Non-native Crayfish Research Articles

First Establishment of an Invasive Crayfish, Orconectes Limosus (Rafinesque, 1817) (Decapoda, Cambaridae) in Nova Scotia, Canada

No native or non-native crayfish species have been recorded in Nova Scotia, Canada. Aquatic surveys and research conducted by the Nova Scotia Museum during the past 25 years have not identified any populations of crayfish in the province. The only native species of crayfish in Maritime Canada is believed to be Cambarus bartonii (Fabricius, 1798), which, along with the non-native Orconectes limosus (Rafinesque, 1817) and Orconectes virilis (Hagen, 1870), have in the past been restricted to New Brunswick (Ganong, 1887; Crocker & Barr, 1968; McAlpine et al., 1991; McAlpine et al., 1999). The evidence presented here supports other recent information (McAlpine et al., 2007) that non-native crayfish are becoming more prevalent in the region and that this may require policy measures aimed at control. On 9 August 2005, SL observed an adult crayfish excavating a burrow on the south side of Freshwater Lake in Cape Breton Highlands National Park, Nova Scotia. Over the next three months, two shed crayfish exoskeletons were collected in the lacustrine areas of the lake. An adult crayfish was captured by SL in a shallow bay on the northeast corner of the lake on 2 September 2005. This specimen was photographed and measured (total length 81 mm). After confirming that the species was Orconectes limosus, a limited trapping program was conducted in 2006 to collect basic information about the population.

A Cost-Benefit Analysis of Introducing a Non-native Species: The Case of Signal Crayfish in Sweden

A conventional bioeconomic model is used for a cost-benefit analysis of introducing the non-native signal crayfish, which has an eradicating impact on the stock of the native noble crayfish. The values of the noble and signal crayfish populations are measured as present values of their net future revenues. The results indicate that the net benefit of an introduction is positive if the intrinsic growth rate or the carrying capacity of the noble crayfish is below 40% that of the signal crayfish. This means that, only if there are significant biological differences between the two species, economic gains can be realized by allowing introduction of the signal crayfish.

Threat of non-native crayfish introductions into Turkey: global lessons

Introductions of crayfish species from their home range to new environments have been carried out in many parts of the world. The most important introduced crayfish species are Procambarus clarkii, Pacifastacus leniusculus, Cherax destructor, C. quadricarinatus, Orconectes limosus, O. rusticus and Astacus leptodactylus. The environmental impact of crayfish introductions can be positive, negative or neutral. However, native crayfish populations in Europe have been negatively affected by introductions of non-indigenous crayfish species from America. Negative effects of non-native crayfish introductions included displacement of native crayfish species, transfer of disease (crayfish plague), consumption of fish eggs, reduction of fish stocks, consumption of large amounts of macrophytes, indirect and direct effects on other invertebrates and upsetting production in rice fields. As a result of non-native crayfish introductions, the natural harvest and crayfish industry in Europe have been severely affected. Large quantities of Turkish A. leptodactylus were harvested (approximately 7,000 tonnes annually) and exported to Europe before the crayfish plague was observed in these populations. The total harvest of A. leptodactylus in Turkey reduced dramatically to 320 in 1991 after the plague. Therefore, although Turkey currently has no known non-native crayfish species, there is a threat of non-native crayfish introduction in order to increase crayfish productions and subsequent harvest. The North American spiny-cheek crayfish, O. limosus, has been spreading quickly down the River Danube and could soon reach neighboring countries including Turkey. The North American signal crayfish, P. leniusculus is known from Greece and could be a threat to native stocks if it is introduced into Turkey for aquaculture. Additional threats may come from the release of other North American species, which are widely available through the aquarium trade. We conclude that the spread of non-native crayfish introductions throughout Turkey will increase local problems, because introductions of non-native crayfish in many parts of the world have been known to have caused important reductions in population density and numbers of native crayfish species. Furthermore, freshwater ecosystems may be altered by such introductions and the economic viability of native crayfish species fisheries could be severely reduced in Turkey.

Detritus processing by endemic and non-native Hawaiian stream invertebrates: a microcosm study of species-specific effects

In studies of detritus processing in streams, invertebrate detritivores are often pooled into functional groups of species that have similar feeding modes. Differ- ences among functional groups in detritus processing are well-known, but differences among species within functional groups are rarely considered. Introductions of non- native species and losses of native populations are changing the composition of detriti- vore assemblages in many streams, and a species-specific approach is needed to under- stand the effects of these changes on detritus processing. In this study, we compared the rates at which the native and non-native invertebrate detritivores from streams on the Island of Hawai' i processed detrital leaves. Experimental treatments consisted of single detritivore species and species-pairs. Results from species-pairs were used to determine whether interspecific interactions increased (facilitated) or decreased (inhib- ited) rates of detritus processing. Results of the single-species treatments indicated that the endemic shrimp Atyoida bisulcata and the non-native crayfish Procambarus clarkii significantly increased rates of leaf processing compared with controls with no ani- mals; two other non-native and one other endemic species did not have significant ef- fects. For all species-pairs, observed processing rates were not significantly different from rates predicted in the absence of interaction, i.e., the sum of the effects of each species alone. At present, P. clarkii is the only leaf-shredding stream invertebrate in Hawai'i. P. clarkii processed detrital leaves >10 times faster than the other species, and any facilitory or inhibitory interactions between P. clarkii and other species are likely to be small relative to the effects of P. clarkii alone. Results of the experiments suggest

Aggression by Non-Native Crayfish Deters Breeding in California Newts

Adaptations used to defend against native predators may not be effective against introduced predators. For this reason perturbations caused by introduced species often affect the distribution and abundance of native prey organisms (Diamond & Case 1986). Predation is a strong selection pressure over time and results in antipredator adaptations in prey. Many adaptations are behavioral; these adaptations allow prey to exist in an environment where predation risk varies during ecological time (Lima & Dill 1990). The behavior of an organism reflects a complex of adaptations that have evolved in response to selection pressures from native predators (see Dill 1987; Lima & Dill 1990). When a nonnative organism is introduced, the interactions between the native and introduced species are often unpredictable. Introduced species can affect native organisms in a variety of ways. Resource exploitation, competition, and predation by nonnative species are well studied topics (see Diamond & Case 1986; Simberloff 1981). The current issues surrounding amphibian decline have prompted researchers to examine the effects of introduced predators on native amphibians (Hayes & Jennings 1986; Pechmann & Wilbur 1994). In most studies direct predation on larvae and/or eggs was found to be the primary detrimental effect on native amphibians (Cory 1963; Hayes & Jennings 1986; Bradford 1991; Bradford et al. 1993; Bronmark & Edenhamn 1994; Gamradt & Kats 1996). In southern California, California newts (Taricha torosa) have been declining and have recently been listed as a species of special concern (Jennings & Hayes 1994). In a previous study (Gamradt & Kats 1996), we observed an inverse relationship between the distribution of Cali-

The white-clawed crayfish,austropotamobius pallipes, in Great Britain and Ireland with particular reference to its conservation in Great Britain

Great Britain and Ireland still contain some of the best stocks of Austropotamobius pallipes in Europe despite the fact that since the early 1980s many populations have been devastated by the effects of crayfish plague and competitive exclusion by non-native crayfish. Austropotamobius pallipes is the only crayfish native to Great Britain and Ireland but in recent years a number of introductions of foreign crayfish have been made into Great Britain, for aquacultural, culinary and aquarist purposes. This has resulted in four non-native crayfish species becoming established in thewild, wheretwo, Pacifastacus leniusculus and Astacusleptodactylus, have formed large, harvestable populations, particularly in southern England. Although A. pallipes in Great Britain and Ireland is protected by national and European legislation, this has not been enough to protect it from crayfish plague and, in Great Britain, from non-native crayfish. In an attempt to protect A. pallipes even further, legislation has been implemented in England, Scotland and Wales which bans the keeping of ail non-native crayfish, except wherethey are being prepared for human consumption. P. leniusculus is, however, exempt from this ban in certain parts of southern Great Britain dueto its high preponderance on crayfish farms and in the wild. Ireland already bans the introduction of non-native crayfish. It is hoped that the new legislation, plus the heightened profile which A. pallipes has