1. Student Resource: All About Halibut Distribute a copy of the Student Resource: All About Halibut to each student and show the Halibut Slide Show. More advanced students can also use the Internet Resources. Discuss the life history of the halibut.
What changes does this fish experience as it matures?
Answer: Halibut begin as eggs. The eggs change to larva and finally, at six months, to fully formed fish. When the larva are about an inch long, the left eye migrates over the snout to the right side of the head, and the color of the left side fades. At this point they have become fully-formed fish.
- Does it stay in the same place as it grows and changes? Explain.
Answer: Free-floating eggs and larvae float for up to 6 months and are transported up to several hundred miles by deep currents of the North Pacific. As the larvae grow they become lighter, rise nearer to the surface and migrate to the shallower waters, floating on the surface currents. Most young halibut ultimately spend from 5-7 years in rich, shallow nursery grounds. Generally, young halibut are found close to shore, and older, larger individuals in deeper water near the edge of the continental shelf. However, in the summer months, larger halibut move towards shallower water. Halibut up to 10 years of age migrate often in a clockwise direction east and south throughout the Gulf of Alaska. Older halibut don't migrate as much. These older fish often use both shallow and deep waters over the annual cycle.
- How does each stage move? Water currents? Muscle movement? Explain.
Answer: In the egg and larval stages up to about 6 months the Halibut is moved by currents both across and up and down the water column. Older halibut use their muscles to move.
- What does it need to survive at the different stages of its development?
Answer: Larva feed mostly on plankton. Mature halibut are able to eat a large variety of fishes. In fact, halibut will feed on almost any animal they can fit in their mouths including: sand lance, octopus, crab, salmon, hermit crabs, lamprey, sculpin, cod, pollock and flounder. Halibut need a sandy bottom in which they can hide and wait for prey.