A brief explanation of stock-density indices (PSD and RSD-P), catch per unit effort (CPUE), and relative weight (Wr). Stock density indices are utilized to quantify and describe size structure. Stock density indices were proposed by Anderson and Wege (1978) and further modified by Gabelhouse (1984) with a model based on five length categories. Stock density indices are utilized as a fish quality index that describes fish in terms of specific length categories. Proportional stock density (PSD) = Number of fish ≥ quality-length X 100 Number of fish ≥ stock-length The objective range for PSD values is typically 30-60, and indicates a fish population comprised of an acceptable mix of all fish lengths. Values below the objective range indicate a population dominated by smaller fish; while values above the objective range indicate a population dominated by larger fish. Relative stock density of preferred-length fish (RSD-P) = Number of fish ≥ preferred-length X 100 Number of fish ≥ stock-length The objective range for RSD-P values is typically 5-10. Values less than the objective range indicate a smaller than desired proportion of preferredlength fish in the population; while values greater than the objective indicate a population with a higher than desired proportion of preferredlength fish. Catch per unit effort (CPUE) = Number of fish Defined period of effort In this report CPUE refers to the number of fish per net night (gill net/frame net) or the number fish per hour electrofished.
Relative Weight (Wr)= W X 100 Ws W= weight of the fish Ws = standard weight for a fish of that length. (Wege and Anderson 1978) Wr is an index utilized to gauge the general condition of the fish (i.e., how much does a fish weigh for its length). Wr values of 95-105 are commonly cited optimum values. Wr values as low as 80 are commonly viewed as acceptable in freshwater fisheries management.
Fish species minimum length categories (mm) utilized for stock-density indices calculations. Species Bigmouth Buffalo Black Bullhead Black Crappie Bluegill Bluegill X Gr. Sunfish Channel Catfish Common Carp Freshwater Drum Green Sunfish Lake Herring Largemouth Bass Muskellunge Northern Pike Pumpkinseed Rock Bass Shorthead Redhorse Smallmouth Bass White Bass White Crappie White Sucker Yellow Bullhead Yellow Perch Stock Quality Preferred Memorable Trophy 280 460 610 760 940 150 230 300 380 460 130 200 250 300 380 80 150 200 250 300 80 150 200 250 300 280 410 610 710 910 280 410 530 660 840 200 300 380 510 630 80 150 200 250 300 130 200 280 350 430 200 300 380 510 630 510 760 970 1,070 1,270 350 530 710 860 1,120 80 150 200 250 300 100 180 230 280 330 150 250 330 410 510 180 280 350 430 510 150 230 300 380 460 130 200 250 300 380 150 250 330 410 510 100 180 230 280 360 130 200 250 300 380
Bister et al. (2000), Gabelhouse (1984)
Common name, scientific name, and abbreviation for fish species mentioned. Common Name Bigmouth Buffalo Black Bullhead Black Crappie Bluegill Bluegill X Gr. Sunfish Channel Catfish Common Carp Common Shiner Emerald Shiner Fathead Minnow Freshwater Drum Golden Shiner Green Sunfish Iowa Darter Johnny Darter Lake Herring Largemouth Bass Muskellunge Northern Pike Orangespotted Sunfish Pumpkinseed Rock Bass Shorthead Redhorse Smallmouth Bass Spottail Shiner Sunfish1 White Bass White Crappie White Sucker Yellow Bullhead Yellow Perch
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Scientific Name Ictiobus cyprinellus Ameiurus melas Pomoxis nigromaculatus Lepomis macrochirus Lepomis macrochirus x Lepomis cyanellus Ictalurus punctatus Cyprinus carpio Luxilus cornutus Notropis atherinoides Pimephales promelas Aplodinotus grunniens Notemigonus crysoleucas Lepomis cyanellus Etheostoma exile Etheostoma nigrum Coregonus artedi Micropterus salmoides Esox masquinongy Esox lucius Lepomis humilis Lepomis gibbosus Ambloplites rupestris Moxostoma macrolepidotum Micropterus dolomieu Notropis hudsonius Lepomis spp. Morone chrysops Pomoxis annularis Catostomus commersoni Ameiurus natalis Perca flavescens
Abbreviation BIB BLB BLC BLG BGH CCF COC COS EMS FAM FRD GOS GSF IOD JOD LAH LMB MUS NOP OSF PUS ROB SHS SMB SPS SUN WHB WHC WHS YEB YEP
sunfish including bluegill, bluegill hybrids, and green sunfish.