lifestyle at this size is confirmed further by changes 

 in chromatophore patterns from a ventro-dorsal to 

 a dorso-ventral patterning gradient (McConathy et 

 al. 1980; Vecchione 1981). Estimates based upon 

 field data (Summers 1968, 1983; Vecchione 1981; 

 Table 2) put the age of transition at <1 mo. 



Table 2.— Growth rate comparisons for young Loligo pealei. 



Growth of laboratory-reared Loligo pealei (Fig. 1) 

 was slower than that of either L. vulgaris (Turk et 

 al. 1986) or L. opalescens (Yang et al. 1986) reared 

 in similar tanks at slightly colder temperatures. 

 Growth of L. pealei in our previous culture experi- 

 ment (Yang et al. 1980) was 3.1 mm ML at 40 d, 

 and this datum fits with Figure 1 and the growth 

 curve. Daily growth rate estimates (derived from 

 the instantaneous growth rates) were 2.28%/day for 

 L. vulgaris, 2.55%/day for L. opalescens, and 2.09%/ 

 day for L. pealei. Table 2 compares the published 

 estimates of growth rate in L. pealei. It is clear that 

 estimates from field samples are far higher than our 

 laboratory results of 4-6 mm/month with L. pealei 

 (temperatures are generally comparable). The fast- 

 est growth rates we have measured in laboratory- 

 reared squid during the first three months have been 

 19 mm/month in L. vulgaris and 18 mm/month in 

 L. opalescens (mean rates are closer to 7 and 6 

 mm/month, respectively). Extrapolating these data 

 in either direction (field vs. laboratory) is difficult 

 because growth rates must be calculated over short 

 periods (i.e., <1 mo) and under similar circiimstances 

 to be compared directly. Our laboratory results with 

 L. pealei are probably low estimates compared with 

 its growth rate in nature; they are low compared 

 even with L. vulgaris and L. opalescens grown in 

 our laboratory. However, since growth is clearly ex- 

 ponential in form in these three squid species as well 

 as other cephalopods (Forsythe and Van Heukelem 

 in press), the numerical value of growth rate in milli- 



meters per month will increase disproportionally 

 fast as the animal gets larger; thus the L. pealei data 

 extrapolated to 60 or 90 mm ML would compare 

 more favorably with most other growth estimates 

 in Table 2. The growth rate estimates of Vecchione 

 (1981), Harrigan (1985), and the first estimate by 

 Verrill (1881), all based upon size-frequency data, 

 seem to be excessive in view of laboratory and field 

 growth data on cephalopods (Forsythe and Van 

 Heukelem in press). Based upon our rearing ex- 

 perience with Loligo spp., we estimate that L. pealei 

 in nature could grow as fast as 20 mm/month dur- 

 ing the first few months if conditions were optimal. 



Acknowledgments 



This research was supported by NIH grant num- 

 ber DHHS RR01024. We thank John W. Forsythe 

 for reviewing the manuscript. 



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