LIFE HISTORY AND LARVAL DEVELOPMENT OF 

 THE GIANT KELPFISH, HETEROSTICHUS ROSTRATUS GIRARD, 1854 



Carol A. Stepien 1 



ABSTRACT 



Life history data from about 1,200 giant kelpfish, including age, length, and weight relationships, are 

 described and analyzed. Additionally, differences in habitats and behavior between larvae, juveniles, and 

 adults are reported. Female giant kelpfish were found to be larger than males at given ages past sexual 

 maturity. Age data indicate that females live longer and all individuals larger than 28 cm TL collected 

 in this study were females. Males guard the algal nests until hatching, about 2 weeks after spawning. 

 Giant kelpfish from nests collected in the field were reared in the laboratory, surviving for up to 9 months. 

 Feeding and development of laboratory-reared larvae were compared with field-collected specimens. In 

 situ, they school in the kelp canopy until 2 months old, gradually developing juvenile coloration and becom- 

 ing increasingly thigmotactic and solitary. Giant kelpfish reach sexual maturity at 1-1.5 years, at which 

 time they commence to defend territories in given plant habitats. 



The cryptically colored giant kelpfish, Heterostichus 

 7 , ostratus, is abundant in southern California kelp 

 forests and surrounding subtidal plant habitats. 

 Heterostichus is one of the largest members of the 

 clinid family, reaching a length of 41.2 cm and an 

 age of 5 yr (J. E. Fitch in Feder et al. 1974). Al- 

 though ranging from British Columbia, Canada, to 

 Cape San Lucas, Baja California, Mexico, it is most 

 commonly found from Point Conception to central 

 Baja in depths of 35 m (Roedel 1953). Giant kelpfish 

 occur in three different colormorphs— red, brown, 

 and green— which closely match the color of their 

 surrounding plant habitats (Hubbs 1952; Stepien 

 1985, 1986). They additionally exhibit four different 

 dark melanin patterns, which appear superimposed 

 on the basic color of the fish and, unlike color- 

 morphs, can change rapidly (Stepien 1985, 1986). 

 Giant kelpfish spawn year-round, but most fre- 

 quently during spring months (Limbaugh 1955; 

 Feder et al. 1974). The eggs are attached to algal 

 nests with entangling threads that extend from the 

 egg membranes (Holder 1907; Feder et al. 1974). 

 The males alone guard the nests from predators 

 until hatching, averaging 2 wk after spawning 

 (Coyer 1982). Giant kelpfish are relatively well- 

 developed at hatching and are planktonic for several 

 weeks. They school in the kelp canopy until they are 

 about 6 cm long, then develop juvenile coloration 



department of Biological Sciences, University of Southern 

 California, Los Angeles, CA 9008S; present address: Marine 

 Biology Research Division A-002, Scripps Institution of Ocean- 

 ography, University of California at San Diego, La Jolla, CA 92093. 



and become solitary, living close to nearshore algae 

 (Limbaugh 1955). 



Although Heterostichus larvae are not uncommon 

 in the nearshore ichthyoplankton, their development 

 has not been previously described. Heterostichus egg 

 morphology was described by Barnhart (1932), and 

 the egg-laying process was described by Holder 

 (1907). Matarese et al. (1984) published two draw- 

 ings of kelpfish larvae. Although diet and some 

 aspects of general life history have been described 

 qualitatively by several investigators (Hubbs 1920, 

 1952; Roedell 1953; Limbaugh 1955; Quast 1968; 

 Hobson 1971; Feder et al. 1974; Hobson et al. 1981; 

 Coyer 1982) and one quantitative study was con- 

 ducted on feeding and distribution of juveniles and 

 adults in giant kelp (Coyer 1979), specific morpho- 

 metric data for larval, juvenile, and adult stages 

 have not previously been reported. This paper 

 presents life history data, including the following: 1) 

 Differences in larval, juvenile, and adult habitats and 

 behavior; 2) size, weight, and age relationships, in- 

 cluding differences between males and females; and 

 3) the sequence of larval development and meta- 

 morphosis. 



MATERIALS AND METHODS 



Collection and In Situ Observations 



In situ observations were made during approx- 

 imately 280 scuba dives from 1978 to 1983, the 

 majority in the vicinity of the University of South- 

 ern California's Catalina Marine Science Center 



Manuscript accepted March 1986. 



FISHERY BULLETIN: VOL. 84, NO. 4, 1986. 



809 



