Fish stories

Biologists participating in the 2022 International Year of the Salmon expedition documented the first occurrence of the lowcrest hatchetfish (Argyropelecus sladeni) in Alaska waters. This species of hatchetfish was reported from the Commander Basin in the western Bering Sea in 1992. Marine hatchetfishes (family Sternoptychidae) are exceedingly rare in Alaskan waters. Only three earlier Alaskan occurrences of sternoptychid fishes are known, corresponding to the species: A. lychnus, Sternoptyx obscura, and an unidentified specimen assigned to the genus Argyropelecus. In the coming months, we anticipate adding this new record and specimen of lowcrest hatchetfish, along with a few other interesting findings from the IYS cruise, in the fish collections at the University of Alaska Museum.

Sternoptychids spend their time in water depths where light is a precious tool due to its scarcity. The large upward pointing eyes helps these fishes track faint outlines of potential prey times. The downward facing rows of light producing organs (known as photophores) likely help hatchetfish minimize the contrast made by their own downward projecting profiles against the faint light coming from above.

(Photo by Tommy Sheridan)

The fish collection at the UAMN is now the repository of three paratypes of Trachydoras gepharti (UAM 3877), a species of doradid hard-nosed thorny catfish described from the Orinoco basin by Sabaj & Arce Hernández in 2017. These specimens were collected in 2004 from the Ventuari River. Other specimens from that collection are now housed in museum collections from across the world. The holotype specimen (ANSP 203169) is housed at the Academy of Natural Sciences in Philadelphia.

We used so-called 'DNA barcoding' to determine the species identity of lampreys found in the stomachs of Northern Pike (Esox lucius) caught in May 2021 in Alexander Creek (Susitna River drainage) as part of efforts by the Alaska Department of Fish & Game to eradicate or control invasive populations of this species. Interestingly, DNA barcoding shows that these pike stomachs contained both Arctic (Lethenteron camtschaticum) and Pacific lamprey (Entosphenus tridentatus) remains! Southcentral Alaska represents an overlapping species boundary between these two species. The Pacific lamprey becomes progressively more widespread and common to the south and east. The Arctic lamprey shows the opposite pattern and becomes the dominant species of lamprey in Bering Sea draining rivers of Alaska.

Olin Halsten with the Center for Environmental Management of Military Lands (Colorado State University) documented an odd looking population of salmon while conducting surveys on Shemya Island (Aleutian archipelago). DNA sequences from three individuals collected by Halsten point to sockeye / kokanee salmon (Oncorhynchus nerka). A passing reference from a 1974 environmental impact statement suggests these fish are descendants from translocated kokanee salmon. The tissue samples provided by Halsten are archived at the University of Alaska Museum (UAM 4014).