Northern Madtom
Noturus stigmosus
Species Description
The Northern Madtom is species of the family Ictaluridae (North American Catfishes) that is rare on both the provincial and global scale. Northern Madtom are distinguished from the 8 other species of catfish in Ontario by their small size (average 8cm in length), stout body shape, and 2-3 dark saddle-shaped markings on the back, which are accompanied by 2 pale, eye-sized spots ahead of the dorsal fin.
Although this fish may be small, it boasts a strong defence against predators (and sometimes the overzealous biologist) as the dorsal and pectoral fins support sharp spines that have poison glands that can cause painful wounds.
Four pairs of the characteristic catfish whiskers, known as barbels, protrude out from the snout. Being a nocturnal benthic feeder, these sensitive whiskers aid in detecting preferred prey items including small aquatic invertebrates like midges, mayflies, and caddisflies.
They construct nests under flat rocks or burrows and spawn in the summer. Unlike most species of fish, Northern Madtom males guard their eggs and protect their young for a few weeks after they hatch.
Habitat
The Northern Madtom can tolerate a range of habitat conditions. While typically found in large creeks and rivers with a moderate to strong current, they can also occur in lakes. Northern Madtom prefer clear waters with sand, gravel or rocky bottoms but can also be found in slightly turbid water with aquatic vegetation.
“Swimming Tongues”
There are nine species of Ictalurid catfishes in Ontario that are characterized by wide, flat heads, eight barbels (whiskers) around their mouth, an adipose fin, spines in their pectoral and dorsal fins, and lack of scales. They are most active at night and have a sharp sense of taste and smell. They can detect substances in the water at low concentrations as they have taste buds on their body that are densely packed on their barbels. This allows them to find food in dark or turbid waters.
The Channel Catfish, another Ictalurid found in the Sydenham, is the largest species of catfish native to Canada. They have the keenest sense of taste of any vertebrate in the world and, because of this, are referred to as “swimming tongues.”
Distribution in the Sydenham
The Northern Madtom is found in the Ohio River, western Lake Erie, and Lake St. Clair drainages. It is critically imperilled in Ontario, Michigan, Ohio, and Illinois and is one of the rarest species of freshwater fish in Ontario. It is only found at four locations in Canada, all of which are in southwestern Ontario, including the Thames, St. Clair, and Detroit rivers as well as Lake St. Clair. Despite targeted sampling by Fisheries and Oceans Canada in recent years, the Northern Madtom has only ever been detected twice in the Sydenham River – once in 1929 near Alvinston and once in 1975 near Florence. The species is considered likely to be extirpated from the watershed.
Threats to Northern Madtom
The main threats to the Northern Madtom include habitat destruction, siltation and excessive turbidity, nutrient loadings, toxic compounds, climate change, and competition from non-native fishes such as Round Goby.