FISHERY BULLETIN; VOL. 72, NO. 4 



RESULTS 



In the course of the study six batches of larvae 

 were obtained from Haliotis rufescens, while three 

 productive spawnings occurred with//, corrugata 

 and H.fulgens. Year-round spawning in//, rufes- 

 cens was predicted by Boolootian, Farmanfar- 

 maian, and Giese (1962) and Young and DeMar- 

 tini (1970) from field sampling for gonad indices. I 

 found spawning adults every month of the year 

 (1969-71) in samples taken from Estero Bay (cen- 

 tral California) and in the present study with //. 

 rufescens from southern California, laboratory 

 spawnings were obtained in January, February, 

 April, September, November, and December. 

 Haliotis corrugata and H. fulgens spawned only 

 during the months of April, June, and October. 

 Members of the shallowwater species, //. 

 cracherodii, held in the laboratory for another 

 study, spawned in early spring and early fall. 

 Haliotis sorenseni produced viable gametes only 

 during late winter (Leighton, 1972). 



DEVELOPMENT AND HATCHING 

 IN EGGS 



At 14°-16°C (ambient for La Jolla during most of 

 the year) eggs of all species hatched within 18-24 

 h. Generally, development to hatching appeared 

 normal over a rather broad thermal range. At 

 hatching, however, consequences of inappropriate 

 incubation temperatures became pronounced as 

 trochophore larvae at and near thermal limits be- 

 came highly abnormal in appearance and be- 

 havior and usually succumbed within 48 h, par- 

 ticularly at higher temperatures. Bizarre ciliated 

 bodies predominated at high extremes of tempera- 

 ture while retardation and paralysis occurred at 

 lowest temperatures. Commonly torsion was in- 

 complete in larvae held at subnormal tempera- 

 tures. A consequence of ensuing abnormality and 

 mortality near thermal limits is apparent in the 

 series of curves generated for development during 

 the first several days of larval life. Attrition at 

 upper and lower extremes and relatively high 

 survival and rapid growth at optimal tempera- 

 tures is reflected in the sharply peaked curves for 

 larval development rate versus temperature. In 

 H. rufescens, for example, eggs developed in an 

 apparently normal manner over the range 

 10°-23°C, but larval grovvd:h after hatching became 

 restricted to the comparatively narrow range 

 13.5°-20.0°C (Figure 2). The apparent shift of the 



Incipient 

 Cephalic Tentacle 



Operculate 

 Veliger 



Inflote-stiell 

 Veliger 



Cop-shel I 

 Veliger 



Troctiophore 

 Larva 



48 hours 



15 20 



TEMPERATURE (°C) 



Figure 2. — Development of eggs of Haliotis rufescens held at 

 different temperatures over a period of 48 h. Mortality occurred 

 above 20°C after 14 h. 



3- 



2- 



>- 

 < 



O H. rufescens 

 A H. corruggtg 

 D H fulgens 



10 15 20 



TEMPERATURE CO 



25 



30 



Figure 3. 



-Hatching time for eggs of three species of Haliotis 

 incubated at several temperatures. 



peaks of curves with time to suggest true optima 

 at temperatures about 2°C lower than observed in 

 trochophore larvae was found in all species 

 studied due to supraoptimum mortality. 



Hatching time was strongly dependent on 

 temperature and ranged between 10 and 72 h. 

 Both H. corrugata and //. fulgens, at tempera- 

 tures supporting rapid but normal growth (their 

 respective thermal optima), reached the point of 

 hatching sooner than did //. rufescens (Figure 3). 

 Strongest contrast in specific development rate is 

 seen in the stage attained at supraoptimum tem- 

 peratures (2°-3°C above optimum). In 2 days: //. 



1140 



