Composite Training Unit Exercises and Joint Task ... - Govsupport.us

COMPTUEX/JTFEX EA/OEA Final Chapter 4This EA/OEA uses behavioral observations of trained cetaceans exposed to intense underwater soundunder controlled circumstances to develop a criterion and threshold for behavioral effects of sound.These data are described in detail in Schlundt et al. (2000) and Finneran and Schlundt (2004). These dataare the most applicable because they are based on controlled, tonal sound exposures within the tacticalsonar frequency range, and because the species studied are closely related to the majority of animalsexpected to be located within the SOCAL OPAREA.This section begins by presenting the behavioral effects threshold that is used for the harassmentauthorization request based on input from the NMFS. The section then describes the scientific basis forthe derivation of a different threshold that Navy believes reflects the current status of the science for midfrequencysonar sources. The section ends by addressing the likelihood for exposure of mammals tosound over extended periods of time (regarding the issue of potentially displacing a resident population)and the potential for auditory masking.Threshold Level for Harassment from Behavioral EffectsFor this specified action, based on coordination with NMFS, the threshold for behavioral response (sub-TTS) modeled in the acoustic exposure analysis for cetacea in this EA/OEA includes an analysis of thepotential for exposures at or above a received sound level of 173 dB re 1 μPa 2 . Therefore, the thresholdfor behavioral effect for this specified action is:173 dB re 1 µPa 2 -s at 1 m (received EL)NMFS recommended Navy include analysis of this threshold based on NMFS’ evaluation of databehavioral observations of marine mammals under controlled conditions, described in the next subsection,plus NMFS’ interpretation of two additional studies (Nowacek et al, 2004 and NMFS 2005). While thisbehavioral effects threshold continues to undergo discussion, Navy is presenting an analysis of potentialfor behavioral effects and requesting harassment authorization at the NMFS-required level. Additionally,Navy is providing the analyses to the 190 dB re 1 μPa 2 -s, presented below, which Navy believes to mostaccurately reflect scientifically-derived behavioral reactions from sound sources that are most similar tomid-frequency sonars.The use of the 173 dB re 1 μPa 2 -s was required by NMFS as a precautionary measure given there remainunique circumstances present in attempting to quantitatively predict the potential effects of sonar oncetaceans. These unique factors are: (1) the newness of the quantitative modeling approach, and (2) theanimals affected are wild animals vice animals in captivity. The Navy has agreed to the use of the 173 dBre 1 μPa 2 -s threshold for this EA/OEA. Establishment of an appropriate threshold will continue to becoordinate between Navy and NMFS.For this EA/OEA, all marine mammals predicted to receive a sound exposure with EL greater than orequal to 173 dB re 1 μPa 2 -s but less than 195 dB re 1 μPa 2 -s are considered as potentially experiencingbehavioral effects that NMFS considers may cause Level B harassment. These raw acoustic exposuresare evaluated in consideration of species’ behavioral ecology, their expected occurrence in the exercisesareas, and the use of mitigation measures to determine the species and number of harassment incidents.Behavioral Effects in Cetaceans Exposed to Sonar-Like SoundsAs described above, Navy believes behavioral observations of trained cetaceans exposed to intenseunderwater sound under controlled circumstances are an important data set in evaluating and developing acriterion and threshold for behavioral effects of sound. Behavioral observations are described in detail inFebruary 2007 4-32