Abstract
The Cook Inlet population of beluga whales (Delphinapterus leucas) is listed as endangered1 and is not recovering. The cause of the continued decline is unknown; however, poor reproductive success is one of many hypotheses being considered. Currently, invasive research is prohibited and the only way to assess reproduction in this population is through aerial calf counts taken over the course of a few days every one to two years. The use of darting biopsies is being considered as a minimally invasive way to identify pregnant females and compare pregnancy rates with other populations. Bristol Bay belugas are the closest genetically, ecologically and geographically population to the Cook Inlet beluga stock2 and are considered an ideal comparative control group for the endangered population.
Ongoing live captures in Bristol Bay have provided the opportunity to compare progesterone values in both blood and blubber obtained from the same animal. As soon as possible after capture, blood was collected in serum separator tubes from the periarterial venous rete on the dorsal side of the flukes using a 1.3-cm, 19-gauge butterfly catheter after the skin was disinfected with alcohol. The tubes were stored in coolers and later spun to separate serum which was frozen and later sent to a diagnostic laboratory (Endocrinology Laboratory, Cornell, Ithaca, NY 14850) for analysis. Blubber was obtained using a punch biopsy or from trocars used during satellite tag placement after the skin was disinfected with alcohol. A small subsample of blubber close to the skin was separated for blubber hormone analysis which requires only 100 mg of tissue. Blubber was frozen at ultralow temperatures and later sent to NOAA's Southwest Fisheries Science Center for analysis using their immunoassays and a steroid isolation protocol.3
Preliminary data from live captures in Bristol Bay demonstrate promise in the ability to accurately diagnose pregnancy from analysis of blubber. Serum and blubber from 24 (14 females, 10 males) captured animals were analyzed for progesterone. Samples from eight females contained high levels of progesterone in both blubber and serum, consistent with pregnancy. Four females had low levels of progesterone in both sample types. Samples from the 10 males also had low levels in both samples. Two females had blubber values for which pregnancy is uncertain (i.e., levels between those found in known pregnant and non-pregnant females) when compared to published values from small Delphinids3,4 and bowhead whales for reference.5 One had a serum progesterone level suggestive of pregnancy while the other had a serum level consistent with not being pregnant. In female dolphins, less than 2% of all measured blubber progesterone values have been measured within this ambiguous range.
Acknowledgements
The authors would like to acknowledge and thank the members of the research and capture crews. Special thanks go to Helen Chythlook, Bristol Bay Native Association, for helping to coordinate boat drivers and other local participants. This work was supported with funds and staff from Georgia Aquarium and NOAA/NMML with additional support from the Alaska SeaLife Center, Alaska Department of Fish and Game, Mystic Aquarium, Shedd Aquarium, and Point Defiance Zoo & Aquarium. Activities authorized by NMFS Scientific Research Permits (782-1719; 932-1489; and 14245), ADF&G (06-16) and NMML (AFSC/NWFC 2012-1) Animal Care and Use Committees, and the Bristol Bay Marine Mammal Council. Also, we greatly appreciate logistical support from the Togiak National Wildlife Refuge, the Kanakanak Hospital, and the City of Dillingham.
* Presenting author
Literature Cited
1. NMFS. Conservation plan for the Cook Inlet beluga whale (Delphinapterus leucas). Juneau, AK; 2008.
2. O'Corry-Crowe GM, Dizon AE, Suydam R, Lowry LF. Molecular genetic studies of population structure and movement patterns in a migratory species: the beluga whale, Delphinapterus leucas, in the western Nearctic. In: Pfeiffer CJ, ed. Molecular and Cell Biology of Marine Mammals. Malabar, FL: Krieger Publishing Company; 2002:53–64.
3. Kellar NM, Trego ML, Marks CI, Dizon AE. Determining pregnancy from blubber in three species of delphinids. Marine Mammal Science. 2006;22(1):1–16.
4. Kellar NM, Trego ML, Chivers SJ, Archer FI. Pregnancy patterns of pantropical spotted dolphins (Stenella attenuata) in the eastern tropical Pacific determined from hormonal analysis of blubber biopsies and correlations with the purse-seine tuna fishery. Marine Biology. 2013;160(12):3113–3124.
5. Trego ML, Kellar NM, Danil K. Validation of blubber progesterone concentrations for pregnancy determination in three dolphin species and a porpoise. PLoS ONE. 2013;8(7):e69709. doi:10.1371/journal.pone.0069709.