Pacific and California Halibut: Large and Unusual Fish
More Than Just a Food Source
To many people, halibut are simply a good food source. They are actually very interesting animals. They are a type of flatfish. Flatfish have flattened bodies, as their name implies, and swim on their sides. At the start of their lives they look like other fish. As they grow, they gradually change their orientation in the water so that they are moving with their right or left side facing the water surface and their other side facing the ocean floor. In addition, the eye on their lower side slowly shifts in position until it lies next to the eye on their upper side.
Pacific halibut are the largest flatfish and can grow to be huge creatures. The biggest animal on record is one that measured just over eight feet in length and had an estimated weight of around five hundred pounds. California halibut are also known as California flounders. They too can be big fish but generally don't grow as large as Pacific halibut. They reach a maximum length of five feet. The maximum recorded weight of a California halibut is seventy-two pounds.
The fish hide by resting on the ocean bottom and covering themselves with sand or other sediments to camouflage their body. They are ambush predators and feed on fish and marine invertebrates. Both are found on the Pacific coast of North America.
Types of Halibut
There are two kinds of true halibut—the Atlantic halibut (Hippoglossus hippoglossus) and the Pacific halibut (Hippoglossus stenolepis). The Pacific halibut is found along the Pacific coast of the United States and Canada from California to Alaska. It's also found along the coasts of Russia, Japan, and Korea and in the Bering Sea. The California halibut has the scientific name Paralichthys californicus and is found from Washington to Baja California.
The first part of the word "halibut" comes from the middle English word hali or haly, which means holy. The second part of the name is derived from the middle Dutch or German word butte, meaning flatfish. The earliest appearance of the word "halibut" is found in fourteenth century documents. Halibut were once considered to be a special fish and were eaten on holy days.
The Pacific and California halibut belong to the order of fish known as the Pleuronectiformes. The Pacific halibut belongs to the family Pleuronectidae within the order Pleuronectiformes. The California halibut is currently classified in the family Paralichthyidae. Until quite recently, it was classified in the family Bothidae.
Identifying the Fish
Like other flatfish, Pacific and California halibut have a flattened body and swim on their side. Both of their eyes are located on their upper surface. This surface has a mottled olive green, grey, brown, or black pattern, which helps the fish blend in with the sandy or muddy ocean floor. The lower surface is generally white. The white colour helps to camouflage the fish against the bright sky when they are swimming away from the ocean bottom and are viewed from below. Halibut do have scales, but they are small and smooth and are buried in the skin.
The body of a Pacific halibut has a triangular shape due to its pointed dorsal and ventral fins. Most Pacific halibut swim with their right side uppermost, but a very small percentage—reportedly only 1 in 20,000 fish—have their eyes on their left side and swim with their left side uppermost. The fish are known for their large mouths.
A California halibut has an oval body. Unlike the case in the Pacific halibut, the long dorsal and ventral fins of the fish aren't triangular. California halibut have either their right or their left side uppermost. They have the ability to modify the colouration on their upper surface to blend in with the ocean bottom. They also have large mouths that contain many teeth. The teeth are sharp and can potentially give a human a nasty bite.
Diet and Predators
Even though they often spend time hiding in sediment on the ocean bottom, Pacific halibut are strong swimmers. They are carnivores that feed on other fish such as cod, pollock, turbot, rockfish, sculpins, and herring as well as on invertebrates such as shrimp, crabs, and octopuses. Most of their hunting occurs on the ocean floor, but sometimes they move into open ocean to catch their prey.
California halibut are generally found in shallower water than Pacific halibut. Their main food is small fish, especially anchovies and sardines. They also eat squid. Like other halibut, they generally lunge at their prey from their hiding place but may chase the prey through open water if it escapes.
Halibut have several predators, including humans, killer whales, sea lions, and sharks. Pacific and California halibut are popular food fish for people. Their flesh is white in colour and has a flaky texture and a pleasant taste. Some meals of fish and chips use halibut as the fish.
The Pacific halibut spawns in the winter, especially from December to February. The fish migrate from the shallower water of their feeding grounds to deeper water, where they release their eggs and sperm. A female produces from five hundred thousand to over four million eggs, depending on her body size. Many of these eggs are eaten by predators, but some survive. Females don't begin laying eggs until they are between eight and twelve years of age, while males become mature when they are around seven to eight years old.
California halibut mate between February and September and move into shallower water to breed. Fertilization is external. Females start releasing eggs at around four or five years of age while males begin releasing sperm when they are two to three years old.
The fertilized eggs of halibut rise to the surface layer of the ocean and hatch into larvae after about fifteen days. The larvae and young fish are free-floating for about six months and are carried long distances by ocean currents. They feed on animals in the surrounding plankton. Plankton is a collection of tiny and microscopic plants and animals in the ocean. The organisms in the plankton cannot move on their own or are very weak swimmers.
The body of a young halibut gradually flattens and one eye migrates to the other side of the fish. In addition, the mouth twists so that most of it is on the upper side. Pigment appears on the upper side of the fish's body. The animal finally settles on the ocean bottom, lying on its side with its pigmented surface upwards.
The longest known lifespan for a Pacific halibut is fifty-five years. California halibut have lived for as long as thirty years.
Pacific Halibut Migration
Tag and release programs have shown that some Pacific halibut—especially young ones—participate in long distance migrations as well as seasonal migrations. The initial sites where the young halibut settle are referred to as nursery grounds. After living there for two or three years, the youngsters migrate to a permanent home. This journey may take several years. Older halibut may migrate, too. The longest recorded migration of a Pacific halibut took the fish from the Aleutian Islands to Oregon, a journey of 2,500 miles.
Food and Nutrition for Humans
Halibut are an important food resource for humans. They're caught in commercial, subsistence, and recreational fisheries. The fish are rich in protein and are a great source of B vitamins and certain minerals. They are also low in saturated fat and contain omega-3 fatty acids, which are believed to have important health benefits.
Omega-3 fatty acids may improve the health of our cardiovascular system, improve brain function, and reduce inflammation. They may also play a role in reducing the risk of some types of cancer. Although halibut contain these potentially beneficial fatty acids, they also contain a moderate amount of mercury, so their consumption should be limited. Salmon and sardines are a lower-mercury source of omega-3 fatty acids.
A California halibut can be seen at the 5:55 mark in this video about marine life around the Californian Channel Islands. The islands form a chain off the coast of Southern California.
Discovering More About the Pacific and California Halibut
In addition to being a nutritious food, living halibut are interesting creatures. Their development is very unusual. They are potentially long-lived animals and there's still a lot to be learned about their behaviour.
I think it's a great shame that the fish are often appreciated for their food value but not for their natural history. The vast majority of YouTube videos about the two fish describe how to catch them and how to prepare them for a meal instead of showing their life in the ocean.
Hopefully the populations of both the Pacific halibut and the California halibut will continue to be monitored and carefully managed throughout their range. It's important that some of these fish live their full lifespan and help us learn more about the fascinating world of underwater sea life.
- "Pacific Halibut (Hippoglossus stenolepis)" from the Alaska Department of Fish and Game
- "California Marine Sportfish Identification: Flatfishes" from the California Department of Fish and Wildlife
- "California Halibut Identification" from the California Department of Fish and Wildlife
- California halibut facts from the Monterey Bay Aquarium
- Nutrients in Pacific and Atlantic halibut from SELFNutritionData
- Potential benefits of omega-3 fatty acids from Colorado State University Extension
© 2012 Linda Crampton