A target strength and length relationship for striped bass and white perch

For hydroacoustic studies in which estimation of fish size and absolute abundance is desirable, researchers must either develop a relationship between target strength and fish length or borrow one from the literature. The purpose of this study was to provide a relationship between target strength and total length for two economically and ecologically important sympatric species: striped bass Morone saxatilis and white perch M. americana. We measured the dorsal aspect target strength of 12 white perch and 22 striped bass with a 120-kHz split-beam hydroacoustic system. The calculated target strength (TS [decibels]) to length (L-cm [cm]) relationships were as follows: white perch TS = 26.48 log(10)L(cm) - 69.45 (r(2) = 0.81, P < 0.001); striped bass TS 15.37 log(10)L(cm) - 56.26 (r(2) = 0.80, P < 0.001); and a combined model TS = 15.613 log(10)L(cm) - 56.47 (r(2) = 0.82, P < 0.001). Each of these models differs substantially from the equations of Love (1971) and Foote ( 1987), which are commonly used in acoustic studies when the actual relationships are lacking.