in the RW system, adult mysids; palaemonid shrimp, 

 Palaemonetes pugio; and a variety of marine or 

 estuarine fishes were fed to the squid at least twice 

 daily. 



Zooplankton were washed carefully in clean sea- 

 water. Mysids and palaemonid shrimp were treated 

 overnight with quinacrine, while erythromycin 

 and/or tetracycline were used to treat fish (Yang 

 et al. 1980b, 1983a, b). Before feeding, all foods 

 were counted or weighed and slowly acclimated 

 to the temperature and salinity of the cultured 

 water. 



Dead squid and dead food organisms from 

 previous feedings were removed by siphoning once 

 or twice daily from the CT or RW systems. Daily 

 food consumption in the RW was derived by sub- 

 tracting the weight of uneaten food remains siph- 

 oned each day from the weight of food organisms 

 added daily to each culture system. Daily feeding 

 rate (wet weight) is expressed as the percentage of 

 food consumed by the total estimated biomass of the 

 squid. Daily biomass of squid was estimated by 

 multiplying the number of live squid on a given day 

 by the average weight of an individual squid on that 

 day. Daily squid weight estimates were projected 

 from linear regression of the weights of freshly dead 

 squid against time. All measurements and wet 

 weights (WW) were usually made with freshly dead 

 squid although live squid were occasionally used. 

 Badly damaged or partially cannibalized squid were 

 not measured or weighed for this analysis. The ini- 

 tial squid population was derived from the number 

 of dead or sacrificed specimens removed from the 

 culture systems. 



Overhead fluorescent lights provided illumination. 

 In the CT systems for both experiments there was 

 constant light that measured 11 to 15 lux in the mid- 

 dle of the water column. In the RW systems there 

 was also constant light although light only filtered 

 in through plastic-covered holes in the polystyrene 

 tops. In L.O. 1981 it measured 17 lux in the center 

 of the RW and 0.5 to 0.7 lux at each end. In L.O. 

 1982 it measured 4 to 7 lux near the ends under the 

 opaque top and 11 lux near the center where light 

 passed through the clear plastic. 



Statoliths from hatchlings of known age in L.O. 

 1982 were dissected from the squid and decalcified 

 in a 1:1 mixture of 4% EDTA in distilled water and 

 0.2 H sodium cacodylate buffer (pH 7.4). Decalcifica- 

 tion facilitated the counting of rings in statoliths 

 from squid age 65 d or younger, but older statoliths 

 were distorted by the process. The rings were 

 counted from photographs taken with a Leitz Com- 

 biphot II and Kodak copy film #4125. 



FISHERY BULLETIN: VOL. 84, NO. 4 



RESULTS 



Water Quality 



There were no obvious differences in growth or 

 survival between squid cultured in artificial sea- 

 water (L.O. 1981) and filtered natural seawater 

 (L.O. 1982). Water quality in the CT systems was 

 maintained in very good condition due to the short 

 culture period, while water quality in the RW system 

 was more difficult to maintain because of the long 

 grow-out period and the greater biomass of squid 

 and food organisms. In L.O. 1981 (Fig. 2) from days 

 180 to 190 the estimated total biomass reached the 

 maximum peak of 1,706 g (cf., Fig. 7), which is 

 equivalent to 155 g/m 3 of rearing water volume. 

 After the 160th day, food organism biomass in- 

 creased to between 300 and 400 g/day. As a result, 

 the amount of nitrate-nitrogen gradually accu- 

 mulated to over 23.0 mg/L during the period from 

 day 180 to day 193 (Fig. 2). On day 164, 1,900 L 

 (17% of total volume) of fresh Instant Ocean was 

 replaced in this system. However, the nitrate- 

 nitrogen level did not drop in proportion to the per- 

 cent water change. Concurrently, pH dropped to 

 7.75 by day 169 and dissolved sodium bicarbonate 

 (Atz 1964; Bower et al. 1981) was introduced to the 

 system to adjust the pH above 7.9. The sodium bicar- 

 bonate solution required very strong aeration to be 

 effective when it was put into the culture water. A 

 similar trend of slightly increased nitrate-nitrogen 

 and decreased pH occurred (about day 200) in L.O. 

 1982 (Fig. 2). This was corrected in the same 

 manner. 



The vegetative macroalgae, Gracilaria tikvahiae, 

 was cultured in the water conditioning tank of the 

 RW system in L.O. 1982 to remove ammonia and 

 prevent the accumulation of nitrate-nitrogen, but 

 its effectiveness was not clear. 



Incubation and Hatching of Eggs 



Average hatchling size in both experiments was 

 2.7 mm ML (range 2.3-2.8 mm ML) with a hatching 

 success of over 90%. In L.O. 1981, hatching began 

 on 14 October and lasted until 17 October. Embry- 

 onic development required 27 to 30 d at 15 °C. The 

 hatching period lasted 4 d, compared with L.O. 1982 

 that took 5 to 6 d. The period of embryonic develop- 

 ment in L.O. 1982 was not precisely known because 

 the eggs were collected in nature. Development of 

 eggs within the same egg cluster was different de- 

 pending upon the capsule position within the cluster. 

 Moreover, hatching time within the same capsule 



774 



