Nutritionally important food items for crayfish have been difficult to identify and little information exists for third instar (first‐feeding) crayfish. In this study, three major groups of potentially‐important foods were fed to communally‐reared third instar crayfish (Procambarus clarkii) and weight gain and survival were measured over a 30 day period. Mean weight gain (% increase) of crayfish fed the zooplankton Daphnia magna alone or in combination with other food items, ranged 2, 277–3, 239%, while mean weight gain of crayfish fed unidentified aquatic bacteria, the aquatic macrophyte Myriophyllum spicatus, combinations of bacteria and plant, or a negative control ranged 254–767%. No significant interaction of food items was detected. Bacteria appear to be a utilizable nutritional source for juvenile crayfish, but, using the methods employed in this study, do not support maximum rates of weight gain. Thus, pond management strategies that maximize zooplankton populations at the time of crayfish hatching might be beneficial.

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Culture of orconectid crayfishes in the midwestern USA offers the potential of contributing to a year‐round supply of fresh product as summer/fall production would augment winterhpring production in the southern USA. However, relatively little basic biological information exists for this potential new aquaculture crop. In this study, the authors reared juvenile (third instar) Orconectes virilis and Orconectes immunis at either 10, 15, 20, 25 or 30 C and measured weight gain and survival over a 21 day period. Orconcctes immunis juveniles were larger than O. virilis at the third instar and gained weight more rapidly in this experimental system. Gains in weight and length for both species increased as temperature increased from 10 to 25 C. Both values were lower in crayfish reared at 30 C, though number of molts was the same in crayfish reared at 25 or 30 C. Thus, there appears to be a bioenergetic cost of rearing orconectid crayfishes in temperatures above 25 C. Further, incremental growth with successive molts was influenced by water temperature.

Sunfishes Lepomis spp. are cultivated as sport fish, and recently interest has been shown in culturing them as a food fish based on commercially available feeds that vary in composition according to the life stage of the fish. We evaluated seven commercial larval starter feeds with northern bluegill L. macrochirus macrochirus and redear sunfish L. microlophus in the effort to relate growth performance to diet nutrient composition. The dependent variables were production weight, survival rate, feed conversion ratio, and mean individual weight and length. The proximate composition and fatty acid and amino acid compositions of feeds were related to the dependent variables. Survival rate ranged from 84% to 96% for bluegills and from 15% to 35% for redear sunfish, and individual mean weights ranged from 67 to 238 mg and from 31 to 78 mg for these two species. Relating the compositional analysis of feeds to the dependent variables indicated that isoleucine influenced mean individual weight for both species. Northern bluegill growth performance suggested a negative correlation with carbohydrates, while redear sunfish growth indicated a positive relationship with energy. This study shows that commercial starter feeds can vary greatly in how they influence sunfish growth performance. Further study is needed to determine what dietary variables, including factors other than nutrient profiles, are most important.