Assessing cetacean populations using integrated population models: an example with Cook Inlet beluga whales

Abstract

Effective conservation and management of animal populations requires knowledge of abundance and trends. For many species, these quantities are estimated using systematic visual surveys. Additional individual‐level data are available for some species. Integrated population modeling (IPM) offers a mechanism for leveraging these data sets into a single estimation framework. IPMs that incorporate both population‐ and individual‐level data have previously been developed for birds, but have rarely been applied to cetaceans. Here, we explore how IPMs can be used to improve the assessment of cetacean populations. We combined three types of data that are typically available for cetaceans of conservation concern: population‐level visual survey data, individual‐level capture–recapture data, and data on anthropogenic mortality. We used this IPM to estimate the population dynamics of the Cook Inlet population of beluga whales (CIBW; Delphinapterus leucas) as a case study. Our state‐space IPM included a population process model and three observational submodels: (1) a group detection model to describe group size estimates from aerial survey data; (2) a capture–recapture model to describe individual photographic capture–recapture data; and (3) a Poisson regression model to describe historical hunting data. The IPM produces biologically plausible estimates of population trajectories consistent with all three data sets. The estimated population growth rate since 2000 is less than expected for a recovering population. The estimated juvenile/adult survival rate is also low compared to other cetacean populations, indicating that low survival may be impeding recovery. This work demonstrates the value of integrating various data sources to assess cetacean populations and serves as an example of how multiple, imperfect data sets can be combined to improve our understanding of a population of interest. The model framework is applicable to other cetacean populations and to other taxa for which similar data types are available.

Distribution and habitat use by endangered Cook Inlet beluga whales: Patterns observed during a photo‐identification study, 2005–2017

“…Whether the NMFS abundance trends reflect true changes in abundance or instead demonstrate how sensitive the methods used to estimate abundance are to changes in spatial distribution is unclear. An integrated population model, derived from the aerial survey data, hunt data, and our photo‐id data, had noted a change in group sizes detected during aerial surveys in 2010–2016, but concluded that it was uncertain whether the apparent decrease in group sizes was real or instead reflected a decrease in the proportion of groups counted by the survey (Jacobson et al, 2020). The contrast between our higher counts after 2010 and NMFS lower population estimates and smaller group sizes after that year are noteworthy and may suggest that temporal and spatial aggregation patterns have shifted in recent years.…”

A Systematic Review Demonstrates How Surrogate Populations Help Inform Conservation and Management of an Endangered Species—The Case of Cook Inlet, Alaska Belugas

“…Realizing the diminished population status of CIB, Alaska Natives drastically reduced their hunting practices voluntarily between 2000 and 2004 through co-management agreements. The last CIB confirmed take by subsistence hunting was in 2005, with no co-management agreements being requested for CIB harvest since the end of the 2006 season (Huntington, 2000;NMFS, 2016;Jacobson et al, 2020). A "take" is defined by the U. S. Marine Mammal Protection Act as any action that seeks "to harass, hunt, capture, or kill or attempt to harass, hunt, capture, or kill any marine mammal" [16 U.S.C.…”

Incorporating Batch Mark–Recapture Data into an Integrated Population Model of Brown Trout

“…Integrated population models have been used extensively in fisheries (Wilberg et al 2005;Punt et al 2010;Brenden et al 2012;Goethel et al 2015;Jacobson et al 2020;Moremede et al 2020) and wildlife management (Rhodes et al 2011;Arnold et al 2018;Horne et al 2019;Messmer et al 2020). However, their use is typically FIGURE 8.…”