River Herring Numbers Continues to Rise at Upper Mystic Lake while Depleting Elsewhere

For the past three years, the arrival of spring has brought not only the river herring to the Mystic Lakes to spawn, but also dedicated monitors observing their passage up the fish ladder. Each year the herring count has steadily increased from the 21,025 herring initially reported in 2012. This past year amounted to an impressive 31,063 river herring.

Yet, never before has the count increased at the dramatic rate observed this year. The first herring sighted in the Upper Mystic Lake arrived on April 30th, since then monitors have counted an incredible 42,982 herring! This mass migration has shown no signs of slowing and we are excited what the rest of the counting season holds. 2015 is proving to be a monumental year to observe the river herring at the Mystic Lakes!

Why are we seeing so many fish this year?  Other sites are seeing unusually low counts this year (read about it here).  One exciting possibility is that we are seeing the positive result of building the fish ladder at Upper Mystic Lake.  At the age of 3 or 4, herring tend to return to the fresh water areas in which they were born.  This is now the fourth year since the fish ladder installation.  

What we may be seeing, then, is a real increase in the adult population of herring that call the Mystic their spawning home. By effectively expanding the breeding habitat into Upper Mystic Lake, we may have provided more opportunity for more juvenile fish to successfully survive to adulthood. It is probably too early to come confidently to this conclusion, but if it’s true, it would be a tremendous success story of local wildlife conservation, documented entirely by citizen science volunteers.   

For more information about the herring life-cycle see the Gulf of Marine Research Institute's explanation, linked here. Stay tuned.  We will be consulting with experts at the Division of Marine Fisheries over the next weeks and month, and let you know what their interpretation of these exciting numbers is.

In the meantime, keep up the amazing citizen science work!

Posted by Andrea Ritter