GROWTH, BEHAVIOR, AND SEXUAL MATURATION OF 



THE MARKET SQUID, LOLIGO OPALESCENS, 



CULTURED THROUGH THE LIFE CYCLE 



W. T. Yang, R. F. Hixon, P. E. Turk, M. E. Krejci, 

 W. H. Hulet, and R. T. Hanlon 1 



ABSTRACT 



Loligo opalescens, a commercially important species of the eastern Pacific, is the first pelagic cephalopod 

 to be cultured through the entire life cycle. Squid were cultured twice to viable second generation progeny 

 in closed seawater systems using artificial and natural seawater. The reasons for success compared with 

 previous attempts were 1) increased depth in the culture tank, 2) improvements in water conditioning 

 methods, and 3) an increase in availability, density, and species diversity of food organisms. The diet 

 consisted of live zooplankton (predominantly copepods), mysid and palaemonid shrimp, and estuarine 

 fishes. Mean daily group feeding rates of subadults and adults were 14.9% and 18.0% of body weight. 

 Growth was fast, increasing exponentially the first 2 months of the life cycle (8.35% increase in body 

 weight per day) then slowing to a logarithmic rate thereafter (5.6-1.6% increase per day). Growth rings 

 in statoliths corresponded to one per day for the first 65 days. Maximum life span was 235 and 248 days 

 in the two experiments, with a maximum size of 116 mm dorsal mantle length. Viable eggs were pro- 

 duced within 172 and 196 days, respectively. Eggs developed in 30 days at 15°C. Survival through the 

 life cycle was low, with the highest mortality occurring in the first few weeks when squid made the transi- 

 tion from feeding on yolk to active predation on fast-moving plankton. Fin or skin damage and senescence 

 after reproduction accounted for late mortality. The laboratory life cycle of less than a year is compati- 

 ble with existing field data that propose either a 1- or 2-year life cycle, depending upon the season of 

 hatching. 



Since 1975 we have been studying loliginid squid to 

 develop methods of providing a consistent supply 

 for neuroscience research. These studies include 

 aspects of fishery biology (Rathjen et al. 1979; Hix- 

 on 1980a, b, 1983; Hixon et al. 1980), capture and 

 maintenance methods (Hanlon et al. 1978, 1983; 

 Hulet et al. 1979; Hanlon and Hixon 1983), behavior 

 (Hanlon 1978, 1982), and mass-culture methods 

 (Hanlon et al. 1979; Yang et al. 1980a, b, 1983a, b). 

 Much of the baseline information acquired through 

 these controlled culture experiments will also be im- 

 portant to the fisheries biology of commercially ex- 

 ploited loliginid squids (cf., Roper et al. 1983). 



About 20 major attempts have been made to 

 culture loliginid squids through the life cycle, but 

 none have been successful (see review in Yang et 

 al. 1980b), even though wild-caught mature females 

 of Loligo and Doryteuthis spawn readily in captiv- 

 ity (Hamabe 1960; Fields 1965; Takeuchi 1969, 1976; 

 Hurley 1977; Arnold et al. 1974; Hanlon et al. 1983). 

 Fields (1965) attempted unsuccessfully to culture 

 Loligo opalescens as early as 1947. Hurley (1976) 



'The Marine Biomedical Institute, The University of Texas 

 Medical Branch, 200 University Boulevard, Galveston, TX 77550- 

 2772. 



reared L. opalescens for 100 d to a mantle length 

 (ML) of 13 mm. Hanlon et al. (1979) reared this 

 species to 17 mm ML in 79 d and, based upon that 

 work, reared L. opalescens from hatching to sub- 

 adults (Yang et al. 1980b, 1983a). We have now im- 

 proved previous culture methods by increasing the 

 rearing population density and by improving the 

 space requirements for young and adult squid. With 

 a more consistent supply of foods and improvement 

 of water management, we have now successfully 

 cultured this squid twice from egg to second genera- 

 tion, thus closing the life cycle. 



MATERIALS AND METHODS 



Two culture experiments are reported herein: 

 L.0. 1981 (full life cycle partly published in Japanese 

 by Yang et al., 1983b); and L.O. 1982 (full life cy- 

 cle). A third experiment, L.O. 1980, was published 

 by Yang et al. (1980b, 1983a) and is referenced for 

 comparison in the Discussion and figures. 



For L.O. 1981, freshly laid eggs were obtained 

 from wild-caught squid kept in holding tanks at Sea 

 Life Supply (Sand City, CA 93955). Eggs were col- 

 lected from spawning grounds in Monterey Bay, CA 

 for experiment L.O. 1982. Eggs were air-shipped 



Manuscript accepted February 1986. 

 FISHERY BULLETIN: VOL. 84, NO. 4, 1986. 



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