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Relative Weight ( W r ) as a Field Assessment Tool: Relationships with Growth, Prey Biomass, and Environmental Conditions
Author(s) -
Liao Hongsheng,
Pierce Clay L.,
Wahl David H.,
Rasmussen Joseph B.,
Leggett William C.
Publication year - 1995
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1995)124<0387:rwwraa>2.3.co;2
Subject(s) - lepomis , biomass (ecology) , predation , benthic zone , biology , chironomidae , stock assessment , invertebrate , ecology , zoology , fishing , larva
We evaluated the relative weight ( W r ) condition index as a field assessment tool with pumpkinseed Lepomis gibbosus and golden shiner Notemigonus crysoleucas , focusing on sources of variability and potential of W r as a predictor of growth, prey availability, and environmental conditions in 10 southern Quebec lakes over 2 years. To allow calculation of W r , we developed standard weight ( W s ) equations for both species, using the regression‐line‐percentile (RLP) technique. The proposed W s equation in metric units (grams wet weight and millimeters total legnth, TL) for pumpkinseed is log 10 W s = –5.179 + 3.237 log 10 TL; for golden shiner it is log 10 W s = –5.593 + 3.302 log 10 TL. Spatial and temporal variation in W r was highly significant and largely asynchronous in both species, although spring values were lowest in most lakes. The W r 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 W r and growth in either species. Pumpkinseed W s were positively correlated with total benthic invertebrate biomass: stock length W r was positively correlated with chironomid biomass, and quality length W r 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 W r and growth in field populations should be reconsidered, but that W r could be cautiously used as a working index of prey availability. We recommend empirical or experimental verification when W r is used as an assessment tool in field populations.