Observed Growth, Survival, and Caudal Fin Ray Deformities of Intensively Cultured Razorback Suckers

Abstract

Abstract Approximately 65% of the razorback suckers Xyrauchen texanus hatched at Colorado Division of Wildlife's (CDOW) Fish Research Hatchery (FRH) in 1993 exhibited fin deformities. A subsample of razorback suckers hatched from eggs obtained in 1994 were used in feeding trials to determine if feed brand and type (i.e., nutrition) caused these deformities. Other possible causes considered in the study design included environmental factors and genetic predisposition. Four razorback suckers, two males and two females, were spawned at the Horsethief Canyon State Wildlife Area, Fruita, Colorado. Each of the four crosses of known parental identity were assigned to lots and transferred to the FRH for hatching and rearing. Three subsets of 200 larvae from each cross were fed different commercial diets. All lots fed Fry Feed Kyowa grew more quickly than lots fed Hatchfry Encapsulon or Hatchfry Encapsulon supplemented with Spirulina. Growth of larvae from all lots fed the Encapsulon diets was similar, with no apparent benefit realized from Spirulina supplementation. Upon termination of the feeding trial, all experimental larvae exhibited varying degrees of fin deformity. Larvae not included in the feeding trial rarely displayed fin deformities, although they were also fed Fry Feed Kyowa and were reared in the same trough as their siblings. Because feed, environmental conditions, and parents were identical during each trial, the fin deformities were attributed to handling stress.