Invasive Red Swamp Crayfish Procambarus Research Articles

State of the ART: Using artificial refuge traps to control invasive crayfish in southern California streams.

Invasive species are a widespread threat to stream ecosystems across the planet. In Southern California, USA, the invasive red swamp crayfish Procambarus clarkii (Girard, 1852) poses a significant threat to native aquatic fauna. Studies have suggested that artificial refuge traps (ARTs) resembling crayfish burrows can be used to remove invasive crayfish, but, to date, no studies have focused on optimizing ART design and deployment to maximize crayfish catch. This month-long study tested the effect of modifications on ART diameter, color, and soak time on P. clarkii catch effectiveness across 160 traps. We evaluated catch data by creating multiple candidate generalized linear mixed models predicting P. clarkii catches with different modeling parameterizations and a priori hypothesized predictor variables. During the study period, ARTs removed a total of 240 red swamp crayfish with no incidental bycatch. Larger P. clarkii (2-6-cm carapace length) were found more frequently in 5.1-cm-diameter traps, and smaller P. clarkii (1-4 cm) were found more frequently in 2.5-cm-diameter traps. Catch numbers varied between trap types, with black-colored 5.1-cm-diameter traps removing the greatest amount of the total P. clarkii caught in the study (mean = 0.27, SD = 0.29; 35% of the total caught) and black-colored 2.5-cm-diameter traps removing the least amount (mean = 0.09, SD = 0.55; 12% of the total). Further, ART deployment duration was an important predictor variable for candidate models, where ARTs with 4-d and 7-d deployment durations had lower catch/unit effort than traps with 1-d and 2-d deployments. This factorial experiment is the 1st study to suggest specific design modifications to ARTs that optimize invasive red swamp crayfish removal without incurring non-target incidental bycatch. This study demonstrates that ARTs can be a valuable tool for conservation managers interested in restoring streams through invasive crayfish removal, especially where there are sensitive biological resources.

Environment and host-related factors modulate gut and carapace bacterial diversity of the invasive red swamp crayfish (Procambarus clarkii)

The invasive red swamp crayfish Procambarus clarkii is present in most of the Portuguese rivers with well-known economic and environmental impacts, being also an important reservoir for many fungal and bacterial pathogens that can affect native aquatic fauna. Here the bacterial microbiota of the gut and carapace of the red swamp crayfish from three distinct localities in Portugal was characterized, using a metataxonomic approach. We tested whether biological measurements (sex, cephalotorax lenght, body condition and stress through glucose measurements) and sampling locality can be used as predictors of alpha and beta bacterial diversity. Results showed that the carapace microbiota are more responsive to differing environmental conditions than the gut microbiota, which are likely more affected by host factors, such as sex. Additionally, we have also found several potential pathogens in the microbiota of the analyzed crayfish. Our data provide a relevant baseline of the red swamp crayfish microbiota but highlight the need for further research, namely to fully characterize its role as a vector for bacterial diseases in freshwater ecosystems.

Diet of a semiaquatic invasive mammal in northern Italy: Could it be an alarming threat to the endemic water vole?

The American mink Neovison vison has been introduced to Italy for fur farms in the 1950s. Since the 1970s, free-ranging individuals are present in north-eastern Italy, where an expanding population still occurs. In our work, we aimed at assessing the seasonal diet of invasive American mink introduced to north-eastern Italy. Thus, a total of 195 mink scats (N = 73, June 2007; N = 57, September 2007; N = 65, February 2008) were collected. Scats were washed and food remains isolated and classified through comparison with reference collections and atlases. Absolute and relative frequencies, as well as the estimated volume of each prey category were computed. The endemic Italian water vole Arvicola italicus represented the staple of the diet of the American mink in June (relative frequency: 20.4%, total volume in diet: 38.1%) and September (relative frequency: 22.7%, total volume in diet: 52.0%). Other small mammals, amphibians (Rana spp. and Pelophylax spp.) and the invasive red swamp crayfish Procambarus clarkii were mostly consumed in cold months, when water voles are not available. Differently from other study areas, wading birds and fish were rarely consumed, possibly because of their low local availability, if compared with small mammals. No law currently protects the endemic water vole, which may be furtherly threatened by the potential range expansion of invasive minks. Therefore, eradication of this alien carnivore should be recommended before local population decline of water vole become irreversible, and before minks reach populations of native riverine mustelids, i.e. the western polecat and the Eurasian otter.

Variable effects of an invasive species on the reproduction and distribution of native species in pond networks

Abstract The arrival of non‐native species in a community can be deleterious for native species. The joint investigation of several descriptors of native populations susceptible to invaders, under different invasion contexts, may help in predicting the outcome of their co‐occurrence with invasive species. Moreover, empirical studies seldom document the relative importance of the effects of invasive species on native species compared with other factors. Using survey data, we evaluated whether reproduction (larval density) and distribution of breeding sites of three amphibian species (Rana dalmatina, Lissotriton helveticus, and Triturus marmoratus) were related to the presence of invasive red swamp crayfish Procambarus clarkii, compared to other native predators, habitat, and landscape features, in two pond networks that differed in invasion intensity. The red swamp crayfish was only negatively associated with the larval density of one amphibian species studied. Its effect size was similar to that of some native predators, and much smaller than that of the canopy cover of ponds. Amphibians were widespread in the two pond networks. The occupancy of only one species in each network was negatively related to crayfish presence, while the occupancy of all species was negatively related to fish presence. The distribution of amphibian breeding sites was positively associated with aquatic vegetation cover. Negative associations between amphibians and red swamp crayfish were detected only in a few cases, even in the most invaded area, and thus results were less alarming than in previous studies. Differences in ecological traits of native amphibians and interactions with other environmental factors may explain the variable effects of red swamp crayfish on native amphibian populations.

Effects of intrapopulation phenotypic traits of invasive crayfish on leaf litter processing

The impact of invasive alien species (IAS) on an ecosystem is primarily studied at the species level, whereas the functional impacts of their genetic and phenotypic traits are poorly investigated. We used two laboratory based experiments to assess how intrapopulation phenotypic traits (size, sex, and number of claws) of the invasive red swamp crayfish Procambarus clarkii affect invertebrate shredders and leaf processing. Leaf consumption was significantly affected by the size and number of claws but not by the sex of the crayfish. Bigger animals presented a higher overall consumption but, in contrast, the mass of leaves consumed per unit crayfish body mass decreased with size. Indeed, the production of particulate organic matter followed the same trend, suggesting that the higher metabolic needs of smaller animals are responsible for their higher feeding activity on leaf litter. Claw loss in P. clarkii also led to increased leaf consumption and may be related to increased energy requirements for claw regeneration. Our results highlight the importance of also considering the phenotypic traits within populations for better understanding the impacts of IAS on ecosystem processes.

A Proposal for the Feasible Exploitation of the Red Swamp Crayfish Procambarus Clarkii in Introduced Regions

AbstractThe invasive red swamp crayfish Procambarus clarkii is a human‐mediated introduced species in the Iberian Peninsula. The species was introduced for economic reasons in the south of the Peninsula, but it is currently abundant and widespread in Portugal and Spain. As an invasive species, it is regulated by different laws in the Iberian Peninsula. Thus, although exploitation of this crayfish is permitted by the central government in Spain, the species is subjected to severe restrictions in Portugal. Moreover, regional governments in Spain only allow recreational fishing of P. clarki, except in southern Spain where there is an industrial activity based on the red swamp crayfish. We propose compromise measures in order to reconcile the economic exploitation of this aquatic resource and environmental concerns. The proposal mainly consists of the sale of live male specimens of P. clarkii and of dead (processed) female specimens. Biological invasion resulting in new established populations of P. clarkii in the wild would therefore be impossible. Transformation of P. clarkii into an economic resource with minimum environmental hazard seems feasible.

First evidence of microfungal “extra oomph” in the invasive red swamp crayfish Procambarus clarkii

This paper represents the first attempt to study the microfungal flora contained in the digestive system of the most widespread aquatic invasive invertebrate in the world: Procambarus clarkii (Cambaridae, Decapoda). Understanding its bioinvasion, in terms of ecological risk and environmental impact, requires a multidisciplinary approach that considers consequences on all levels, from macroscopic to microscopic. In this study, we investigated both the population dynamics and the dietary habits of the red swamp crayfish captured within a natural biotope in Northern Italy. The diet was mainly based on plant detritus. The analysis of microfungal flora in the crayfish stomach revealed a fairly constant composition, unrelated to season and diet. Since most of the fungi were associated with detritus and some species were particularly frequent, we formulate the hypothesis that the fungi may be selected to decompose plant material in the digestive tract, thus providing a source of energy to the crayfish. Procambarus clarkii is also shown to be a potential vector of plant diseases as some of the 45 isolated fungal taxa are potentially phytopathogenic.

Population dynamics of an epibiont Ostracoda on the invasive red swamp crayfish Procambarus clarkii in a western Mediterranean wetland

Recently, the American entocytherid ostracod Ankylocythere sinuosa was discovered for the first time in Europe to inhabit widely distributed populations of the invasive American crayfish Procambarus clarkii in the Iberian Peninsula. Based on this finding, the aim was to describe the population dynamics of exotic entocytherids for the first time beyond their original area, and to analyse the main variables modulating temporal demographic patterns. We monitored a population of A. sinuosa and its host, P. clarkii, in the Pego-Oliva wetland (Eastern Iberian Peninsula) monthly for 1 year. Crayfish entocytherid loads strongly related to crayfish weight, moult-related exoskeleton hardening stage and water temperature. The proportion of earliest juvenile entocytherid instars, an indicator of recent hatching periods, also related to water temperature and conductivity. According to our results, the most important factors affecting entocytherid dynamics are individual crayfish moulting events, which diminish ostracod load, together with water temperature and ionic concentration, both influencing the life cycle of the exotic epibiont ostracod A. sinuosa.

Tribute to Francesca Gherardi, scientist and editor

Francesca Gherardi, Associate Professor at the Department of Biology of the University of Florence, was a brilliant Italian zoologist and ethologist, and one of the most well-known and active experts on alien aquatic species. Since her masters degree in Biology (1979) and her PhD in Animal Biology (Ethology) (1987), both obtained at the University of Florence, Francesca studied the behaviour and ecology of aquatic animals. Initially, most of her research concerned social recognition in crustaceans: she was particularly renowned for her studies on hermit crabs and crayfish, her principal model organisms. Then, from the 1990’s onwards she worked in the field of invasion biology, her main interest until her death. Francesca devoted herself with enthusiasm and energy, not only to the problem of the invasive red swamp crayfish Procambarus clarkii, by revealing several aspects of its behavioral ecology, and by developing with her collaborators different methods for its control, but she gradually became an international expert on crayfish and more generally on aquatic alien species. In all aspects of her life, she was constantly driven by a continuous curiosity, thirst for knowledge and a will to face challenges; this was expressed by exploring and frequently opening new research fields. And she transmitted her drive and passion to the many students she supervised. One of the last papers with her contribution is published in this issue of Aquatic Invasions by Vera Goncalves, her Portuguese PhD student working on the interaction between Procambarus clarkii and the zebra mussel Dreissena polymorpha, an issue of recent increasing interest in Francesca’s team. Francesca Gherardi Florence, Italy, 12 November 1955–14 February 2013 (Photograph by Stephanie Peay)