California Department of Fish and Wildlife

California Halibut Studies

Environmental Scientist Travis Tanaka with a California halibut captured during a research cruise. CDFW file photo.

California halibut is one of the most important commercially-fished species among the state-managed fisheries. The Northern and Central California Finfish Research and Management Project obtains basic length, weight, age, and reproductive information from sampled landings in central and southern California ports.

  • Fishery-independent Trawl Surveys: The Project initiated a series of fishery-independent trawl surveys, one in Monterey Bay and one in the Santa Barbara Channel, to obtain basic biological information on legal- and sublegal-sized halibut, as well as associated bycatch species. The Monterey Bay surveys occurred in 2007 and 2010, and the Santa Barbara Channel survey occurred in 2008.

    • Cruise Report: California Halibut (Paralichthys californicus) Trawl Survey of North Monterey Bay (2010) Adobe Reader required
    • Cruise Report: Southern California Fishery-Independent Halibut Trawl Survey (2008) Adobe Reader required
    • Cruise Report: Fishery-Independent Trawl Survey in Monterey Bay (2007) Adobe Reader required

Staff from the California Recreational Fisheries Survey (CRFS), along with some Northern and Central California Finfish Research and Management Project staff, are monitoring the most frequently-used boat launch ramps in the San Francisco Bay area and collecting similar data from recreationally-caught halibut.

  • San Francisco Bay Age- and Length-at-First Maturity and Fecundity Study: In September 2009 the Project was awarded a grant through the Bay-Delta Sport Fishing Enhancement Stamp Fund for research to determine age and length at first maturity and fecundity for California halibut within San Francisco Bay. Data collection began in April 2012 and will continue through June 2014. Whole halibut or halibut carcasses from various sizes of halibut are being collected from commercial passenger fishing vessels (CPFVs), commercial trawl and hook-and-line fishing vessels, private skiffs at public launch ramps, and research trawl vessels. Each halibut used for the study will be examined macroscopically and microscopically to determine stage of maturity, and aged using otoliths. Mature females will also be assessed for fecundity.

  • San Francisco Bay Hooking Mortality Study: In 2009 the SFMP completed its second year of a hooking mortality study for halibut initiated in 2008 within San Francisco Bay. This study evaluated the potential impact of various gear types on released halibut. Upon landing, the type of hook, hooking location, and length of the fish were recorded. Selected halibut were retained at the Aquarium of the Bay for observation. View the unpublished study report. Adobe Reader required
  • Statewide Stock Assessment: The CDFW has collected and summarized recent and historical data for use in a statewide stock assessment for California halibut. Historical and current catch and biological data were included. This is the first statewide evaluation of the California halibut resource. View the completed assessment.
  • California Halibut Sex Determination Guide Adobe Reader required

Environmental Scientist Kristine Lesyna examines a California halibut. Photo credit: Angler James Garvey.      Halibut caught during Hooking Mortality Study. CDFW photo by Adrienne Vincent.

Ageing Studies

In 2009 the Project began to determine the age of California halibut using thin sections of otoliths (ear bones) collected from fish sampled primarily in the commercial and recreational fisheries. Otoliths are mounted in epoxy resin, thin sections are cut using a diamond saw, and ages are determined under high magnification. Two readers independently age each otolith and when agreement is reached, the age, length, sex, and other sampling data are entered into a database. As of August 2013 more than 1,000 otoliths have been aged from southern and central California. The photos below show two of the best thin sections we have aged, that of a 7-year old and a 12-year old female halibut sampled in San Francisco Bay in 2012. Most otoliths are not nearly as easy to read as these are.

Otolith section from 7-year-old California halibut. CDFW file photo.      Otolith section from 12-year-old California halibut. CDFW file photo.