Evaluation of seismic sources for repelling sea turtles from hopper dredges

Hopper dredges are an effective way to both widen and deepen channels to accommodate deep draft shipping traffic. These dredging operations are required to comply with the Endangered Species Act of 1973 (Dickerson et al., 1991, Studt, 1985). It has been found that sea turtles can be entrained and killed during normal dredging operations. The five species of sea turtles that occur in the southeastern united states which may be harmed by dredging operations are the loggerhead (Caretta caretta), the green (Chelonia mydas), the Kemp\u27s ridley (Lenidochelys kemnii) , the hawksbill (Eretomochelys imbricata) , and the leatherback (Qermochelys coriacea). Because of their geographic distribution and life history attributes, the National Marine Fisheries Service (NMFS) has concluded that only the Kemp\u27s ridley, the loggerhead, and the green sea turtle may be at risk by hopper dredging activities (Joyce, 1982). Due to the need to keep shipping channels open and the concern over the unacceptable mortality of sea turtles caused by hopper dredges, NMFS has suggested that repulsion from the hopper dredges could be one method to reduce the incidental take of sea turtles. We investigated the potential usefulness of pneumatic energy sources (air guns) to repel loggerhead sea turtles from dredge heads. This method assumes that sea turtles have the capacity to perceive these pulses, either through auditory or tactile receptors