Aquatic Invasive Species Problems and Concerns

Threatened Impact of Aquatic Invasive Species

Potential threats may be evidenced by the degree of negative impact these species have upon the environment, industry and the economy. Negative impacts include:

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  loss of native biodiversity;
  
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  threaten ESA listed species;
  
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  alterations in nutrient cycling pathways;
  
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  decreased habitat value of infested water;
  
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  threaten aquaculture production;
  
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  decreased water quality;
  
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  stunted fish populations due to dense biomass of introduced species;
  
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  decreased recreational opportunities;
  
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  increased safety concerns for swimmers;
  
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  increased costs of canal maintenance;
  
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  decreased property values;
  
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  fouled water intakes;
  
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  impacts on power generation and water transfer;
  
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  increased risk of flooding due to increased biomass in water or clogging lake outlets;
  
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  impeded water flow and interference with efficiency of water delivery systems;
  
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  impacts to human health.
  

The following section on freshwater animals and plants provides information on non-indigenous species and discusses species of concern. These draft lists are intended to provide a basis for discussion and further work identifying the presence, distribution, status, and threat of AIS. These will be updated, maintained, categorized and standardized as new information is received and assimilated.

Freshwater Animals and Plants

Freshwater Animals

A draft list of restricted freshwater nonindigenous animals in Arizona is included in Appendix B. The list is incomplete as the introductions of nonindigenous animals are continuous and the impacts of each may not be fully understood. Currently, more funding and research is needed regarding the management and control of AIS animals.

The Quagga mussel has been found in Arizona waters and is considered to be a priority AIS due to the degree of impact in the Colorado River Basin.

There are no native species of crayfish in Arizona. Currently, Arizona has two non-native crayfish species that were originally introduced as a means of aquatic vegetation control, fishing bait, and aquaculture. Crayfish have had an immense adverse effect on the ecosystem they were introduced into, decreasing overall biodiversity of fish, amphibians, and macroinvertibrates. Crayfish have spread rapidly through the state and the introduction of additional crayfish species is of great concern.

Bullfrogs were initially introduced as a food source in Arizona. Bullfrogs compete with and often times prey on many aquatic animal species and have detrimental effects on native fish and amphibian populations. Bullfrogs often have detrimental effects on protected native species such as the Chiricahua leopard frog and Mexican garter snake.

Other species of concern include New Zealand mudsnail, gizzard shad, redshiners, and mosquitofish.
More detailed information on these priority species is included in Appendix C.

Freshwater Plants

Some invasive non-indigenous freshwater weeds pose a serious threat to Arizona state waters while the impacts of others are still undetermined. The freshwater nonindigenous plant species found in Arizona are listed in Appendix C, along with information on pathways of introduction and more detailed information on priority plant species and their impacts.

Hydrilla (Hydrilla verticillata), Brazilian elodea (Egeria densa), and Parrotfeather (Myriophyllum aquaticum) are freshwater submersed species of concern in Arizona.
Purple loosestrife (Lythrum salicaria) is a priority emergent species that has spread throughout the continental US, but has not yet become established in Arizona. Through education of the public we have the opportunity to exclude this ecosystem-altering invader from our state.
Giant Salvinia (Salvinia molesta) is a priority floating plant that is currently found in the Lower Colorado River. This aquatic fern has had major impacts to slow moving waters in the southeast U.S. and around the world.
Algae
Although algae are taxonomically different from submersed and emergent aquatic vegetation, ecologically they are similar enough to include in a section on nonindigenous plants. As a group, algae are relatively cosmopolitan and noxious, and sometimes potentially toxic, blooms of cyanobacteria (more closely related to true bacteria than algae but included in this section) can occur in almost any water body given proper conditions for this to happen (usually associated with eutrophication). Large blooms of algae can and have caused numerous fish kills due to hypoxia/anoxia. Such events often occur on a seasonal basis.
It is beyond the scope of this plan to address problems concerning eutrophication and toxicity of most species. In some cases, eutrophication is a natural condition of the waterbody in question while others are human caused. Cultural eutrophication, and its effects, is currently handled by agencies such as the Arizona Department of Environmental Quality who will assign limits on algae growth and water quality either on a regional or case-by-case basis. Since algae identification is not easily done in the field and since few in the state have the capability to accurately identify species, limited data exists on the spread or current distribution of noxious or potentially toxic species.
One algal species appears to be a relatively recent introduction and has caused numerous and large fish kills; Prymnesium parvum. This species produces a potent ichthytoxin (prymnesin) and was first observed in Apache Lake in the Spring of 2004 following a fish kill. It then appeared to spread to downstream reservoirs causing fish kills of increasing magnitude. Since this time, numerous fish kills have been reported in urban lakes in the Phoenix Metropolitan area both connected and unconnected to the Salt River watershed. The exact environmental requirements for P. parvum growth and toxicity are not completely understood. Current research is attempting to make these determinations.
Due to its devastating effects on gilled aquatic organisms, both native and introduced, we include P. parvum in the priority species list.

Directory: limnology -> AIS
AIS -> State of Arizona Aquatic Invasive Species Management Plan
AIS -> Arizona State Aquatic Invasive Species Management Plan
AIS -> Acknowledgements

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