210 



Fisher/ Bulletin 100(2) 



reported autumn catches (Lange and Waring, 1992) were 

 higher at night than in our study, but still lower than day- 

 time catches. 



The behavior of squid at both prerecruit and recruit 

 sizes therefore appears to be different in the winter and 

 spring than ui the autumn. The prerecruit nighttime catch 

 in winter and spring was half, or more than half of day- 

 time catches, as opposed to 9% in autumn. For recruits, 

 there was an even gi-eater difference among seasons. In 

 winter, almost 1.5 times as many squid were caught at 

 night, than by day. In spring the nighttime catch was T2''k 

 of the daytime catch, twice the proportion of the autumn 

 catch. Vovk (1978; 1985) and Maurer and Bowman ( 1985) 

 have documented large changes in the diet of squid in dif- 

 ferent seasons, relating these changes in feeding activity 

 and dietary preference to changes in the size composition 

 of the squid population, movements of squid in search of 

 food concentrations, seasonal abundance of prey, and envi- 

 ronmental conditions that affect both prey and predator 

 Vovk (1985) noted that in autumn L. pealeii are daytime 

 predators and do not feed extensively at night when they 

 occur at shallow depths. In autumn, squid are more abun- 

 dant near the seafloor by day (Brodziak and Hendrickson, 

 1999). Vovk (1985) also noted that feeding activity was 

 generally low from December to April and related this to 

 possible prey abundance. Perhaps the different diel behav- 

 ior patterns of L. pealeii in winter and spring, when they 

 appear to be more available to capture by bottom-trawls, 

 are related to a lower prey abundance and a requirement 

 for more time to be spent searching for prey. Some of these 

 differences might be temperature related as well. In the 

 autumn, with strong vertical stratification of the water 

 column, there may be some physiological benefit for squid 

 to move off the bottom at night into warmer waters. In 

 winter and spring when there is no vertical stratification, 

 no advantage is conferred by a strong diel migration as 

 seen in the autumn. 



Comparisons in performance and catchability of the two 

 trawl nets used in the spring and autumn sui-\'eys (Yankee 

 36 and Yankee 41) have been conducted (Sissenwine and 

 Bowman, 1978), but any differences in catchability were 

 confounded by diel and vessel differences. In our study, we 

 corrected for diel differences, and vessel differences were 

 not found to be significant (NEFSC/'*). 



Squid catches are more abundant in the autumn sur- 

 veys than in winter and spring (Serchuk and Rathjen. 

 1974; Lange and Waring, 1992; Lange and Sissenwine-). 

 This difference may be related to the recruitment of large 

 numbers of small squid, present m shallow water, in au- 

 tumn. Temperature, however, is a major factor limiting 

 distribution. In winter and spring much of the continental 

 shelf water is below the preferred temperature minimum 

 for the species (ca. 8°C) (Summers, 1969; Serchuk and 

 Rathjen, 1974; Murawski, 1993); therefore squid are ap- 

 parently less abundant than in the autumn surveys when 



*• NEFSC (Northeast Fisheries Science Center). 1996. Report 

 of the '21st Northeast Regional Stock Assessment Workshop 

 (SAW 21). Center Reference Document 90-05, 200 p. jAvail- 

 able from NEFSC, 166 Water St., Woods Hole, MA 02543.1 



temperature is not a limiting factor The greatest differ- 

 ences between autumn and spring or winter sui-veys are 

 most apparent in the NE, whei-e a large portion of the 

 stock may be outside the sui-veyed area owing to tem- 

 perature limits (e.g. off the shelf or south of Cape Hat- 

 teras). In the MAB there are few differences in catches be- 

 tween spring and autumn at depths deeper than 27-55 m. 

 Spring numbers are higher than autumn numbers from 

 111 to 185 m. The patterns between autumn and winter 

 catches are similar to each other at that depth. Catches 

 are always lower in winter than in autumn, but the differ- 

 ences arc only significant from 27-110 m depth. 



In winter and spring sui-veys, catches were highest from 

 1 1 1 to 185 m, both in the NE and the MAB. Catches were 

 higher, in both surveys, in the MAB than in the NE. These 

 patterns also were obsei-ved for L. pealeii in survey anal- 

 yses from 1967 to 1971 (Summers, 1969; Serchuk and 

 Rathjen, 1974), from 1970 to 1977 (Lange, 1980), and from 

 1975 to 1986 (Lange and Waring, 1992). This finding may 

 imply that geographic distribution is relatively stable for 

 L. pealeii. during February and March, at least within the 

 areas sui-veyed. In autumn sui-veys. Serchuk and Rathjen 

 (1974). Lange (1980). and Lange and Waring (1992) also 

 reported highest catches in the MAB. However, Serchuk 

 and Rathjen ( 1974) showed a relatively higher abundance 

 of squid taken from 56-110 m depth than that obsei-ved in 

 our study, where mean numbers per tow in the depth zone 

 27-55 m were greater than three times higher than those 

 in the zones 56-110 m and 111-185 m. The difference be- 

 tween the 27-55 m zone and deeper strata was less notice- 

 able in the NE, although mean numbers-per-tow were al- 

 most twice as high in the 27-55 m zone. The differences 

 may result from diurnal adjustments, or from the inclusion 

 of more years of data in the sui-vey database. Lange ( 1980) 

 found mean numbers-per-tow in the NE autumn to be high- 

 est from 111 to 185 m depths. 



Biological analysis 



We found that squid mature at greater lengths than pre- 

 viously reported for L. pealeii (NEFSC"*). Figure 3 (C-F) 

 shows that using stage 3 or greater to indicate maturity 

 may be an adequate proxy for females. For example, the 

 size at which 50*^^ of females are mature is 198 mm with 

 stages 3 and 4, and 207 mm with only stage 4 (Fig. 3C). 

 Such a proxy may be valuable for samples with few obser- 

 vations of stage-4 females (e.g. the body mass at 50% 

 maturity is 120 g with stages 3 and 4 [Fig. 3D1 ). 



For males, however, the size difference between stage 

 3 and stage 4 is considerable, and substantial somatic 

 growth is required to develop from stage 3 to stage 4. Com- 

 bining the two maturity stages in males is therefore un- 

 supported biologically, and the combined data would un- 

 derestimate size at 50'^r maturity. 



That mature squid are largest in winter and smallest 

 in autumn samples (and intermediate in size in the early 

 INEFSCl and late |LIS| spring) has been noted previous- 

 ly (Summers, 1971; Lange, 1980; Macy, 1980). Prior to 

 the availability of age data for the species, the size dif- 

 ferences at maturitv were ascribed to different year class- 



