Dead tomcod washed up on West Beach

Observation by Sara Germain:

Dozens of tomcod washed up on West Beach today. A fisheries biologist reported seeing a couple pods of 20 beluga along the coast over the weekend, perhaps it was related to the beluga?

LEO Says:

Thank you Sara for sharing this observation. There have been other observations about tomcod die-offs in recent years, but this is the first in association with pods of beluga whales. While beluga do feed on fish including tomcod, and are know for hunting fish in groups, we do not have records in LEO of any related beaching of fish. We will reach out to the broader network for more knowledge on beluga behavior. A summary of past LEO posts on tomocods is provided below. Also see comments from Verena Gill and colleagues, about beluga whale effects on salmon behavior. M. Brubaker

Comment from Verena Gill and colleagues, NOAA Fisheries:

I have never seen salmon beach themselves in response to belugas. I have seen belugas in a few feet of water use their tails to perhaps stun the fish but maybe this was on the Susitna Delta and the banks were so slick, muddy and steep with a fast current that fish beaching would not have occured. I was talking to Madi Kosma who is currently in Nome doing drone work with belugas for her PhD. She showed me some footage of belugas right next to the shore possibly chasing tomcod. She said they have been chasing tomcod all week. But she has not seen any tomcod beached and like us she has heard these fish do not jump.

I am curious if the tomcod were freshly dead on the beach, around the time the belugas were observed nearby. I do know that salmon will jump out of water (not their normal jumping behaviors) to avoid belugas, and this is particularly true along the banks of Eagle River. However, these steep banks don't allow the fish to beach themselves. We have seen belugas get very close to shore, south of Cairn Point (before the Port's fill), chasing salmon, but I never saw salmon beach themselves.

AI Comment from GPT 5:

Belugas were noted locally, but in similar events documented around the region, investigators have focused on multiple potential stressors and recommended sampling to determine cause. Here is how the related posts line up with this observation:

• Dead Smelt (Osmerus mordax) and Tomcod (Microgadus proximus) Scattered for Miles along Beach (Teller, Jun 2019): Widespread smelt and tomcod mortality with unknown cause; “suboptimum environmental issues” were suspected. In 2019, unusually warm river water and low oxygen were linked to salmon deaths, and seabird necropsies indicated starvation.

• Krill (Thysanoessa spinifera) Found Washed Up on Beach (Unalaska, Jul 2019): Krill washed up while humpback whales fed offshore; samples were tested for toxins. Krill die‑offs have been associated with hypoxia, excess sediment, and temperature changes.

• Dead Tomcod (Microgadus proximus) on Beach (Teller, Jun 2020): Repeated tomcod mortality; recommended collecting fish and water samples. Potential drivers discussed included hypoxia, algal blooms, high temperatures, storm activity, chemical spills, and runoff.

• Lots of dead krill washed up on Sarichef Island (Shishmaref, Sep 2022): Krill die‑off with no definitive cause; hypotheses included hypoxia, sediment, and temperature shifts.

• Fish die off near Kotzebue (Cape Blossom, Sep 2022): Beach full of fish; harmful algal toxins were considered given high Alexandrium in Norton Sound and concurrent krill die‑off. A storm event was also noted as a possible factor. Guidance emphasized testing freshly dead fish to rule out infections and assess toxins. Tests of the fish did not show any sign of harmful algae.

Taken together, prior posts in this region highlight several working hypotheses—hypoxia, warm water, storm activity, and harmful algal toxins (including Alexandrium)—and emphasize sample collection to sort among them [2019–2022 posts cited above]. While marine mammals have been observed near some events (e.g., humpbacks during the Unalaska krill stranding), a causal link was not established in those posts.

If sampling is possible, the approaches described in 2020 and 2022 could help here: retain a few freshly dead tomcod (clear eyes, pink gills, no strong odor) chilled for toxin and pathology screening, and collect concurrent water samples for temperature, dissolved oxygen, and phytoplankton/HAB analysis, including Alexandrium [2020 Teller; 2022 Shishmaref; 2022 Cape Blossom].