4.1 Time since recolonization
Time since recolonization affects the prey composition of sea
otter diets. Although clams comprise the majority of the diet in all
regions of POW, there were differences in prey items across
recolonization zones. The areas of POW that have been colonized for the
least amount of time (zone 3, colonized for > 7 years) had
the lowest species diversity in prey and highest energy recovery rates.
In this zone, clams were overwhelmingly present in the diets of sea
otters. This was similar to previous studies in mixed sediment
communities in Southeast Alaska, where sea otters focus on fewer,
high-quality prey species (e.g., sea urchins in rocky habitats, large
clams in soft-sediment habitats) in newly occupied areas, and eventually
diversify prey species as sea otter populations persist . Lipid content
in sea otter diets was consistent across recolonization zones, but
overall energy rate gain was slightly higher in zone 3, which may be due
to the ability to obtain larger prey in newly colonized areas. Foraging
records for the areas where sea otters had been present the longest
(zone 1, colonized for > 30 years) had an intake rate that
was comparable to previous studies where sea otters were at carrying
capacity . This shows that the sea otters in this recolonization zone of
POW are likely at or near carrying capacity, which is in line with
modeling from aerial survey data from the region .
When considering sea otter diets and how sea otter invertebrate removal
can affect the nearshore system, it is important to look at diet
variation across recolonization zones as diets in the newly colonized
areas were less diverse, which is similar to past studies in Alaska . In
rocky habitats of Southeast Alaska and British Columbia, sea otters in
newly colonized regions consumed a majority of red sea urchins . In the
present study, the areas we observed where sea otters are newly
colonizing were soft-sediment habitat ripe with large butter clams,
which were the overwhelmingly predominant prey item.