I-ISIIKKY lUU.l.KTIN: VOL, 86, NO. 1 



criteria established by Lux (1964) have been rou- 

 tinely used to monitor relative abundance of 

 three stocks of yellowtail flounder, Limanda fer- 

 ruginea (Storer), in the commercial fishery off the 

 New England coast (Fig. 1 ). Lux calculated CPUE 

 indices for otter trawlers ranging from <26 gross 

 registered tons (GRT) to 100 GRT based on trips 

 in which yellowtail flounder accounted for bQ^/< or 

 more of the total landed weight between 1942 and 

 1961. A fishing power coefficient was then com- 

 puted for each of several GRT categories as the 

 ratio of CPUE to a standard GRT category CPUE 

 for the entire timespan. A separate set of fishing 

 power coefficients was computed for each of the 

 three stocks. Lux's (1964) work improved upon an 

 earlier analysis of yellowtail flounder CPUE by 

 Royce et al. ( 1959) which was based only on rela- 

 tively small vessels ranging in size from 5 to 50 

 GRT that dominated the fishery during the 

 1940's. 



Since 1964, numerous technological innova- 

 tions have drastically changed the character of 

 the New England fishing fleet as traditional side 

 trawlers have gradually given way to larger, 

 more efficient stern trawlers equipped with so- 

 phisticated electronic navigation and hydroa- 

 coustic devices. This gradual alteration in the 

 fleet characteristics over time suggests that pre- 

 viously documented relationships among vessel 



categories may no longer be applicable to the cur- 

 rent fishery, and that use of nominal effort in 

 CPUE calculations will tend to overestimate rela- 

 tive abundance in the more recent years 

 (Westrheim and Foucher 1985). Long-term de- 

 clines in yellowtail flounder abundance on each of 

 the principal fishing grounds (Clark et al. 1984) 

 also indicate that current catchability coefficients 

 may differ from previous values. Accordingly, up- 

 dated fishing power coefficients are required to 

 adequately assess changes in effective fishing ef- 

 fort and CPUE which have occurred during the 

 past two decades. Further, to obtain annual effort 

 and CPUE estimates over such a broad period of 

 years, techniques for computing relative fishing 

 power should incorporate a time element in the 

 analysis. 



In this paper we examine variation in CPUE 

 with respect to fishing area, depth, vessel tonnage 

 class, season, and year for three stocks of yellow- 

 tail flounder on Georges Bank, Southern New 

 England, and Cape Cod grounds between 1964 

 and 1983. Before evaluating differences in rela- 

 tive fishing power among vessel classes, we inves- 

 tigate potential interactions between tonnage 

 class and area and tonnage class and depth 

 within each year, and partition the data to mini- 

 mize tonnage class-area interactions. For each 

 stock, fishing power coefficients are examined for 



68 67 66 



Figure 1.— Yellowtail flounder stocks off the coast of New England (After Lux 1963). 



92 



