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.

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After World Wars I and II large amounts of explosive ordnance remained undetonated. Already deployed ordnance was left uncollected and excess supplies were disposed of, sometimes recklessly. The result is that much of this unexploded ordnance (UXO) still exists in the environment, much of it throughout the world's oceans, where it continuously presents a risk of serious harm to people and the environment. The purpose of this paper is to present a marine UXO risk assessment that could aid managers working in marine industries in mitigating the risks presented by marine UXOs. Using existing marine UXO literature, a list of 21 plausible UXO risk events was generated and then categorized into risk levels of low, medium, high, and very high using a novel risk matrix approach. The common pathways that determine interactions between people and marine UXOs were identified and the efficacy of a series of risk mitigation strategies were examined within the context of the identified risks. Risk Management For Unexploded Ordinance (UXO) In The Marine EnvironmentAbout the Authors: Jana Aker is a graduate student in the Marine Affairs Program at Dalhousie University. She is originally from Sydney, Nova Scotia, and obtained her undergraduate degree in biology from Cape Breton University in 2010. Her interests include marine protected areas, conservation and shipping impacts and regulations. In summer 2012 she will be involved with the establishment of the St. Ann's Bank marine protected area off of the east coast of Cape Breton Island. Jana can be reached at jana.aker@dal.ca.Brett Howard is a Master of Marine Management Candidate at the Dalhousie University Faculty of Management. She has a background in marine ecology and conservation and is interested in the interface between marine science and international law and policy. Her career aspirations are to help develop marine management strategies that encourage sustainable and safe marine resource extraction. Brett can be reached at brett.howard@dal.ca.Mike Reid is a Candidate in the Masters of Marine Management program at Dalhousie University. His research interests include maritime history, wetland management practices and the politics of commercial activity on and under the high seas. He is currently preparing to undertake a project that will attempt to establish historical baselines for wetland coverage within the province of Nova Scotia. Mike can be reached at pmreid@dal.ca.

The shifting baseline syndrome describes a gradual lowering of human cognitive baselines, as each generation accepts a lower standard of resource abundance or size as the new norm. There is strong empirical evidence of declining trends of abundance and body sizes of marine fish species reported from docks and markets. We asked whether these widespread trends in shrinking marine fish are detectable in popular English-language media, or whether news writers, like many marine stakeholders, are captive to shifting baselines. We collected 266 English-language news articles, printed between 1869 and 2015, which featured headlines that used a superlative adjective, such as ‘giant’, ‘huge’, or ‘monster’, to describe an individual fish caught. We combined the reported sizes of the captured fish with information on maximum species-specific recorded sizes to reconstruct trends of relative size (reported size divided by maximum size) of newsworthy fishes over time. We found some evidence of a shifting baseline syndrome in news media over the last 140 years: overall, the relative length of the largest fish worthy of a headline has declined over time. This pattern held for charismatic fish species (e.g. basking sharks, whale sharks, giant mantas), which are now reported in the media at smaller relative lengths than they were near the turn of the 20th century, and for the largest species under high risk of extinction. In contrast, there was no similar trend for pelagic gamefish and oceanic sharks, or for species under lower risk of extinction. While landing any individual of the large-bodied ‘megafish’ may be newsworthy in part because of their large size relative to other fish species, the ‘megafish’ covered in our dataset were small relative to their own species—on average only 56% of the species-specific maximum length. The continued use in the English-language media of superlatives to describe fish that are now a fraction of the maximum size they could reach, or a fraction of the size they used to be, does reflect a shifting baseline for some species. Given that media outlets are a powerful tool for shaping public perception and awareness of environmental issues, there is a real concern that such stories might be interpreted as meaning that superlatively large fish still abound.

Crab species Carapace width (mm) Source Acanthocyclus gayi 24.0 Garth (1957) Acanthocyclus hassleri 25.0 Rathbun (1930) Achelous spinimanus 110.0 Williams (1984) Callinectes sapidus 168.0 Williams (1984) Cancer antennarius 118.0 Rathbun (1930) Cancer borealis 143.0 Williams (1984) Cancer irroratus 119.0 Williams (1984 Cancer pagurus 130.0 Ingle (1997) Cancer productus 157.5 Rathbun (1930) Caphyra rotundifrons 13.0 Jenkins (2012) Carcinus aestuarii 65.0 sealifebase.org Carcinus maenas 79.4 Rathbun (1930) Cyclograpsus lavauxi 28.0 McLay (1988) Dotilla fenestrata 12.0 Hartnoll (1973) Dyspanopeus sayi 29.7 Williams (1984) Dyspanopeus texanus 27.0 Rathbun (1930) Eurypanopeus depressus 25.0 Williams (1984) Eurytium limosum 43.0 Williams (1984) Grapsus grapsus 80.0 eol.org Hemigrapsus sanguineus 42.0 Richerson (2017) Heterozius rotundifrons 23.0 McLay (1988) Hyas araneus 76.5 Miller & O'Keefe (1981) Liocarcinus depurator 51.0 Hayward & Ryland (1995) Macrocoeloma diplacanthum 12.8 Rathbun (1925) Menippe adina 10.0 tpwd.texas.gov Menippe mercenaria 129.0 Williams (1984) Mennipe nodifrons 72.0 Rathbun (1930) Metacarcinus gracilis 91.0 Rathbun (1930) Metacarcinus magister 198.0 Rathbun (1930) Micropanope sp. 6.5 Williams (1984) Mictyris longicarpus 25.0 ala.org.au Mithraculus forceps 38.0 Williams (1984) Mithraculus sculptus 26.4 Rathbun (1925) Necora puber 109.0 Hearn (2002) Neohelice granulata 32.0 Angeletti & Cervellini (2015) Ovalipes catharus 150.0 McLay (1988) Ovalipes ocellatus 87.0 Williams (1984) Pachygrapsus crassipes 48.0 eol.org.au Pachygrapsus transversus 26.4 Williams (1984) Panopeus herbstii 62.0 Williams (1984) Paragrapsus gaimardii 48.0 Campbell & Griffin (1966) Percnon gibbesi 28.0 Williams (1984) Petrolisthes armatus 14.0 Masterson (2007) Pilumnus caribaeus 21.6 Rathbun (1930) Rhithropanopeus harrisii 21.3 Williams (1984)