Sanctuary Integrated Monitoring Network
Monitoring Project

Giant Sea Bass Monitoring

Summary to Date

The project began in 1997 when charter boat owners and divers Kathy deWet-Oleson and her husband Jim Oleson located an aggregation of giant sea bass, Stereolepis gigas, at Anacapa Island and started a monitoring project. They teamed up with sport fishermen and CINMS to continue monitoring sea bass sightings. The primary method of observations initially included divers with video cameras, however they were able to increase observation time using video cameras on tripods, reducing the need for divers in the water and increasing the observation time to 10 hours per day.

Three regions where sea bass sightings were more frequent became established as preferred areas 1, 2, and 3. While dives were conducted throughout the year, between May and September sightings increased and corresponding dive effort increased to a maximum of 24 dives per month.

Photo ID of individual fish was conducted as well.

During observations, all instances of the following behavior were recorded: color patterns, pattern change, utilization of the reef and water column, swimming activity, cleaning activity, boom sounding, and interspecific and intraspecific interactions. In addition, basic oceanographic information including temperature, visibility, current direction, and current strength were noted.

Monitoring Trends

  • Aggregating Behavior: Giant sea bass sightings occurred consistently between May and September with a peak noted in July and August. This corresponds with the reported spawning season of the giant sea bass. As of 2002 no documented spawnings have been observed in the wild. Seasonal Occurrence May-September: As of July 1997, the largest aggregation recorded at Anacapa is 30. The majority of aggregations consists of 12 or fewer individuals. Coloration: Color and pattern variable based on observations. Video shows fish approaching reef lighter color and turn darker as settle on the reef. Darkening and/or spotting combined with a raised dorsal fin also occurs when approached by another sea bass.
  • Cleaning Relationships: Giant sea bass frequently use cleaning stations including species such as senoritas, island kelpfish, blue-banded gobies, topsmelt, juvenile giant kelpfish, juvenile calico bass, and juvenile sheephead. Sounds from the Giant Sea Bass: They often make a loud booming sound primarily when startled or when disputing territory. This behavior has been recorded when a sea bass solicits cleaning and does not get a response. Predators of the Giant Sea Bass: On one dive in 2000 a boom was heard and immediately after a sea bass pursued by a 5-6 ft shark was observed.
  • Identification of Individuals: Individuals with unique or unusual markings are catalogued. One individual was regularly seen at a specific location, disappeared, and was spotted at the same site 6 months later. Hook Ups and Spears: While giant sea bass are protected, many are still caught by fishermen and many others are observed with fishing line or fishing related injuries. One of the goals of this project is to better educate the public on the rules and regulations protecting this species through presentations and outreach.
  • After the Season of the Sea Bass: Divers found fish in gradually deeper water from September through late November. Any divers who encounter a giant sea bass are asked to please submit field notes and fill out a data sheet to further out knowledge on this species.


Little is known about the giant sea bass, however they were once common on the California coast. They are currently listed on the IUCN list as “critically endangered,” however giant sea bass are not ESA listed.

Study Parameters

  • Range/Biogeography
  • Habitat association
  • Behavior
  • Habitat
  • Distribution
  • Migration/movement patterns
  • Abundance
  • Density

Study Methods

Frequency of Data Collection:
1997-2000: 2 dive trips per month year round, with a minimum of 2 dives each month both on and off the original site. Between May and September, when sightings are more frequent, the dive effort is increased to up to 24 dives per month. 2000-2002: Random dives were conducted less frequently from May to September to allow more behavioral observations and photo identification.

Data Type:
Notes or video are used to document behaviors including color patterns, pattern change, utilization of the reef and the water column, swimming activity, cleaning activity, boom sounding, and both inter and intra species interactions. Notes on basic oceanographic information including temperature, visibility, and direction and strength of the current are also recorded.