factory was established for oil production. It is 

 worth noting here that during the time of World 

 War I (1916-18) almost the entire catch of dog- 

 fish from British Columbia was exported as 

 "grayfish" to the U.S. fresh fish market. 

 Extraction of Vitamin A 



No doubt the greatest industrial use of the dog- 

 fish took place about 1937-47 when the species was 

 fished intensively in Puget Sound and surround- 

 ing waters. Their rich, oily livers were in demand 

 as a valuable source of natural vitamin A. The 

 livers contain 50-75 percent oil, and the vitamin 

 A content of the oil is 5,000 to 30,000 U.S. Phar- 

 macopeia (U.S. P.) units per gram (Harrison and 

 Samson, 1942). 



The first extraction of vitamin A from shark 

 liver oil was begun on a commercial scale about 

 1936-37, and the dogfish fishery was underway in 

 Puget Sound in 1937-38 (Harrison and Samson, 

 1942). The fishery was on a small scale until 

 about 1940, then, with the entry of the United 

 States in World War II and the loss of foreign 

 sources of vitamin A from cod liver oil, the fishery 

 increased in intensity. In 1940 the average price 

 paid to the fishermen for the livers was 5.7 cents 

 per pound, but by 1943 the average price was 46 

 cents per pound and at one point reached a high 

 of 54 cents (Bonham et al., 1949). The intensity 

 of the fishery undoubtedly had a marked effect on 

 the size of the dogfish population. Barraclough 

 (1953) reports a decline in availability of the 

 species in Hecate Strait beginning in 1944. 



Dogfish liver oil has high vitamin A potency. 

 Bonham et al. (1949) note that oil rendered com- 

 mercially from livers of dogfish taken in the 

 waters in and around Washington varies from 

 5,000 to 25,000 U.S.P. units of vitamin A per 

 gram. The vitamin values increase several hun- 

 dred percent when the fish attain sexual maturity, 

 and the content is greater in winter than in other 

 seasons. In contrast, Templeman's (1944) lab- 

 oratory extractions of vitamin A from Canadian 

 dogfish liver oil ranged from 300 to 19,700 U.S.P. 

 units per gram with an average value for imma- 

 ture females of 1,183 units, for mature males of 

 1,662 units, and for mature females of 2,780 units. 

 (For purposes of comparison, pharmaceutical cod 

 liver oil must contain not less than 850 U.S.P. 

 units of vitamin A per gram (Bailey, 1952).) 

 Hirao, Yamada, and Kikuchi (1959) report vita- 



min A values of spiny dogfish flesh from 329 to 

 5,220 U.S.P. units per 100 grams of flesh. Liver 

 oil from the same fish contained from 2,080 to 

 38,800 U.S.P. units of vitamin A per gram. 



Following the end of World War II, two major 

 events occurred that had a devastating effect on 

 the west coast fishery for dogfish. First, foreign 

 sources of vitamin-rich fish oils again became 

 available, and second, vitamin A was synthesized 

 in 1947. Soon after this the dogfish fishery col- 

 lapsed except for relatively small volumes landed 

 for reduction and an extremely limited food 

 market. 



During World War II the Canadian govern- 

 ment became interested in the east coast dogfish 

 liver oils and their vitamin content, but the prices 

 paid to the fishermen were too low to develop a 

 fishery (Tern pieman, 1944). 



Oils obtained from dogfish are of value today 

 chiefly as raw materials for other industrial proc- 

 esses. The liver oil is sulfurized and used as a 

 rubber extender, and the body oils are used in the 

 tanning of leather (Bailey, 1952). 

 New England Industrial Fishery 



The late 1940's saw the beginning of a new kind 

 of fishery in New England — the so-called trash 

 or industrial fishery — in which nonfood species, 

 including spiny dogfish, were landed in great 

 quantities for reduction to meal and oil. Sayles 

 (1951) marks 1948 as the start of the trash fishery 

 at southern New England ports with the processed 

 meal destined for use as supplements in hog and 

 poultry feeds. 



The amount of dogfish used was small at the 

 start of the industry. For example, the species 

 composition of a sample from one boat that 

 landed at New Bedford in October 1949 included 

 only 1 dogfish in the sample of 536 fishes (Snow, 

 1950), but by 1956, 259,000 pounds of spiny dog- 

 fish were landed by the industrial fleet at New 

 Bedford (Edwards and Lux, 1958). The dogfish 

 represented 1 percent of the total industrial land- 

 ings and were caught off No Mans Land, mostly 

 in November and December. 



In 1957 the Southern New England industrial 

 landings of spiny dogfish were slightly more than 

 5 million pounds (3 percent of the total), with 

 most of them landed at Point Judith, R.I. 

 (Edwards, 1958a). There were two peaks in the 

 landings of dogfish, one in the spring and one in 



LIFE HISTORY OF SPINY DOGFISH 



547 



