1977), BMDPIV, to determine the significance of differences 

 between slopes and adjusted means of the various length-weight 

 functions (Winer 1971). 



A total of 5,388 L. pealei and 2,798 /. illecebrosus were ob- 

 tained from nine cruises during the 3-yr study period (1975-77). 

 Of this total, 750 L. pealei and 20 /. illecebrosus were of indeter- 

 minable sex and not considered in this study. There were also 

 3,026 L. pealei and 193 /. illecebrosus which were damaged 

 during the capture or preserving process, preventing accurate 

 measurement of weight; these were also excluded. 



The number of individuals in any sample does not necessarily 

 reflect the size of the survey catches or the relative abundance of 

 either species in any area, season, or year. This is often a func- 

 tion of time available to separate and freeze the samples. 

 Generally, however, both species are more available in autumn 

 than in spring, and while /. illecebrosus may be taken in great 

 quantities during the summer, L. pealei is usually too far inshore 

 to be captured in an offshore survey. Loligo pealei are most 

 abundant in the area south of Cape Cod and are only occa- 

 sionally found north of Georges Bank, while /. illecebrosus are 

 generally more available from southern New England and 

 Georges Bank areas, with significant catches also taken in the 

 Gulf of Maine and Nova Scotian areas. Examples of seasonal 

 distributions from U.S. surveys in 1977 are presented for L. 

 pealei and /. illecebrosus in Figures 3 and 4. 



RESULTS 



Statistical Summary 



Statistical summaries of L. pealei and /. illecebrosus length 

 and weight data are presented in Table 2. Lengths ranged from 

 2.1 to 42.5 cm for L. pealei and from 4.9 to 45.0 cm for /. illec- 

 ebrosus, with an overall average of 17.0 and 22.3 cm. Weights 

 averaged 133 and 243 g, ranging from 4 to 752 g and from 3 to 

 861 g, for L. pealei and /. illecebrosus. Male L. pealei were con- 

 sistently larger (mean lengths and weights) in all areas, seasons, 

 and years, than female L. pealei; while on the average, female /. 

 illecebrosus were larger than the males of that species. Size com- 

 parisons, for each species, between areas and seasons were not 

 made, since not all samples were random with respect to length. 



Regression parameters (a and b), standard errors of estimates, 

 and Pearson correlation coefficients (r) for L. pealei and /. illec- 

 ebrosus length- weight relations are presented in Table 3, by sex 

 and overall, for each year, season, and area. Correlation coeffi- 

 cients indicate that generally between 76% and 96% (r^ x 100) 

 of the variation between dorsal mantle length and total weight 

 of L. pealei may be accounted for by these regression equations. 

 The low value for the regression of females from siunmer 

 samples (64%) may possibly be explained by small sample size 

 (35 individuals) and a narrow range of lengths. For /. 

 illecebrosus, between 41 % and 96% of the variation is explained 

 by the various regressions. The relatively low correlations for /. 

 illecebrosus in some groups (all 1977 data, males in 1977 and in 

 spring, and all data from Georges Bank, the Gulf of Maine, and 

 Nova Scotia) indicate that regression equations may not always 

 be adequate for that species. However, examinations of 

 residuals about the regression lines, plotted against predicted 

 loge weights indicated no systematic departures from the fitted 

 equations which would imply a better model. 



Comparison of the length-weight relationships of male versus 

 female L. pealei, for all samples, shows a difference in weight, 



by sex, through the entire length range. This difference is also 

 evident when considering the relationships in each area sep- 

 arately. Generally, females less than about 13 cm are lighter 

 than males of the same length, while females greater than about 

 17 cm are heavier than the males. Length-weight relationships 

 by year (pooled over season and area) and those by season 

 (pooled over area and year) also showed differences between 

 sexes, again with females <13-17 cm weighing less than males at 

 the same lengths and those greater than that range weighing 

 more. The simimer sample shows only a slight difference be- 

 tween sexes. Comparisons of length-weight relationships by 

 year, season, and area, for each sex separately and combined, 

 indicate that differences in each category are more evident in the 

 male than in the female samples. Individuals of a given length, 

 for both sexes, were lightest in summer than spring, and heaviest 

 in the autumn, though larger females were heavier in the spring 

 than they were later in the year. The most robust males were 

 from the Middle Atlantic and southern New England areas, 

 while females from Georges Bank and southern New England 

 were heavier at any given length than those from the other areas. 

 The regressions for the Gulf of Maine are not given since the 

 weight of only five L. pealei were obtained. 



Differences between the length-weight relationships of male 

 and female /. illecebrosus were not as consistent as those of L. 

 pealei. The overall /. illecebrosus regressions (pooled over year, 

 season, and areas) were almost identical. Though great dif- 

 ferences were exhibited between sexes in the spring and Nova 

 Scotian samples, the relationships from the other areas and 

 seasons were similar for each sex. Comparisons by year, season, 

 and area, overall and for each sex separately, indicate that the 

 greatest difference is exhibited by both males and females, 

 among areas, where the Nova Scotian samples had a nearly 

 linear length-weight relationship (b = 0.827 and 1.170 for males 

 and females and 1.242 overall). 



Analyses of Covariance 



Analysis of covariance was used to test if observed differences 

 in the regression equations of each species were statistically 

 significant (Tables 4, 5). In the analyses, the //g the adjusted 

 means are equal, is based on the prior assumption that the 

 slopes are equal. Significance in the test of equality of slopes in- 

 dicate differences in the populations, and the Hq is not tested. 

 Differences between sexes were examined with tests of slopes 

 and adjusted means, pooling data over all years, areas, and 

 seasons for each sex. Consistencies in these differences were 

 checked by testing differences between sex within each season 

 (data pooled over years and areas), within each area (data 

 pooled over seasons and years), and within each year (data 

 pooled over seasons and areas). Seasonal differences were 

 tested, with pairwise tests of data combined over all areas, sexes, 

 and years, for each season. Area and annual differences were 

 tested with data pooled over years, sexes, and seasons, and over 

 areas, sexes, and seasons. 



Significant differences (P:i0.05) were exhibited in slopes be- 

 tween male and female L. pealei (Table 4a), with the slope of the 

 female equation significantly greater than for the males. This 

 difference was also significant during the spring and autumn, 

 and in each area, and year. In each case, the slope of the female 

 regression was significantly larger than for the males. 



Tests between seasons (Table 4b) showed significant dif- 

 ferences in slopes between spring and summer and between sum- 



