California Halibut Studies

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.

  • Green sturgeon post-release impacts in central California halibut trawl fishery: This project is collaborating with central California commercial halibut trawl fishermen, NOAA Fisheries Santa Cruz office, and the West Coast Groundfish Observer Program, to place satellite tags on green sturgeon caught as bycatch in the halibut trawl fishery...learn more
  • Cruise Report: California Halibut (Paralichthys californicus) CDFW/NMFS Light Touch Trawl Survey of North Monterey Bay (2013)
  • Cruise Report (PDF): California Halibut (Paralichthys californicus) Trawl Survey of North Monterey Bay (2010)
  • Cruise Report (PDF): Southern California Fishery-Independent Halibut Trawl Survey (2008)
  • Cruise Report (PDF): Fishery-Independent Trawl Survey in Monterey Bay (2007)

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.

  • Length- and age-at-maturity study: The Project was awarded a grant through the Bay-Delta Sport Fishing Enhancement Stamp Fund for research to determine length- and age-at-maturity for male and female California Halibut within San Francisco Bay. In a collaborative partnership with Moss Landing Marine Labs, California Halibut maturity was additionally studied from fish collected along the open central California coast. The results from these studies were combined to assess maturity, using histological parameters, in the central California region as a whole and have now been published in an article available in the journal link opens in new windowCalifornia Fish and Game (PDF). Comprehensive estimates of length- and age-at-maturity, using macroscopic parameters, for halibut were previously available from the southern California region (Love and Brooks 1990). Using those data, the article discusses regional differences in maturation between southern and central California. Additionally detailed descriptions useful in determining reproductive phase and spawning state for California Halibut are presented.
    • Data summary:
      • In central California, 50% of males were mature by 27.0 cm (1.1 yr) and 50% of females were mature by 47.3 cm (2.6 yr), according to histological parameters.
      • In southern California, 50% of males were mature by 22.7 cm (1.3 yr) and 50% of females were mature by 47.1 cm (4.3 yr), according to macroscopic parameters.
    • Annual Summary of CPFV Morning Star Halibut Catch 2012: View the unpublished study report (PDF)
    • Annual Summary of CPFV Morning Star Halibut Catch 2013: View the unpublished study report (PDF)
  • 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 (PDF).
  • 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 (PDF)
  • External Sex Determination of California Halibut
    CDFW instructional video by Kristine Lesyna

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 three of the best thin sectioned halibut otoliths we have aged, from top to bottom: a 7-year old female, a 9-year old female, and a 12-year old female, all sampled from the San Francisco Bay recreational fishery from 2012 to 2014. 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 9-year-old California halibut. CDFW file photo.

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

Recruitment Studies

Relative Contribution of Local Recruitment to the San Francisco Bay California Halibut (Paralichthys californicus) Fishery Inside the Golden Gate (PDF)
by Max Fish, Bay-Delta Study, CDFW

Assessing Halibut in Their Natural Habitat

Currently there is no acceptable, cost-effective method for determining the abundance of halibut in their natural, soft-bottom ocean or estuarine habitat. CDFW's Marine Protected Area (MPA) Project conducts transects inside and outside of MPAs, using remotely operated vehicles (ROV), to determine relative abundance of selected species of fish and invertebrates. While the focus is primarily on species associated with hard bottom habitats and kelp beds, some ROV transects encounter soft bottom. Halibut tend to bury most of their bodies in soft substrate when they are inactive or waiting to ambush prey, but occasionally the ROV will encounter one completely exposed.

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

Environmental Scientist Kristine Lesyna examines a California halibut. Photo credit: Angler James Garvey.

Halibut caught during Hooking Mortality Study. CDFW photo by Adrienne Vincent.

California halibut. Photo credit: CDFW/MARE