Abstract.— Interest in estimating 

 energy fluxes through populations of 

 marine mammals has been increas- 

 ing as these populations are more 

 frequently recognized to compete 

 with fishermen for commercially ex- 

 ploited fish stocks. Testing for the 

 presence of allometric trends with 

 size in the parameters used to esti- 

 mate these energy fluxes is impor- 

 tant because if such trends exist and 

 are large, it will be inappropriate to 

 apply measurements derived from 

 one size of animal to animals of other 

 sizes, in any given population. To 

 test for (and to measure, if present) 

 allometric effects in a population of 

 small cetaceans, morphological mea- 

 surements (energetics parameters) 

 related to estimating energy flux 

 were taken from 35 spotted dolphins 

 iStenella attenuate!) ranging in size 

 from 77 to 210 cm total length, cap- 

 tured incidental to fishing operations 

 in the eastern tropical Pacific Ocean. 



Significant allometric (nonlinear) 

 changes with size were observed in 

 23 of the 25 parameters measured; 

 no trends were isometric (linear). 

 Most of the significant trends were 

 expressed primarily during the first 

 two or three years of life (5-30 kg 

 wet weight). Thus, parameter esti- 

 mates for small dolphins (less than 

 about 30 kg wet weight) should be 

 derived from measurements on ani- 

 mals near the specific size of inter- 

 est. Estimates for larger animals, 

 with the exception of several surface 

 area measurements, could be esti- 

 mated reasonably well from any 

 specimens greater than about 30 kg 

 wet. 



Although the energy fluxes and 

 standing stock of energy represented 

 by animals younger than 2-3 years 

 are relatively small compared with 

 the total population, constraints 

 resulting from the energy character- 

 istics of the smaller animals may ex- 

 ert significant control over popula- 

 tion energy flux, implying that the 

 rapid changes in energetics param- 

 eters of the younger animals should 

 not be ignored. 



Allometry of energetics parameters 

 in spotted Dolphin (Stenella 

 attenuata) from the eastern tropical 

 Pacific Ocean 



Elizabeth F. Edwards 



Southwest Fisheries Science Center 

 RO.Box 27 1 , La Jolla. CA 92038 



Manuscript accepted 14 May 1993. 

 Fishery Bulletin 91:428-439 ( 1993). 



Estimating cetacean population en- 

 ergy fluxes, in particular energy con- 

 sumption in the form of commercially 

 valuable fishes, is important because 

 many commercially exploited fish 

 populations are decreasing in abun- 

 dance yet must be shared by both 

 human and cetacean predators. The 

 existence in cetacean populations of 

 allometric trends (nonlinear changes 

 with size) in morphological charac- 

 teristics related to energy processing 

 complicates energy flux estimation 

 for these animals because the size 

 range of cetacean specimens avail- 

 able for study tends to be very nar- 

 row. If allometric trends are present 

 and large, measurements from that 

 narrow size range cannot be assumed 

 to apply equally to all other sizes in 

 the population. 



Neither commercial nor noncom- 

 mercial sources of cetacean speci- 

 mens generally provide an adequate 

 range of sizes from which to deter- 

 mine whether allometric trends ex- 

 ist. Specimens available from com- 

 mercial sources will include only 

 those sizes sought by the fishery. For 

 example, morphological samples from 

 large cetaceans (whales) tend to be 

 dominated by adult (and when preg- 

 nant females are captured, by fetal) 

 specimens because the larger indi- 

 viduals have more commercial value. 

 Juveniles are rarely captured. Mor- 

 phological samples from small ceta- 

 ceans (dolphins and porpoises) are 

 rare for all sizes because these ani- 

 mals are rarely the subject of directed 



fisheries. Specimens from noncom- 

 mercial sources are generally avail- 

 able only as beached or stranded 

 individuals, or where observer pro- 

 grams are employed to monitor kill 

 rates of both target and nontarget 

 species. These noncommercial speci- 

 mens tend to be too rare to provide 

 an adequate sample of sizes. 



In addition to these sampling bi- 

 ases in age and species composition, 

 the data collected are generally un- 

 suitable for deriving estimates of en- 

 ergy flux. Although considerable mor- 

 phological data exist for commercially 

 exploited large whales (e.g., Fujino 

 1954, 1956; Omura and Fujino, 1954; 

 Omura and Sakiura, 1956; Ohsumi, 

 1960; Nishiwaki et al., 1963; Lockyer, 

 1981, a and b, and references there- 

 in) and a few similar reports exist 

 for small cetaceans (e.g., Sergeant, 

 1962;, Perrin, 1975; Yasui, 1980; 

 Perrin et al., 1987), these data gen- 

 erally include only a standardized set 

 of external morphological measure- 

 ments used primarily for taxonomic 

 purposes. Taxonomic data tend to be 

 inappropriate for deriving estimates 

 of energy flux because many size 

 classes and most of the morphologi- 

 cal measurements required specifi- 

 cally for energetics estimates are 

 missing. 



Although some estimates have 

 been developed for energy process- 

 ing in neonate through adult large 

 whales (Lockyer, 1981, a and b), al- 

 lometric trends in energetics param- 

 eters have never been examined in 



428 



