Abstract. - Serum progesterone 

 and testosterone levels, as measured 

 by radioimmunoassay, were used to 

 estimate the mean length at attain- 

 ment of sexual maturity (LSM) in a 

 sample of 124 female and 31 male 

 incidentally-killed Dall's porpoises 

 Phocoenoides dalli. Females with 

 serum progesterone levels greater 

 than 1.34ng/mL were considered 

 mature. The LSM for females was 

 estimated at 169.0cm using Kasu- 

 ya's "summation" technique. A tech- 

 nique to fit a two-phase regression 

 model to the male data produced an 

 estimated LSM for males of 183.0 

 cm. Overall, the estimates for the 

 LSM in this study agreed well with 

 previously published reports using 

 histological and morphological mea- 

 sures of sexual maturity. Hormonal 

 estimation of maturity is proposed as 

 a rapid, inexpensive, and potential- 

 ly non-lethal alternative technique in 

 odontocete populations. 



Use of Serum Progesterone 

 and Testosterone to Estimate 

 Sexual Maturity in Dall's 

 Porpoise Phocoenoides dalli 



Jonathan L. Temte 



Hatfield Marine Science Center, Oregon State University, Newport Oregon 97365 

 Present address. Department of Zoology, University of Wisconsin 

 Madison, Wisconsin 53706 



Manuscript accepted 17 October 1990. 

 Fishery Bulletin, U.S. 89:161-165 (1991). 



Estimation of the mean age and length 

 at the attainment of sexual maturity 

 in odontocetes has traditionally relied 

 upon morphological or histological 

 parameters, thus necessitating whole 

 animal preparations. Examination of 

 reproductive tissue allows for the de- 

 termination of maturity. When this 

 information is coupled with age/length 

 data, the age or length at attainment 

 of sexual maturity for females and 

 males in a population can be deter- 

 mined using a variety of methods 

 (DeMaster 1984). These methods, 

 however, implicitly require the collec- 

 tion of dead marine mammals in the 

 field. 



Several authors have used radioim- 

 munoassay (RIA) to assess reproduc- 

 tive condition in living odontocetes. 

 For example, RIA of progesterone 

 has been used as an indicator of luteal 

 function in Tursiops truncatus, Del- 

 phinus delphis (Kirby and Ridgway 

 1984, Sawyer-Steffan et al. 1983), 

 and Stenella longirostris (Wells 1984). 

 Likewise, measurements of serum 

 testosterone by RIA have been used 

 to assess male sexual condition in T. 

 truncatus (Harrison and Ridgway 

 1971) and S. longirostris (Wells 1984). 



Temte and Spielvogel (1985) dem- 

 onstrated that serum progesterone 

 concentration, as measured by RIA, 

 was a good predictor of corpus lu- 

 teum mean diameter in a sample of 

 32 incidentally-killed pregnant or lac- 

 tating Dall's porpoises Phocoenoides 

 dalli from the northwestern North 



Pacific Ocean. Furthermore, they 

 noted that 17 sexually immature fe- 

 males (no corpora present in ovaries) 

 had very low concentrations of serum 

 progesterone (Table 1). 



In this study the results of proges- 

 terone and testosterone RIA in 124 

 female and 31 male Dall's porpoises, 

 respectively, were used to estimate 

 the mean length at attainment of sex- 

 ual maturity (LSM) in this species. 

 The results are compared to those ob- 

 tained using traditional histological 

 techniques to demonstrate the effec- 

 tiveness of this inexpensive and non- 

 lethal technique. 



Methods 



Blood samples 



During June and July of 1982, per- 

 sonnel of the National Marine Mam- 

 mal Laboratory (NMFS) obtained 

 blood samples from a total of 105 

 Dall's porpoises that were inciden- 

 tally-killed in Japanese salmon gill- 

 nets in the North Pacific Ocean. The 

 following groups were represented in 

 the sample: 21 non-pregnant, non- 

 lactating females in which the matur- 

 ity status was not known (149-199 

 cm, standard body length); 30 preg- 

 nant females (167-200 cm); 23 lac- 

 tating females (167-200cm), and 31 

 males in which the maturity status 

 was not known (101-210 cm). Sam- 

 ples of whole blood were drawn and 

 centrifuged using methods described 



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