Dorsal Mantle Length — Total Weight Relationships of 



Squids Loligo pealei and Illex illecebrosus from 



the Atlantic Coast of the United States 



ANNE M. T. LANGE AND KAREN L. JOHNSON' 

 ABSTRACT 



Leng(h-weight data were collected from the Northwest Atlantic, for two commercially important species of 

 squid, Loligo pealei ani Illex illecebrosus, during nine research vessel cruises between 1975 and 1977. These data, 

 in total and by year, sex, season, and area of capture, were fit to length-weight relationships of the form 

 W = ai*. Analyses of covariance indicate that for each species, differences exist between relationships determined 

 for each area. For L. pealei, differences also exist between sex and among years and seasons. However, com- 

 parisons of sums of total observed weight versus sums of total weight, predicted by equations obtained for all 

 data within a given set, indicate that the net results of using a single equation for each species is about as precise 

 as using separate equations for each sex, area, season, and year. These equations are: H ' = 0.25662/.^*'^^^^ forL. 

 pealei and H= 0.04«10i '■''•''"' for /. illecebrosus. 



INTRODUCTION 



Two species of squid — the long-finned squid, Loligo pealei, 

 and the short-finned squid, Illex illecebrosus — are of commer- 

 cial importance off the northeastern United States. Loligo pealei 

 is distributed primarily from Cape Hatteras to the Gulf of 

 Maine with some seasonal occurrence in the Gulf of Mexico and 

 as far north as New Brunswick (Summers 1969). Commercial 

 concentrations of L. pealei are found primarily from Cape Cod 

 to about Baltimore Canyon. /Ilex illecebrosus ranges from New- 

 foundland to Florida with commercial concentrations from the 

 Middle Atlantic area, near Baltimore Canyon, to New- 

 foundland (Squires 1957). Until the late 1%0's these species 

 were taken commercially off the United States in quantities 

 ranging from 400 to 5,000 t (metric tons) per year (average 1 ,805 

 t for 1930-67). Comparable amounts (< 5,000 t) of /. il- 

 lecebrosus were taken annually off Newfoundland by coastal 

 Canadian fishermen. However, with development of interna- 

 tional fisheries in these areas, catches increased rapidly in the 

 early 1970's, reaching 56,700 t (/,. pealei and /. illecebrosus) in 

 1973 off the United States and 80,600 t (/. illecebrosus) in 1977 

 off Canada. 



The life history and population dynamics of these two squid 

 species, especially /. illecebrosus, are not fully understood. The 

 relationship of growth in length to increase in weight can be 

 used, in conjunction with length-frequency samples from the 

 commercial fishery, to convert catch in weight to catch in 

 number. Population size in number may be more appropriate 

 than biomass in analyzing the status of the squid stocks, since 

 individuals increase weight so rapidly. Mesnil (1977), Summers 

 (1971), and Squires (1967) presented studies of the growth and 

 life cycles of these species but did not provide length-weight rela- 

 tionships. Mercer (1973p provided length-weight functions for 

 male and female /. illecebrosus from Newfoundland waters, but 



'Northeast Fisheries Center Woods Hole Laboratory, National Marine 

 Fisheries Service, NOAA, Woods Hole, MA 02543. 



^acer.M.C. 1973. Length-weight relationship of (he ommastrephid squid, //■ 

 lex illecebrosus {LeSuew). Annu. Meet. Int. Comm. Northwest All. Fish. 1973, Res. 

 Doc. 72, Serial 3024. [Mimeogr.) 



these may not be appropriate for /. illecebrosus off the United 

 States. Similar studies had not been made for L. pealei. 



The objectives of this study were to: 1) calculate dorsal mantle 

 length-total weight relationships for Loligo pealei and Illex il- 

 lecebrosus from the northwest Atlantic off the U.S. coast; 2) 

 analyze differences in length-weight relationships from different 

 areas, seasons, and years, and by sex; and 3) determine the ap- 

 propriate application of these relations to empirical data fro."! 

 the commercial fishery (i.e., is a single relationship appropriate 

 for all areas, seasons, and sexes, or must several functions be 

 used to adequately represent the population?). 



METHODS 



Samples of L. pealei and /. illecebrosus, for length-weight 

 analysis, were collected from the Nova Scotian to Middle Atlan- 

 tic areas (Fig. 1) during research vessel bottom trawl surveys 

 conducted in 1975-77 (Table 1). Standard bottom tows, based 

 on a stratified random sampUng design (Grosslein 1969), were 

 made and subsamples of each species of squid taken from tows 

 in a given strata were frozen whole and returned to the North- 

 east Fisheries Center, Woods Hole Laboratory, Woods Hole, 

 Mass., for analysis. These were generally random subsamples, 

 but in areas or seasons, when few individuals in the upper or 

 lower size ranges were obtained, length stratified random 

 samples were used to ensure representation of the entire size 



Table 1. — Survey cruises in the northwest Atlantic in which Illex illecebrosus and 

 Loligo pealei were obtained for length-weight analysis. 



Year 



Cruise 

 code 



Country 



Season 



Area 



Mid-Atlantic— Nova Scotia 

 Mid-Atlantic— Nova Sootia 

 Mid-Atlantic— Nova Scotia 

 Mid-Atiantic— Nova Scoda 

 Mid-Adantic— Nova Sootia 

 Mid-Adantic — Nova Scoria 

 Mid-Atlantic— Nova Sootia 

 Mid-Adantic— Georges Bank 

 Mid-Adantic— Nova Scotia 



