A Shoshone-Bannock fisheries technician installs an egg box filled with Chinook
salmon eyed-eggs.
By KEATS CONLEY
Anadromous Fish Program, Fish and Wildlife Department, Shoshone-Bannock Tribes
PANTHER CREEK — Panther Creek, a tributary of the upper Salmon River, is an aboriginal fishing area for the Shoshone and Bannock peoples. Once, Panther Creek supported as many as 2,000 spawning Chinook Salmon, but mining activities completely wiped out the population by the late-1960s.
In 2014, the Shoshone-Bannock Tribes began supplementing Panther Creek with Chinook Salmon using a “concrete-to-gravel” approach. Pahsimeroi Fish Hatchery provides eyed-eggs, which the Tribes transport to Panther Creek in coolers and plant in custom-made incubators called “egg boxes.” The egg boxes are buried in the riverbed and anchored in place with rebar. In the spring, fry can swim out of the box to rear in the creek just like natural fish.
Determining if and how well egg boxes work is challenging. Unlike hatchery juveniles released as smolts, fish from egg boxes cannot be physically marked with an adipose fin clip or other tag. They do not imprint on a hatchery—instead, they rear naturally in the gravel and should return to Panther Creek as adults. Both as juveniles and as adults, fish from egg boxes look just like natural fish. To determine if egg boxes worked, we rely on trapping fish, coupled with genetics.
In 2018, the Tribes operated the first picket weir in Panther Creek to count returning adult Chinook Salmon and collect tissue samples for genetic analysis. The weir forms a V-shaped fence across the creek, funneling upstream-swimming adult Chinook through a chute and into a trap box. Staff check the trap box each morning and collect a small tissue sample from each fish. We then analyze the tissue samples using genetics to determine if the parents of the fish came from a hatchery or not. By using a database that tracks all of the parent fish used as broodstock for the Panther Creek egg box program, we can calculate the proportion of outmigrating juveniles and returning adults that came from an egg box.
The Tribes trapped 146 Chinook Salmon at the Panther Creek weir in 2018. This year we analyzed those tissue samples to determine if any of the 2018 adults came from egg boxes outplanted in 2014 (i.e., as 4-year old adults). Unfortunately, we found that none of the 2018 returns came from egg boxes. However, 2014 was the program’s pilot year. In following years, changes in box design and installation techniques drastically improved juvenile production. We estimated egg boxes contributed only 6% of juvenile production in Panther Creek in 2014, increasing to 22% in 2015 and 53% in 2016. Weir trapping in 2019 will determine if any adults were produced from egg boxes in 2015, when the Tribes supplemented almost 700,000 eggs in Panther Creek—the highest amount in the program’s history.
This year will be critical in determining the contribution of the egg box program to the recovery of Chinook Salmon in Panther Creek. So far, the Tribes have trapped over fifty adults in Panther Creek, with more still making their way up to the weir. We hope our genetic evaluations will show that some of these fish started their long journey from an egg box.