Methods for hatching margined madtom eggs

We used the margined madtom Noturus insignis as a model species to develop egg-hatching techniques for other madtom species. Twelve methods were teste d at water temperatures between 22 degrees C and 30 degrees C, but only one method produced consistent, high hatches of madtom eggs. Use of broodfish to incubate eggs was not effective because they ate their tank-spawned egg masses. Consequently, madtom eggs must be artificially incubated. Use of so dium sulfite, Na2SO3, to facilitate artificial incubation by separating mad tom egg masses is not effective because it causes premature hatching and su bsequent low survival of larvae. Agitation strong enough to tumble eggs and high temperature appear to be key in consistently producing good hatches. We obtained hatch rates greater than 65% for 14 of 16 margined madtom egg m asses by incubating them at 28-30 degrees C within a 6-mm-bar-mesh plastic basket positioned over an air stream strong enough to keep egg masses in co nstant motion. The larvae hatched in about 7 d at 28 degrees C, and the mea n number of degree-days for hatching was 205 +/- 14 (N = 6).