Life History, Contaminant and Histopathologic Assessment of Beluga Whales, Delphinapterus leucas, Harvested for Subsistence in Cook Inlet, Alaska, 1989-2005
Kathy Burek-Huntington, Kim Shelden, Kim Goetz, Barbara Mahoney, Dan Vos, Jessica L. Reiner, Jennifer Hoguet, Greg O'Corry-Crowe
Throughout the State of Alaska, ranging from the eastern Beaufort Sea to Bristol Bay, and within the boundaries of Cook Inlet, belugas are an important subsistence resource for Native communities. Cook Inlet belugas (CIBs, Delphinapterus leucas) are geographically and genetically isolated from the other Alaska beluga stocks. CIBs are critically endangered and reside year-round adjacent to Anchorage. Prior to 1999, there were no restrictions on the number of CIBs subsistence harvested. Following a voluntary suspension of the hunt and a moratorium in 1999, harvest of a limited number (1-2 CIB per year) occurred until 2007. This report provides a retrospective analysis of samples collected from subsistence harvested CIBs from 1989 to 2005. Data include prey items from stomach contents, reproductive parameters from ovaries and testes, contaminant analysis from blubber and liver (including several persistent organic pollutants (POPs), per- and polyfluroalkyl substances (PFAS), and total mercury), and pathology including gross and histologic findings. The purpose of this review is two-fold: to develop a baseline from CIBs harvested during the period of population decline (i.e., 1991-2004) and to determine if there are any indicators to explain what may be causing the current decline since 2010. Harvested CIBs were on average 20 years old (range 2-33 years old). Eulachon and salmon were the primary prey item consumed. This was not unexpected because the hunt coincided with the arrival of anadromous fish returning to the inlet's rivers to spawn. Of 11 females in the harvest whose reproductive tracts were examined, 2 (18%) were not pregnant, 2 (18%) were newly pregnant, and 7 (64%) had term fetuses or had recently given birth. The high proportion of CIB females who were pregnant or recently postpartum is likely due to the timing of the harvest which began prior to and continued throughout the CIB birthing season which ranges from July through October. Of the contaminants examined, both mirex and mercury showed a significant increase in concentration with body length with no detectable difference between sexes. This is likely due to the weak offloading tendency of mirex and limited transference of mercury from mother to fetus. Concentrations of many of the other POPs analyzed (e.g., PCB, DDT, chlordanes, HCH, chlorobenzenes, and α-HBCD) were significantly higher in males than in females, and within females, concentrations were higher in those that were pregnant versus lactating. PBDEs and α-HBCD significantly increased from 1995 to 2005 for both sexes, with males showing higher concentrations of α-HBCD than females. Overall, levels were higher in CIBs than other Alaska beluga populations which may be due to proximity to Anchorage and industrial activities. On gross pathology, the parasitic nematode Crassicauda giliakiana was prevalent in 64% of CIB kidneys, which is higher than in other Alaska beluga populations. On histopathology, most of the lesions in blubber, kidney, lung, and stomach were confirmed to be caused by parasitic nematodes or were consistent with the effects of these parasites. Overall, histopathology of harvested CIBs does not differ markedly from other beluga populations. There is some suggestion that pollutants such as flame retardants have increased over time, but it is unclear if levels would significantly affect CIB fetal development although congenital defects have recently been documented in this population. Of note, CIBs do have a high rate of C. giliakiana in the kidneys compared to other beluga populations. Determining whether this parasite has an effect on renal function in severe cases would be of interest. Because only the skin and blubber are consumed by hunting communities, and in relatively small amounts, it is unlikely that parasites or pollutants would accumulate to levels that would cause illness or death in humans. Based on these findings, the lack of the CIB population recovery is unclear.
, Shelden, K.
, Goetz, K.
, Mahoney, B.
, Vos, D.
, Reiner, J.
, Hoguet, J.
and O'Corry-Crowe, G.
Life History, Contaminant and Histopathologic Assessment of Beluga Whales, Delphinapterus leucas, Harvested for Subsistence in Cook Inlet, Alaska, 1989-2005, NOAA Tech. Memo. NMFS-AFSC-440, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935389
(Accessed March 27, 2023)