Halibut are right-handed or dextral, with both eyes on the dark or right side. 

 Probably one halibut in about 25,000 is left-handed or sinistral. The mouth is large, 

 about one-third the head length, with jaws equally developed and carrying strong 

 incurved teeth. The pigmentation on the dark side is variable and tends to assume 

 the color pattern of the ocean's bottom. This protective coloration enables the fish to 

 avoid detection by both predators and intended prey. 



Occurrence 



Halibut is a demersal species generally found on the continental shelf in North 

 Temperate waters. Its distribution both in the Pacific and the Atlantic tends to be 

 within bottom water temperatures ranging from 37° to 46° Fahrenheit (3° to 8° 

 Centigrade), which encompass what is scientifically referred to as the boreal zone. 



Commercial setline catches in the Northeastern Pacific have been made as deep 

 as 600 fathoms, i.e. 3600 feet or about 1100 meters, but most halibut in the Pacific 

 are found in waters from 15 to 150 fathoms (Figure 2). 



Pacific halibut have been recorded along 3,500 miles of the North American 

 coast from Santa Rosa Island off Santa Barbara, California to as far north as Norton 

 Sound, near Nome. The species also exists across the continental shelf in Bering 

 Sea, some 700 miles, and throughout an additional 2,000 miles along the Asiatic 

 Coast, from the Gulf of Anadyr in the north to as far south as the Island of 

 Hokkaido, Japan. 



Reproduction and Development 



Spawning takes place over a fairly protracted period of the year. From November 

 to March mature males and females are found concentrated at places along the edge 

 of the continental shelf at depths from 125 to 250 fathoms, that is, in water 750 

 to 1,500 feet deep. 



While some females may mature as young as about 8 years of age, others may 

 be immature until as late as 16 years of age, with the average age of first maturity 

 for females considered to be 12 vears. Males, on the other hand, mature much 

 vounger and the average age of first maturity of males is about 7 to 8 years of age. 



Spawning probablv occurs annually and a large female mav produce from 2 to 

 3 million eggs yearly. The number of eggs is proportionate to the weight of the fish. 



The eggs, which are about Vs inch in diameter, are spawned in deep waters 

 at the edge of the continental shelf, and fertilization takes place at that time (Figure 

 3). The germinal disc of the egg goes through the normal processes of cell division to 

 form the embryo, which lives off the yolk that makes up the main mass of the egg 

 (Figure 4). 



Figure 3. Early stage of halibut ovum showing 

 germinal disc. Size: 3.3 mm. (1/8 inch). 



Figure 4. Developing halibut embryo. 

 Size: 2.5 mm. (1/10 inch). 



