YANG ET AL.: CULTURE EXPERIMENTS OF LOLIGO OPALESCENS 



Mean growth was 16 mm/month for this period. 

 Doubling times for weight increased from 12 d at 

 day 60 to 42 d at day 240, and for length from 31 

 d at day 60 to 109 d at day 240. 



The length-weight relationships of squid in L.O. 

 1981 and 1982 are illustrated in Figure 10 and are 

 compared with data on wild squid (Fields 1965). The 

 slopes of the curves are slightly higher in laboratory- 

 reared animals, indicating that these squid are 

 heavier per unit length than wild squid. Table 3 illus- 

 trates differences in predicted weights for repre- 

 sentative mantle lengths from L.O. 1982 data versus 

 Fields' (1965) data. The length-weight relationship 

 for males vs. females in L.O. 1981 is shown in Figure 

 11; no significant differences between sexes were 

 detected (P > 0.05). 



Statoliths from 55 early hatchlings (L.O. 1982) 

 aged 21 to 79 d (± 5 d) were examined to correlate 

 statolith ring numbers with the age of individual 



70 



•3 



LU 



LU 



60 



50 



40 



30 



20 



10 



•••••• L.O. 1981 



W = 0.0002 L 2 - 56 r 2 = 0.96 

 n= 104 



— L.O. 1982 



W = 0.0002 L 2 - 60 r 2 = 0.98 

 n = 81 1 



— Wild Loligo opalescens 

 (Fields, 1965) 

 W= 0.0013 L 2 - 15 



— i — i — i — i — i — i — i — i — i — i — i — i 

 20 40 60 80 100 120 



MANTLE LENGTH (mm) 



Figure 10.— Comparison of length-weight relationship of squid 

 cultured in L.O. 1981 and 1982, and squid collected in the field 

 at Monterey Bay, CA by Fields (1965). 



Table 3.— Examples of length-weight differences between L.O. 

 1982 and the data of Fields (1965). Reference Figure 10. ML = 

 mantle length; WW = wet weight. 



L.O. 1982: 

 Fields 

 (1965) 



ML (mm) 



WW (g) 

 WW(g) 



25 



50 



75 



100 



125 



0.86 

 1.31 



5.22 

 5.80 



15.00 

 13.90 



31.70 

 25.90 



56.60 



41.90 



squid (Fig. 12). The linear relationship between the 

 number of rings (R) and the age in days (D) for 43 

 statoliths aged 21 to 65 d was R = -7.24 + 1.13 

 D, with an r 2 value of 0.90. Counts of rings dif- 

 fered from the actual age by an average of ±4.2 d 

 (range -12 to +8 d). 



Survival 



Figure 13 compares survival in the two experi- 

 ments. The longest lived squid were 248 d in L.O. 

 1981 and 235 d in L.O. 1982. Survival dropped below 

 50% on day 15 in L.O. 1981 and on day 2 in L.O. 

 1982. In L.O. 1982, the early rapid population reduc- 

 tion was due to the removal of newly hatched squid 

 for a different experiment. Mortality rates slowed 

 after the early heavy population reduction; 10% sur- 

 vival occurred on day 120 in L.O. 1981 and on day 

 49 in L.O. 1982. In all cases, mortality gradually 

 slowed after 60- to 70-d posthatching. Survival 

 reduction after day 180 in both experiments was 

 considered to be related to spawning (Figs. 13A, B). 



In L.O. 1981 experiment (Fig. 13A), 50% survival 

 of 391 squid transferred to the large RW system oc- 

 curred at day 114, but at day 84 for the 129 squid 

 left in the same small CT system. For example, 10 

 d after transfer the squid in the CT system had 30% 

 mortality whereas those in the RW system experi- 

 enced only 20% mortality. Thus, transferring squid 

 at about 60 d gave better results by reducing the 

 mortality from fin and skin damage that accrues in 

 the smaller CT system. 



In the middle of L.O. 1981 (day 108) cannibalism 

 was observed. The fins and/or posterior mantle were 

 clearly eaten in some squid; these squid differed 

 from those that died from fin damage or from 

 scraping on the bottom of the tank since the latter 

 developed lesions near the tip of the mantle (Fig. 

 14). From days 108 to 206 there were 16 partly 

 eaten squid in the RW system (7% of the popula- 

 tion on day 108), compared with two squid (of 10 

 total) in the CT system between days 157 and 

 172. Slightly higher levels of cannibalism (19% 

 between days 97 and 191) were observed in L.O. 

 1982. 



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