Fish and wildlife, Invasive species management, Restoration
Sunfish Removal for Native Aquatic Species Conservation in McGee Wash, Arizona
Case Study by the Conservation and Adaptation Resources Toolbox
Status
Ongoing

Location

States

Arizona

Ecosystem

River/stream

Subject

Aquatic environment
Endangered and/or Threatened species
Fishes
Invasive species
Non-native
Restoration
Riparian areas
Rivers and streams

Introduction

A fish in a person's hand
Image Details

In 2016, biologists from Arizona Game and Fish Department (AZGFD) surveyed McGee Wash, a tributary to Trout Creek in west-central Arizona, and found an abundance of Green Sunfish (Lepomis cyanellus). From this survey it appeared that McGee Wash had become overrun with Green Sunfish, a non-native fish that has successfully established populations in warm water lakes and streams throughout Arizona. McGee Wash is located on State Trust and private land (Fort Rock Ranch) and flows for approximately 12 km with about 2 km of perennial water. Biologists suspect sunfish have become established in these perennial waters by successfully moving upstream from Trout Creek when the streams are connected by high flow events.

Historically, McGee Wash supported a unique assemblage of native warmwater fishes as well as amphibians such as Lowland Leopard Frogs (Lithobates yavapaiensis), Black-necked Gartersnakes (Thamnophis cyrtopsis), Arizona Toads (Anaxyrus microscaphus), and Sonora Mud Turtles (Kinosternon sonoriense). Preliminary survey results in 2016, however, indicated particularly low fish abundances of Desert Suckers (Catostomus clarkii) and Roundtail Chub (Gila robusta), both iconic fish species in the Lower Colorado River drainage basin.

Key Issues Addressed

McGee Wash supports a unique assemblage of native fishes that include Desert Suckers and Roundtail Chub. However, non-native Green Sunfish have established a population in the wash  and are outcompeting native fish species. Green Sunfish have high invasion potential as they prefer the warm, shallow waters in systems like McGee Wash that are mostly pools connected by series of riffles and runs. Stream habitat complexity from undercut banks, Cottonwood, Ash, and Willow tree roots and debris, and rocks all provide suitable cover habitat for sunfish. Green Sunfish are highly predatory generalists, and will feed on small, juvenile native fishes and amphibians. As a result, native populations of Desert Suckers and Roundtail Chub, which rely on the same prey base, have decreased in abundance in McGee Wash. Management must therefore focus on controlling non-native sunfish in order to restore native fish populations.To mitigate the negative effects of non-native sunfish on the native fish community, biologists from Arizona Game and Fish Department (AZGFD) implemented regular mechanical removals starting in 2017 through today. 

Project Goals

  • Take inventory of non-native and native aquatic species in McGee Wash
  • Eradicate populations of non-native Green Sunfish via mechanical removal
  • Restore populations of native Desert Suckers and Roundtail Chub

Project Highlights

Blitz Approach to Mechanical Removal: Equipped with a range of methods, project members have completed 36 survey passes in McGee Wash since August 2017, including 10,000 sunfish removed within the first year of sampling.

  • Intensive Mechanical Removal: Baseline surveys by AZGFD in 2016 indicated high abundances of non-native sunfish, prompting mechanical removals starting in August 2017. To date, surveys are conducted every month to actively monitor sunfish and remove them if detected, with a goal of three consecutive sampling efforts without any Green Sunfish.
  • Effective Green Sunfish Suppression: Since 2017, project biologists have been successful in reducing populations of Green Sunfish with 36 total surveys to date. In July 2019, project biologists did not observe any sunfish, and they removed only a handful of sunfish from October to January 2020. This is a stark contrast to the over 4,800 sunfish removed during the first two sampling trips in summer 2017. Nevertheless, complete eradication has not been achieved, as biologists have still found sunfish in limited numbers in a few “problem pools”.
  • Resilience of Native Fishes: As sunfish populations have decreased, biologists have observed an increase in abundances of native Desert Suckers and Roundtail Chub. In 2018, biologists documented hundreds of fry and young-of-year Desert Suckers, which outnumbered the sunfish observed. Although not completely eradicated, sunfish populations have been sufficiently reduced to support native fish recovery. 
  • Effects of Streamflow: McGee Wash has naturally intermittent flow conditions that serve as dry barriers to Trout Creek farther downstream during summer. This prevents sunfish from recolonizing upstream, yet during winter high flow conditions can connect McGee Wash and Trout Creek. Despite high flows in winter 2019, biologists suspect that sunfish did not move upstream back into McGee Wash.
  • Multi-Species Benefits for Amphibians: Since the initial 2016 survey, project members have observed more egg masses, tadpoles, and adult lowland leopard frogs concurrent with sunfish removal. For example, project members counted 934 adult frogs total during the September 2019 survey.
  • Non-Native Aquatics Treatment Techniques: A “blitz” approach was employed, using different netting mechanisms (hoop nets, seines, and minnow traps), angling, and backpack electroshocking. Within the first year, over 10,000 sunfish were removed from project locations by using these mechanical removal techniques. 

Lessons Learned

A strand of toad eggs
Image Details

Effective sunfish suppression in McGee Wash requires regular, consistent site visits to monitor progress. Project members extensively monitor different habitat types using different removal mechanisms year round, even when returning for several consecutive months without detecting sunfish. Backpack electrofishing has been the most effective mechanism for catching and subsequently removing sunfish in the habitat types of McGee Wash. The project team regularly samples over the winter, usually when traditional fish surveys are less productive, and are still able to remove sunfish. The only setback occurred when sunfish were able to spawn in 2018, which led to more difficulties with sampling equipment to catch the small fry and young-of-year fish.

The highest number of sunfish removed in a single trip was over 2,500 in August 2017. More recently, less than 10 sunfish were removed during sampling trips in late 2019. Despite these low numbers, biologists still find both adults and young-of-year sunfish, which suggests that the population either still persists in difficult to sample locations, or have moved upstream during high flow events that connect McGee Wash to Trout Creek. A few “problem pools” with deep undercuts make it difficult for biologists to visually detect all sunfish. Even if complete sunfish eradication is achieved, McGee Wash would still need to be monitored to prevent any possibilities of recolonization.

McGee Wash contains relatively homogenous habitat of mostly pools and some riffle/runs compared to larger stream or river systems with problematic non-native fish. As such, sunfish suppression is perhaps more feasible here solely with mechanical removal than in areas of more complex habitat types. Other nearby areas that have had complete success with sunfish eradication, such as East Ash Creek (another tributary in the Trout Creek Watershed; sunfish have been eradicated since 2016), also incorporate dry barriers with removal. McGee Wash does have a natural dry barrier during the dry summer months, but is susceptible to becoming connected during high flow events.

Lastly, project biologists from AZGFD have built a strong relationship with a nearby private ranch (Fort Rock Ranch) for sampling access. Building local partnerships is imperative for addressing conservation needs in systems like McGee Wash. 

Next Steps

  • Ongoing Recovery Effort: Continue mechanical removal and monthly monitoring until all Green Sunfish are removed from McGee Wash.
  • Build Diverse Native Aquatic Populations: Stock more native fish species such as Longfin Dace (Agosia chrysogaster), Roundtail Chub, and Sonora Sucker (Catostomus insignis). This includes Roundtail Chub and Sonora Sucker translocations from Francis Creek, Burro Creek, Boulder Creek and Cane Springs Pond (Bill Williams watershed). This project will also continue to monitor for native lowland leopard frogs, Sonora Mud Turtles, Arizona Toads, and Black-necked Garter Snakes.
  • Outreach and Education: Increase public education on the importance of native aquatic species conservation in Arizona.

Funding Partner

  • Arizona Game and Fish Department State Wildlife Grants (SWG)

Resources

Contacts

  • Brett Montgomery, Native Trout and Chub Specialist, Arizona Game and Fish Department: bmontgomery@azgfd.gov
  • Matt Chmiel, Fisheries Program Manager (Kingman Region), Arizona Game and Fish Department: mchmiel@azgfd.gov
  • Andy Stites, Aquatic Wildlife Specialist, Arizona Game and Fish Department: astites@azgfd.gov

Case Study Lead Author

Suggested Citation

Koeberle, A.L. (2020). “Sunfish Removal for Native Aquatic Species Conservation in McGee Wash, Arizona.” CART. Retrieved from https://www.fws.gov/project/sunfish-removal-native-species-conservation.

Programs

The Conservation and Adaptation Resources Toolbox logo which includes a butterfly flying over a stream with a fish in it. On the stream bank there are two trees and a windmill.
For over eight years, CART enhanced collaborative conservation efforts at all scales by facilitating issue-based, not geography-based, peer-to-peer knowledge sharing. By connecting hundreds of individuals from dozens of organizations across North America, CART helped bridge the gaps between work at...
Program

Partners

Species