determine whether green crabs reach a size refuge from predation and whether factors including starvation, availability of alternate food sources, or habitat complexity would influence the probability of lobster attacking or feeding on green crabs. In our trials, lobster origin had no significant effect on crab predation; lobsters, irrespective of origin, were more likely to consume small (<40 mm carapace width [CW]) and medium (40–65 mm CW) crabs than larger (>65 mm CW) ones. Nevertheless, even small lobsters (73–76 mm carapace length, 300 g) were able to kill and consume the largest green crabs (78 mm CW, 100 g). Green crabs were less likely to be attacked or eaten when an alternative food source was present, suggesting that the lobsters were preying on the crabs, rather than simply killing them in a dispute over territory. The addition of a shelter provided a refuge for the green crabs; however, the crabs were only able to avoid being injured or eaten if this shelter was structurally complex. The green crab is slowly spreading westward around the island of Newfoundland, and so its long‐term effects, interactions with other organisms, and contribution to the diet of Newfoundland lobsters remain to be seen.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 548:31-45 (2016) - DOI: https://doi.org/10.3354/meps11674 Linking eelgrass decline and impacts on associated fish communities to European green crab Carcinus maenas invasion K. Matheson1,*, C. H. McKenzie1, R. S. Gregory1, D. A. Robichaud2, I. R. Bradbury1, P. V. R. Snelgrove3, G. A. Rose4 1Fisheries and Oceans Canada, Ecological Sciences Section, Northwest Atlantic Fisheries Centre, St. John’s, Newfoundland and Labrador A1C 5X1, Canada 2LGL Limited, Sidney, British Columbia V8L 3Y8, Canada 3Department of Ocean Sciences and Biology Department, Memorial University of Newfoundland, St. John’s, Newfoundland and Labrador A1C 5S7, Canada 4Centre for Fisheries Ecosystems Research, Fisheries and Marine Institute of Memorial University of Newfoundland, St. John’s, Newfoundland and Labrador A1C 5R3, Canada *Corresponding author: kyle.matheson@dfo-mpo.gc.ca ABSTRACT: Following their first detection in Newfoundland in 2007, populations of invasive European green crabs Carcinus maenas (Linnaeus, 1758) have increased and spread throughout eelgrass Zostera marina meadows. Green crabs can reduce eelgrass biomass by damaging rhizomes and plant shoots when burrowing for shelter and digging for prey. Empirically demonstrating large spatial-scale impacts of green crabs on eelgrass and subsequent cascading effects on the ecosystem has proven difficult because of the general absence of effective baseline studies prior to an invasion of green crabs. We conducted surveys in Placentia and Bonavista bays, Newfoundland (20 sites) to compare eelgrass and associated fish communities before and after an invasion of green crabs. We analyzed eelgrass surveys from 1998 and 1999 (before green crab) and again in 2012 (after green crab) using a Before-After-Control-Impact (BACI) study design in order to isolate effects of crab-induced eelgrass loss from effects independent of green crabs. Underwater video sampling evaluated eelgrass change over time and indicated a 50% decline in eelgrass percent cover since 1998 at sites with green crabs, and eelgrass declines up to 100% at sites with highest abundances and longest established presence of green crabs. Beach seining showed a sharp decline in abundance and biomass of fish (~10-fold between sites with and without green crabs) and indicated changes in fish community structure after green crab arrival at a site. Our results suggest cascading effects on fish communities and substantial potential impacts in coastal ecosystems occur following green crab invasion. KEY WORDS: Invasive species · Green crab · Eelgrass · Fish community · Before-After-Control-Impact · BACI Full text in pdf format PreviousNextCite this article as: Matheson K, McKenzie CH, Gregory RS, Robichaud DA, Bradbury IR, Snelgrove PVR, Rose GA (2016) Linking eelgrass decline and impacts on associated fish communities to European green crab Carcinus maenas invasion. Mar Ecol Prog Ser 548:31-45. https://doi.org/10.3354/meps11674 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 548. Online publication date: April 21, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Our goal was to quantify tree- and branch-level components of growth response to three silvicultural treatments (STs), and weevil incidence in white pine ( Pinus strobus L.) from large, central populations in Ontario (ON) versus small, isolated populations in Newfoundland (NL). Light levels were 100%, 42.0%, and 20.4% transmittance for the full-sun, intermediate-shade, and high-shade STs. After 8 years, the overall incidence of weevil infestation was 42.1%, 23.4%, and 13.7% for the full-sun, intermediate-shade, and high-shade STs, respectively (P < 0.001). Weevil impact on total height and volume averaged –13.2% and –11.8%. Analysis of dominant lateral shoots showed that ON populations had 32% longer shoots than the NL populations. Bud set difference was a primary determinant of shoot-length growth differences between regions: Julian days 171 and 184 for the NL and ON populations, respectively. The primary determining factors related to shoot length were the number of needle bundles and region, driven by light levels and day length, respectively, and the internode length, probably through inbreeding effects. Total height and diameter showed a positive curvilinear relationship to light level. To maximize fitness, NL conservation strategies should also now consider introducing adaptive trait variation in the context of anticipated climate change.

The mussel aquaculture industry has raised concerns following the discovery of green crab Carcinus maenas in Placentia Bay Newfoundland in August 2007. Post-larval green crabs have been found in feral mussel beds in high densities in Europe. If this is true for other green crab populations, mussel seed transfers from Placentia Bay could provide a vector for post-larval juvenile crab transfer to other areas like Notre Dame Bay where provincial mussel aquaculture is concentrated. Green crab is currently not found in this area of Newfoundland. Newly settled green crab juveniles were collected and used in a series of lab scale mitigation trials. Crab and seed mussels were exposed to thermal shocks applicable and feasible for mussel seed management in Placentia Bay. Crab mortality was measured in the treatments and seed mussels were monitored for stress response using the lysosomal destabilization assay. Exposure to heated salt water to 45, 50 and 55°C was effective in culling juvenile green crab while causing minimal stress to mussel seed. The method can be employed in mussel seed management and transfer operations where there are concerns related to potential introductions of hitch-hiking green crab.

Impact of three silvicultural treatments on growth, light-energy processing, and related needle-level adaptive traits of Pinus strobus from two regions

Populations of green crab (Carcinus maenas) have expanded within Newfoundland, and this has raised concern from fish harvesters and scientists regarding bivalve predation in coastal areas on species such as juvenile sea scallops (Placopecten magellanicus). We used 2 microcosm experiments to determine (1) the effects of water temperature (5°C and 12°C) on scallop predation; (2) scallop size selection in small and large green crabs and a large indigenous predator, the rock crab (Cancer irroratus); and (3) bivalve prey selection in large green crabs between softshell clams (Mya arenaria), blue mussels (Mytilus edulis), and sea scallops. Overall, green and rock crabs captured 4 times more scallops in warm water (12°C) than cold (5°C). Large green (60–70 mm) and rock (75–90 mm) crabs captured similar numbers of scallops, selected medium-size (30–40 mm) scallops, and avoided small (10–20 mm) scallops. Small green crabs (40–50 mm) captured only small scallops. Large green crabs selected softshell clams ...

Effects of claw autotomy on green crab (Carcinus maenas) feeding rates

BackgroundVariability in the ecological impacts of invasive species across their geographical ranges may decrease the accuracy of risk assessments. Comparative functional response analysis can be used to estimate invasive consumer-resource dynamics, explain impact variability, and thus potentially inform impact predictions. The European green crab (Carcinus maenas) has been introduced on multiple continents beyond its native range, although its ecological impacts appear to vary among populations and regions. Our aim was to test whether consumer-resource dynamics under standardized conditions are similarly variable across the current geographic distribution of green crab, and to identify correlated morphological features.MethodsCrabs were collected from multiple populations within both native (Northern Ireland) and invasive regions (South Africa and Canada). Their functional responses to local mussels (Mytilus spp.) were tested. Attack rates and handling times were compared among green crab populations within each region, and among regions (Pacific Canada, Atlantic Canada, South Africa, and Northern Ireland). The effect of predator and prey morphology on prey consumption was investigated.ResultsAcross regions, green crabs consumed prey according to a Type II (hyperbolic) functional response curve. Attack rates (i.e., the rate at which a predator finds and attacks prey), handling times and maximum feeding rates differed among regions. There was a trend toward higher attack rates in invasive than in native populations. Green crabs from Canada had lower handling times and thus higher maximum feeding rates than those from South Africa and Northern Ireland. Canadian and Northern Ireland crabs had significantly larger claws than South African crabs. Claw size was a more important predictor of the proportion of mussels killed than prey shell strength.DiscussionThe differences in functional response between regions reflect observed impacts of green crabs in the wild. This suggests that an understanding of consumer–resource dynamics (e.g., the per capita measure of predation), derived from simple, standardized experiments, might yield useful predictions of invader impacts across geographical ranges.

Effects of temperature, body size, and chela loss on competition for a limited food resource between indigenous rock crab (Cancer irroratus Say) and recently introduced green crab (Carcinus maenas L.)