Stonecat catfish (Noturus flavus) – photo by Robert Muller
GET TO KNOW
The Rouge River watershed is home to a couple of crazy cats – or more specifically, a couple species of “madtom” catfish. Known to dart frantically about when frightened, these small members of the Noturus genus of North American catfish (Family Ictaluridae) have earned the nickname “mad-toms” or crazy cats.
FUN FACT: Madtoms (like all catfish) do not have typical fish scales. Instead, they have smooth skin that is very receptive to the sense of taste. It is estimated that catfish have in excess of 100,000 taste receptors that help them locate food by detecting minute amounts of proteins in the water. A great many of these taste receptors are located on the catfish’s “whiskers” (barbels). However – just to be sure it can find that food – the catfish’s entire body is covered with taste receptors. (Note: Catfish also have a very keen sense of underwater hearing that helps them detect potential predators.)
Conservationists view the various species of madtoms as good indicators for evaluating water quality because they require high dissolved oxygen levels and are highly sensitive to pollutants (especially salts and heavy metals). Their presence in a watershed is a strong indicator of good water quality. Currently, there are an estimated twenty-nine distinct member species of madtoms across North America. However, many species are critically endangered and survive as only tiny populations in small, isolated ranges; and it is quite possible that a few of such species have recently passed into extinction. The Scioto Madtom (Noturus trautmani), a species only ever found in one creek in Ohio, was declared extinct by the U.S. Fish and Wildlife Service on September 29, 2021.
In recent fish surveys conducted by FOTR, a few individual tadpole madtom (Noturus gyrinus) and stonecat (Noturus flavus) were found. Tadpole madtom were found in three lakes: two in Oakland County – Morris and Simpson; and one in Wayne County – Ford Lake near the Fair Lane Estate in Dearborn. Stonecat were found along the northern stretch of the Main branch from Troy to Southfield and one small stonecat made its way down the Main branch to Detroit’s Rouge Park in 2020. This cat was miles from the small population in Troy found by the DNR in 1998.
Tadpole madtoms and stonecats are two of the more common and widespread of madtom species and their presence in the Rouge River appears to be very limited. Yet the fact that stonecats are now found in the Main branch from Troy to Southfield and even in Detroit is hopeful. Dissolved oxygen levels in the Main branch have vastly improved from the 1990s when they only met the level necessary to support fish (5 mg/L) 67% of the time, to meeting it 97-98% of the time in 2010 (Indicator Report). This water quality improvement came about following massive projects to control sewer overflows started in the 1990s. Detroit and some downstream communities are working to control their overflows with a projected completion date in 2037.
Stonecat were found in the Upper branch by the DNR in the 1990s but FOTR’s recent surveys have turned up none. An additional threat to these cats is the extensive use of road salt. FOTR Stonefly Searchers began testing Rouge streams for chloride as part of Winter Salt Watch in 2020. Many sites had levels in the toxic range in winter 2020 and 2021 (map). Testing was added in the spring of 2021 and macroinvertebrate communities were found to be poorer at sites with higher salt concentrations (2021 Spring Bug Hunt Report). The Upper branch had particularly high levels throughout. (see Notes for information on how to reduce road salt impact)
HABITAT & LIFE CYCLE
Catfish in the Noturus genus are small, shy, and nocturnal. In general, these little fish prefer to hide under rocks or woody debris during the day and feed at night. They feed heavily on aquatic macroinvertebrate larvae and plankton. However larger madtoms, such as the stonecat, may also eat eggs and young fry of other fish species.
The various species of madtoms have a spring breeding season that is tied to species-specific changes in water temperature. Male madtoms construct breeding nests by digging shallow cavities under flat rocks and then attract females by releasing pheromones. Several madtom species are also known to use discarded items such as glass bottles and soda cans in which to lay their eggs. FOTR volunteer biologist Bruce McCulloch, who studied madtoms, reported finding stonecat eggs in a broken glass bottle and stonecats coming out of an inverted and submerged toolbox while electroshocking in Canada. Meanwhile, females visit numerous different nests to deposit egg clutches. Depending on species, each egg clutch may contain as many as 75 to 500 eggs. Once hatched, new, baby madtom catfish (known as fish larvae) remain helpless and attached to their yolk sac for several weeks before maturing into small, but independent, fry.
Male madtoms are known for providing an extensive amount of parental care. They stand guard over the nest and clean/aerate the eggs for the entire incubation period. And, in most (possibly all) of the species, males forego foraging (and eating) for up to a month in order to continue the care and protection of helpless larvae until they are mature enough to swim off as independent, young fry.
Stonecats, which average about 8,” are the largest of the madtoms (see main photo image). In the wild, they are believed to live for five to six years. Stonecats like rocky habitats and seek out the shallower, faster moving river riffles with rocky substrate bottoms and larger rocks that provide shelter.
Tadpole madtoms average only 4” in length and live only about three years in the wild. Although these little fish hide and nest under rocks, they like quiet waters with soft substrate bottoms and plentiful plant cover. Therefore, they are often found in quiet pools and slow-moving backwaters. The body shape tapers toward the caudal fin and somewhat resembles the frog tadpoles after which they were named.
Many people believe that catfish sting with their barbels (whiskers), but this is not true. Catfish have no ability to intentionally inflict a “sting,” and their barbels are soft and completely harmless. What is sometimes mistaken for a sting is the occasional (human induced) puncture from the tip of a spine associated with the dorsal and pectoral fins. Fin spines do contain a mild toxin (similar to bee toxin). Small madtoms are generally considered to have sharper fin spines and a slightly stronger toxin than most larger catfish. However, it should be noted that when a human receives a fin puncture from a catfish it is the catfish who is actually the innocent victim. After all, it is the human who has forcibly removed the catfish from its watery home, and it is the human who is holding the poor catfish against its will in an environment where it cannot breathe. So, don’t blame the catfish!
At this time, both stonecat and tadpole madtom are considered secure species, although some sources indicate that their numbers are experiencing an overall gradual decline. As noted, both are sensitive, indicator species, and it is important that we work to provide a clean, well-oxygenated river habitat for their home.
Private property owners can take important steps to preserve and restore the quality of our river water by reducing the use of rock salts and other deicers, reduce/eliminate the use of lawn fertilizers and pesticides, and creating rain gardens to reduce storm water run-off to the river. By working together, we can save the watery home of these cute, little river-cats.
NOTES on Chemical Deicers: While some use of deicers is necessary, the best practice is to use the absolute smallest amounts possible.
Traditional deicers are based on chloride (salts) formulations that are obviously harmful to freshwater river species. Such deicers include such as rock salt (sodium chloride) and various potassium chloride products.
Alternative deicers based on glycol formulations are often marketed as “environmentally friendly” and “pet safe.” Glycol-based deicers are used in vast quantities at airports to deice aircraft and runways and are sold in small quantities for home use. Glycols (alcohols) are generally perceived to be less environmentally harmful than chloride formulas.
Many studies have been conducted on the effects of glycol deicers that indicate environmental concerns. A study conducted for the World Health Organization in 2000 and one conducted for the EPA noted similar concerns. Based on the Environmental Impact / Benefit study performed for the EPA (Abt Associates, April 2012):
1. Most deicers contain a variety of chemical additives, many of which are individually toxic.
2. Deicers based on propylene glycol degrade quickly in a body of water, but also consume large amounts of the available dissolved oxygen during the degradation process. This can lead to anoxic water conditions and suffocation of fish and aquatic insects.
3. Deicers based on ethylene glycol are considered more overall toxic to aquatic organisms than those based on propylene glycol, and, ethylene glycol also consumes a great deal of dissolved oxygen while degrading in water.