Robert J. DiStefano

A Reassessment of the Conservation Status of Crayfishes of the United States and Canada after 10+ Years of Increased Awareness

Abstract The American Fisheries Society Endangered Species Committee herein provides a list of all crayfishes (families Astacidae and Cambaridae) in the United States and Canada that includes common names; state and provincial distributions; a comprehensive review of the conservation status of all taxa; and references on biology, conservation, and distribution. The list includes 363 native crayfishes, of which 2 (⟨ 1%) taxa are listed as Endangered, Possibly Extinct, 66 (18.2%) are Endangered, 52 (14.3%) are Threatened, 54 (14–9%) are Vulnerable, and 189 (52.1%) are Currently Stable. Limited natural range continues to be the primary factor responsible for the noted imperilment of crayfishes; other threats include the introduction of nonindigenous crayfishes and habitat alteration. While progress has been made in recognizing the plight of crayfishes, much work is still needed.

The Bait Industry as a Potential Vector for Alien Crayfish Introductions: Problem Recognition by Fisheries Agencies and a Missouri Evaluation

Abstract “Bait-bucket introductions” related to the fishing bait industry are the suspected primary cause of alien (non-indigenous) crayfish introductions that have damaged North American aquatic ecosystems. Our 2008 survey of U.S. and Canadian fisheries agencies revealed that 49% of respondents reported aquatic resource problems that were believed to have been caused by bait-bucket introductions of alien crayfishes. Most respondents reported existing regulations designed to address those problems; however, only 4% prohibited the use of live crayfish bait. Our 2002–2007 examination of Missouri bait shops revealed sales of illegal and invasive alien crayfishes by bait shop proprietors who could not identify the species they were selling. Fisheries agencies should consider more effective bait regulations and education to prevent negative impacts to aquatic biodiversity, habitat, and fisheries that can result from alien crayfish introductions.

Imperiled crayfishes use hyporheic zone during seasonal drying of an intermittent stream

Abstract Despite the prevalence and importance of intermittent streams, few studies have examined their use by crayfishes. We documented persistence in an intermittent stream and use of the hyporheic zone by 2 imperiled crayfishes, Orconectes williamsi and Orconectes meeki meeki, upon stream drying. During 2005 to 2007, we monitored summer flows and crayfish densities in 10 riffles in a Missouri (US) Ozark stream to document stream drying and crayfish persistence. Stream drying variables were riffle wetted area (m2) and current velocity (m/s). Crayfish density estimates were obtained with a quadrat sampler. We sampled monthly (May–August 2006) to examine crayfish response to decreased flows, and excavated dry quadrat samples (to 30 cm depth) after surface flows ceased. Over 2 periods during summer 2007, we used baited traps in the stream and a downstream reservoir where the stream terminates to examine whether crayfish migrated from the stream to permanent water in response to drying. Riffles dried significantly by July, few had surface water present by August, and all were rewetted by the following June. Annual June densities of O. williamsi remained stable throughout the study, whereas densities of O. m. meeki were lower in 2007 than 2005. Both species burrowed to the hyporheic zone during drying, and crayfish densities were similar to those estimated in riffles before drying. We found no evidence that either species migrated to permanent water in the reservoir during drying. Use by crayfish of the hyporheic zone during drying and interannual persistence in intermittent streams suggests that hyporheic habitats are important for conservation of these crayfishes. Our study contributes to the increasing body of knowledge that indicates the importance of intermittent streams for conservation of freshwater biodiversity.

A SAMPLING METHOD TO ASSESS LOTIC CRAYFISH COMMUNITIES

Abstract Crayfish are widely recognized as an important ecological component of stream systems, but there has been limited work to develop and evaluate the reliability of sampling methods for lotic crayfishes, especially efforts that are temporally and spatially comprehensive. We desired a quantitative method to assess crayfish communities in streams with rocky substrate. Our objective was to develop a method to obtain and compare representative density estimates with acceptable variance and reasonable effort, and to illustrate use of the method by using it to 1) describe and compare diurnal habitat associations by lotic crayfish, and 2) detect density changes over time. Our study encompassed four sites on two rivers, two seasons, and 8 y (1991–1998) to evaluate a 1-m2 quadrat sampler, and a sampling method that stratified effort among five macrohabitats to reduce variability. This method performed well for both seasons, detecting spatial differences among macrohabitats and temporal differences among years. Spatial differences were expressed as macrohabitat selectivity by the crayfish community, and showed a consistent trend across streams and seasons. In particular, macrohabitats with slower current velocities consistently had the highest densities. Temporal differences included documentation of decreased densities in several macrohabitats across 5 y. Sampling precision, measured by coefficients of variation, was acceptable but not considered high. Statistical power was good for detecting spatial differences, but reduced and variable for detecting temporal changes. Our findings 1) demonstrate the use of stratifying quantitative sampling for lotic crayfish communities by habitats, 2) confirm the importance of evaluating sampling methods, and 3) illustrate the consistent way in which Ozarks crayfish communities used available macrohabitats.

Reproductive Biology of the Crayfish Orconectes luteus (Creaser) in a Missouri Stream

Abstract The reproductive biology of the crayfish Orconectes luteus (Creaser) from the Jacks Fork River, Missouri, was studied. Data on reproduction, fecundity and growth were obtained from monthly or semimonthly collections over 27 mo. Females oviposited in March or April, depending on water temperature, and the young became independent by May or June. Seasonal growth and molting began when water temperatures exceeded about 9 C in spring and ceased when water temperatures dropped below 8 C in fall. About one-third of the male and female crayfish became sexually mature their first year of life. Adult males began molting to the reproductive state (Form I) in September and October and returned to the nonreproductive state (Form II) in April and May when the females were carrying eggs and young. Newly hatched young went through two molts before becoming independent from the female in the third instar. A significant positive relation was found between crayfish size and number of ovarian eggs, pleopodal eggs and size of pleopodal eggs. Significantly greater numbers of ovarian vs. pleopodal eggs were found at both sites.

An assessment of life-history studies for USA and Canadian crayfishes: identifying biases and knowledge gaps to improve conservation and management

Abstract. Life-history knowledge is central to basic and applied ecology, but recent reviews show that knowledge of life histories of many freshwater invertebrates is incomplete because of difficulty in conducting such studies or a general decline of interest in natural-history research. We review and summarize published life histories for crayfishes native to the USA and Canada. We document the rate of accumulation of crayfish life-history knowledge and biases and gaps in life-history knowledge by taxonomic group, geography, habitat preference, and conservation status. A total of 78 published studies (59 papers; several included life-history information for multiple species) covering 42 (12%) of the 347 USA and Canadian crayfishes recognized as of 2007 met our criteria for crayfish life-history studies. Life-history studies were lacking for crayfishes of conservation concern and stygobitic or primary burrowing-habitat specialists. Life-history knowledge is relatively complete for low-diversity freshwater ecoregions of northern and western North America, but lacking for high-diversity freshwater ecoregions of the southeastern USA. From 1972 to 2007, an average of 3.40 new crayfish species/y were described, whereas 0.63 species/y were added to the list of crayfishes with published life-history studies. Thus, taxonomic knowledge is expanding faster than ecological or life-history knowledge of these same species, inevitably limiting our ability to manage and conserve them. We conclude with suggestions for increasing publication of crayfish life-history studies, and priorities for regions, taxonomic groups, and life-history traits that require urgent attention. We also present a database of existing crayfish life-history studies for researchers interested in life-history questions and to provide a foundation for traits-based inquiries into crayfish macroecology and applied questions in conservation like the prediction of extinction and invasion risk.

Invasive Crayfish Orconectes neglectus Threatens Native Crayfishes in the Spring River Drainage of Arkansas and Missouri

Abstract Invasive species are one of the major threats to biological diversity. Invasive species of crayfish are known to negatively impact native species in aquatic ecosystems. We recently found that an Ozark endemic crayfish, Orconectes neglectus, has been introduced into the Spring River drainage of southern Missouri and northern Arkansas and appears to have the potential to negatively impact the native communities. We used quantitative kick netting along the Spring River and selected tributaries to determine the distribution and abundance of O. neglectus and its potential to impact native crayfish species. The native crayfishes Orconectes eupunctus, a species of special concern, and Cambarus hubbsi appear to no longer occur throughout much of their former range in the Spring River drainage where O. neglectus is now abundant. Orconectes eupunctus, C. hubbsi, and O. neglectus mainly used fast-flowing riffle and run habitats with a mix of gravel, cobble, and boulder, whereas the other common species collected, Orconectes punctimanus and Orconectes ozarkae, were more generalists in habitat use and were found at all sampled sites. Orconectes eupunctus and C. hubbsi were positively associated with each other, but negatively associated with O. neglectus, despite their similar habitat use. These results provide evidence that O. neglectus is expanding its range, possibly to the detriment of O. eupunctus and C. hubbsi. An intensive field survey and manipulative experiments would be required to confirm the disappearance of the native species, and the mechanisms involved.

Relative Performances of Four Preservatives on Fish and Crayfish

Abstract We evaluated the effects of four common preservatives on central stonerollers Campostoma anomalum and virile crayfish Orconectes virilis to aid in the selection of a method for preserving fish diet samples in the field. Thirty specimens of each species were allocated to each of eight treatments: 10% formalin; 25, 50, 75, and 100% isopropanol; 75 and 100% ethanol; and freezing at –15°C. After 180 d, specimens were evaluated for color change, physical tone, and quality of tissue preservation. After 90 d and 180 d, changes in central stoneroller total length and wet weight and in crayfish carapace length, chela width, and wet weight were evaluated. Freezing preserved fish and crayfish with the least effect on coloration and physical tone. All treatments except 25% and 50% isopropanol prevented tissue decay. All treatments caused decreases (<3% after 180 d) in fish total length. Formalin increased fish weight (12%; 180 d), but all other treatments caused decreases (10–37%; 180 d); freezing had the le...

Ecological effects of lead mining on Ozark streams: In-situ toxicity to woodland crayfish (Orconectes hylas).

The Viburnum Trend mining district in southeast Missouri, USA is one of the largest producers of lead-zinc ore in the world. Previous stream surveys found evidence of increased metal exposure and reduced population densities of crayfish immediately downstream of mining sites. We conducted an in-situ 28-d exposure to assess toxicity of mining-derived metals to the woodland crayfish (Orconectes hylas). Crayfish survival and biomass were significantly lower at mining sites than at reference and downstream sites. Metal concentrations in water, detritus, macroinvertebrates, fish, and crayfish were significantly higher at mining sites, and were negatively correlated with caged crayfish survival. These results support previous field and laboratory studies that showed mining-derived metals negatively affect O. hylas populations in streams draining the Viburnum Trend, and that in-situ toxicity testing was a valuable tool for assessing the impacts of mining on crayfish populations.

Efficiency of a Quadrat Sampling Technique for Estimating Riffle-Dwelling Crayfish Density

Abstract Quantitative sampling of crayfish can be challenging as a result of clustered distributions produced by a variety of factors. We tested the efficiency of a 1-m2 quadrat sampler for estimating the density of riffle-dwelling crayfish. Sampling efficiency was evaluated in an Ozark Plateau stream through a mark–recapture study. We stocked three marked crayfish per square meter into 12 enclosed riffle sections (range, 46–53 m2) and then randomly sampled five 1-m2 quadrats in each of the 12 sections. Sampling efficiency was determined by comparing the estimates of crayfish density to the known density of marked crayfish. We found crayfish sampling efficiency (mean, 69%) to be comparable to that in studies evaluating the quadrat sampler for stream fish, although efficiency across our study riffles ranged widely, from large underestimates (27%) to positively biased overestimates (140%). Coefficients of variation revealed that replicating habitat units within a stream or stream reach may provide more prec...