What predicts a sea otter in Kachemak Bay

Sea otters are a keystone species: where they are, they decide what the kelp
forest looks like, because they eat what eats the kelp. They are federally
protected, their numbers rise in some places and fall in others, and managing
them well means knowing how many a stretch of coast can hold.

**That number — carrying capacity — depends on habitat, and habitat is exactly
what is poorly mapped in most of Alaska.** Species distribution models that
work well elsewhere assume good habitat data and long records of where the
animals have been. Southcentral Alaska has neither.

What the study did

The team used only open-access data and a presence-only model — MaxEnt,
maximum entropy — which needs nothing more than records of where otters have
been seen and habitat layers across the area. They asked which subtidal
features predict where northern sea otters (Enhydra lutris kenyoni) occur in
Kachemak Bay: substrate, algal cover, bathymetry, rugosity.

What predicts an otter

In order of influence:

1. Bathymetry — depth
2. Shell litter on the bottom
3. Filamentous algae
4. Understory kelp

Shell litter is the telling one. It is the leftovers of the otters' own meals,
which makes it both habitat and evidence.

What it leaves out, deliberately

Prey. Carrying capacity is set by food, and like many studies elsewhere this
one did not model prey directly because the data does not exist here. The
authors recommend it for the next round.

Why it matters past otters

The method's appetite for data is small: sightings plus scattered habitat
layers. That makes it usable for **other mobile marine megafauna in
data-poor waters** — and predicting where protected species will be is how
conflicts over fishing grounds and disturbance get avoided before they start.

Sources

Hasan, E. L., K. B. Gorman, H. A. Coletti and B. Konar. 2024. Species
distribution modeling of northern sea otters (Enhydra lutris kenyoni) in a
data-limited ecosystem. Ecology and Evolution 14(3): e11118. Written from
the National Park Service's summary, a work of the United States government
in the public domain.