Samples of larval and juvenile fishes were collected at two depths weekly during spring and summer 1983 near the mouths of backwater areas in Pool 13 of the Upper Mississippi River. The study was conducted to determine the relative value of these habitats as nursery areas for fishes present and to note any interactions that might occur between the backwaters which are being rapidly lost to siltation, and the main channel. The larvae and juveniles collected represented 13 families divided into 27 lower taxa. Cyprinidae, Clupeidae, and Sciaenidae made up 90% of the total catch. Both larvae and juveniles were more abundant near the surface than near the bottom. Densities differed greatly among the three backwater areas studied. Larval fishes were grouped on the basis of their relative abundance in the backwaters or main channel. Overall, more larvae were captured in the backwaters than in main-channel habitats, indicating that backwaters were more productive. In the main channel, densities were greater downstream from the mouths of the backwaters than upstream-possibly indicating that (1) larval fish drifted out of the backwater areas, (2) water rich in nutrients or zooplankton that flowed into the main channel created productive downstream sites that were used as nursery areas, or (3) adult fishes selected downstream sites as spawning areas. Juvenile forms were more abundant in the backwater areas then in the main-channel habitats, some bottom-dwelling fishes excepted.

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Chemical methods were developed and evaluated for dissolving the matrix surrounding eggs of channel catfish (Ictalurus punctatus), which permits eggs to be incubated in cylindrical jars. Screening tests identified several dissolving agents, and four solutions appeared most suitable: (1) 1.5% Na2SO3; (2) 1.5% Na2SO3 plus 0.2% papain; (3) 1.5% L‐cysteine‐HCl plus 0.2% papain; and (4) 1.0% Na2SO3, 0.5% L‐cysteine‐HCl plus 0.2% papain. Production‐level testing on whole egg masses demonstrated that hatching success of channel catfish eggs chemically separated and incubated in jars averaged 20.5% higher than with traditional trough‐and‐paddle incubation methods. No significant differences in fry deformities or survival were found among the nine treatments and controls. A trend toward higher percent hatch and higher fry viability was detected when eggs were separated from medium‐sized egg masses (601–900 g) more than 24 h after the eggs were spawned. Chemical separation of eggs reduced fungal disease problems and labor associated with egg incubation. This process has been used for several years in a variety of cultural situations. Other fish species with adhesive eggs have been successfully incubated with variations of this technique.

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