Crayfish Assemblages Research Articles

Reach- and Watershed-Scale Associations of Crayfish within an Area of Varying Agricultural Impact in West-Central Indiana

Abstract We studied the associations of crayfish with reach-scale instream habitat and water quality variables and watershed-scale variables of riparian and watershed land cover, runoff, impervious surfaces, and hydrologic soil type in west-central Indiana. Crayfish assemblage was measured by abundance, species richness, and diversity (Shannon's H) at 180 sites. The western portion of the study area, within the Interior River Lowland ecoregion, has been heavily impacted by agriculture, while the eastern portion, within the Interior Plateau ecoregion, is more heavily wooded and less impacted. The ability of variables at each spatial extent to predict crayfish assemblage was assessed using multiple linear regression analysis. Reach-scale models were better predictors of crayfish assemblage than watershed-scale models. A variety of habitat and water quality characteristics, principally instream cover, appeared as important predictors. Forested riparian and watershed land appeared as significant watershed-sca...

Does the Density of Invasive Rusty Crayfish Affect Stream Macroinvertebrates?

AbstractRusty crayfish (Orconectes rusticus) have invaded streams of the upper Susquehanna River catchment (New York, USA), replacing native crayfish and probably increasing overall crayfish density. Crayfish are important consumers and agents of disturbance in aquatic communities, so the introduction and expansion of rusty crayfish could affect the invaded community through the change in crayfish species composition, the increase in crayfish density, or some combination of the two. Other macroinvertebrates are prey of, competitors with, or subject to disturbance by crayfish and so are likely to be affected by changes in the crayfish assemblage. We conducted correlative field sampling and an enclosure experiment to investigate the effects of invading O. rusticus on the abundance, diversity, and composition of the stream macroinvertebrate assemblage. We sampled crayfish and macroinvertebrates at 13 sites on 4 streams in the upper Susquehanna River catchment that varied in crayfish species composition and density. Total macroinvertebrate abundance, taxon richness, diversity, and density of individual taxa were not significantly correlated to either total crayfish density or the relative abundance of O. rusticus. We also conducted an experiment in stream enclosures to test the effects of O. rusticus density on the macroinvertebrate assemblage. Increasing crayfish density caused a significant decrease in total macroinvertebrate density but did not significantly affect macroinvertebrate taxon richness or diversity. The density of some individual taxa were also significantly affected by crayfish density. Our experiment shows that rusty crayfish density can affect the stream community; the mechanism of these effects, and whether they differ from those of native species, remain to be determined.

Biological Response Signature of Oil Brine Threats, Sediment Contaminants, and Crayfish Assemblages in an Indiana Watershed, USA

The Patoka River watershed contains a divergent landscape of oil and gas exploration, intensive agriculture, and surface mining mixed with National Forest, Wildlife Refuges, and a large recreational reservoir. We evaluated species diversity among different land uses, including, commercial, forested, residential, and agriculture, and determined relationships among disturbance scale, habitat requirements, contaminants, and patterns in species distributions. Primary burrowing species, Cambarus polychromatus, Cambarus cf diogenes (Lacunicambarus A), and Fallicambarus fodiens, were tolerant of higher concentrations of contaminants than aquatic tertiary burrowing species. Cambarus polychromatus was among the last species of crayfish at the most disturbed sites, while it was absent from pasture and agricultural landscapes that allowed cattle access along banks. Four species of Orconectes were found in the reference and agricultural landscapes within the watershed, including O. immunis, O. indianensis, O. inermis inermis, and O. propinquus. Orconectes indianensis distribution was determined by the presence of rock habitat and absence of contaminants. No Orconectes species were found in acid mine leachate-affected streams with high levels of molybdenum. Cambarus laevis was found in the highest-quality reference areas, which were associated with karst habitats and no contaminants. Burrowing crayfish species were associated with the oil derricks in the lower and middle watershed, which contained increased concentrations of strontium, phosphorus, and various organic parameters associated with oil brine PAHs.

Associations of watershed vegetation and environmental variables with fish and crayfish assemblages in headwater streams of the Pedernales River, Texas

AbstractIntermittent headwater streams serve important functions for humans and wildlife in semi‐arid rangelands. Increases in ashe juniper coverage in central Texas over recent decades are believed to have negatively impacted stream flows. Few studies have examined relationships between aquatic species and environmental factors in these systems as well as the influence of juniper coverage on assemblage structure. During summer 2003 and spring 2004, we examined species–environment relationships to infer potential effects of juniper cover on aquatic ecology relative to local‐scale and watershed‐scale environmental variables. Fish and crayfish species assemblages and physicochemical variables were investigated in spring‐fed headwater tributaries of the Pedernales River, Texas. Fish abundance was much higher in summer 2003, whereas crayfish abundance was higher in spring 2004. Fish species richness was lower during spring 2004, possibly due to below average precipitation during spring 2004 that reduced deep‐water refugia. Higher abundance of crayfish in spring 2004 samples was probably due to their ability to survive low‐flow conditions, and a release from fish predation pressure. Fish assemblage structure was more strongly associated with local abiotic factors during spring 2004 when flow was reduced, whereas structure during summer 2003 samples suggested a relatively greater influence of predation. In general, juniper cover was weakly associated with fish and crayfish assemblages, although it tended to be positively associated with relatively high‐quality habitat for sensitive taxa (flowing runs with coarse substrate; deep, connected pools). We suggest that intermediate levels of juniper cover in the region provide indirect benefits to aquatic organisms. However, short‐term, local environmental factors appear to have a much greater influence than watershed vegetation on fish and crayfish assemblages in these intermittent streams. Copyright © 2007 John Wiley & Sons, Ltd.

Crayfish assemblage shifts in a large drought‐prone wetland: the roles of hydrology and competition

Summary1. Faster growing, larger and/or more aggressive crayfish species are predicted to dominate permanent waterbodies. We tested this prediction using a 9 year dataset for two species of crayfish (Procambarus alleni and Procambarus fallax) co‐existing in a sub‐tropical flowing slough in southern Florida. Using a series of laboratory and mesocosm experiments we also compared life history traits and performance of the respective species to test mechanisms that could explain dominance shifts in the local crayfish assemblages.2. Over the 9‐year period, P. alleni densities were the greatest in shallower, shorter‐hydroperiod areas bordering the slough, while P. fallax densities were higher in deeper, longer‐hydroperiod central areas. These areas were separated by 0.8–2 km of continuous wetland with no apparent barriers to movement between them.3. Density of P. fallax was not strongly affected by any measures of hydrological variation, while P. alleni density increased with more severe drought conditions. Following the strongest droughts, P. alleni colonized areas in the centre of the slough where they had been absent or scarce in wetter years.4. We conducted experiments to compare growth rates, drought tolerance, and competitive dominance of these species. P. alleni survived drought conditions better, had higher growth rates, and was the dominant competitor for space and food. While drought probably limits P. fallax in the drier slough habitats, neither drought sensitivity nor interspecific competition with P. fallax can explain decreases of P. alleni with wetter conditions.5. Our results indicate that a competition‐colonization tradeoff cannot explain the crayfish compositional dynamics in this wetland because P. alleni is both the best competitor and the best at surviving in and colonizing areas with the strongest droughts. Future attention should focus on the potential for selective effects of predators that co‐vary with hydrology.6. The traits (large size, fast growth, competitive dominance) exhibited by P. alleni, which is absent in long‐hydroperiod wetlands, are those exhibited by dominant crayfish in permanent lakes and streams containing fish. Although these traits make crayfish less vulnerable to fish in some lakes and streams, life‐history models of community structure across permanence gradients suggest the opposite traits should be favoured for co‐existence with fish.

Habitat Use and Selection within Ozark Lotic Crayfish Assemblages: Spatial and Temporal Variation

Abstract Habitat selection by small (≤ 15.0 mm carapace length (CL)) and large (> 15.0 mm CL) individuals of the crayfish, Orconectes marchandi, O. ozarkae, O. punctimanus, and Cambarus hubbsi was examined at 4 sites in 2 streams in the Spring River watershed. Replicate quadrat samples were collected from riffle, run, pool, emergent vegetation, stream margin, and backwater habitats during the summers of 1998 and 1999. A 3-factor ANOVA was used to determine effects of habitat, species, and year on crayfish density for each site and stream. Habitat selection by crayfish was determined by comparing habitat used to habitat available for each species and size class. There were significant temporal differences in habitat used by some species-size classes of crayfish, but significant species by habitat interactions were detected at all sites for both crayfish size classes. Small O. ozarkae and O. punctimanus used mainly vegetated habitat, whereas both size classes of C. hubbsi used mainly riffles and runs. Large...

Recolonization by Warmwater Fishes and Crayfishes after Severe Drought in Upper Coastal Plain Hill Streams

AbstractExtreme hydrologic disturbance, such as a supraseasonal drought, can dramatically influence aquatic communities. Documentation of the responses of aquatic communities after such disturbances provides insight into the timing, order, and mechanisms of recolonization. Postdisturbance recolonization of streams depends on many factors, including the region and characteristics of the disturbance relative to the disturbance regime. A supraseasonal drought that ended in the fall of 2000 resulted in the desiccation of numerous small streams or stream segments in northern Mississippi that were normally perennial. We repeatedly sampled fish and crayfish during predrought and postdrought periods in seven stream reaches that dried and five that remained flowing during the drought. From immediately after the drought until early summer of 2001, postdrought fish and crayfish assemblages differed from predrought assemblages in dry sites but not in flowing sites. The initially slow recolonization rates increased considerably during early spring 2001 so that by June 2001 fish catch per unit effort, species composition, and species richness in dry sites no longer differed significantly from predrought values. The fish recolonization process was highly ordered, as indicated by significant patterns of species nestedness over time in dry sites. Crayfish numerical recovery followed a pattern similar to that for fish, and we captured more crayfish in June 2001 than in the predrought period. Patterns in fish and crayfish population size structures over time indicated that repopulation was due to both immigration and reproduction. Recolonization was indicative of high mobility, particularly during spring and early summer. Although the fauna was quite resilient to stream desiccation, the effects on fish species composition and fish and crayfish size structure persisted 1 year after the drought.

The importance of crayfish in the breakdown of rhododendron leaf litter

1. Rhododendron (Rhododendron maximum) is a common evergreen shrub in riparian areas of the southern Appalachians, where its leaves can comprise a large proportion of leaf litter in streams. However, they are relatively refractory and generally considered a low quality food resource for detritivores.2. Our objective was to assess whether macroconsumers [primarily crayfish (Cambarus bartonii)] influence rhododendron leaf breakdown in a forested southern Appalachian stream in both summer (when leaves other than rhododendron are relatively scarce) and autumn (when other leaves are relatively abundant). We conducted two leaf decay experiments, one in summer and one in autumn, using pre‐conditioned leaves. Macroconsumers were excluded from the benthos of a fourth‐order stream using electric ‘fences’; we predicted that excluding macroconsumers would reduce the decay rate of rhododendron leaves in both summer and autumn.3. In both experiments, breakdown rate was lower in exclusion treatments. Macroconsumers accounted for approximately 33 and 54% of rhododendron decay in summer and autumn, respectively. We attribute this effect to direct shredding of rhododendron by crayfish. Biomass of insect shredders, insect predators and fungi did not differ between control and exclusion treatments, indicating that insectivorous sculpins (Cottus bairdi) had no effect on rhododendron decay and that omnivorous crayfish did not exert an indirect effect via alteration of insect or fungal biomass.4. The influence of shredding insects varied between summer and autumn. In summer, when other, more palatable leaf types were not available, rhododendron leaf packs appeared to provide ‘resource islands’ for insect shredders. There was a significant inverse relationship between insect shredders and leaf pack mass in the summer exclusion treatment: insects were the only organisms eating leaves in this treatment and, as shredder biomass increased, remaining leaf pack mass decreased. In the control treatment, however, we did not see this relationship; here, the effect of insect shredders was presumably swamped by the impact of crayfish. In autumn, when other leaves were abundant, insect shredder biomass in rhododendron leaf packs was less than one‐third of summer values.5. Even at low density (approximately 2 m–2) crayfish were able to influence an ecosystem process such as leaf decay in both summer and autumn. Given the threatened status of many crayfish species in the United States, this finding is especially relevant. Even small alterations in crayfish assemblages, whether via loss of native species and/or introduction of exotic species, may have significant repercussions for ecosystem function.

Changes in the Distribution of Stream-Dwelling Crayfishes in the Schoharie Creek System, Eastern New York State

Changes in the distribution of crayfishes in the Schoharie Creek drainage, eastern New York State, are assessed, based on historical records and surveys conducted in 1982-83 and 1996. The native crayfish assemblage in this region probably consisted of only three species: Cambarus bartonii, C. robustus, and Orconectes propinquus. In 1982-83, six crayfishes (C bartonii, C. robustus, O. immunis, O. obscurus, O. propinquus, and O. rusticus) were collected in the drain? age. In 1996, all the crayfishes except O. obscurus were found again, and an additional species (O. virilis) was captured at one site. Between the two survey periods, O. rusticus markedly expanded its range, while the range of O. propinquus decreased and the relative abundance of other species declined. The habitat use of each species is examined.

Unsaturated Fish Communities in African Rivers

Unsaturated Fish Communities in African Rivers