How Much Do California Halibut Move Around?

Associate Marine Biologist Ken Oda with a California halibut. (DFG photo by Travis Tanaka)

Question: I have a question about the halibut out at San Clemente Island. Is it a self-contained population due to the long distance between the island and mainland? If so, is it harder for this island population to mix and propagate with the mainland coastal halibut? I understand that all fertilized fish eggs, larvae and fry drift with the sea currents, but wouldn’t it be easy to overfish this one “homegrown” species of fish at San Clemente Island? (Steve)

Answer: Halibut do move inshore-offshore and along the coast to spawn. They also follow feed and follow favorable ocean conditions. Unfortunately, there is no good answer to your question regarding the fish at San Clemente Island, mostly because no data is available.

According to Department of Fish and Game (DFG) Associate Marine Biologist Travis Tanaka, more than 26,800 coastal mainland halibut were tagged as part of a halibut study performed in Southern California from 1992 to 1997. The study seemed to indicate that migration was related to the size of the fish, but this was not statistically proven. Most of the fish in the study (64 percent) were recaptured in the same region as the original capture. However, halibut larger than 550 millimeters (21.9 inches) in length averaged 29.5 kilometers (18.3 miles) in travel. At the same time, smaller halibut less than 550 millimeters averaged from 4.6 to 5.6 kilometers (2.9-3.5 miles) of travel. The greatest distance of travel was accomplished by a 559 millimeter (22 inch) halibut, which traveled 319 kilometers (198.2 miles). The lesson here is that fish do move, and in the case of this particular study, the movement was mostly to the north. (The results of this study can be found in DFG’s scientific journal, California Fish and Game, vol. 85, no. 2.)

To assess the population size of San Clemente Island fish, someone would have to tag many of them, then catch them again and see where they ended up. Extensive tagging studies require money and time — two resources that are in pretty short supply.

You are correct regarding fertilized halibut eggs. Halibut are broadcast spawners, meaning that when conditions are right, the males and females release their sperm and eggs into the water, and a meeting of the two by random chance takes care of the rest. Currents created during El Nino events improve recruitment (survivability of individuals) because the fertilized eggs will stay closer to the shore where they can settle out. While young halibut may spend their first few years around San Clemente Island, they won’t necessarily stay there. The same applies to juvenile halibut along the mainland coast. They will move.

To determine whether the halibut were being overfished, we would need to know the historical stock size and current stock size and conduct a formal assessment of the population. We don’t have that information right now. However, a fishery scientist contracted by the DFG is currently completing a first-ever statewide stock assessment of California halibut. These assessments do not look at micro populations, but rather at the big picture.

For more halibut information, please see the Marine Region’s State Finfish Management Project’s webpage at

Legal to use a throw net to catch baitfish in a private lake?
Question:Can I use a throw net to catch baitfish (threadfin shad) in a private lake? Since it is private, it should be fine, right? (Dennis B.)

Answer: DFG regulations generally do not apply in any water that is self-contained without any hydrological connection to state waters, or to any fish that are planted by the owner or person in control of the property. In these waters fishing methods are not governed by DFG regulations. However, it would be a violation of the law to transport fish alive from the water where they were taken (California Code of Regulations Title 14, section 1.63).

What do hunters do about fleas and ticks?
Question:I’m not a hunter but am wondering if there is a concern for hunters having to deal with fleas and/or ticks jumping off a cooling carcass when field dressing the animal? (Kelly B., Los Angeles)

Answer: Many animals have fleas and ticks and hunters are encouraged to protect themselves from bites by using appropriate sprays or products to reduce the chance of bites and diseases like Lyme disease.

Laws for CCW handguns in your car
Question:If you have a California license to carry a concealed weapon (CCW), can you have a round chambered in your semi-auto pistol in your car, or an empty chamber and a loaded mag? If it’s a revolver, must the next chamber be empty? Section 2006 in the Fish and Game Code only talks to long guns, right?  Where do they talk about handguns? (Jim M., Modesto)

Answer: Fish and Game law only restricts rifles and shotguns. Handguns are not similarly restricted in Fish and Game law. Check the California Penal Code for answers to your handgun questions.

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Carrie Wilson is a marine biologist with the California Department of Fish and Game. While she cannot personally answer everyone’s questions, she will select a few to answer each week. Please contact her at

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