NICHOLSON: ATLANTIC MENHADEN PURSE-SEINE FISHERY 



1959 to 115,600 tons in 1966. In the North At- 

 lantic area, the Point Judith, Gloucester, and 

 Portland fleets, which began menhaden fishing 

 about 1949, accounted for most of the increases 

 between 1950 and 1960. Menhaden were not 

 landed at Portland after 1957 or at Gloucester 

 and Point Judith after 1962. 



CALCULATION OF FISHING EFFORT 



In any searching fishery where the sizes and 

 types of vessels vary, the unit of fishing effort 

 is diflncult to define. Marr (1950) found a pos- 

 itive linear relation between mean catch per boat 

 week and boat length in the Pacific sardine 

 {Sardlnoi)s sagax) fishery off Oregon. He se- 

 lected the modal boat-length group as a standard, 

 calculated the catch per boat week of boats in 

 this group for each year, and based his estimates 

 of apparent abundance on this index. He was 

 unable, however, to estimate total effort except 



by dividing the total catch of all vessels by the 

 catch per unit of the standard group. 



Silliman and Clark (1945), studying the Pa- 

 cific sardine fishery off California, linked groups 

 of identical vessels and estimated apparent 

 abundance from the catch per boat week of these 

 groups. They estimated the total effort by di- 

 viding the total catch by the catch per boat week 

 of the linked grouji, assuming that the catch per 

 boat week of the selected vessels was represent- 

 ative of the catch per boat week of the fleet, and 

 using a base season for each of the three areas 

 they studied. Recognizing the effect of differ- 

 ences in vessel size on catch per unit of effort, 

 they used a standard multiple regression to esti- 

 mate total effort in each area by relating in a 

 single equation the length and horsepower of each 

 vessel, the number of vessels, and the number of 

 weeks. 



Clark and Daugherty (1950) extended the 

 study by Silliman and Clark through the 1948-49 



Table 4. — Atlantic menhaden purse-seine catch by year and area. 



North 

 Atlantic 



Middle 

 Atlantic 



Chesapeoke 

 Bay 



South 

 Atlantic 



North Corolino 

 fall fishery 



Total 



769 



