Water rushes mercilessly through the lush green riparian corridor, sweeping everything along its path in a flash flood. The canyon is used to it, and so are the many inhabitants who call this creek called Aravaipa home.
What looks like destruction in flood form is actually time to shine for native fish species in the creek. In addition to thriving riparian habitat, the 22-mile perennial creek hosts seven native fish species. And while biologists marvel at the impressive assemblage that live here, others worry that pending demands to extract the creek water could harm the ecosystem in the future.
“The native fish evolved in what we call ‘flashy’ systems,” said Dr. Peter Reinthal, ecology and evolutionary biology professor at the University of Arizona. Reinthal has been leading the biannual monitoring survey since 2002, after picking the project up from W.L. Minckley who started the survey back in 1963. With over 50 years of research, Aravaipa Creek is the one of the most extensively studied native fish community in the Gila River basin.
The monitoring system tracks the numbers of Aravaipa creek’s native and non-native fish species swimming in multiple destinations within the creek. The survey has become a collaboration between U.S. Fish and Wildlife Service, U.S. Bureau of Land Management, Arizona Game and Fish Department and the Nature Conservancy, which all have vested interests in conservation and management efforts in Aravaipa Canyon because of what a unique ecosystem it is in the arid desert of the Southwest.
Grabbing squirming, silvery bodies out of a bucket, a team of students and government agency representatives identify each freshly seined fish for the record books. The fish practically wriggle right out of their hands as the team calls out the catches, categorizing by age and species. Two juvenile agosias, Three adult agosias. Look, it is a loach minnow!
Rarely exceeding 2 1/2 inches in length, both the loach minnow and the spikedace swim under the ripples of Aravaipa’s clear, cobble-bottomed stream.
“Most people do not even realize that these little fish even exist in such intense environments,” said Victoria Hoaglin, a fisheries and wildlife management major at the University of Arizona.
“Aravaipa is one of those places that you can still find these federally endangered fish. Nowhere else do you ever really get that chance,” said Hoaglin. “It is kind of a unique feeling, especially with our native Arizona fish. A lot of them do not exactly have success stories.”
Of the roughly 30 native fish species endemic to Arizona, about two-thirds are listed as either threatened or endangered. Both the loach minnow and the spikedace used to swim the waters of the Gila River Basin, as well as streams of New Mexico and Sonora, Mexico. Now they only occur naturally in about eight places in Arizona. Their increasingly vulnerable habitat continues to dwindle, as demands for an already scarce water supply grows.
“The destruction of habitat is the biggest threat to our native fish species,” said Hoaglin. “Aravaipa Canyon was determined by Congress to be a ‘Wilderness Area,’ it has been protected as such since 1984 which has allowed the present fish population to survive.”
Such protection has historically included all of the land and water that flows in the canyon, including the flood water that contributes to its natural hydrograph. Within these protected waters, invasive species such as the green sunfish, red shiner and the yellow bullhead catfish have become a threat to native endangered fish such as the spikedace and loach minnow.
“The green sunfish are highly piscivorous, which means they eat other fish,” said Heidi Blasius, a fish biologist with the Bureau of Land Management. “The red shiners are very competitive and also very aggressive fish. The yellow bullhead are also piscivorous.”
A diet survey conducted a few years ago on the yellow bullhead by BLM and partners found many loach minnows in the bullheads’ stomachs, said Blasius.
According to Doug Duncan from the U.S. Fish & Wildlife Service, listing a species under the Endangered Species Act is based on threats, therefore down-listing a species is based on removal and mitigation of those threats. In this case, the responsibility of removal and mitigation of invasive species falls on the Bureau of Land Management.
“We have initiated mechanical removal projects in the system where we eliminated the green sunfish with partners,” said Blasius. “Now I have funding to try to eliminate the yellow bullhead. In addition to the yellow bullhead, we would be taking out the red shiners, too.”
This year, only a few bullhead were caught in the middle of the canyon. “There were fewer non-natives than we have ever had before,” said Reinthal about this November’s survey results. This could be a result of the BLM’s long term mechanical removal projects, as well as a recent flood that occurred just two weeks before the survey.
Though human intervention via removal operations have been helpful to the decline of invasive species, Reinthal said the natural flooding helps keep the invaders suppressed by moving them downstream. “The flood flows are necessary to keep the non-natives knocked down,” said Reinthal. “That’s because the non- natives, the fish in Aravaipa, are primarily from the Southeast, which is slow-moving water.” When the rapid flood waters hit the scene, the exotic non-natives just go with the flow and beyond the fish barriers, designed to keep them from re-entering upstream.
Aravaipa Creek’s decline in non-native fish species does not mark the end of struggle for the endangered natives. Protecting the flow that helps protect its inhabitants has become an issue in recent years since the Freeport-McMoRan Inc. set its sights on extracting the excess floodwater for copper mining.
“More floodwater flows through the Aravaipa Wilderness Area in an average year than is needed to maintain natural ecosystem functions;” said Freeport-McMoRan’s water extraction model developed by SWCA Environmental consultants. Freeport-McMoRan hired SWCA Environmental consultants to support them in the case on why they should be allowed to harvest excess “discharge,” although the model for extraction addresses neither extraction method, nor impacts on resources.
Over 40 years of research started by Minckley and continued by Reinthal indicates that “short-lived native fish show positive responses to flooding, while nonnative fish show negative responses, indicating that natural flooding patterns are critical to maintenance of the native fish community.” Besides the flood impact on invasive SPEC, according to Reinthal, floods are needed to replenish the nutrients for the riparian habitat.
The floods also flush sediment out to revitalize the ecosystem. The loach minnow go down into the rubble and rocks, which are subject to compaction. “If you do not wash out all of the sediment, a lot of the invertebrate and algae, which form the basis to the food web, don’t grow. So you lost food resources for the fish species,” said Reinthal.
In the Arizona Supreme Court case, General Adjudication of All Rights to Use Water in the Gila River System and Source, Reinthal served as an expert witness and cited scientific data relevant to minimal water needs of Aravaipa Canyon Wilderness Area.
“So, what we had to argue was how much water was needed to maintain the characteristics of the wilderness areas as it was set into law in 1984 and expanded on in 1991,” said Reinthal, who claims that all of the water is necessary.
“So far, they have not made a decision,” said Reinthal.
Monique Irish is a reporter for Arizona Sonora News, a service provided by the School of Journalism at the University of Arizona. Reach her at firstname.lastname@example.org