Population changes in a whale breeding ground revealed by citizen science noninvasive genetics unique microsatellite profiles of southern right whales

Historical exploitation, and a combination of current anthropogenic
impacts, such as climate change and habitat degradation, impact the
population dynamics of marine mammalian megafauna. Right whales (Eubalaena
spp.) are large cetaceans recovering from hunting, whose reproductive and
population growth rate appear to be impacted by climate change. We apply
noninvasive genetic methods to monitor southern right whale (E. australis,
SRW) and test the application of noninvasive genetics to minimise the
observer effects on the population. Our aim is to describe population
structure, and interdecadal and interannual changes to assess species
status in the Great Acceleration period of Anthropocene. As a basis for
population genetic analyses, we collected samples from sloughed skin
during post-migration epidermal moult. Considering the
exploration-exploitation dilemma, we collaborated with whale-watching
companies, as part of a citizen science approach and to reduce ad hoc
logistic operations and biopsy equipment. We used mitochondrial and
microsatellite data and population genetic tools. We report for the first
time the genetic composition and differentiation of the Namibian portion
of the range. Population genetic parameters suggest that South Africa
hosts the largest population. This corresponds with higher estimates of
current gene flow from Africa compared to older samples. We have observed
considerable interannual variation in population density at the breeding
ground and an interdecadal shift in genetic variability, evidenced by an
increase in the point estimate inbreeding. Clustering analyses confirmed
differentiation between the Atlantic and Indo-Pacific, presumably
originating during the ice ages. We show that population monitoring of
large whales, essential for their conservation management, is feasible
using noninvasive sampling within non-scientific platforms. Observed
patterns are concurrent to changes of movement ecology and decline in
reproductive success of the South African population, probably reflecting
a large-scale restructuring of pelagic marine food webs.