Investigation of Crayfish Control Technology FINAL REPORT COOPERATIVE AGREEMENT NO. 1448-20181-02-J850 Matthew W. Hyatt Arizona Game and Fish Department Wildlife management Division / Research Branch 2221 W. Greenway Road Phoenix, AZ 85023 ii CIVIL RIGHTS AND DIVERSITY COMPLIANCE The Arizona Game and Fish Department prohibits discrimination on the basis of race, color, sex national origin, age, or disability in its programs and activities. If anyone believes they have been discriminated against in any of the AGFD’s programs or activities, including its employment practices, the individual may file a complaint alleging discrimination directly with the AGFD Deputy Director at: Arizona Game and Fish Department Office of the Deputy Director, DOHQ 2221 West Greenway Road Phoenix, Arizona 85023-4399 (602) 942-3000 or The Office for Diversity and Civil Rights U.S. Fish and Wildlife Service 4040 North Fairfax Drive, Suite 130 Arlington, Virginia 22203 AMERICANS WITH DISABILITIES ACT COMPLIANCE The Arizona Game and Fish Department complies with all provisions of the Americans with Disabilities Act. If you require this document in an alternative format, please contact the AGFD Deputy Director as listed above or by calling TTY at (800) 367-8939. iii EXECUTIVE SUMMARY North America is home to 390 native species of crayfishes, 75% of the world’s total. No native crayfish occur in Arizona or the Colorado River basin of western North America; however, they have been widely introduced to this landscape and have become widespread and abundant throughout the Colorado River basin. Nonindigenous crayfishes have greatly altered North American lake and stream ecosystems, harmed fisheries, extirpated many populations of native crayfishes, and contributed to the global extinction of at least one native crayfish species. The economic cost alone of a small subset of freshwater Nonindigenous species in the United States has recently been estimated at 4.1 billion dollars annually. In Arizona, crayfish pose a serious threat to the long-term survival of many species of native fishes and amphibians. Due to the potential harmful effects to native flora and fauna, there is a need for the development of methods to control or eradicate Nonindigenous species. This report provides a complete literature review of methods that have been tested for the purpose of controlling or eradicating nonindigenous crayfishes and methods that have not been tested, but have potential. Five broad categories of control were considered: legislative, mechanical, biological, physical, and chemical. Legislative control, while in effect at both the state and national level, has been unsuccessful. Mechanical control methods include manual removal, trapping, and electrofishing. Trapping, despite being the most common method used, has failed in every case to eliminate or even control crayfish. Biological control includes the use of fish predators, diseases, and microbial insecticides. Although some cases demonstrated an inverse relationship between the presence of fish predators and crayfish numbers, in no case did fish predators eradicate a population of crayfish. Crayfish plague is lethal to non-North American crayfish, but not to North American crayfish. If a strain of this disease lethal to North American crayfish could be developed, it might prove to be an effective method of control. Physical methods include de-watering, habitat destruction, and barriers. The ability of crayfish to travel over-ground for long distances and to survive for long periods of time in their burrows during dry periods, renders physical methods useless in most cases. Chemical methods include biocides, rotenone, and pheromones. Although rotenone will kill crayfish, any dosage sufficient to cause crayfish mortality results in the death of almost all other living organisms first. Research on the potential of using pheromones as a means of control has just recently begun. Early results of these studies do not look promising, but pheromones may prove effective in helping detect low density crayfish populations. Biocides proved to be the only method with any potential for eradicating or controlling crayfish. iv TABLE OF CONTENTS EXECUTIVE SUMMARY iii INTRODUCTION 1 CONTROL CATEGORIES 5 LEGISLATIVE 5 MECHANICAL 11 Manual 11 Trapping 12 Electrofishing 22 BIOLOGICAL 23 Fish Predators 23 Diseases 26 Microbial Insecticides 28 PHYSICAL 29 De-watering 31 Habitat Destruction 32 Barriers 32 Other 35 CHEMICAL 35 Biocides 36 Rotenone 56 Pheromones 59 CONCLUSIONS 63 LITERATURE CITED 73 FIGURES Figure 1. Schematic diagram of commercial Swedish Trappy. 14 Figure 2. Modification of standard minnow trap used to harvest crayfish and reduce unwanted fish capture in lakeside ponds used to rear endangered native fish at Lake Mohave, Arizona/Nevada. 17 Figure 3. Schematic diagram of a refuge trap. 18 Figure 4. Schematic diagram of a small mesh trap. 20 Figure 5. Proposed design of catchpit at West Tanfield Fishery. 25 TABLES Table 1. Differential importance1 of different anthropogenic vectors of crayfish introductions in Europe and North America. 2 Table 2. Effect of fish predators on adult (A) and juvenile (J) crayfish population size. 25 Table 3. Concentrations (mg/L, except mg/L for Baythroid) that produced 100% mortality for rusty crayfish and bluegills in static tests at 12oC. 43 Table 4. Estimated costs of chemical treatments. 55 1 INTRODUCTION North America is home to 390 native species of crayfishes, 75% of the world’s total (Lodge et al. 2000). There is at least one native crayfish species in each of the 48 continental United States except for Arizona, which has no native species (Hobbs 1989). Moreover, there are no crayfish species native to the Colorado River basin of western North America, including the Gila River drainage of Arizona and New Mexico. However, crayfish have been widely introduced to this landscape and have become widespread and abundant throughout the Colorado River basin. In several well documented cases, nonindigenous crayfishes have greatly altered North American lake and stream ecosystems, harmed fisheries, extirpated many populations of native crayfishes, and contributed to the global extinction of at least one native crayfish species (Lodge et al. 2000). The economic cost alone of a small subset of freshwater nonindigenous species in the United States has recently been estimated at 4.1 billion dollars annually (Pimentel et al. 1999). In Arizona, crayfish pose a serious threat to the long-term survival of many species of native fishes and amphibians. Introductions of nonindigenous crayfish around the world can be attributed to a variety of vectors (Table 1). Crayfish first appeared in Arizona waters about 30 years ago when they were stocked by Arizona Game and Fish Department (AZGFD) and U.S. Fish and Wildlife Service (USFWS) for the purposes of aquatic weed control (Dean 1969) and as forage for sport fish. It has also been suggested that the appearance of non-native crayfish in other states is a result of deliberate stockings by crayfish trappers, who wished to expand their operations (Bills and Marking 1988). Other mechanisms by which crayfish are introduced to the wild include their discard by aquarium enthusiasts and 2 escape or release from bait buckets, both reasonable explanations for the present widespread distribution of nonindigenous crayfish in the state (Inman et al. 1998). Table 1. Differential importance1 of different anthropogenic vectors of crayfish introductions in Europe and North America (Lodge et al. 2000). Vector of crayfish introduction Europe North America 1. Canals Decreasing importance Decreasing importance 2. Legal stocking in natural waters Decreasing importance Decreasing importance 3. Illegal stocking in natural Remains important Decreasing importance waters 4. Aquaculture Increasing importance Increasing importance 5. Live food trade Increasing importance Increasing importance 6. Aquarium and pond trade Remains important Increasing importance 7. Biological supply trade Not important Increasing importance 8. Live bait Decreasing importance Increasing importance 1In the absence of data comparable across vectors, we relied on expert opinion. Collecting data to quantify the importance of different vectors should be a priority. Due to the potential harmful effects to native flora and fauna, there is a need for the development of methods to control or eradicate nonindigenous crayfish species. According to Peay and Hiley (2001), the feasibility of eradicating, or even controlling, a population of crayfish is dependent on a number of factors: - Is there any method of determining whether or not a control method has been effective? - Is there a method capable of killing/ removing all the alien crayfish in a target area, or at least sufficient to prevent the population from spreading? - Is there a method specific to alien crayfish, and if not, is its use acceptable? Peay and Hiley (2001) suggest that unless the endpoint is known and identifiable, there is a risk of very large expenditure of resources without achieving eradication, or even 3 control. Consequently, basic understanding of crayfish population dynamics is needed in order to assess the potential for eradication. The fundamental problem of any attempt to eradicate a population is the difficulty of achieving and detecting 'zero' population (Peay and Hiley 2001). In order for any methodology designed for the eradication of nonindigenous crayfish to be judged successful, it must be capable of removing sufficient crayfish