|Last fall and winter there was a documented abrupt decline in smelt abundance in Moosehead Lake. It was a bit of a surprise because from 2008 to 2013 there was a steady improvement in lake trout and salmon growth, which is a good indicator that the main forage for these two highly prized gamefish was in abundant supply. Other data from the lake indicated that the decline in smelt abundance was not related to an over-abundance of lake trout since successfully thinning out this population to meet abundance goals. Instead, it was likely a natural fluctuation in the smelt population that may be related to water temperatures or available food. The good news is, this summer sampling indicates that lake trout growth has rebounded nicely, getting a look at the salmon at the end of October. But this does point to a short-coming in the ability to predict smelt abundance which is directly related to the success of salmon and lake trout fisheries.
||Pictured from left to right: Summer interns Zach Pratt (UMO) and Natalie Ameral (Unity College) collect plankton and smelt samples.
In the past, after an examination of smelt runs in the spring, revealed it’s difficult to put a number on a smelt run. It is impossible to count eggs, and typically just noted whether the spawning run was heavy or light. This is totally subjective and not very useful over a long period of time. This summer some new techniques designed to shed light on smelt population dynamics in Sebec and Moosehead Lakes were used. The information gained could be applied to other lakes as well.
This spring plankton nets were deployed in several tributaries with known smelt runs about 10 days after the eggs were deposited in an attempt to catch the newly hatched smelt fry. The goal will be to repeat this work each year to develop a catch curve to compare smelt fry abundance from year to year.
After smelt fry hatch, they immediately drop into the lake downstream. Other smelt studies indicate that the proper food source (plankton) must be available for these very small fish or they will starve soon after they absorb their yolk sac; therefore, it would be useful to monitor smelt abundance throughout the summer months and monitor plankton abundance/species composition.
This summer there was a success at sampling smelt fry from the surface of the lakes in early spring; however, by mid-June sampling at night was needed to capture smelts, since they only come to the surface after the sun sets. Collecting and identifying plankton during these sampling events had been done.
There will be a sampling protocol during the winter which will allow the tracking of smelt populations over time and hopefully detect impending declines before they occur. The environmental conditions that cause the declines may not be able to change, but in some cases, an ability to minimize the impacts by reducing stocking rates of salmon and/or lake trout in advance.
The Natural Resource Education Center at Moosehead (NREC) for providing the funds to purchase the new equipment necessary for this work is appreciated. NREC also paid for one of our interns this summer. This allowed everyone to conduct full creel surveys on Moosehead Lake and First Roach Pd, as well as complete a number of other projects. Funds for the NREC summer internship program come from the Moosehead Lake Togue Derby with Ricky Craven and other donations.