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plants. Hydrilla and other introduced species <br />often create dense canopies that limit light to <br />indigenous species. <br />Introduced nuisance aquatic plants can outcom- <br />pete indigenous plants and form a monoculture <br />that invades the entire littoral zone. Such intro- <br />ductions may have a negative impact on sport <br />fisheries. For example, reduced predation success <br />by largemouth bass in dense macrophyte beds <br />contributes to diminished bass production <br />(Savino and Stein 1982, Engel 1987). <br />Canopy formation also can influence dissolved <br />oxygen levels and primary production within a <br />specific habitat. Oxygen depletion beneath plant <br />canopies is likely due to the physical barrier <br />between the atmosphere and the water. This bar- <br />rier reduces wind-driven water movement and <br />impedes reaeration. Decomposition of decaying <br />plant material associated with the rapid growth <br />of introduced species also exerts an oxygen <br />demand, further reducing ambient oxygen con- <br />centrations. Many nuisance aquatic plants are <br />associated with water quality problems because <br />their monoculture populations cover large <br />expanses with extreme densities with extensive <br />canopies at the water surface. <br />In some instances, the impact of aquatic species <br />introductions may depend on where they are <br />introduced. The smooth cordgrass (Spartina <br />alterniflora) has been used to stabilize shorelines <br />on the east coast. On the west coast, the intro- <br />duction of the species has created problems <br />necessitating removal efforts in estuaries. Grass <br />carp (Ctenopharyngodon idella) have been used <br />for aquatic vegetation control in some places. In <br />other areas, there are concerns that the species <br />could spread and become established because <br />they can increase water turbidity and destroy <br />habitat for juvenile fish. As a means of reducing <br />the risk of grass carp becoming established, the <br />Fish and Wildlife Service has developed a pro- <br />gram to certify triploidy so that introduced indi- <br />viduals should not be able to reproduce. <br />Nevertheless, there is still a degree of controversy <br />over use of grass carp. <br />LESSONS FROM THE STATES: <br />The December 1991 request for input on the <br />identification of options for reducing the risks <br />associated with intentional introductions also <br />included a request for information on existing <br />State regulations that address this issue. The <br />response was varied, with several States provid- <br />ing excellent and extensive information on exist- <br />ing regulations and others responding with a <br />statement of preferred options. By the time of the <br />second request for reviews, this time for the <br />Options Paper in May 1992, several of these <br />same States responded with additional or differ- <br />ent sets of regulations that had been put in place <br />in the interim. Still others offered examples of <br />proposed changes that might become State law, <br />or might not. Because the regulation of non- <br />indigenous species use is an area of increasing <br />State attention and present requirements are so <br />Ruid, this report will not attempt to provide a <br />State-by-State summary of existing regulations. <br />This report will instead provide examples of the <br />Task Force's findings on the range of State regu- <br />lations made available for our review. <br />Most of the States that responded cited some <br />form of regulatory authority over the importation <br />(to the State) or introduction of fishes, in some <br />cases only game species. As noted by the New <br />Mexico Department of Game and Fish (Montoya <br />1992), "this leaves an entire range of aquatic <br />organisms that are unregulated...," e.g., amphib- <br />ians, insects, plants. For those species for which <br />State natural resource agencies did have author- <br />ity, the most commonly cited approach was to <br />use some form of genera] prohibition on import <br />or introduction that was linked to a permit sys- <br />tem. Many States cited no particular criteria by <br />which permit applications are judged. Others <br />varied widely but included likelihood of survival <br />over an annual cycle, potential as a pathway for <br />the introduction of pathogens, actual or potential <br />threats to indigenous species (genetic, competi- <br />tion, predation, or other biological considera- <br />tions), human health hazard, and other biological <br />and socio-economic ramifications. <br />Discussion by many States of components of <br />their general approach and decision-making <br />scheme were also useful to the Task Force in the <br />development and consideration of recommenda- <br />tions. Texas uses a prohibited list approach where <br />"the importation, sale, transport, release and <br />possession" of listed species (of fish, shellfish and <br />plants) are prohibited and all others are reviewed <br />10 <br />