STEPIEN: LIFE HISTORY AND DEVELOPMENT OF KELPFISH 



Table 2.— Mean sizes (TL, mm) and developmental stages of laboratory-reared giant kelpfish 



larvae 0-60 d. 



Age 1 

 (d) 



Mean 

 length 



Range 

 (TL, mm) 



No. 



Developmental features 



7.9 



7.4-8.4 



10 



well-developed mouth, gut, and fin folds; 12 postanal 



serial melanophores 

 12-19 postanal melanophores, first feeding, yolk sac 1/3 



original size 

 20 postanal melanophores, 2 melanophore spots on 



liver, melanophores dorsal to anus, yolk sac disap- 

 peared 

 some ventral caudal fin rays visible, gill rakers formed, 



operculum visible 

 notochord flexion begun in some 

 notochord flexion completed, swim bladder formed 

 caudal fin rays well-developed 

 schooling behavior is pronounced 

 fin rays in rear of dorsal and anal fin folds 

 scattered melanophores on top of head and lower jaw, 



melanophores over gut 

 well-developed schooling and avoidance behavior 

 pectoral, dorsal, and anal fin rays formed 

 continuous line of stellate melanophores above the gut 

 pelvic fins beginning to develop, melanin pigmentation 



in pelvic region 

 orange xanthophore pigmentation on top of the head, 



over the gut and at the base of the caudal fin; teeth 



visible 

 pelvic fins formed, 32 postanal ventral melanophores 

 larvae are pale gold in color 

 schooling no longer pronounced 

 most have settled onto algae 



developed avoidance patterns and fright responses. 

 By 5 wk, schooling was no longer as pronounced and 

 the larvae were observed to stalk their copepod prey 

 very efficiently. 



Larval Feeding 



Unless giant kelpfish larvae were given food with- 

 in the first 48 h, a point of no-return was reached, 

 after which they starved to death even if given food. 

 Best results were obtained if larvae were fed within 

 24 h of hatching. Brachionus (rotifers) and Tetra- 

 selmis (algae) were found in the guts of 2-d-old lar- 

 vae in the laboratory. Three-day-old larvae, even 

 those still having yolk sacs, contained an average 

 of 5.6 Brachionus and 2.9 Tetraselmis (Table 3). 

 High mortality (nearly 60% of those hatched) oc- 

 curred after hatching and through day 5. Dead lar- 

 vae examined had apparently never eaten, despite 

 relatively high levels of appropriately sized food 

 items. 



Gut contents of field-collected kelpfish larvae 

 (estimated to range from to 9 d old) showed that 

 they fed on a wide variety of food items, including 

 single-celled algae, rotifers, mollusk larvae, and bar- 

 nacle and copepod larvae (Table 4). Similar sizes and 

 quantities of food items were consumed by both the 

 laboratory-reared and field-collected larvae (Tables 

 3,4). 



Significantly larger food items were consumed by 

 2-wk-old laboratory- reared larvae, the largest 

 widths being 52% of the mouth size (Fig. 6). Larger 

 copepods were eaten more frequently than rotifers, 

 although both food items were present in guts (Table 

 3). High mortality (ranging from 20 to 40%) also 

 occurred at about 2.5 wk of age in both the 1980 

 and 1982 rearing experiments. At this age, gut ex- 

 aminations indicated that the larvae were switch- 

 ing from the smaller prey (rotifers and algae) to the 

 larger copepods. Older larvae progressively con- 

 sumed larger copepods whose size reached 70% of 

 the mouth width by week 3 (Fig. 6, Table 3). 



Figure 5.— Drawings of laboratory-reared giant kelpfish larvae, 

 made with camera lucida and dissection microscope. (A) Day 

 (after hatching), 6.1 mm TL. (B) Day 4 after hatching, 7.0 mm 

 TL. (C) Day 7 after hatching, 8.4 mm TL. (D) 2 wk, 10.9 mm 

 TL. (E) 3 wk, 11.6 mm TL. (F) 5 wk, 22.2 mm TL. 



Settlement and Metamorphosis 



After 8 wk and at a mean length of 30.6 mm, giant 

 kelpfish larvae had well-developed, pale gold-brown 

 pigmentation. They became increasingly thigmotac- 



817 



