Hatfield and Cadrin Geographic and temporal patterns in size and maturity of Loligo pealeii 



211 



es (Summers, 1971; Lange, 1980; Macy 1980). The obser- 

 vation that immature squid are larger in autumn than 

 in winter and spring was documented by Lange (1980) 

 but not interpreted. Some of this variabiHty might be ex- 

 plained as a function of temperature. If L. pealeii have 

 a life-span of 9-12 months (Brodziak and Macy, 1996), 

 then females that are mature in September-October sam- 

 ples would have hatched between November and January. 

 Females that are mature in March would have hatched 

 around May or June. Brodziak and Macy (1996) showed 

 that squid hatched between November and April had a 

 lower growth rate than those that hatched between May 

 and October. Recent laboratory studies on small L. pealeii 

 have indicated that squid grow significantly faster at high- 

 er temperatures (Hatfield et al., 2001), in accord with 

 results described for other cephalopod species (Octopus 

 bimaculoideg — Forsythe and Hanlon. 1988; L. forbesi — 

 Forsythe and Hanlon. 1989; Sepia officinalis — Forsythe et 

 al., 1994). These laboratory studies also found that the 

 effect of temperature on growth is most pronounced dur- 

 ing the early life cycle of these cephalopods, nominally 

 the first three months. If temperatures experienced by L. 

 pealeii hatching in May and June are warmer than tem- 

 peratures experienced by squid hatching from November 

 to January, then the gi'owth potential will be lower for 

 winter-hatching squid (seen as mature squid in autumn 

 sui^veysi, resulting in the obser\'ed lower size at maturity 

 in autumn versus winter and spring. The same phenom- 

 enon would explain the size differences of immature squid 

 among seasons. The large immature squid caught in the 

 autumn survey are probably the same squid that become 

 the large, mature squid in the winter, spring, and LIS sam- 

 ples. The small immature squid in the spring are probably 

 those squid which become the small mature squid seen 

 in autumn survey samples. If the winter-hatching squid 

 are from southern spawning events, then the temperature 

 difference between winter-spawned and summer-spawned 

 squid may not be very large. However, age data for L. 

 pealeii show that growth rates are generally slower for 

 winter hatched squid. Also, growth studies on L. forbesi 

 have shown that a temperature difference of just 1"C can 

 change growth rates of squid by 2% body weight/day and 

 produce a threefold difference in weight at 90 days after 

 hatching (Forsythe and Hanlon, 1989). 



The high numbers of juvenile squid in the autumn sur- 

 vey were from protracted spawning in inshore waters 

 some 4-5 months previously (documented since Verrill 

 [1882] first reported inshore spawning). The high propor- 

 tion in spring therefore reflects a period of spawning, pos- 

 sibly also some 4-5 months earlier, around September or 

 October of the previous year. Juvenile squid in winter and 

 spring survey samples denote the presence of a hatching 

 component other than the main inshore autumn compo- 

 nent. The high proportion obser\'ed in LIS (May) samples 

 probably reflects an extended winter-spring spawning pe- 

 riod because squid of the size found in Long Island Sound 

 in May could not have been the result of that seasons in- 

 shore spawning. The inshore spawning season does not 

 usually begin until late April and incubation time may 

 require up to 4 weeks at the temperatures at that time 



of year (27 days at 12°C, McMahon and Summers, 1971). 

 Brodziak and Macy ( 1996) showed a pattern of year-round 

 hatching, which is consistent with the patterns suggested 

 by our data. 



Summers (1969), Serchuk and Rathjen ( 1974), and Brod- 

 ziak and Hendrickson (1999) all reported an increase in 

 size of L. pealeii with increasing depth. We found the 

 smallest squid in the shallowest water and the largest 

 squid in the deepest water, confirming that nearshore wa- 

 ters of the continental shelf are a preferred habitat for ju- 

 venile L. pealeii during the autumn (as described by Brod- 

 ziak and Hendrickson [1999]). The pattern of ontogenetic 

 descent exhibited by other loliginid species (L. vulgaris — 

 Worms, 1983; L. gahi—Hatfiek\ et al., 1990; L. vulgaris 

 reynaudii — Augustyn et al., 1992) is consistent in L. pea- 

 leii, but less marked at intermediate depths. 



In winter and spring, mean length is generally higher in 

 the NE and lower in the MAB. In autumn, mean length is 

 generally lower in the NE and higher in the MAB. Lange 

 (1980) showed a similar pattern for immature females 

 from the autumn survey. Males, however, showed the op- 

 posite pattern. Langes (1980) winter and spring survey 

 data showed the same pattern as our study for immature 

 females and all males, except the fully mature squid. 



Commercial samples from early winter (December and 

 January) contained no mature female squid that might 

 produce the winter hatching component evident from age 

 data and aggi-egated sui-vey length-frequency distribu- 

 tions. Egg masses are only found consistently in one small 

 offshore area (off Chesapeake Bay) by commercial fisher- 

 men in the early winter (see Fig. 4). However, the com- 

 mercial samples were from the southern edge of Georges 

 Bank, and the survey data suggest that the winter recruit- 

 ment originates from the southern part of the MAB. The 

 scarcity of mature squid in NEFSC sui-vey samples sug- 

 gests that sampling did not occur consistently in the right 

 areas or seasons to identify major spawning peaks. Whita- 

 ker 1 1978) documented that about 40% of males were fully 

 mature in January and February in the region south of 

 Cape Hatteras, off the coast of South Carolina. There was 

 a large proportion of mature squid in samples from March 

 and April, with 74% of females and 56% of males fully ma- 

 ture. There is evidence for both spawning and hatching 

 in the SNE from March to April; as in 1999, egg masses 

 were caught incidentally from northeast of Hudson Can- 

 yon and up towards the southern flank of Georges Bank, 

 at depths of about 200 m, from mid-March to late April 

 (StommelP). In the 1998 Massachusetts spring survey, in 

 mid-May, a high abundance of small squid, about 30 mm 

 ML, were caught south of Marthas Vineyard, at depths of 

 <27 m (senior author, personal obs.). These observations 

 suggest that spawning is probably protracted, from early 

 to late winter, and early winter spawning is more dom- 

 inant in the southern end of the U.S. continental shelf 

 Thus, the available fishery-dependent samples may not be 

 indicative of the population. The information on age and 

 maturity in Brodziak and Macy (1996) was derived from 



^ Stommell, M. 1999. Personal, comniun. ¥W Nobska, Woods 

 Hole, MA 02543. 



