FISHERY BULLETIN: VOL. 82, NO. 1 



resented the same amount of time as the single GLG 

 interpreted from the labeled region of each tooth. 



A study by Hui (1978) included two tooth extrac- 

 tions made 2.5 yr apart from a captive male bot- 

 tlenose dolphin, Tursiops truncatus (No. 10,"Kona"). 

 Comparisons of longitudinal thin sections of the two 

 teeth led Hui to conclude that "... almost three den- 

 tin layers [GLGs] had been deposited during the 

 intervening period. . . " (p. 1 1). Other than indicating 

 GLG boundaries in figures of the two thin sections 

 (his fig. 3), Hui did not describe the GLGs or their 

 components. 



Three published studies (Sergeant 1959; Sergeant 

 et al. 1973; Hui 1978) have attempted to 

 demonstrate time content in GLGs using teeth of 

 known-age, i.e., captive-born dolphins. All three had 

 access to only a small number of specimens, all of 

 Tursiops truncatus. Apparently, the investigators 

 knew the ages of the specimens before defining and 

 counting dentinal GLGs in the teeth, and no 

 assurance was provided that the GLGs counted cor- 

 responded to annual periods between birth and 

 death. Hui's study demonstrated that GLGs may be 

 defined in such a manner as to verify the age that is 

 already known for a specimen (Myrick 1980a). The 

 incorrect age data (3.3 yr) provided to Hui for one of 

 two "known-age" specimens studied by him (Hui 

 1978) led to his subsequent division of its dentinal 

 layering pattern into three GLGs and a small fraction 

 (Hui 4 ). The original clinical records for the specimen 

 (Hui's No. 29, LACM 54698) show, however, that the 

 dolphin was born on 28 August 1965 and died on 8 

 August 1969, at nearly 4 yr of age. 



Used independently, teeth of known-age animals, 

 single-labeled teeth, or teeth extracted on two dates 

 do not provide reliable means by which to determine 

 tissue accumulation rates fully or to define GLGs 

 with precision. Each method yields only two dates 

 bracketing a segment of layered tissue into which the 

 known elapsed time is divided. Myrick (1980b) de- 

 scribed approaches that combine the use of two or 

 more labels and two or more tooth extractions over an 

 extended period to monitor rates and calibrate 

 GLGs. The present paper is an account of such a 

 study which used TCL-labeled teeth from seven cap- 

 tive Hawaiian spinner dolphins, Stenella longi- 

 rostris. 



MATERIALS AND METHODS 



The study consisted of two phases. The first was a 



retrospective examination of TCL labels in the 

 dolphins' dental tissues produced incidentally by 

 clinical treatments administered during their cap- 

 tivity at Sea Life Park, Hawaii. Teeth were used from 

 four frozen carcasses (Nos. WFP 606, 669, 670, and 

 67 1 5 ), including one specimen of known age, and 

 three live animals (Nos. ACM 103, 104, and 106) 

 from which teeth were extracted in early 1980. 



The second phase was a 1-yr monitoring of tissue- 

 accumulation rates in teeth of three live animals. 

 Each animal was given intramuscular injections of 

 TCL at about 3 -mo intervals and underwent three 

 tooth extractions during the monitored period. 



To restrain the dolphins during injections and 

 extractions, an elevated rigid litter was placed near 

 the edge of the dolphin holding tank in which the 

 water level had been lowered to a depth of 0.5 m. The 

 sloped tank bottom inclined the litter at an angle of 

 20° relative to the water surface. Each dolphin in turn 

 was guided on its belly onto the litter until the front 

 half of its body was above the water surface. In this 

 position the dolphin could be held firmly with little 

 apparent discomfort to the animal. 



The procedure used to extract teeth was adapted 

 for the spinners from the method described by 

 Ridgway et al. (1975) for bottlenose dolphins. The 

 dolphin's mouth was held open by moistened rolled 

 toweling placed around the upper and lower jaws. 

 Carbocaine 6 (5-10 cc) was injected into the right or 

 left interalveolar nerve immediately behind the 

 anterior border of the mandibular foramen. After 

 allowing about 10 min for the anesthetic to take 

 effect, a tooth was removed from the middle of the 

 corresponding mandibular tooth row using an 

 elevator and an extractor. The vacated alveolus was 

 packed with cotton soaked with a ferric solution to 

 control bleeding and promote healing. 



Liquamycin 100, a form of TCL, was injected into 

 the dorsal musculature between the dorsal fin and 

 the blow hole. To reduce the possibility of local 

 inflammation of the tissue — a problem known to 

 result from concentrations of TCL — each dose (25 

 mg/kg body weight) was distributed along the dor- 

 sum at three separate sites. 



Untreated (cut or ground) thin sections and 

 decalcified and haematoxylin-stained (D/S) thin sec- 

 tions are the two most widely used preparations for 

 dolphin teeth in age determination studies (see 

 Perrin and Myrick 1980: 21 ff.). D/S sections pro- 

 duce simpler, more uniform GLG patterns, but de- 



4 Clifford Hui, Naval Ocean Systems Center, San Diego, Calif., pers. 

 commun. 1981. 



'Skeletons are in the synoptic collection at Southwest Fisheries 

 Center, NMFS, La Jolla, Calif. 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



208 



