FISHERY BULLETIN: VOL. 74, NO. 1 



Figure 3. — Size data ior Loligo opalescens. A dot denotes mea- 

 surement made on squid which had died, and x denotes mea- 

 surement made on squid that had been selected while alive to 

 give an indication of the size range of individuals in the tanks. 

 For days 1, 17, and 22, the numbers of squid measured, means, 

 and ranges are given. The upper solid line gives a constant 

 growth rate of 4.5 mm/mo. The lower one gives a rate of 0.5 

 mm/mo. 



to give an indication of the full size range of squid 

 in the tank. Since the squid were not randomly 

 sampled during this time, Figure 3 cannot be 

 taken to give an average growth rate for the 

 population, but it does give an indication of the 

 range of growth rates. There was a large differ- 

 ence in the rates of growth of individuals. Maxi- 

 mum growth rates were nearly 4.5 mm/mo (upper 

 line in Figure 3). Minimum growth rates were 0.5 

 mnVmo (lower line in Figure 3). 



The linear regression equation for the log 

 length-log weight relationship for the developing 

 squid is log weight (mg) = -1.22 + 2.37 log 

 length (mm) with little scatter around the re- 

 gression line. 



Respiration 



Measurements were taken of the oxygen con- 

 sumption of young L. opalescens using a Warburg 

 respirometer and a constant temperature water 

 bath. Measurements were taken at 15°C for squid 



of three different ages and at 10°, 15°, and 20°C 

 for 1-day-old squid (Table 2). Average oxygen 

 consumption values are as follows: 1 day, 10°C, 

 1.5 /ul 02/mg squid h; 1 day, 15°C, 2.5 /aI 02/mg 

 squid -h; 1 day, 20°C, 3.5 /ul 02/mg squid h; 3 wk, 

 15°C, 3.5 )ul 02/mg squid h; 8 wk, 15°C, 3.7 /xl 

 02/mg squid h. These measurements may be ar- 

 tificially high because of the crowding which oc- 

 curred in the small respiration vessels. It was ob- 

 served, however, that the oxygen consumption 

 tended to decrease (at a given temperature) with 

 increasing number of animals present in the 

 same vessel. It is possible that these lower rates 

 occurred because some of the animals became 

 moribund in the crowded conditions. But this is 

 not likely, since the respiration rates remained 

 constant over the course of the 2-h experiments. 



To compare these measurements to those made 

 by other investigators, conversion factors had to 

 be obtained to transform dry weight to wet 

 weight. The ratio wet/dry was calculated for nine 

 juvenile squid and gave a mean of 5.4 ± 0.21 ( ±2 

 SE). Wet weights were calculated by placing the 

 squid on the weighing pan, blotting it with filter 

 paper, weighing it at measured time intervals, 

 and extrapolating the line obtained to zero time. 



The previous rates expressed in terms of wet 

 weight are: 0.28, 0.46, 0.65, 0.65, and 0.69 ix\ 

 02/mg squid h. These values are similar to those 

 obtained by LaRoe (1971) for 2- and 6-day-old 

 Sepioteuthis sepioidea (0.64 ixVmgh at 23°C) and 

 with the figure of 0.60 fiVmgh for adult L. pealei, 

 calculated from data in Redfield and Goodkind 

 (1929). 



Table 2. — Oxygen consumption rates for Loligo opalescens. 

 Respiration vessels had a volume of 18 ml and contained approx- 

 imately 5 ml seawater. The duration of the experiments was 2 h. 



DISCUSSION 



It is extremely difficult to assess the role which 

 an animal such as L. opalescens plays in the 

 California Current ecosystem. Estimates of popu- 

 lation size of adults are very poor because of the 

 difficulties involved in sampling large active 



180 



