A Comparison of Relative Weight and Nutritional Status among Four Fish Species in Two Impoundments

Abstract

Relative weight (W,) was originally developed to assess the physiological status of largemouth bass. Later it was expanded to other centrarchids and, more recently, to noncentrarchids without consideration of how well the concept may fit other taxa. Our goal was to compare the ability of W, to convey physiological information among species. We considered the following alternative hypotheses: that the relationship of W, to physiological status would vary according to phylogeny, according to ecological specialization, or according to morphology. We collected data (water, protein, lipid, liver, gonad and viscera percentages) from 2 16 fish of four species (bluegill, largemouth bass, black crappie, chain pickerel) from two Virginia impoundments. All but one populationspecific multiple regression model explained a significant amount of variation (F > 2.3 1, P < 0.05). Both bluegill models explained the least amount of variation (adjusted R' < 0.15). Piscivore models fit the data best (adjusted R~ > 0.45). Correlations of lipid to Wr were lowest for bluegills (3 = 0.1 1 and 0.15). Variables describing energy storage and short-term growth were positively related to Wr in all species; however, the strength of this correlation coincided with trophic role. We concluded that differences in physiology and life history affect interpretation of Wr (and other whole-body condition indices) among species. Further, W, may convey less physiological information for ecologically plastic species (e.g., bluegill) if they are treated as a honlogeneous population. INTRODUCTIONIn fisheries science, the use and application of the condition index of relative

Condition Indices as Surrogates of Energy Density and Lipid Content in Juveniles of Three Fish Species

“…As a result, fisheries scientists seek appropriate means of identifying wellconditioned individuals to investigate population-level measures of fitness and survival. Unfortunately, the relationships among condition indices and energy and lipid content are seldom compared among species with different ecological niches and life history strategies to assess the versatility of condition indices (but see Copeland et al 2008).…”

Length-Weight Relationships and Growth Patterns of Eight Indigenous Fish Species from Lancang River, Southwest China

“…Relative weight (W r ) conveys important physiological components of fsh life history (e.g., lipid storage, body morphology, and growth rate) and ofers a strong, accessible metric for managers to assess the overall health and ftness of fsh populations, as well as population-level responses to ecosystem disturbances [30]. According to Anderson and Neumann [31], a relative weight (W r ) of an individual or population less than 100 may indicate problems, such as low prey availability or high predation pressure; a relative weight (W r ) greater than 100 indicates sufcient prey or low predation pressure.…”