We evaluated the relative weight (Wr) condition index as a field assessment tool with pumpkinseed Lepomis gibbosus and golden shiner Notemigonus crysoleucas, focusing on sources of variability and potential of Wr as a predictor of growth, prey availability, and environmental conditions in 10 southern Quebec lakes over 2 years. To allow calculation of Wr, we developed standard weight (Ws) equations for both species, using the regression-line-percentile (RLP) technique. The proposed Ws equation in metric units (grams wet weight and millimeters total legnth, TL) for pumpkinseed is log10Ws = -5.179 + 3.237 log10TL; for golden shiner it is log10Ws = -5.593 + 3.302 log10TL. Spatial and temporal variation in Wr was highly significant and largely asynchronous in both species, although spring values were lowest in most lakes. The Wr index frequently varied with length, prompting us to examine relationships in stock and quality length fish separately. We found little evidence for a relationship between Wr and growth in either species. Pumpkinseed Wrs were positively correlated with total benthic invertebrate biomass: Stock length Wr was positively correlated with chironomid biomass, and quality length Wr was positively correlated with gastropod biomass. The relative weight of quality length golden shiners was positively correlated with chironomid biomass. Our results and those of other studies suggest that the common assumption of a relationship between Wr and growth in field populations should be reconsidered, but that Wr could be cautiously used as a working index of prey availability. We recommend empirical or experimental verification when Wr is used as an assessment tool in field populations.
|Original language||English (US)|
|Number of pages||14|
|Journal||Transactions of the American Fisheries Society|
|State||Published - May 1995|
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Aquatic Science