LEIGHTON: INFLUENCE OF TEMPERATURE ON ABALONES 



length at 1 yr of age in four species reared in the 

 laboratory varied over a range greater than 10mm 

 (Table 3). 



INFLUENCE OF TEMPERATURE ON 

 GROWTH RATE OF JUVENILES 



Several growth experiments were conducted 

 with juveniles of the three species of abalones to 

 gain comparative data and to establish respective 

 temperatures of maximum growth rate. Juveniles 

 were reared for month-long periods in 10-liter 

 plastic containers held at six temperatures be- 

 tween 12° and 30°C. Both H. corrugata and H. 

 fulgens displayed enhanced growth rate above 

 20°C. Haliotis rufescens, however, grew best 

 below 20°C and, in fact, grew but slightly less at 

 the coldest temperature, 12.5°C (Table 4, Figure 

 8). H. fulgens again showed a superior growth 

 rate. While a mean daily shell growth approach- 

 ing 90 A' was observed at its temperature of 

 maximum growth rate (26°C), some individuals 

 increased in shell length as much as 130 n per 

 day. 



DISCUSSION 



Seven species of Haliotis occur in southern 

 California waters ranging vertically from the in- 



Table 2. — Variation in size of juvenile Haliotis of identical 

 parentage, age, and growing environment. 



Table 3. — Size of Haliotis at completion of first year growth in 

 the laboratory. 



'Recent observations on growth of over 100 juvenile H. fulgens suggest 

 the three individuals represented here were exceptionally rapid growers. 

 Projection of growth of juveniles presently 8 mo old suggest the mean size 

 at 1 yr under laboratory conditions may fall closer to 25 mm. 



tertidal to depths over 35 m. Depth distribution is 

 stratified specifically, although in certain areas 

 (i.e., in the presence of localized upwelling) over- 

 lapping does occur. Vertical and latitudinal dis- 

 tribution appears most closely related to tempera- 

 ture. The Point Loma (San Diego) shelf from to 

 35 m supports all California abalone species 

 (Table 5). Colder water species may be found in- 

 tertidally in northern California (H. rufescens, H. 



Table 4. — Daily shell elongation rate for groups of juvenile Haliotis reared for month-long jjeriods at different 



temperatures (microns/day). 



Species and 

 date 



Temperature (°C ± 1.5°; 



12 



15 



18 



21 



24 



27 



30 



H. rufescens 



Oct. 1971 

 Jan. 1972 

 Mar. 1972 

 Dec. 1972 



Mean 



609 



64.5 



77.3 



70.0 



27.3 



(') 



H. corrugata 



Jun. 1972 

 May 1973 

 Jun. 1973 



Mean 



26 



57 



41.5 



29 

 55 

 45 



43.0 



30 

 62 

 72 



54.7 



46 

 54 

 91 



63.7 



53 



60 

 63 



58.7 



28 

 68 



48.0 



14 



14.0 



H. fulgens 



Mar. 1973 

 May 1973 

 Jun. 1973 



Mean 



23 

 21 



22.0 



29 

 21 



21 



237 



63 



55 

 56 



580 



70.3 



858 



88.0 



54 

 54.0 



'H. rufescens did not survive in the 27'C containers. 



These data are averages for groups of 8 to 15 individuals reared in each of six 1 0-liter plastic drums. In the case of H. corrugata 

 and H. fulgens. temperatures were raised throughout for the third experiment to cover the supraoptimal range. Juveniles used in 

 these experiments ranged from 5 to 20 mm. 



1143 



