Margined madtom (Noturus insignis) COSEWIC assessment and status report 2012: chapter 6
Biology
General
The general biology of margined madtom was summarized by Goodchild (1990) and Taylor (1969). The margined madtom is a secretive nocturnal species that hides among rocks and boulders in rivers and streams. This fish is a benthic feeder, feeding on insects that live on the stream or river bottom. Due to its scarcity and small size, the margined madtom has not been extensively studied. Little is known about its movements or migrations.
The margined madtom spawns in spring or summer but very little is known about its spawning habits. Males guard egg masses that are laid in nests located under flat rocks in gently flowing water above and below riffles. Disturbance causes guardian males to abandon or eat the eggs (Stoeckel and Neves 2000).
It has been observed that males mouth the eggs while guarding the nests (Stoeckel and Neves 2000). This action has been observed in other madtom species and it is speculated that this type of egg manipulation helps to aerate the eggs (Burr and Mayden 1982).
Artificial propagation of the margined madtom by egg hatching and induced spawning has been investigated as a means to recover the species (Stoeckel and Neves 2000, 2001). In captivity, optimum hatching success was obtaining by using strong agitation to tumble the eggs and high temperatures of 28-30° C. It is possible that high temperatures are required for optimum hatching success in the wild, which would restrict the distribution of this species to warmer water bodies.
There are no records of juvenile or immature margined madtom captures in Canada. This does not necessarily mean that margined madtom is not reproducing because it is doubtful that all fish caught were introduced specimens. It is likely that the sampling gear does not select for these fish. These elusive, nocturnal fish hide amongst boulders and gravel making them difficult to capture. They are best captured at dusk with chemicals, electrofishing, or seining.
Nutrition and Interspecific Interactions
The margined madtom is known to eat cladocerans, ostracods, gammarids, midges, and debris (Smith 1985). Gutowski and Stauffer (1993) examined the stomach contents of 403 margined madtoms collected throughout 1988 and 1989 in Pennsylvania and found that insects in the families Baetidae, Chironomidae and Simuliidae were present in stomach samples in proportions higher than those in the environment. The margined madtom ate insects that were most active and most available between midnight and dawn.