Materials and Methods 



Validation 



Fertilized eggs of C. hippurus and C. equiselis were 

 obtained between January 1982 and February 1983 

 from captive broodstock held at the University of 

 Hawaii's Waikiki Aquarium (WA); the Kewalo Re- 

 search Facility (KRF) of the Southwest Fisheries 

 Center Honolulu Laboratory, National Marine Fish- 

 eries Service; and The Oceanic Institute, Waimanalo, 

 HI. Larvae of both species were reared at the WA 

 in 4,000 L circular fiber glass tanks with flow- 

 through water exchange and under shaded natural 

 light condition. Water temperature ranged between 

 23° and 27°C. Both species were fed an unlimited 

 supply (a density of 1-5/mL) of cultured copepod, 

 Euterpina acutifrons, and Artemia sp. until they 

 were large enough to accept chopped fish and squid 

 (about 30 d after hatching), which were then pro- 

 vided several times during the day. These fish were 

 fed to satiation. One 167-d-old and three 191-d-old 

 C. hippurus were reared at the KRF under similar 

 environmental conditions and feeding regime as at 

 the WA. 1 These juvenile C. hippurus were trans- 

 ferred to 8 m diameter tanks when they were about 

 25 cm long. 



One to three larvae of C. equiselis were sampled 

 on the day of hatching (D-0), and each day thereafter 

 (D-l, D-2, D-4, etc.). However, after the fourth day, 

 there were few survivors, so only a single specimen 

 was taken at intervals of 4 d from D-l 9. Three lar- 

 vae of C. hippurus were sampled on D-4 and single 

 specimens were sampled at various intervals or ob- 

 tained after accidental deaths for validating the 

 growth increments. Other larvae were sampled from 

 other batches on D-0, D-l, and D-2 for measure- 

 ments. Specimens were sampled around noon. Total 

 length of the larvae was measured under a micro- 

 scope with an ocular micrometer while the specimen 

 was alive or within an hour after death. To facilitate 

 measurement, each larva was put on a glass slide, 

 extended to its full length, and measured. For the 

 examination of otoliths, the larva on the slide was 

 immersed in 70% ethanol and allowed to fix for an 

 hour. The larva was then removed from the ethanol 

 bath, blotted, and mounted in Euparal, 2 a water solu- 

 ble mounting medium, and covered with a cover slip. 



Otoliths could be examined in the squashed whole 

 mount without extracting them. 



After measuring the fork length of juvenile and 

 adult dolphins with a caliper to the nearest milli- 

 meter, otoliths were extracted, cleaned, and mounted 

 whole To extract the otoliths, the head was removed 

 from the body, and the flesh removed from the head 

 to expose the skull. With a saw or knife, most of the 

 supraoccipital and roof of the skull were removed. 

 After careful removal of the brain, the sagittae 

 (largest of the three otoliths) could be found in the 

 sacculi located anteriorly on the right and left sides 

 of the first vertebra at the caudal end of the brain 

 cavity. Under a dissecting microscope, the sagitta 

 was teased out of the sacculus, and extraneous 

 tissues were brushed away. The pair of sagittae was 

 then placed on a clean glass slide, permitted to dry, 

 and mounted in Euparal. Segments of monofilament 

 line slightly thicker than the sagittae were placed 

 on both sides of the sagittae to prevent the cover slip 

 from crushing it. 



After clearing for a month, presumed daily incre- 

 ments on a sagitta were enumerated using a com- 

 pound binocular microscope with transmitted light 

 at 600 x magnification. Increments were counted 

 starting from the core out to the edge of the post- 

 rostrum, or from the core to the tip of the rostrum. 

 Usually, counts could not be made in a direct line 

 from the core to the edge of the rostrum or post- 

 rostrum of the sagitta; rather, a somewhat circuitous 

 route was taken from one area of the sagitta to 

 another by following a prominent growth increment. 

 Increments were also counted inward from the edge 

 to the core. Two independent age estimations were 

 made separately on the rostrum and postrostrum on 

 a sagitta to verify the age of fish. In some samples, 

 it was possible only to make a single age estimate 

 since the sagitta was incomplete, having just a 

 rostrum or postrostrum. The reader had no infor- 

 mation such as specimen size or previous counts to 

 prevent bias in the counting. 



The arithmetic mean of 3-14 counts was used to 

 estimate a fish's age The number of counts from the 

 rostrum and postrostrum varied from as few as 3 

 for a larva to 14 for a sagitta of a juvenile The rela- 

 tionship between counts of otolith increments and 

 days was assessed for both species by regression 

 analysis. 



'Thomas K. Kazama, Southwest Fisheries Center Honolulu 

 Laboratory, National Marine Fisheries Service, NOAA, Honolulu, 

 HI 96812, pers. commun. October 1984. 



2 Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



Growth of Wild Specimens 



Juveniles of both species were dip netted from 

 Kaneohe Bay, HI. Large juveniles and adults of both 

 species were obtained from private and chartered 



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