Overwintering Locations, Migrations, and Fidelity of Radio-Tagged Dolly Varden in the Hulahula River, Arctic National Wildlife Refuge, 2007–09

Abstract

ABSTRACT. Essential overwintering habitats for anadromous Dolly Varden Salvelinus malma on Alaska's North Slope appear to be limited to a small number of perennial springs, primarily in eastern Brooks Range drainages. Because future petrochemical development in the region continues to be a possibility, and development would require large quantities of freshwater, we sought to identify and document the overwintering areas used by Dolly Varden in the Hulahula River, eastern Brooks Range. In August 2007, we implanted 52 Dolly Varden with multi-year radio transmitters at a known overwintering area in the lower Hulahula River. Other wintering areas were located during 11 aerial surveys conducted over the next 2.5 years. A stationary receiver located in the lower Hulahula River provided migration timing information. Radio-tagged Dolly Varden used four discrete areas with perennial springs for overwintering in the Hulahula River drainage. The springs, totaling approximately 12 km in stream length, were located between river km 40 and 105. Radio-tagged Dolly Varden migrated downstream on their way to the Beaufort Sea in early June. Most tagged fish known to have survived the summer at sea returned to the Hulahula River during late July and August, but seven fish overwintered in other North Slope drainages. Within the Hulahula River drainage, 15 fish overwintered in more than one area during the three winters of the project, but only the four identified perennial spring areas were used. These data clearly indicate that the perennial springs in the Hulahula River are essential overwintering habitats for Dolly Varden.

New Insights into the Biology of Anadromous Dolly Varden in the Canning River, Arctic National Wildlife Refuge, Alaska

“…Data were recorded on FL, sex (based on the distinctive kype or rostrum notch in males: Morton ), and spawning condition (prespawner or nonspawner based on bright orange or red coloration of prespawners and silver or pale coloration of nonspawners, as illustrated in Brown et al. ) for each fish. Anesthetized fish were placed in a V‐shaped cradle, and water was delivered to their gills throughout the surgery.…”

“…Following the first tagging season, fall or spring aerial surveys were conducted to document tagged fish that may have migrated into other eastern Arctic rivers with known spawning and overwintering habitats: these were (from west to east) the Anaktuvuk River (Bendock ), tributaries of the Sagavanirktok River between the Echooka River and Accomplishment Creek (Craig and McCart ; Furniss ), the Kavik River, the Hulahula River (Brown et al. ), spring systems on the Aichilik and Egaksrak rivers (Craig and McCart ), the Kongakut River (Craig and McCart ; Brown et al. ), and the upper Firth River including Joe Creek (Kristofferson et al.…”

“…), spring systems on the Aichilik and Egaksrak rivers (Craig and McCart ), the Kongakut River (Craig and McCart ; Brown et al. ), and the upper Firth River including Joe Creek (Kristofferson et al. ; Harris et al.…”

“…Brown et al. () used similar transmitters and tracking procedures with Dolly Varden in the Hulahula River and reported transmitter identification out to as much as 5 km or more in the same eastern Arctic rivers. Therefore, we expected similar reception quality during our aerial surveys.…”

“…Finally, we used a two‐proportion Z ‐test of the null hypothesis that the uncorrected interdrainage exchange rate for fish tagged in the Canning River was similar to that reported by Brown et al. () for fish in the Hulahula River (0.205).…”