Black Redhorse

(Moxostoma duquesnei)

Status: Threatened (COSEWIC 2015, ESA 2016)

Table of Contents:

Species Identification
Diet
Habitat and Range
Biology and Behaviour
Similar Species
Threats/Reasons for Being at Risk
Conservation and Recovery Strategies
How You Can Help

Photo by Neil Hamrick: https://commons.wikimedia.org/w/index.php?search=black+redhorse&title=Special:MediaSearch&go=Go&type=image

Species Identification:

The Black Redhorse is a fish species that is a member of the sucker family. They are about 50 cm long and can weigh up to 1 kg. The Black Redhorse is generally grey-silver in colour, but they can have undertones of dark grey, brown, olive-brown, or silver-blue along their spine. Along the sides of the Black Redhorse has colour tones of silver-blue, and their bellies are white or cream. They have slate grey fins but the bottom ones can also have an orange-rust colour to them. The Black Redhorse also has a long, upturned snout with a sucker-like mouth.

Diet:

The Black Redhorse is a benthic feeder, which means they are a bottom feeder. They forage on the bottom of rivers in the sediment looking for crustaceans, algae and aquatic insects. Juvenile Black Redhorse will feed primarily on plankton.

Photo by David Ellis: https://flic.kr/p/DsJeaM

Map taken from Government of Ontario: https://publications.gc.ca/collections/collection_2016/eccc/CW69-14-220-2015-eng.pdf

Habitat and Range:

The Black Redhorse can be found mostly in the Mississippi and around the Great Lakes. They also have small populations throughout Eastern North America, from Alabama and Mississippi all the way north to Southern Ontario and Michigan, east to New York and Oklahoma and Minnesota to the west. Historically the Black Redhorse was only located in Southern Ontario around the Great Lakes, but scattered sightings have been reported in areas throughout Southern Ontario before Toronto, and then north up into Owen Sound, and east over to Lake Simcoe, which is a southern region of The Land Between. Ontario is the only province in Canada where you can find this species.

Adult Black Redhorse prefer clear and warm water rivers or deep streams, and sometimes shallow areas of lakes. Juvenile Black Redhorse populations like to inhabit shallow pools or areas of rivers with low current.

Biology and Behaviour:

Black Redhorse fish mature around the age of 5. Migration upstream to their breeding grounds begins around April when temperatures stay above 10°C. Spawning season will occur in late May, and while the females do not change, male Black Redhorse will change color from blue-silver to green-black. The female will lay anywhere between 4,000 and 12,000 yellow eggs that are no larger than 3 mm, and then the male will fertilize them. They are placed in low current areas over fine gravel or small rock sediment areas. Eggs can take around 180 days to hatch, where they will remain in the area until they grow large enough to find suitable habitat and feeding grounds. Exact predators are unknown, but they are expected to be larger fish species and raptors.

Photo by Brett Albanese: https://flic.kr/p/GrptpU

Similar Species:

Golden Redhorse look very similar to the Black Redhorse, but Black Redhorse have larger lateral scales that do not overlap. They also have 9 lower pelvic fins instead of 10. You can also tell the difference between the Black Redhorse and other Redhorse species by their tail. The Black Redhorse has a slate grey tail, while other species like the River Redhorse, Copper Redhorse, Shorthead Redhorse, and Greater Redhorse have a red tail.

Threats/ Reasons for being at Risk:

1. Pollution: The two largest populations of Black Redhorse are in the Grand River and the Thames River, both of which are becoming increasingly polluted from urbanization and agriculture. Much of Southern Ontario is made up of agricultural fields, many of which are very close to our river systems and are easily polluted by fertilizers and pesticides. These chemicals settle into the sediments and are ingested by the Black Redhorse where they remain in their system and build up. Garbage, road salt, and human sewage are also other pollutants in our rivers that are impacting all species that live there.

2. Climate change: Drought can have impacts on Black Redhorse populations since it reduces the amount of flow and limits their breeding grounds. Droughts that happen after breeding are also a huge issue since eggs could end up being surfaced. On the other hand, flooding can be another problem since high flow would damage or destroy breeding grounds. Flooding is becoming increasingly problematic, especially in Southern Ontario where the two largest populations reside. Climate change will continue to produce sudden and extreme weather events that could decimate populations of Black Redhorse.

3. Human disturbance: Human disturbance like dredging and recreational boating and fishing can have impacts on populations if breeding grounds are disturbed by increased water flow from passing boats, or are destroyed from dredging. Dams are not considered a threat, but they can be a factor that limits populations and dispersal.

4. Invasive species: There have been dramatic ecological changes to our freshwater ecosystems in the last few decades. Changes in productivity, food webs, as well as the introduction of the Round Goby, Zebra and Quagga Mussels has made vast changes to our water systems and has impacted many important native species. Invasive vegetation also has the potential to choke out native vegetation and take over important breeding grounds for the Black Redhorse. Increased vegetation will also impact water flow and lead to increased dredging.

Photo by David Ellis: https://flic.kr/p/CvdJmb

Conservation and recovery strategies:

The Black Redhorse and their habitat are protected under Ontario’s Endangered Species Act, and indirectly protected by the federal Fisheries Act. However, there are currently no recovery strategies in place for this species, since this species lacks sufficient scientific research. While the Black Redhorse is considered a “least concern” species globally and is generally safe, the only populations in Canada occur in Ontario, and these populations are considered close to Extirpation. Conservation and recovery strategies should be put into place for the Canadian population, starting with increased research and creating a plan for recovery.

How can you help?

Report any sightings of the Black Redhorse to The Land Between, iNaturalist, or the Natural Heritage Information Centre.
Keep the shoreline on your property natural and free of chemicals.
Get in touch with local organizations and government agencies to help protect your local watersheds.
Participate in citizen science shoreline and water rehabilitation projects with local organizations.
Do not release any invasive species into the wild, and make sure you are not relocating any aquatic invasive species when travelling from one area to another.

Additional Resources:

Government of Ontario’s Black Redhorse page
COSEWIC 2015 Assessment and Report on the Black Redhouse

Photo by Brian Wulker: https://flic.kr/p/kQPoER

Sources:

Government of Ontario. 2014. Black Redhorse. Retrieved from: https://www.ontario.ca/page/black-redhorse

COSEWIC. 2015. COSEWIC assessment and status report on the Black Redhorse Moxostoma duquesnei in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xii + 50 pp. https://publications.gc.ca/collections/collection_2016/eccc/CW69-14-220-2015-eng.pdf