ENTERPRISE, Ore. – This spring, ODFW staff deployed large nets in Wallowa Lake to monitor fish population trends and assess the impact of lake trout on other species. The nets will be in place for about four weeks for research purposes only and are not part of a fish removal effort.

Anglers on Wallowa Lake are encouraged to steer clear of nets (buoy-marked areas) while trolling and fishing.

In addition to general monitoring of the fish, ODFW and the Nez Perce Tribe will be looking specifically at the catch of lake trout which are large, predatory fish native to the Great Lakes region of North America. They were introduced to Wallowa Lake in the 1960s and have since persisted on their own. In some lakes in the western United States, introduced lake trout have decimated other species present which is a concern particularly for Wallowa Lake kokanee.

While ODFW has not yet found any evidence that lake trout are negatively impacting other fish species in Wallowa Lake, given the importance of species such as kokanee and the planned reintroduction of sockeye salmon, it is vital that state and tribal biologists gain a clearer picture of lake trout population dynamics.

“We’re working on trying to understand trends in fish populations in Wallowa Lake, and these nets will allow for long term sampling efforts without injuring sensitive species like bull trout,” said Kyle Bratcher, ODFW District Fish Biologist.

Anglers will see up to two temporary nets in Wallowa Lake. Both are large nets known as “Merwin” traps. They consist of a long panel of fine mesh netting leading into a series of funnels that trap fish swimming along the shore. The fish are unharmed while they wait in the large holding pen to be released.

ODFW will be using both the large Merwin traps and gillnets to capture and survey fish. While gillnets are typically more harmful to the fish they catch, these nets are set strategically and are only fished for four to six hours to avoid excessive catch and injury of non-target fish. Anglers likely won’t encounter gillnets because they will be set during the evenings and only deployed for a short duration. However, the Merwin traps will remain in place for three to four weeks. Anglers and boaters should not approach these nets, which will be marked with buoys or floating walkways.

Unlike streams that are shallow with discrete habitats where fish can be located, in large, deep lakes like Wallowa Lake, fish are difficult to catch with methods like electrofishing. Typically, these lakes are sampled with passive methods like trap nets and gillnets that entrap passing fish. By using these methods, biologists can gain insights into fish population interactions within Wallowa Lake to better manage for conservation and recreational fisheries while limiting impacts to sensitive species.

If you have any questions or see any unauthorized access to nets set in the lake, please contact ODFW in Enterprise at 541-426-3279.