New Paper - Detecting population trends for US marine mammals

Easton R. White January 05, 2022

We have a new paper out today on trends for US marine mammal populations.

Easton R. White, Zachary Schakner, Amber Bellamy, and Mridula Srinivasan Detecting population trends for US marine mammals. Conservation Science and Practice

A few key takeaways:

Despite their importance, we found that only 20\% (n = 49) of marine mammal stocks had some form of trend analysis to study changes over time
We found that of marine mammal stocks with trend analysis, 61\% were increasing, 12\% of stocks were decreasing, and 27\% percent were defined as stable. This is good news! But we still need to assess more stocks
We also used various time series techniques to show that seven sampling events over more than 10 years were needed for a high statistical power. This is very different than previous estimates for marine mammals

$(Left column) Estimated relative abundance for three well-studied species: Killer whale (Orcinus orca—Northern Resident Stock), beluga whale (Delphinapterus leucas—Cook inlet stock), and humpback whale (Megaptera novaeangliae—CA/OR/WA stock); (middle column) statistical power (fraction of subsamples with significant trends from linear regression) for different lengths of sampling; (right column) statistical power as a function of the length of the time series and number of sample$

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