Comparative Biochemistry and Physiology Part A 133 (2002) 43–52 1095-6433/02/$ - see front matter  2002 Elsevier Science Inc. All rights reserved. PII:S1095-6433 Ž 02 . 00108-3 The effects of noise on the auditory sensitivity of the bluegill sunfish, Lepomis macrochirus  Amy R. Scholik*, Hong Y. Yan Mechanosensory Physiology Laboratory, School of Biological Sciences, University of Kentucky, Lexington, KY 40506, USA Received 4 December 2001; received in revised form 14 March 2002; accepted 24 March 2002 Abstract As concerns about the effects of underwater anthropogenic noises on the auditory function of organisms increases, it is imperative to assess if all organisms are equally affected by the same noise source. Consequently, auditory capabilities of an organism need to be evaluated and compared interspecifically. Teleost fishes provide excellent models to examine these issues due to their diversity of hearing capabilities. Broadly, fishes can be categorized as hearing specialists (broad hearing frequency range with low auditory thresholds) or hearing generalists (narrower frequency range with higher auditory thresholds). The goal of this study was to examine the immediate effects of white noise exposure (0.3–2.0 kHz, 142 dB re: 1 mPa) and recovery after exposure (1–6 days) on a hearing generalist fish, bluegill sunfish (Lepomis macrochirus). Noise exposure resulted in only a slight, but not statistically significant, elevation in auditory threshold compared to fish not exposed to noise. In combination with results from our previous studies examining effects of noise on a hearing specialist fish, the fathead minnow (Pimephales promelas), this study provides evidence supporting the hypothesis that fish’s auditory thresholds can be differentially affected by noise exposure.  2002 Elsevier Science Inc. All rights reserved. Keywords: Auditory brainstem response; Centrarchidae; Cyprinidae; Hearing generalist fish; Hearing specialist fish; Threshold shift; Underwater noise; White noise 1. Introduction Recently, there has been heightened concern about the effects of underwater noise on freshwater and marine organisms. This is a result of the increasing amount of noise in the underwater acoustic environment associated with anthropogen- ic sources (Richardson et al., 1995; Gordon and Moscrop, 1996). Though sounds generated from boats and ships are considered the main sources, there are a vast number of anthropogenic noise  Part of the results was presented at the 18th International BioAcoustic Council meeting, Cogne, Italy, 3–6 September, 2001. *Corresponding author. Tel.: q1-859-257-7410; fax: q1- 859-257-1717. E-mail address: arschol@uky.edu (A.R. Scholik). sources, including underwater explosions, sonars, air guns, dredges, ocean science studies, hydroe- lectric dams, fishing equipment with acoustic deterrent devices, and noises associated with oil and gas production (Richardson et al., 1995; Rich- ardson and Wursig, 1997). Though most of these ¨ sources generate noise only as a by-product, many produce it intentionally. Regardless, there are an expansive number of potential noise sources an aquatic or marine organism may encounter in its environment. Despite the amount of noise in the underwater environment, there have been few studies directly addressing the auditory effects of noise on aquatic organisms. Many behavioral studies have been conducted, but they may not give a comprehensive