FISHERY BULLETIN: VOL. 70, NO. 2 



lOOi- 



> 

 < 

 O 



in 



o 

 111 



ill 



111 



< 

 > 



< 



Z 20 - 



o 



cr 



UJ 



a 



10 



14 16 



TEMPERATURE CO 



18 



Figure 2. — Percentage of larvae firmly settled at 15 

 days. Points are averages for duplicate observations. 

 Settlement was considered complete when larvae could 

 no longer be dislodged by jetting a stream of water from 

 a pipette. 



A marked variation in growth rate existed, 

 even among those individuals which were pro- 

 vided surfaces (such as plastic and glass beak- 

 ers) on which diatom growth appeared to be 

 quite uniform. In one case, 19 individuals were 

 retained in a liter beaker and provided mixed 

 diatoms. At an age of 85 days some had at- 

 tained a shell length of 4.5 mm while others were 

 as small as 1.4 mm. The largest had formed 

 four respiratory pores, yet the smallest was just 

 beginning to form the first. Size attained at 100 

 days (15-19°C) ranged from 3.0 to 5.6 mm 

 (mean, 4.25, SD ± 0.63 mm, n = 19). By 130 

 days the range was 4.0 to 8.0 (mean, 5.53 ram, 

 SD lb 1.01 mm) in the same group (Figure 4). 



DESCRIPTION OF JUVENILE 

 SHELL FEATURES 



The most conspicuous feature of recently set- 

 tled and minute haliotids (less than 500 fx long) 

 is the asymmetrical outline resulting from dex- 

 tral growth of the persistomial shell. Through 



1 



o 



15 



Ijj 

 u) 10 



<0 



>- 



g 5 



± 



X 



± 



12 



14 16 18 



TEMPERATURE CO 



20 



Figure 3. — Days to settlement of at least 75% of Haliotis 

 sorenseni larvae from groups held at five different tem- 

 peratures. Not more than 75% of the larvae at 12°C 

 successfully settled, and none of those at 10 °C reached 

 this stage. 



Si- 



Figure 4. — Growth of larval and juvenile Haliotis sor- 

 enseni in 1-liter beakers provided mixed diatoms as food. 

 Ranges of shell length are shown by vertical lines. 



376 



