Effects of air gun energy releases on the northern anchovy

Eggs, larvae of several ages, and adult specimens of the northern anchovy were exposed to acoustic energy from air gun seismic sources. Unlike earlier studies that exposed specimens to one or a few shots from the source, these exposures used a series of air gun shots using devices of various chamber sizes, simulating realistic exposures that might be experienced by wild fish in the vicinity of a seismic survey vessel. Exposure protocols ranged from the equivalent of single, distant passes of a typical seismic array to multiple passes at very short range. Air gun charging pressures were varied to simulate changing ranges. Histological examination of exposed specimens revealed no evidence of gross morphological damage caused by exposure. Comparison of survival with control groups showed subtle effects in the younger (2–4 days) larvae. Exposure of adults resulted in some damage to swimbladders, particularly for fish exposed at the surface where water particle motion effects are pronounced, but no significant...