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Evaluation of the Relative Weight ( W r ) Index for Assessment of White Crappie and Black Crappie Populations
Author(s) -
Neumann Robert M.,
Murphy Brian R.
Publication year - 1991
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1991)011<0543:eotrww>2.3.co;2
Subject(s) - percentile , fish <actinopterygii> , mathematics , zoology , population , body weight , statistics , biology , demography , fishery , endocrinology , sociology
We evaluated a large data set and confirmed that current standard weight ( W s ) equations for white crappies Pomoxis annularis and black crappies P. nigromaculatus are length‐biased. We applied the regression‐line‐percentile (RLP) technique to length‐weight data for 27,002 white crappies (175 populations) and 21,709 black crappies (80 populations) to develop new 75th‐percentile W s relationships. The proposed W s equations are log 10 W s (g) = −5.642 + 3.332 log 10 T L (mm) for white crappies and log 10 W s (g) = −5.618+ 3.345 log 10 TL(mm) for black crappies; TL is total length. There was no systematic bias evident in W r values ( W r = 100· W / W s ; W is individual fish weight) calculated with the RLP‐generated equations. Frequency distributions of population‐mean W r values were consistent with those from studies of other fish species. No regional trends in W r were observed. Moderate correlations were found between W r and population structure. Relative weight was generally highest in the spring, decreased after spawning, and increased throughout the summer and fall.