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

COMPTUEX/JTFEX EA/OEA Final Chapter 33.3.2.3.4 Endangered FishThere is one endangered fish species, the Southern California Stock of steelhead that may inhabit theSOCAL area. However, the likelihood of steelheads occurring in the SOCAL OPAREA duringCOMPTUEX/JTFEX activities is very rare. There was only one sighting of a steelhead near the SOCALOPAREA in 2002 (7.5 mi [12 km] north of Camp Pendleton). Because it is very unlikely that steelheadmay enter the SOCAL OPAREA, steelhead are not discussed in detail in this EA/OEA.3.3.2.3.5 Hearing in FishFish vary greatly in their ability to detect underwater sounds (see Hastings and Popper, 2005 for areview). Hearing specialists, such as the Atlantic herring, have relatively good auditory capabilities. Inthese fish, the swim bladder is acoustically coupled to the inner ear (Popper, 1996). However, most otherspecies of fish, including mackerel, tuna, and flatfish, are not hearing specialists and either have no swimbladder or, if it is present, it is not coupled acoustically to the inner ear. Although it is difficult tocompare the hearing capabilities of terrestrial and marine vertebrates, the sensitivity of hearing specialistsis similar to that of other vertebrates after standardization of units (Popper and Fay, 1993).The upper limit of hearing in herring ranges from 4 to 13 kilohertz (kHz) (Enger, 1967). The upper limit ofhearing in fish without a swim bladder-inner ear type of coupling is only ~1.0–1.2 kHz (Enger, 1967). Theherring is also relatively sensitive to sound. At 300–1,000 Hertz (Hz) its hearing threshold is ~80 decibels(dB) re 1 micropascal (μPa) (Enger, 1967). However, at high frequencies, hearing thresholds rise rapidlywith increasing frequency. It is a minimum of 135 dB at 4 kHz. Atlantic cod do not have a directconnection between swim bladder and inner ear and are less sensitive to sound than are some other speciesof fish (Olsen, 1969). The hearing threshold for most marine species is ~140 dB at 1–1.5 kHz, and specieswith the best hearing ability are relatively insensitive to sounds above 2–3 kHz (Wodinsky and Tavolga,1964; Hawkins, 1993).Fish within the same taxonomic grouping have similar hearing abilities because of their anatomicalsimilarities (Popper and Fay, 1993; Popper, 1996). There is great diversity in the hearing abilities of thesedifferent groups of fish (Popper and Fay, 1993). Some of the differences may be attributable to differencesin measurement procedures. The three audiograms available for cod demonstrate SPL values at the mostsensitive frequency that vary by 30 dB. Yellowfin tuna may not be very sensitive to sound impulses; theirthreshold is 107 dB, a relatively high (poor) value. Table 3.3-6 summarizes best hearing thresholds forvarious species of fish.February 2007 3-26