California halibut are large, toothed flatfish found in nearshore waters and may be described as being an estuarine-inner shelf species. They are visual ambush predators that range from Magdalena Bay, Baja California north to the Quillayute River in Washington, being most abundant from central California to Baja California. Though they may be found in ocean waters as deep as 600 ft (183 m), they are most often caught by anglers in 10 to 90 ft (3 to 27 m) of water. California halibut are broadcast spawners, and eggs are fertilized externally. Adults migrate from the continental shelf into shallow coastal waters and bays before spawning, usually from February through September. Eggs are pelagic (free floating). Larvae develop with one eye on each side of the head. As California halibut mature and reach the post-larval stage (20-29 days), one eye migrates to the other side so that both eyes are on the same side. California halibut may be right- or left-eyed.
California halibut are usually uniformly brown to brownish-black on the eyed side, and have the ability to change skin color patterns to camouflage with the substrate. They may have white spots, especially juveniles, which often fade after death. The non-eyed side is usually entirely white, though some mottling may occur. The lateral line is most distinctive and is highly arched above the pectoral fin. The mouth is large with conical teeth. The maxilla (top jaw bone) extends beyond the eye. There are less than 77 soft dorsal rays.
Pacific halibut vs. California halibut
In the Pacific halibut (Hippoglossus stenolepis), the maxilla extends only to the front edge of the eye, whereas the maxilla extends beyond the eye in California halibut. Pacific halibut have more than 80 soft dorsal rays and the eyes are always on the right side of the head whereas California halibut will have less than 77 soft dorsal rays and the eyes may be on the right or left side (dextral or sinistral).
California halibut is one of the most important recreational species in Southern California, and commercially-fished species among the state-managed fisheries. The Southern California Fisheries Research and Management Project obtains Essential Fishery Information (EFI) such as length, weight, age, and sex of halibut from commercial landings in Southern California ports and from sport-caught fish. 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. Choose from the links below for more information about California halibut.
- Fishery Independent Trawl Surveys
Staff began collecting an index of California halibut abundance in Southern California in 2018.
- 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.
- 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)
- 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 California 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.
- San Francisco Bay Hooking Mortality Study: In 2009 CDFW staff completed the 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 (Video)
CDFW instructional video by Kristine Lesyna
California Halibut Trawl Surveys
The goal of this study is to develop a fishery-independent index of juvenile California Halibut abundance. The index can be used to inform management on the status of the resource, and provide predictions for recruitment to the fishery in Southern California. Because juvenile halibut spend their first couple of years exclusively in shallow offshore locations and embayments, conducting swept area trawl surveys can be used to evaluate distribution, relative abundance, and expected contributions to the fishery.
Starting in April 2018, CDFW staff began conducting biannual trawl surveys in the spring and fall months using a 25 ft. otter trawl. Trawls are deployed in 13 primary locations ranging from San Diego to Los Angeles. Ten 10-minute trawl surveys are conducted in 8 to 20 ft. depths at each location, and all of the fish caught are identified and measured. All halibut greater than 3 inches are internally tagged with a Passive Integrator Transponder (PIT) tag that allows for identification of specific individuals when recaptured. This study uses similar methods to those used by CDFW from 1993-1995, including net parameters, survey locations, depths, and trawl times. Following these past protocols presents the opportunity to evaluate current population abundance relative to results obtained in the 1990s and establishes a new baseline for comparison to future surveys.
Across two years and four sampling surveys, the average halibut abundance varied greatly among locations but was similar between years (Figure 1); there was no significant difference between spring and fall surveys. Protected locations like bays and harbors yield a significantly higher number of juvenile halibut per area compared to coastal locations. Halibut are the third most abundant species caught while trawling, although they are the most abundant fisheries species (Table 1).
Comparing the most recent (2018-2019) and past (1993-1995) study periods, halibut density was similar among all years except for 1994 which was significantly higher at all but one location (Figure 2). It is also interesting that commercial halibut landings between these two time periods were also similar (Figure 3). Both recent and past trawl study time periods occurred during similar warm temperature regimes, with 1994-1995 being classified as a 'moderate' El Nino and 2018-2019 classified as a 'weak' El Nino. Based on the significant greater number of juvenile halibut in 1994 at a size of approximately 6-8 inches (~1 year old), CDFW would have predicted a large increase in commercial landings of halibut 5-7 years later (1999-2001) when they would be approximately 6-8 years old and 25-29 inches in length, the typical size landed in the Southern California fishery.
Figure 1. Average number of halibut observed per 300m2 at each location. Black bars represent the average of spring and fall surveys in 2018 and white bars represent 2019 surveys. The error bars represent one standard error.
Figure 2. Average number of halibut observed per 300m2 at each location. The white, grey, and black bars indicate 1990’s data, and blue shaded bars represent the more recent survey years. The error bars represent one standard error.
Figure 3. Commercial landings in pounds of California halibut in Southern California from 1990 to 2019. The large black circles represent the time periods of the past (1993-1995) and more recent (2018-2019) trawl surveys. The asterisk indicates when a predicted spike in landings would be seen based on the 1994 trawl data.
Table 1. The total number of species sampled across all locations for 2018 and 2019 sampling periods, ranked in order of most to least abundant.
||Total Number Caught
|Barred Sand Bass
|Spotted Sand Bass
|California Butterfly Ray
|Pacific Jack Mackerel
|Pacific Angel Shark
|Pacific Staghorn Sculpin
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.
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