Attendees looking att he Pettit Lake Weir while on a tour May 19.
By DANA HERNANDEZ
PETTIT LAKE — The Shoshone-Bannock Tribes hosted a tour of the newly completed Pettit Lake Weir facility on May 19.
The tour consisted of viewing the smolt fish that were trapped at the weir overnight and viewing the process of tracking and clipping the fish, which was done by Lead Technician Rob Trahant and Project Leader Rebecca Croy. Kurt Tardy who manages the Shoshone-Bannock sockeye salmon recovery program gave the tour to attendees.
Tardy also acknowledged the design team, HDR and the ground team, Clear Water Construction who built the weir. He also acknowledged his team, Trahant and Croy and said, “Whatever I do, these two are behind the scenes that make things go, they do a lot of hard work and spend a lot of days out here,” said Tardy.
A ground breaking event for the facility took place in the fall of 2020. The Pettit facility is located 18 miles from Stanley and will serve as the sockeye salmon restoration site. The Shoshone-Bannock Tribes have been managing the recovery of the sockeye salmon, from getting it listed as an endangered species to rebuilding the Pettit Lake Weir, which sits just down the stream from the older weir.
Tardy said, “The lake is primary for the recovery of the sockeye and it’s near and dear to the Shoshone-Bannock Tribes. The sockeye is tied to the Tribes’ culture and has the longest and highest distance to travel than any other fish. We will continue the process to restore it to future generations.”
Kurt Tardy next to a salmon adult trap box.
He went on to say, they replaced the unsafe previous design that trapped everything. The problem was the water back up that led to safety concerns with the staff because they had to stay up all night and take naps in the trucks in order to clean the weir 24/7 just to be able to continue operating it.
The new weir maintains the original stream channel and can handle a wide range of flows, and is also raised to stop the migrating salmon. Tardy said, “The design runs clean, it captures fish, and requires less handling and is less intrusive.”
To create the structure, they had to divert all the water in the stream. Tardy said, “To create something new and improved, you have to destroy something, unfortunately, but we wanted as little impact as possible. We did not want to destroy the old environment more than we had to. We maintained the same footprint of where the old weir was and put back everything from trees and rechanneling the river exactly the way it was.”
The construction crew helped maintain the integrity and saved the trees and willows. In a few years the area will be revegetated and will look like they had little impact to the area. The last plan is to hydro seed the entire area, they are going to give back to nature what they took from building it.
So far, the facility has handled 2,000 out migrating juvenile salmon, all of which were wild in origin. The weir is an efficiency weir and it will not capture everything and some of the fish will go out the back side and continue their migration. Since they handled 2,000 out migrating salmon at a 30% efficiency rate, they are estimating a migration for this year to be 8,000-9,000 migrants leaving Pettit Lake and is something not seen in more than 10 years.
The captured fish will go through processing, which is done by Trahant and Croy, and who only tag 10% with pit tags and genetically mark the rest of them, overall they handle 30% of the fish at the weir.
When first pulling the smolts from the weir, Trahant and Croy check each fish to see if the anal fin is clipped, they keep the fish that have the fin intact and release the ones whose fin is clipped. The clip is small and is used for genetic sampling and to mark recaptures. The clip provides identification of who the fish’s parents were, when it entered the lake, what origin it is and which one from that is the male or female. Tardy said they want to maintain a hands off approach as much as possible while collecting research to make sure what they are doing is being adaptively managed in the right direction.
Overall, it’s knowing what parent grouping is most successful so they can adjust what goes into the lake. The recaptures give an efficient estimate on how well the weir is doing. “We want to continue building what we started, last year, we had 38 fish and we want to see an increase every year and an increase in the average overtime,” said Tardy.
A juvenile smolt fish being checked for fin clipping.
The weir is also a bi-purpose weir for adult sockeyes, it uses stainless steel boxes and during the fall season the boxes will be raised straight up out of the water for adult salmon trappings. There are groves on the structure where picket panels are placed in each bay, this allows the sockeye adult salmon that swim upstream to navigate their way across the picket panels to the head gate and into the adult trap box. The trap box is 6 feet deep with a pulley floor system and can hold up to 50 adult salmon. There will also be a cascading flow from the creek into the head box and trap box. Tardy said, “the box is an innovative design and is friendly for the fish and for us.”
The smolts that are captured and marked now, will be returning to Pettit Lake as adults in 2023. The out migration for sockeye salmon smolts in the spring lasts from mid-April to the beginning of June. The adult sockeyes are in the process of migrating back to Idaho now and once they return they spawn in October and early November. Tardy said at the end of the first week of November they go out and do red counts to estimate the success of the spawns from the lake. He also said the likely hood of an adult sockeye returning to the Pettit Lake is very high due to the fish’s otolith bone, which senses where it came from so it can return to the correct lake of origin. The otolith bone also tracks the different water chemistries along its journey and Tardy said they can track when it has turned into a smolt and how long it has been in the ocean.
Fort Hall representatives at the Pettit Lake Weir.
Tardy said the Pettit returning fish also have to go thru the Sawtooth hatchery. He said, “we have to make some improvements in that hatchery as we move forward, it does not do a good job at trapping the returning adult sockeye. It works great with chinook, but not sockeye.”