Abstract.— Laboratory experi- 

 ments were conducted to determine 

 how growth and survival of early- 

 life-history stages of California hali- 

 but Paralichthys californims are in- 

 fluenced by temperature, and how 

 optimal temperature ranges may 

 change with ontogeny. As halibut 

 developed from eggs to juveniles, 

 highest survival occurred at increas- 

 ingly higher temperature ranges. 

 Within tolerance limits, growth and 

 development rates of all early-life- 

 history stages were directly propor- 

 tional to temperature. Eggs hatched 

 successfully at 12, 16. and 20°C; at 

 8 and 24 °C they died prior to embryo 

 formation. Larval survival 17 days 

 after hatching was 23-46% at 16, 20, 

 and 24 C C, but almost all larvae died 

 at 12°C after an initial period of high 

 survival. At 8°C, larval development 

 ceased at the early yolksac stage. 

 Survival of 3-month-old juvenile hali- 

 but was significantly greater at 20, 

 24, and 28°C (57-76%) than at 16°C 

 (31%). Temperature also affected 

 settlement rate; when the tempera- 

 ture of 1 -month-old larvae was raised 

 from 16°C to 20°C, settlement oc- 

 curred about a week sooner than set- 

 tlement of larvae remaining at 16°C. 

 Tolerance ranges of halibut early- 

 life-history stages determined in the 

 laboratory approximate tempera- 

 tures encountered by halibut in the 

 field; high densities of newly-settled 

 halibut larvae and juveniles have 

 been collected in shallow areas of 

 bays where temperatures are often 

 higher than the open ocean inhabited 

 by young larvae. These warmer in- 

 shore nursery grounds could enhance 

 growth and survival of halibut 

 juveniles. 



Effects of Temperature 

 on Early-life-history Stages 

 of California Halibut 

 Paralichthys californlcus 



Dena M. Gadomski 



VANTUNA Research Group. Occidental College 

 1600 Campus Road. Los Angeles. California 9004! 



Present address: National Fishery Research Center — Columbia River Field Station 

 U S Fish and Wildlife Service, Star Route, Cook. Washington 98605 



Steven A/I. Caddell 



Section of Ichthyology. Natural History Museum of Los Angeles County 



900 Exposition Boulevard. Los Angeles. California 90007 



Present address GATX. 2000 E. Sepulveda Boulevard, Carson. California 90810 



Manuscript accepted 6 May 1991. 

 Fishery Bulletin, U.S. 89:567-576 (1991). 



The California halibut Paralichthys 

 caMfornieus (family: Paralichthyidae) 

 is important to commercial and rec- 

 reational fishermen in central and 

 southern California. Adult halibut 

 spawn in nearshore waters (Frey 

 1971, Lavenberg et al. 1986) and 

 eggs hatch in about 2 days at 16°C 

 (Gadomski et al. 1990). Lavenberg 

 et al. (1986) collected halibut larvae 

 year-round within the 75 m contour 

 of the Southern California Bight, 

 with greatest abundance during 

 winter and spring. When larvae are 

 about 1 -month-old and 8 mm stan- 

 dard length, they metamorphose and 

 settle to the bottom (Allen 1988, Ga- 

 domski et al. 1990). Although spawn- 

 ing has not been observed in bays and 

 estuaries, high densities of newly- 

 settled halibut larvae and juveniles 

 have been collected in these areas, 

 often in waters as shallow as one 

 meter (Allen 1988, Kramer 1990). It 

 is not known at what stage of devel- 

 opment inshore movement occurs, 

 and whether the mechanism of trans- 

 port is passive or active. The advan- 

 tages of estuarine nursery areas for 

 juvenile fishes have been often cited 

 (McHugh 1967, Pearcy and Myers 

 1974, Boehlert and Mundy 1988). 

 Estuaries commonly have greater 



food availability and protection from 

 predation and adverse weather con- 

 ditions. 



As early development progresses, 

 halibut may experience an increas- 

 ingly higher range of temperatures 

 due both to the distribution changes 

 described above and to seasonal tem- 

 perature differences. When eggs and 

 young larvae are in nearshore waters 

 of southern California during winter 

 and spring, typical surface tempera- 

 tures are about 13-17°C (Petersen et 

 al. 1986). Juveniles in inshore waters 

 during summer months commonly 

 experience temperatures above 20°C, 

 and shallow areas may be as warm as 

 24 °C (Kramer 1990). Thus, one ad- 

 vantage of inshore migration might 

 be higher temperatures, which could 

 result in enhanced juvenile growth. 



Fishes generally have temperature 

 ranges at which growth and survival 

 are optimum. These may differ with 

 age; young of some species prefer 

 warmer temperatures than adults 

 (Norris 1963, McCauley and Huggins 

 1979). Early-life-history stages may 

 also have different optimal tempera- 

 tures, which may reflect field tem- 

 poral and spatial distributions. For 

 example, sole Solea solea larvae from 

 North Sea coastal regions require 



567 



