43U 



Niin-imtivc Species — Our Living Rcsoiincx 



100% effective and can never eliminate all 

 threats from nonindigenous aquatic species. 

 Therefore, rapid response and control tech- 

 niques must be identified and in place to control 

 and limit damages caused by nonindigenous 

 ANS. This approach is being used to control 

 ruffe. 



Control is intended to reduce the effects of 

 nonindigenous aquatic species through eradica- 

 tion, reduction in numbers to tolerable levels, 

 and exclusion from sensitive areas. Three gen- 

 eral control methods exist to prevent the spread 

 of these species: chemical, biological, and phys- 

 ical. Proper evaluation and use of selective 

 chemicals may provide effective cimtrol of non- 

 native aquatic species with an apparent mini- 

 mum of ecological hazard or other side effects. 

 Increasing concern exists, however, about the 

 long-term environmental safety and impacts of 

 chemicals used to control nonindigenous aquat- 

 ic species. Efforts to control sea lamprey 

 (Perromyzon marimis) in the Great Lakes are a 

 prime example of chemical control. This control 

 has been highly successful in reducing the pop- 

 ulation size of an invading species, but carries 

 an enormous price tag: more than $10 million 

 annually (U.S. Congress 1993). 



Carefully planned biological-control pro- 

 grams may provide rapid, cost-effective control 

 and pose negligible ecological problems. The 

 success rate for biological-control programs 

 typically ranges from 16% to 36% (Meyers et 

 al. 1989) and improperly screened biological- 

 control agents have themselves become nui- 

 sance species in the past (e.g., blue tilapia 

 [Tilapia aiirea]; McClelland 1992). 



Although often very expensive, physical 

 control of aquatic nuisance species can be an 

 appropriate technique in certain circumstances. 

 Physical control has been used to control nui- 

 sance aquatic weeds like Eurasian watermilfoil 

 {Myriophylhim spicatum ). 



Since no single method is likely to provide 

 the necessary level of control, a comprehensive, 

 integrated control strategy combining tech- 

 niques is usually necessary for an effective con- 

 trol program. Few, if any, control methods are 

 without some environmental risk. When proper- 

 ly used, and with continual monitoring for 

 effectiveness and ecological side effects, envi- 

 ronmentally sound control of at least some 

 aquatic nuisance species can be achieved, as in 

 the Great Lakes sea lamprey control program. 



Detection and monitoring strategies serve as 

 early warning systems that first identify new 

 invasions and then track ranges and popula- 

 tions. This strategy complements or integrates 

 prevention and control to allow for early inter- 

 vention and assessment of management actions. 



The capability for early detection of new inva- 

 sions will allow managers to implement strate- 

 gies for limiting their spread and reducing neg- 

 ative effects. Timely detection of non-native 

 aquatic species that are or could become nui- 

 sances can also help identify gaps in prevention 

 procedures. Monitoring of those organisms will 

 not only allow rapid response if harmful situa- 

 tions arise but will also allow verification or 

 repudiation of assumptions that may have been 

 made during assessments before intentional 

 releases. 



Because of extremely limited resources, 

 cooperative ventures and collaborations 

 between agencies are essential for collecting 

 monitoring information. The Detection and 

 Monitoring Committee of the ANS program is 

 developing a national network to coordinate and 

 provide infonnation regarding occuri'ences of 

 known nonindigenous aquatic species. This net- 

 work is intended to provide managers and 

 researchers with an important tool for determin- 

 ing the status of a particular nonindigenous 

 aquatic species, its potential and known effects, 

 and proven or potential control techniques. 



By and large, three interrelated problems 

 associated with nonindigenous ANS remain 

 unsolved: (1) detennining levels of acceptable 

 risk; (2) setting thresholds or other variables 

 above which more formal decision making and 

 costly approaches for control are invoked; and 

 ( 3 ) identifying trade-offs in terms of costs and 

 economic ramifications in the face of uncertain- 

 ty as to probable success in controlling ANS. 

 Current federal methods and programs to iden- 

 tify risks of potentially harmful nonindigenous 

 aquatic species have many shortfalls — includ- 

 ing long response times. 



Summary 



Nonindigenous aquatic species are wide- 

 spread in the United States. While many of 

 these organisms have been intentionally intro- 

 duced, many others dispensed via unintended 

 introductions. The potential for ecological and 

 economic harm resulting from introductions of 

 nonindigenous aquatic species can be large. For 

 example, zebra mussels seem to be jeopardizing 

 a number of native North American mussel 

 species (Williams et al. 1993) and could result 

 in economic losses in excess of $3 billion (U.S. 

 Congress 1993). The actual extent of problems 

 associated with non-native aquatic species 

 remains largely unknown. The ability to detect 

 new species and limit their dispersal before they 

 become problematic is critical if we are to limit 

 future nonindigenous species problems. 



