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.

  • 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) PDF Reader required
    • Final Report
    • Appendix A: Essential Fishing Habitat Consultation and Concurrence
    • Appendix B: Endangered Species Act Memo and Biological Assessment
    • Appendix C: National Environmental Policy Act Categorical Exclusion and Concurrence Email
    • Appendix D: Endangered Species Act Concurrence
    • Appendix E: Protected Species Monitoring and Mitigation Protocol
    • Appendix F: Monterey Bay National Marine Sanctuary Permit
    • Appendix G: Cruise Report - Investigation into the Feasibility of Use and Seafloor Interaction of Light-Touch Trawl Gear in the Former Trawl Grounds of Monterey Bay
    • Appendix H: Economic Survey
    • Appendix I: An Economic Analysis of the Catch Composition in a "Light-Touch" Trawl Gear Survey Targeting California Halibut in the Monterey Bay, California
    • Appendix J: Protected Species Observing Distances
    • Appendix K: Protected Species Sighting Record
    • Entire Document (Large file size: 7 MB)
  • Cruise Report: California Halibut (Paralichthys californicus) Trawl Survey of North Monterey Bay (2010) PDF Reader required
  • Cruise Report: Southern California Fishery-Independent Halibut Trawl Survey (2008) PDF Reader required
  • Cruise Report: Fishery-Independent Trawl Survey in Monterey Bay (2007) PDF 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. PDF 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 PDF 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 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.

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, as in the photo below, taken in southern California in 2014.

California halibut. Photo credit: CDFW/Marine Applied Research and Exploration.