Ausable River group bolsters federal salmon study

By Mike Lynch

First they studied fins. Now they’ll study fish feces.

In a new population study, the U.S. Fish and Wildlife Service this fall used fish DNA to examine salmon populations in Champlain Lake tributaries. 

Next spring, the Ausable River Association will augment the work, applying environmental DNA methods at the Boquet River to find young salmon. 

ASRA Biodiversity Manager Carrianne Pershyn said her organization will be using eDNA to look for evidence of fry (newly hatched fish) near spawning beds known as redds. The efforts will help the agency track spawning success and allow researchers to target their fish surveys where evidence is found.

Federal researchers embarked on a 9-year stocking study in 2021. It relies on parentage based tagging, a novel method of tracking fish by tracing their familial roots through DNA. This method requires taking part of a fin from a captured salmon and matching it against a salmon DNA database to determine the fish’s roots. 

The study is evaluating salmon in the Lake Champlain watershed, including the Saranac, Boquet, and Ausable rivers. 

The data gathered will help the agency evaluate their stocking methods and determine which genetic strains of salmon are reproducing successfully. It aims to build upriver runs and natural reproduction.  

While the federal study relies on DNA from fish fins, eDNA studies rely on getting genetic material from free floating particles of genetic material released by fish through skin cells, reproductive cells, or feces. 

Scientists are able to capture the genetic material by running river water through a filter. The material is later tested in a lab. Pershyn said positive results can indicate the presence of the fish within a kilometer of where the water was found. She will be looking at smaller target areas. 

ASRA started the field work last spring by collecting eDNA from redd sites from Willsboro to Lewis on the Boquet.

The test results from 2021 are due this winter, she said. Those results will help guide ASRA’s upcoming water sampling plan. 

While last year’s lab results took a long time to process, Pershynn said the results from the spring samples are expected to come back in just a couple weeks, which will allow the fish and wildlife workers to return to the sites promptly. 

Traditionally, small fish have been detected in rivers and streams through electrofishing. This method entails sending an electrical current through the water to temporarily stun and then net the fish.

Pershyn said the environmental DNA technique would eliminate “extensive” electrofishing.

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In addition to being used for the multiyear stocking study, the eDNA results will be submitted to the the publicly-available Aquatic eDNA Atlas, a federal database that can be used for state and regional research efforts and management plans, including the larger Lake Champlain salmon restoration efforts, Pershyn said. 

The data will also serve as a baseline to track future range changes for the salmon population, help guide land protection efforts, and can be used to detect invasive species. 

ASRA has been doing environmental DNA studies in the Ausable River watershed for several years to study the distribution of native brook trout and non-native ones in the headwaters of the Ausable River watershed.