Conceptual Models Should Make Sense out of Relationships (Text Version)

Seal
Receptor/response: Fewer fish means females must travel further to find food. Increased time away from pups means they may not get as much milk.

Since sea ice breaks up earlier, mother seals may lose track of their pups. Separated from their mothers, pups may be forced out on their own before they are ready, and have less chance of survival.

The Yupik People
Source and effect: Especially with walrus and seal populations declining, the Yupik’s last reserves to feed themselves are the very fish whose breeding grounds are being reduced.

Walrus
Receptor/response (effect): Because the edge of the sea ice is further out to sea in deeper water, walrus — which rest on the ice and feed on the bottom — must dive deeper to feed and find less food, causing their weakened condition. Walrus are looking thinner, and their blubber is less nutritious.

Killer Whales
Receptor/response, secondary stressor: Fewer fish and seals prompt orcas to turn to sea otters for food.

Primary and secondary stressors:
Global warming is Causing sea ice retreat in the Arctic.

Kelp
Receptor/response: More grazing by sea urchins means less kelp.

Tertiary stressor: Less kelp means less nursery area for fish.

Sea Otters
Receptor/response: Since there are fewer seals, orcas have begun preying on sea otters.

Secondary stressor: Sea otters eat sea urchins.

Sea Urchins
Receptor: With less predation by sea otters, sea urchin populations increase.

Secondary stressor: Sea urchins' favorite food is the kelp that provide the breeding grounds for the fish, so more sea urchins will mean less kelp.

Fish
Receptor/response: Less nursery area means lower survival and recruitment and less fish biomass.

Tertiary stressor: Less fish means less food for walrus, seals, orcas, sea otters, and humans.