Viability of a small, geographically-isolated population of beluga whale, Delphinapterus leucas: effects of hunting, predation, and mortality events in Cook Inlet, Alaska

Hobbs, Roderick C.; Wade, Paul R.; Shelden, Kim E. W.

doi:10.7755/mfr.77.2.4

Cited by 16 publications

(16 citation statements)

References 29 publications

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“…, Hobbs et al. ). These studies generally indicate these threats are associated with lower survival or fecundity, but the challenge remains to quantify their impacts and determine their relative role in CIB population decline.…”

Section: Discussionmentioning

confidence: 99%

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Relationship between per capita births of Cook Inlet belugas and summer salmon runs: age‐structured population modeling

et al. 2020

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Anthropogenic disturbances may alter a population's conservation status if the ability of individuals to survive and breed is affected. We used an adaptation of the Heligman-Pollard model to estimate survival at age of Cook Inlet belugas (CIB; Delphinapterus leucas), an endangered population in south-central Alaska. We developed an age-structured Leslie matrix model, based on the life history parameters survival and fecundity probability, to evaluate the sensitivity of population size and growth of CIB, to variation in estimate values of Chinook and coho salmon abundance in the Deshka River, a major tributary of the Susitna River. Birth effect (e b ) was regressed against Chinook and coho salmon levels for the year of, the year before, and two years before a beluga calf birth. The effect of a range of modifications of salmon availability was illustrated in CIB with a series of simulations. The maximum annual population growths (k) were set at 1.036 (3.6%). Ranges of CIB survival and fecundity probabilities indicated small changes in survival probabilities have a greater impact on population growth than similar changes in birth probability. As either survival (e s ) or fecundity (e b ) was reduced, the annual growth declined, with either e s = 0.961 or e b = 0.388, causing a decreased annual growth of À0.4%. Regressions of Chinook salmon for the year of, the year before, and two years before a birth were all significant at the 5% level as was coho in the year of and year prior to birth. The mechanism model with the best fit was the sum of Chinook and coho in the year of birth and year prior to birth. Simulations showed that if salmon runs remained at their current levels, the CIB population would likely continue its current slow decline and per capita births would continue to be low. The results from this study suggest reproductive success in CIB is tied to salmon abundance in the Deshka River. Current management practices should consider this when setting research priorities, designing new studies, and developing management actions to achieve CIB population recovery targets.

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Section: Discussionmentioning

confidence: 99%

“…While the CIB population decline and lack of recovery are well‐documented (Hobbs et al. , c, Shelden et al. ), data on the mechanisms influencing future population trajectories and potential recovery are lacking (Norman et al.…”

Section: Introductionmentioning

confidence: 99%

Relationship between per capita births of Cook Inlet belugas and summer salmon runs: age‐structured population modeling

et al. 2020

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“…At the population level, this information is necessary to assess demographics and viability and is crucial to the development and long term monitoring of conservation plans (Kersey and Dehnhard, 2014;Labrada-Martagón et al, 2014). For example, the endangered Cook Inlet stock of beluga whales in Alaska (USA) is one such population that will benefit from monitoring reproductive status; improved understanding of the demographics of the population could aid in the identification of factors limiting population recovery (Hobbs et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Testosterone and progesterone concentrations in blow samples are biologically relevant in belugas (Delphinapterus leucas)

Richard

Robeck

Osborn

et al. 2017

General and Comparative Endocrinology

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Steroid hormone analysis in blow (respiratory vapor) may provide a minimally invasive way to assess the reproductive status of wild cetaceans. Biological validation of the method is needed to allow for the interpretation of hormone measurements in blow samples. Utilizing samples collected from trained belugas (Delphinapterus leucas, n=20), enzyme immunoassays for testosterone and progesterone were validated for use with beluga blow samples. Testosterone concentrations in 40 matched blood and blow samples collected from 4 male belugas demonstrated a positive correlation (R=0.52, p<0.0001). Progesterone concentrations in 64 matching blood and blow samples from 11 females were also positively correlated (R=0.60, p<0.0001). Testosterone concentrations (mean±SD) in blow samples collected from adult males (119.3±14.2pg/ml) were higher (p<0.01) than that of a juvenile male (<8years) (59.4±6.5pg/ml) or female belugas (54.1±25.7pg/ml). Among adult males, testosterone concentrations in blow demonstrated a seasonal pattern of secretion, with peak secretion occurring during the breeding season (February-April, 136.95±33.8pg/ml). Progesterone concentrations in blow varied by reproductive status; pregnant females (410.6±87.8pg/ml) and females in the luteal phase of the estrous cycle (339.5±51.0pg/ml) had higher (p<0.0001) blow progesterone concentrations than non-pregnant females without a corpus luteum (242.5±27.3pg/ml). Results indicate that blow sample analysis can be used to detect variation in reproductive states associated with large differences in circulating testosterone or progesterone in belugas.

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“…Population estimates since listing have ranged from 284 to 375 CIB (Hobbs, Shelden, Rugh, Sims, & Waite, ; Shelden et al, ), down from estimates of over 1,000 whales in the late 1970s and early 1990s (Shelden et al, ). This decline was attributed to unrestricted hunting by Alaska Natives in the 1990s (Mahoney and Shelden, ; Hobbs et al, ).…”

Section: Reproductive Status Of Known‐age Female Beluga Whales Necropmentioning

confidence: 99%

Reproductive status of female beluga whales from the endangered Cook Inlet population

Shelden

Burns²,

McGuire³

et al. 2019

Marine Mammal Science

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Following a moratorium on hunting in 1999, comanagement agreements between the National Marine Fisheries Service (NMFS) and two Alaska Native hunting cooperatives allowed takes of only one whale per cooperative per year.However, the population has not shown signs of recovery , and hunting was not permitted after 2006. The seasonal range of the population has steadily contracted from all of Cook Inlet to the point that it is now almost entirely limited to the northern (upper) part (i.e., north of East and West Foreland) during the summer and autumn (Rugh, Shelden, & Hobbs, 2010;Shelden et al., 2015). A lack of basic life-history information has hampered

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Viability of a small, geographically-isolated population of beluga whale, Delphinapterus leucas: effects of hunting, predation, and mortality events in Cook Inlet, Alaska

Abstract: ABSTRACT-A genetically distinct population of beluga whales,

Cited by 16 publications

References 29 publications

Relationship between per capita births of Cook Inlet belugas and summer salmon runs: age‐structured population modeling

Relationship between per capita births of Cook Inlet belugas and summer salmon runs: age‐structured population modeling

Testosterone and progesterone concentrations in blow samples are biologically relevant in belugas (Delphinapterus leucas)

Reproductive status of female beluga whales from the endangered Cook Inlet population

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