Colorado: Native minnows return to the Arkansas River

10 years of research by state biologists helps set stage for restoration

The plains minnow hasn't been seen in its native Arkansas River habitat since the 1960s.

By Summit Voice

SUMMIT COUNTY — Along with restoring charismatic megafauna like lynx, Colorado Parks and Wildlife biologists have also focused attention on the state’s aquatic habitats. In one of the most recent success stories, they’ve been able to bolster populations of rare, native minnows in the Arkansas River, after some pioneering research by the John Mumma Native Aquatic Species Restoration Facility in Alamosa.

Plains minnows (Hybognathus placitus) and suckermouth minnows (Phenacobius mirabilis) are on the Colorado threatened and endangered list.The plains minnow hasn’t been seen in the Arkansas River since the 1960s.

The two species have different requirements for habitat, food and reproduction. Plains minnow primarily feed on algae as well as other microscopic plants and animals, while suckermouth minnows typically feed on larval insects and other microscopic organisms which they glean from the riverbed with their sucker-like mouth, according to Colorado Parks and Wildlife biologists.

Both species declined due changes that have taken place on the Arkansas River during many decades due to water and land development.

“We’ve been working on getting them re-established in portions of their native habitat for over a decade but were unable to reproduce them successfully until recently,” said Paul Foutz, southeast region native aquatic species biologist for Colorado Parks and Wildlife.

Because plains minnows and suckermouth minnows are exceedingly rare, efforts to aid in their recovery were hampered by the fact that very little research was available about the optimal conditions for them to reproduce in a hatchery.

Since 2000, the staff at the aquatic species lab has worked meticulously and persistently to produce viable offspring. Several times they were able to achieve successful reproduction, only to encounter difficulties raising the young fish to maturity.

Colorado Parks and Wildlife hatchery technicians worked in conjunction with fish culturists at Colorado State University and the Albuquerque Aquarium investigating spawning and rearing techniques using methods similar to those that were successful for another small fish, the silvery minnow.

That persistence paid off, as biologists at the aquatic lab, led by hatchery technician Tom Mix, fine-tuned water chemistry and altered culturing techniques to produce the species in larger numbers.

Other factors in achieving successful growth was a greater understanding of the dietary needs of the species and improvements in feeding regimes, as well as a large pool of sexually mature brood fish to inject and spawn, made possible by recent trips to collect more brood fish.

Finally, the aquatic lab in Alamosa also recently built new outdoor fry rearing ponds which enable fish to mature in a more natural environment.

The breakthrough came in 2010, when hatchery staff reared about 38,000 plains minnow and 4,000 suckermouth minnows  in 2011. The fish ranged in size from one to two inches.

As State listed endangered species, re-establishing populations of plains minnow and suckermouth minnow will have no impact on normal agricultural operations.

The original bloodstock of plains minnows came from collections in Kansas on the Salt Fork of the Arkansas River in Barber County.  The suckermouth minnows are offspring of fish that were collected from the wild in Colorado in areas where small populations existed in the Arkansas River.

The small minnows were stocked into the Arkansas River above John Martin Reservoir in the vicinity of the Rocky Ford and Oxbow State Wildlife Areas in November. The fish will be monitored annually to determine the success of the stocking effort.

Their presence is important in maintaining the historic biodiversity within the ecosystem, which lends to greater stability of the ecosystem. They are also considered an indicator species and their presence is a barometer of water quality and quantity.

Minnow species in general are considered a forage-based species located near the bottom of the food chain and are preyed upon by other organisms like fish, birds, snakes, and other wildlife.

Species summaries:

Suckermouth minnow (Phenacobius mirabilis)
Suckermouth minnows are native to the eastern plains of Colorado in the South Platte, Arkansas, and Arikaree Rivers.  Its range extends to most of the Mississippi River basin from Ohio west to Wyoming, and south to Louisiana and Texas. This species has spotty and rare distribution and is currently a state listed endangered species. This small (2-5 inch) fish is slender with a conspicuous dark spot at the base of the tail fin. It inhabits shallow riffles with sand/gravel substrate, but utilizes deeper pools during low flow periods.

Plains Minnow (Hybognathus placitus)
This plains fish is native to the Arkansas, Republican and South Platte basins in Colorado.  Its range includes the Missouri River and western Mississippi River systems from Montana south to Texas.  A few specimens were collected on the eastern plains in the South Platte in the early 1980’s and mid-1990’s. It has not been seen in the Arkansas River since the 1960’s.  It is olive or yellow-green with brassy reflection and grows to about five-inches. It is currently a Colorado state endangered species.

For additional information and pictures of the plains minnow and suckermouth minnow along with some of Colorado’s other native aquatic species, visit the Colorado Parks and Wildlife native aquatic species website website. More information is also online at the Natural Diversity Information Source website.




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