FEEDING BEHAVIOR, FOOD CONSUMPTION, GROWTH, AND 

 RESPIRATION OF THE SQUID LOLIGO OPALESCENS RAISED 



IN THE LABORATORY 



Ann C. Hurley^ 



ABSTRACT 



The squid Loligo opalescens was raised in the laboratory to a maximum age of 100 days on a diet of 

 Artemia nauplii and adults. Newly hatched squid (2.7 mm mantle length) readily attacked Artemia 

 nauplii (length 0.7 mm), Artemia adults (length 5 mm), copepods (length 1 mm), and larval fish 

 (length 4 mm). Feeding rates varied between 35 and 80% of squid body weight per day. Growth rate 

 was highly variable in different individuals, ranging from 0.5 to nearly 4.5 mm mantle length per 

 month. Respiration rates were obtained at 15°C for squid of three different ages and at 10°, 15°, and 

 20°C for 1-day-old squid. 



The squid Loligo opalescens Berry is a common 

 pelagic predator off the west coast of North 

 America from British Columbia to Baja Califor- 

 nia. Because a fishery exists for this species, con- 

 siderable information is available concerning 

 adults in the spawning schools (Fields 1965), but 

 little is known about the early life stages. In a 

 paper on larval squid abundance off California, 

 Okutani and McGowan (1969) found few L. 

 opalescens in their samples; and McGowan (1954) 

 reported that despite considerable effort he could 

 not catch newly hatched L. opalescens over the 

 spawning grounds. 



To obtain information on the early life history, I 

 reared L. opalescens in the laboratory. Several 

 workers have succeeded in rearing decapod 

 cephalopods, but all of the species they used tend 

 to be closely associated with the bottom (Choe 

 1966, three species of Sepia, the squid Sepioteu- 

 this lessoniana, the sepiolid Euprymna berry i; 

 LaRoe 1971, S. sepioidea; Boletzky et al. 1971, 

 four species ofSepiola and two species of Sepietta; 

 Arnold et al. 1972, the sepiolid E. scolopes). At- 

 tempts to raise pelagic species such as Loligo 

 opalescens have met with little success (Fields 

 1965; Arnold et al. 1974). Workers have attrib- 

 uted their failure to lack of food and to infec- 

 tions. I describe here a simple technique for rear- 

 ing early stages of L. opalescens and present data 

 on the growth, respiration, and food requirements 

 of L. opalescens reared for 100 days in the 

 laboratory. 



'Scripps Institution of Oceanography, University of Califor- 

 nia, La Jolla, CA 92093. 



MATERIALS AND METHODS 



Five groups (referred to as groups 1 through 5) 

 of squid have been reared, three ( 1 through 3) of 

 which will be described in detail in this report. 

 Eggs were collected from a water depth of 20 m off 

 La Jolla, Calif, and were maintained in circulat- 

 ing seawater at about 13°C. The young squid 

 were transferred to the rearing tanks after they 

 had hatched. Fields (1965) and McGowan (1954) 

 have described the methods of egg deposition and 

 structure of the egg masses in detail. 



The rearing tanks were cylindrical (122 cm 

 diameter, 36 cm deep) and made of black fiber 

 glass. Tanks were illuminated by fluorescent 

 lights which had a cycle of 18 h light, 6 h dark. 

 During the dark period, lights in other rooms of 

 the aquarium building provided a source of dim 

 light. The tanks were immersed in water baths 

 which kept the temperature within the tanks be- 

 tween 15° and 17°C. Squid were transferred to the 

 rearing tanks with a beaker. Squid in groups 2 

 and 3 were counted during transfer. In group 1, 

 the number of squid was estimated after the 

 squid were in the tank. Groups 1 and 2 began 

 with 300 squid; group 3 began with 250. The 

 water in the tanks was noncirculating. Each tank 

 was aerated by a gently bubbling air supply. The 

 squid in group 1 were transferred to a holding 

 tank on day 62 and on day 76, and on each day 

 their tank was drained, cleaned, and refilled. 

 Tanks 2 and 3 were both similarly cleaned on day 

 49. Dead food was removed from the bottom of all 

 tanks with a siphon, and small amounts of seawa- 

 ter were added to maintain a constant volume. 



Manuscript accepted September 1975. 

 FISHERY BULLETIN: VOL. 74. NO. 1, 1976. 



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