RELATIVE PERFORMANCES OF 4 PRESERVATIVES ON FISH AND CRAYFISH

We evaluated the effects of four common preservatives on central stone rollers Campostoma anomalum and virile crayfish Orconectes virilis to aid in the selection of a method for preserving fish diet samples in t he field. Thirty specimens of each species were allocated to each of e ight treatments: 10% formalin: 25, 50, 75, and 100% isopropanol; 75 an d 100% ethanol; and freezing at -15-degrees-C. After 180 d, specimens were evaluated for color change, physical tone, and quality of tissue preservation. After 90 d and 180 d, changes in central stoneroller tot al length and wet weight and in crayfish carapace length, chela width, and wet weight were evaluated. Freezing preserved fish and crayfish w ith the least effect on coloration and physical tone. All treatments e xcept 25% and 50% isopropanol prevented tissue decay. All treatments c aused decreases (<3% after 180 d) in fish total length. Formalin incre ased fish weight (12%; 180 d), but all other treatments caused decreas es (10-37%; 180 d); freezing had the least effect. Virile crayfish car apace length and chela width did not change significantly due to any t reatment. All treatments except formalin (which caused no change) decr eased crayfish weight (4-16%; 180 d). Considering the additional facto rs of cost and human health and safety, we determined that freezing wa s the best method of preserving crayfish and small fish for our purpos es.