Abstract. — Growth and mortal- 

 ity rates were compared for juvenile 

 California halibut ParaMckthys cali- 

 fornicus from bay and open coast 

 habitats. Growth was estimated by 

 determination of size-at-age using 

 daily increments in otoliths. No sig- 

 nificant difference was observed in 

 size-at-age for juvenile halibut be- 

 tween 6 and 41mm from the bays 

 and open coast. However, age-specific 

 mortality rates estimated for halibut 

 <70 days were highest for newly- 

 settled halibut on the open coast. 

 California halibut settled either in 

 bays or on the open coast, but ulti- 

 mately nearly all of the halibut that 

 settled on the coast entered and used 

 the bays as nursery areas during 

 their first year of life or else they 

 died. The advantages of bays as nur- 

 sery areas may be a decrease in risk 

 of mortality of newly-settled halibut 

 and an increase in growth of larger 

 juveniles that feed upon the abun- 

 dant small fishes in the bays. 



Growth, Mortality, and Movements 

 of Juvenile California Halibut 

 Paralichthys californicus in 

 Shallow Coastal and Bay Habitats 

 of San Diego County, California 



Sharon Hendrix Kramer 



Southwest Fisheries Science Center. National Marine Fisheries Service. NOAA 

 PO Box 271, La Jolla. California 92038 

 Present address: MBC Applied Environmental Sciences 

 947 Newhall Street, Costa Mesa, California 92627 



Manuscript accepted 12 December 1990. 

 Fishery Bulletin, U.S. 89:195-207 (1991). 



The utilization of specialized nursery 

 habitats by juvenile fish is a common 

 phenomenon (Boehlert and Mundy 

 1988, Miller et al. 1986). Many of the 

 fish species that utilize bays as nur- 

 sery areas spawn in offshore waters, 

 and move into bays as late larvae and 

 early juveniles (Boehlert and Mundy 

 1988, Miller et al. 1986). The migra- 

 tion, location, and entry of larvae and 

 juveniles into the bays involve com- 

 plex behaviors that are particularly 

 important on the Pacific coast of 

 North America, where only 10-20% 

 of the coastal habitat consists of 

 estuaries and lagoons, compared with 

 80-90% on the Atlantic and Gulf 

 coasts (Emery 1967). Possible conse- 

 quences of the use of bays as nursery 

 areas include faster growth because 

 of high food production, warm tem- 

 peratures, and decreased predation 

 (Miller et al. 1986, Kneib 1987, Kry- 

 gier and Pearcy 1986). 



The California halibut Paralichthys 

 californicus is a commercially impor- 

 tant flatfish found in southern Cali- 

 fornia coastal waters and bays (Frey 

 1971, Haaker 1975, Allen 1988, Love 

 et al. 1986, Plummer et al. 1983). 

 Eggs and larvae occur over the shelf 

 and seaward, with greatest densities 

 in waters less than 75 m deep and 

 within 6km of shore (Frey 1971, 

 Gruber et al. 1982, Barnett et al. 

 1984, Lavenberg et al. 1986, Walker 



et al. 1987, Moser and Watson 1990). 

 In past studies juvenile halibut rare- 

 ly were taken on the open coast, sug- 

 gesting that bays and lagoons might 

 be the only significant nursery habi- 

 tat (Plummer et al. 1983, Allen 1982, 

 Kramer 1990). 



The objective of this study was to 

 determine the relative importance of 

 bays as nursery areas and to evaluate 

 the movements between bay and 

 open coast habitats. To meet these 

 objectives, I estimated habitat-spe- 

 cific distribution, abundance, and 

 growth and mortality rates of juve- 

 nile halibut from both bay and open 

 coast habitats. 



Materials and methods 



Distribution and abundance 



California halibut were collected dur- 

 ing a 2-year survey (September 1986- 

 September 1988) of the open coast 

 between Mission Bay and San Ono- 

 fre, and two bays, Mission Bay and 

 Agua Hedionda Lagoon (Fig. 1). A 

 stratified random sampling design 

 was used, consisting of four open 

 coast blocks each with three depth 

 strata (5-8m, 9-llm, and 12-14m), 

 and five blocks in Mission Bay and 

 three blocks in Agua Hedionda La- 

 goon, each with three depth strata 

 (0-lm, l-2m, and 2-4m) (Fig. 1). 



195 



