Introduction

The Shorthead Redhorse (Moxostoma macrolepidotum) is a wide-ranging species in North America that needs to be monitored throughout its range. The Shorthead Redhorse is native to central and eastern North America. However, its range has expanded to include areas like the Hudson estuary and Grayson County, Texas. It inhabits small to large rivers and lakes, and lives in the benthic zone. Shorthead Redhorse feed on benthic invertebrates and can consume plant material from the benthic environment that it inhabits. When it spawns, Shorthead Redhorse move into more shallow streams and spawn over gravel or rocky shoals. They will also spawn in springs with swift moving water. The Shorthead Redhorse is important to humans because it is a game fish. It is also important to anglers because of its role in the ecosystem; it is prey for larger game fish such as northern pike and muskellunge. Humans are a huge factor affecting these fish. Dams can be a problem for the Shorthead Redhorse just as they are for bigger game fish such as trout and salmon. Dams that are built upstream make it impossible for Shorthead Redhorse to swim up to more shallow water to breed. Shorthead Redhorse are intolerant to chemicals in the water, either from domestic sewage or from industrial waste like the insecticide chlordane. Other chemicals, such as those found in birth control, bioaccumulate in these fish just as they do others and can be harmful. Monitoring this species is important because by monitoring them, we can track their populations. By doing long term studies on their population ranges and reproduction it will be possible to determine the reasons behind why these fish are expanding their range south, and what specific chemicals harming these fish are not being removed from wastewater.

Geographic Distribution

Historically, the Shorthead Redhorse is native to North America. Its native range includes the Great Lakes, Hudson Bay, Mississippi River, and Lawrence river basins. They ranged across from Quebec to Alberta and as far south as northern Alabama and Oklahoma . Shorthead Redhorse also originally occupied the Atlantic Slope drainages, ranging from the Hudson River in New York to the Santee River in South Carolina. When TVA started building dams in the 1930’s in an attempt to create power, the damns blocked different fish such as striped bass, from moving up stream to their spawning ranges. While some fish ranges have decreased since the construction of the dams, the Shorthead Redhorse’s range has expanded. The Shorthead Redhorse is a “habitat generalist near the core of its range” so it can stand disturbance better than other related redhorse species such as the River Redhorse, M. carinatum. Shorthead Redhorse can now be found in the tidal zones of the Hudson River. They are believed to have invaded the Hudson by way of the Mohawk River and have established themselves in the Hudson estuary. Other areas they have been found in include the Embrras River system in Illinois and the Red River below Lake Texoma dam in Grayson County, Texas.

Ecology

Shorthead Redhorse have a wide habitat range. They live in fresh water and are found in streams, lakes and rivers . Shorthead Redhorse can tolerate clear to cloudy water and likes loose substrate like gravel and sand. These fish are benthic feeders that like to feed in rifles and rifle margins. During a study done in Illinois by Sule et al, they found that “shorthead redhorse consumed items from approximately 60 food categories, primarily in vertebrate taxa”. Twenty-four to sixty-eight percent of their diet was unidentified when stomach contents were analyzed. Also found, 21-50% of the unidentified matter, or 13% of their total diet, was organic matter. Shorthead Redhorse eat the most insects out of all the fish in the sucker family. They can also eat microcrustacea and plant matter . Predators of Shorthead Redhorse vary depending on size. Juveniles can be eaten by northern pike, walleyes, and smallmouth bass. Adult or larger Shorthead Redhorse are eaten by northern pike and muskellunge. The Shorthead Redhorse does not actively compete for food. Because of their wide range of prey and eating the most vertebrates of all the suckers, they do not have a competitor. Humans impact Shorthead Redhorse habitat. The construction of dams blocked free flowing rivers like the Mississippi in which they live, disrupting their spawning migration routes. Shorthead Redhorse are killed easily by pollutants in the water. “The upstream migratory range of shorthead redhorse in a Maryland river decreased due to an increase in chlorinated sewage outfalls”. Factory pollutants are dumped into streams or rivers and will settle onto the bottom. Because such a large portion of the Shorthead Redhorse’s diet is sediment , it ingests high concentrations of the chemicals and can die.

Life History

The Shorthead Redhorse spawning season ranges from March to June, depending on location. In order to spawn, the water temperature has to be between 7 and 16 degrees Celsius. Shorthead Redhorse spawn once a year and will travel either upstream or downstream to reach their spawning ground. Spawning areas are usually smaller rivers or steams. They are locally migrant so they do not travel long distances to get their spawning area. Shorthead Redhorse spawn in shallows at the edges of sand bars or in rifles over gravel substrate. During spawning, females can produce anywhere from 18,000 to 44,000 eggs. It can take anywhere from 2-5, even 6 years for a Shorthead Redhorse to become sexually mature. In northern areas of cooler water, growth rates tend to be lower than more southern, warmer areas. The average life span of the Shorthead Redhorse varies depending on location. More northern locations with cooler water tend to have Shorthead Redhorse that can live to be older than 17 years of age. However, in more southern, warmer water areas, such as the Kankakee River, the average max age is only six to seven. As mentioned previously, the construction of dams has not had a large effect on the population of Shorthead Redhorse, but it has had some effect. The dams affect the Shorthead Redhorse just as they do other fish by blocking migration pathways to spawning areas. Because of the wide range and great abundance of the Shorthead Redhorse, no negative effects of dams have been accounted for in their population.

Current Management

The Shorthead Redhorse is widely abundant across its range and has one of the largest ranges for a sucker. This species is not endangered or threatened and is not currently at risk. There is no current management plan for the Shorthead Redhorse. It is not often a prized fish for anglers because it does not get very big. And while the Shorthead Redhorse is said to be one of the better tasting fish, there are so many little bones throughout the meat that if you did catch one big enough to eat, the meat would not be worth eating. The meat also spoils rapidly in warm temperatures making it hard to transport. Shorthead Redhorse play a positive role in their ecosystems as prey for larger game fish. They can also be used for bait if caught small enough. Humans impact the population the most through chemical contamination of their habitat. Bioaccumulation of chemical is common in fish that feed near the benthic zone, like the Shorthead Redhorse. Domestic pollutants have as much negative effect on Shorthead Redhorse as industrial pollutants do. Pollution can also enter waterways through runoff from agricultural fields or cattle farms. To prevent this, farmers should be required to maintain a larger buffer zone around streams, or they should not be allowed to use pesticides that are harmful to water ecosystem. All domestic and industrial waste should be put through waste treatment and possibly a heavier waste treatment procedure than what is in effect now. For example, we should come up with a treatment for domestic waste that will remove hormones added by oral contraceptives. Currently, there is no way to remove these chemicals.

Management Recommendations

In order to manage Shorthead Redhorse effectively, a count needs to be made for an estimated population size. First, a study needs to be conducted to see if electroshocking during the spawning season will have a negative effect on the rate of successful reproduction. If there is no negative effects the proceeding management plan should be conducted. Counting should be done during the spawning season when Shorthead Redhorse are in smaller tributaries preparing to reproduce. Locate spawning areas where sampling can be done. Electroshock backpacks should be used for smaller streams and electroshock boats should be used for smaller rivers to collect and count population densities in known spawning areas. To assess population size, conduct an angler survey in surrounding areas where Shorthead Redhorse have not been documented. Electroshocking in non-previously populated streams that are connected to rivers or streams inhabited by the Shorthead Redhorse will allow the population range to be documented. These procedures should be done on a year-to-year basis if there is no negative effect of electroshocking, and if there is, allow for one to two years in between each census. In addition to conducting a census to acquire population range and density, certain areas should be protected. Access to spawning areas should be blocked just after the spawning season. This will give the eggs time to hatch and grow, and ensure a new generation of Shorthead Redhorse survival. Spawning areas can be open to anglers during the spawning season. This is because Shorthead Redhorse are the most abundant sucker, so wide ranging and few anglers are interested in fishing for them, their population will not be diminished by angling during their spawning season.

External links

This source gives a list of English names for this fish, including “common mullet.”