Watercraft inspection crews stationed along key Idaho roadways are busier this year following a fall 2023 effort to eradicate invasive quagga mussels discovered in the Middle Snake River near Twin Falls.

Quagga and zebra mussels can cause serious damage to irrigation infrastructure, municipal water systems and hydroelectric power facilities. The mussels can hitch a ride on watercraft and waterborne equipment as it is transported.

Last year’s quagga discovery in south-central Idaho, through routine State Department of Agriculture monitoring, prompted a multi-agency eradication effort — post-treatment monitoring continues — as well as additional state program spending and regulation.

The state has 20 inspection and decontamination stations and five roving crews. New facilities this year are at Bonners Ferry near the Canadian border and Centennial Riverfront Park, near where quagga mussels were discovered in late September. Centennial has special rules.

Crews had inspected 102,000 watercraft and decontaminated just under 5,000 as of Aug. 2, about halfway through the state’s typical recreational boating season, said Nic Zurfluh, ISDA Invasive Species Bureau chief. Both totals are up.

Inspections totaled about 70,000 in the year-earlier period. The current total better reflects individual watercraft such as those hauled by a single vehicle, he said.

“Overall statewide, we see an increase of watercraft inspection, an increase of movement and an increase of compliance,” Zurfluh said.

The legislature this year required all out-of-state watercraft to be inspected and decontaminated at a watercraft inspection station prior to launch. A free inspection at one of the stations is valid in Idaho and other Northwest states.

Out-of-state owners also must buy an Idaho invasive-species program sticker. Inflatable, non-motorized craft less than 10-feet long are exempt.

Another new law requires all watercraft operators, including Idaho residents, to remove drain plugs and to drain all water before transport. All plugs and barriers must remain open during transport.

The department has been communicating the new requirements, which took effect July 1, with help from cooperating agencies, Zurfluh said. This month, ISDA plans public messaging about the importance of cleaning, draining and drying watercraft.

As for drain-related requirements, “it’s up to the boat owner to know the boat and which plugs need to be removed,” he said. However, staff at the inspection stations, ISDA regional offices and local boat shops are available to help people in advance.

At Centennial Waterfront Park near Twin Falls, all watercraft must be inspected before entering the river, and inspected and decontaminated on exit.

So far, entry and exit inspections at Centennial total 7,521 combined, Zurfluh said. Required decontaminations on exit total 3,872. Not all craft entering require decontamination.

ISDA has been working with Twin Falls County on various improvements to the Centennial station, he said. Meanwhile, boaters are “learning about the process and staying patient” and inspectors are getting more efficient.