FISHERY BULLETIN: VOL. 84, NO. 4 



Swimming behavior of newly hatched kelpfish lar- 

 vae, characterized by short periods of swimming 

 interspersed with longer periods of inactivity, is 

 common in many small marine yolk-sac larvae 

 (Hunter 1972; Ellertsen et al. 1980; Weihs 1980). 

 Like kelpfish, some other newly hatched larvae in- 

 cluding cod, Gadus morhua, (Ellertsen et al. 1980) 

 and white seabass, Atractoscion (Cynoscion) nobilis, 

 (Orhun 4 ) swim upside-down for the first 24 h after 

 hatching. This behavior is due to positive buoyancy 

 of the yolk (Hunter 5 ). Kelpfish larvae, in situ as well 

 as in the laboratory, schooled between 2 wk and 2 

 mo of age. Larval schooling is common in species 

 of nearshore fishes which also school as adults 

 (Smith 1981; Hunter 1981) and may serve to in- 

 crease the probability of locating patches of food 

 and/or may help them avoid predation. No reference 

 to larval schooling in fishes that do not school as 

 adults was found in the literature. 



Larval Feeding 



A point of no-return at which starvation occurs 

 even if larvae are fed appears to occur earlier in 

 giant kelpfish (after 36 h) than in fish larvae hatch- 

 ing from pelagic eggs (Hunter 1981) and is probably 

 due to their greater degree of development at hatch- 

 ing (i.e., smaller yolks and well-developed mouths 

 and digestive tracts). Only a small number of species 

 are sufficiently developed to consume exogenous 

 food shortly after hatching (Balon 1984a, b). Early 

 feeding during the yolk-sac stage may be critical for 

 the larvae to develop a "search" image and capture 

 skills (Hunter 1981). 



In this study, high mortality following the yolk- 

 sac stage was apparently due to starvation, despite 

 relatively high levels of appropriate-sized food items. 

 In many marine fishes, relatively low feeding suc- 

 cess is apparently common in field-collected, as well 

 as laboratory-reared, larvae (Hunter 1981). During 

 the first week, field-collected, as well as the labora- 

 tory-reared, larvae consume a wide variety of food 

 items, primarily smaller ones such as unicellular 

 algae. Like Heterostichus, most species of larval 

 fishes have been found to eat many more small prey 

 items than larger ones (Hunter and Kimbrell 1980; 

 Hunter 1981). 



"Orhun, R. M. 1986. Culture and growth of larval and early 

 juvenile white seabass, Atractoscion (Cynoscion) nobilis. M.S. 

 Thesis in preparation, Center for Marine Studies, Department of 

 Biology, San Diego State University, San Diego, CA 92182. 



6 John Hunter, Southwest Fisheries Center La Jolla Laboratory, 

 National Marine Fisheries Service, NOAA, 8604 La Jolla Shores 

 Drive, La Jolla, CA 92038, pers. commun. January 1986. 



High mortality also occurred in the laboratory at 

 about 2.5 wk, when larvae were apparently switch- 

 ing from smaller to larger prey. This may be a 

 critical period when the larvae have to learn to cap- 

 ture larger, faster swimming crustaceans as the 

 primary dietary component in order to obtain suffi- 

 cient caloric intake. Studies on other fish larvae have 

 demonstrated the necessity of increasing prey size 

 with growth (Hunter 1977; Hunter and Kimbrell 

 1980). 



Juvenile and Adult Life History 



Ages of juveniles and adults calculated in the pres- 

 ent study agree with estimates for giant kelpfish 

 determined by J. E. Fitch (in Feder et al. 1974) and 

 by R. Collins 6 . Ages by Coyer (1982), based on 42 

 kelpfish samples, do not agree with those in the pres- 

 ent study. Coyer appeared to have overestimated 

 the oldest kelpfish by 3 yr. This may have been due 

 to the prevalence of "checks" or partially completed 

 false rings on the otoliths which are commonly 

 formed during spawning (Collins and Spratt 1969) 

 and were frequently observed in the present study. 

 Estimated size at sexual maturity (mean 18.6 cm 

 TL) agrees with that reported by Coyer (1982). 



Past the age of sexual maturity, female giant kelp- 

 fish are significantly larger than males and also live 

 several years longer. Size discrepancy between adult 

 males and females may have evolved from the 

 females' behavior of venturing away from their ter- 

 ritories during the spring spawning season into 

 those occupied by males (Stepien 1985, 1986). They 

 are often readily visible at this time while away from 

 plants of matching colors. Large size may help 

 females to avoid predation or, alternatively, may be 

 the result of selection for increased fecundity. 



ACKNOWLEDGMENTS 



Grants and funds supporting this research 

 included Sigma Xi, the Lerner Fund for Marine Re- 

 search, the Theodore Roosevelt Memorial Scholar- 

 ship Fund of the American Museum of Natural 

 History, the University of Southern California 

 Department of Biological Sciences and Graduate 

 School, and a Sea Grant Traineeship. Laboratory 

 facilities were provided by the Catalina Marine 

 Science Center, U.S.C.'s Fish Harbor Research 

 Laboratory, and Southern California Edison (Redon- 

 do Beach). 



6 Robson Collins, California State Department of Fish and Game, 

 Long Beach, CA 90813, pers. commun. March 1982. 



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