This fall, the Massachusetts Division of Fisheries and Wildlife (MassWildlife) is sampling the Quabbin and Wachusett Reservoirs in an ongoing effort to monitor lake trout populations. Each year, with the help of DCR, MassWildlife collects lake trout from the Quabbin Reservoir to examine population characteristics. For the past few years, MassWildlife has also been sampling for lake trout at the Wachusett Reservoir. To capture lake trout, field crews set nets on spawning areas starting at sunset and check them about every 20 minutes. Captured fish are removed from the nets and placed in a livewell. Next, biologists record length, weight, and sex and implant a small Passive Integrated Tag (PIT) in the fish. Prior to release, the adipose fin is clipped to provide an external mark indicating that the fish has been captured before. Data collected provide biologists with an understanding of the current condition of lake trout populations. If fish are recaptured from previous tagging efforts, biologists can calculate individual growth rates. Lake trout are long lived and slow growing and it is not uncommon for a tagged fish to be recaptured 10 years later. In fact, the longest recapture interval recorded was 24 years! When other species like landlocked salmon, smallmouth bass, rock bass, and white perch are captured, biologists record information including length, weight, and sex but do not implant PIT tags.
Lake trout typically spawn in late October and November when the surface water temperatures are around or below 50°F. The spawning grounds are typically shallow, rocky waters on windy shores of the Reservoirs; spawning occurs mostly after dusk. Night sampling on big waters can be cold and icy in November, but the information it provides biologists is well worth the effort. Sampling efforts like this are just one way that MassWildlife monitors the health of the fish resources of the Commonwealth.
In 2018, sampling crews at Quabbin Reservoir captured and released 163 lake trout despite the frigid temperatures and rain experienced throughout November. Of note was a 26-pound male lake trout that was first captured and tagged in 2014 and recaptured this year. On Wachusett Reservoir, crews captured and released 65 lake trout including two 18-pound fish. An article with details about the lake trout sampling effort will be appearing in the next issue of Massachusetts Wildlife magazine, which will be in available in January. In addition, a scientific article has been composed and is currently in the peer–review process with publication expected in 2019.
