Researchers contend that North America enjoys the greatest level of temperate freshwater biodiversity in the world. It is apparent too, that many of these discrete ecosystems are threatened by the encroachment of human activities. The habitat provided by freshwater ecosystems is particularly affected by other upstream impacts to the environment.
The Endangered Species Committee of the American Fisheries Society (AFS) has been compiling information related to imperiled freshwater and diadromous fish for many years. Diadromous fish are those that migrate between both fresh and saltwater. This latest release by AFS is the third compilation released listing endangered, threatened and vulnerable fish found in North America.
Published in the magazine Fisheries, Conservation Status of Imperiled North American Freshwater and Diadromous Fishes paints a disturbing picture of the impacts that habitat loss and nonindigenous species have caused to freshwater fishes. The report suggests that some forty percent of all rivers in North America are in trouble and there has been a 92 percent increase in the number of fish species listed as imperiled since the last report prepared in 1989.
In a press release announcing the report, United States Geological Survey Director Mark Meyers states, "Freshwater fish have continued to decline since the late 1970s, with the primary causes being habitat loss, dwindling range and introduction of non-native species. In addition, climate change may further affect these fish."
Geographic Scope of the Fisheries Study
The new compilation considered all freshwater and diadromous fishes found in Mexico, the United States, and Canada. Species found in offshore islands of the continental United States and Canada were included since it is thought they were originally derived from these same areas. Fish found the Hawaiian Islands were not made part of the research effort.
Collaborators in the research effort spanned the same diverse geographic region with sixteen co-authors presenting the report findings.
The Most Vulnerable Geographic Regions
The report discusses three geographic regions identified as having especially large numbers of imperiled fish, these are the southeastern United States, the mid-Pacific coast, and the Rio Grande and coastal basins of Mexico. The mid-Pacific coast has many species of lamprey, salmonid, and minnow at risk, while the Tennessee River system was found to have the greatest number of fish species in peril.
A number of causes have been identified as factors in the decline in fish stocks. Often the threats to fish are a product of multiple factors
- A recognition that species react with each other in finer scales of biodiversity
- Changes to aquatic habitat caused by landscape altering projects like dams
- Competition, hybridization, predation, and disease caused by invasive nonindigenous species
- Habitat destruction caused by the loss of wetlands and human development
Lead report author and Chair of the AFS Endangered Species Committee Noel Burkhead notes, "Fish are not the only aquatic organisms undergoing precipitous declines. Freshwater crayfishes, snails and mussels are exhibiting similar or even greater levels of decline and extinction."
Researchers involved in this report hope that the information presented can be used by natural resource managers at all levels of government to make better and more informed decisions on issues that impact the aquatic environment.
Alan Sorum - Alan Sorum is the Maritime Operations Project Manager for the Prince William Sound Regional Citizens' Advisory Council (PWSRCAC). Alan is ...
