Rearing of channel catfish, Ictalurus punctatus (Rafinesque), and brown bullheads, I. nebulosus (Lesuer), in floating cages in a pond near Corvallis, Oregon

Abstract

A study designed to evaluate the use of floating cages for rearing fingerling and subadult channel catfish (Ictalurus punctatus) and fingerling brown bullheads (I. nebulosus) on a commercial basis in Oregon's Willamette Valley was conducted at a pond seven miles north of Corvallis, Oregon, from May 23 to October 17, 1970. Fish were stocked in 1.4 m³ floating cages at the rate of 150 fish/cage (110 fish/m³) and fed either a dry, floating feed (Purina Trout Chow) or a moist, sinking feed (Oregon Moist Pellet). Channel catfish were fed 3.0% of body weight/day. Brown bullheads were fed either 3.0 or 4.5% of body weight/day. Water temperature in the experimental pond was above 21 C for approximately 90 days in 1970. A season of 160-210 days of water temperatures over 21 C is usually required to grow catfish from fingerlings to a commercially-usable size of 340-570 g in one season. The fingerling channel catfish had an average weight of 96.4 g and an average fork. length of 195.3 mm at the termination of the experiment. Yield at the end of the experiment averaged 11.8 kg/cage and food conversion ratios averaged 1.9:1. There were no differences among the cages of fingerlings in yield, conversion ratio, or average weight and fork length. There were more small fish in cages where the fingerlings were fed the sinking diet than in the cages where the floating diet was fed. This was probably due to the restricted feeding area required for the sinking diet (a metal tray with a surface area of 0.4 m²), which caused more competition among the fish fed the sinking diet than probably occurred among the fish fed the floating diet. Losses among the fingerling channel catfish averaged 17% of the fish in each cage. Handling was considered to be the chief factor of mortality. Twenty percent of the subadult channel catfish were grown to a commercially-usable size (340 g or more) by the end of their second growing season in Oregon. Yields for the subadults were 31.4 kg for the fish fed the sinking diet and 35.8 kg for the fish fed the floating diet. Conversion ratios were 1.5:1 for the floating diet and 1.8:l for the sinking diet. Losses averaged 4% of the fish in each cage, all of which were attributed to poisoning from tarichatoxin exuded from the skin of the rough-skinned newt (Taricha granulosa granulosa) that was common in the pond. Apparently, the catfish were poisoned when they attacked the newts and bit them. Ninety-five percent of the brown bullhead fingerlings died as a result of severe columnariasis outbreaks in May and June, following handling. Growth data obtained from brown bullheads collected from lakes and reservoirs in central and western Oregon showed that growth under natural conditions in these areas may be sufficient to enable this species of catfish to be used in low-intensity cultural operations. Yields resulting from the use of floating cages for rearing fingerling channel catfish were greater than those observed in previous experiments at the same ponds in which fingerling channel catfish were raised free in the ponds, both with and without artificial feeding. High-intensity culture of channel catfish in ponds in Oregon's Willamette Valley does not appear to be economically feasible. The factor limiting the growth of catfish in this area appears to be low water temperatures.