Passive Acoustic Detection of White Seabass Spawning Aggregations

PIER Research Staff:

Scott Aalbers

Chugey Sepulveda

Captain Tom Fullam

Timeline:

March 2007; on-going.

This project is being conducted to determine if white seabass spawning habitat can be localized using passive acoustic techniques.   

In the Spring of 2007, PIER researchers began acoustically monitoring several Southern California kelp forests to record the sounds produced by white seabass during the Spring/Summer spawning season.  Ambient underwater sounds of the coastal environment were digitally recorded to a portable flash recorder either manually through a hydrophone suspended from a boat, or remotely using a long-term acoustic recorder moored to the seafloor. 

Loggerhead Acoustic Recorder (grey cylinder) being deployed off a boat. The recorder is bolted to a concrete block, keeping it in place on the seafloor. The black node emerging from the recorder is the hydrophone that will receive for sounds underwater.

Audio recordings are focused surrounding periods of known peak spawning activity, which occurs predominantly over the two hour period following sunset from March through July. Nighttime spawning activity is difficult to observe directly and complicates efforts to locate fish spawning aggregations visually, however; underwater sound surveys can alleviate this problem. 

Waveforms of a,b. courtship sounds, c,d,e. spawning sounds, and f. a hydrodynamic boom

This project was initiated based on previous findings from data collected at the Hubbs-SeaWorld Research Institute net pens in Catalina Harbor, which identified the spawning behavior, periodicity, and associated sound production of captive white seabass.  Initial research revealed that male white seabass produce six distinct sound varieties with an identifiable train of sounds that coincided with the release of gametes.

Spectrogram of an identifiable white seabass spawning chant

We propose that the discernible sounds produced during actual spawning can be used to locate spawning aggregations in the field.  Passive acoustic surveys are a rapid, reliable, and non-intrusive method of determining the location of spawning areas utilized by sound producing fish.

Learn more about the biology of the white seabass

Learn more about white seabass fishery and management