by George Heartwell
As time arrives for first spawn the Sturgeon gather from throughout the Lake Michigan basin to return to their natal waters. Males may spawn every other year while females spawn every five to nine years. A mature female can lay 250,000 eggs in the rocky rapids where they catch among the stones. Waiting males are signaled to release sperm over the spawning redd by the female “thundering”. This phenomenon is still under study by biologists. “Along with known physical cues from river temperature and substrate, the fish likely combine visual, acoustic and electrical sense information into an adaptable suite of wide-ranging sensory knowledge, a powerful suite that has undoubtedly assisted Lake Sturgeon in successfully propagating their species for 150 million years’” stated Dr. Chris Bocast of the Wisconsin Sea Grant Institute. At a N’me (the Anishinaabek name for the Lake Sturgeon) release of the Little River Band of Ottawa Indians, I asked a diver, hired by the tribe to film the release from underwater, if he had ever been in the water when the fish were spawning. “Yes!” he replied. “The thundering is deafening!”
Eggs deposited and fertilized, the adult Sturgeon quickly leave the river to return to the receiving waters of Lake Michigan. In 5-8 days, the young fish hatch and immediately burrow into the gravel, feeding off of the yolk of the yoke sack which was so recently their “home”. The newly hatched Sturgeon spends its first year in its natal river. Because it is light-sensitive the fish tends to hide in dark recesses or at the bottom of river holes, coming out at dusk to feed. This evolutionary adaptation surely improves its survivability, lessening the chances of becoming lunch for a Heron. During this year in the river of its birth the Sturgeon takes on the chemical imprint of the water. Eventually, it drifts down-river to the receiving lake (Lake Michigan in the case of our Muskegon River-imprinted Sturgeon) and may travel widely over the next 15-20 years of its life. An interesting fact is that males mature at about 15 years while females mature at 20 years; thus limiting the likelihood of sibling fish reproducing genetically unvaried (and thus weaker) offspring. When spawning age arrives, the Sturgeon, living throughout the Basin, return, mystically, to the river of their birth, the river whose imprint they carry in their body, and begin again the reproduction process.
Sources: The Great Lake Sturgeon, ed. Nancy Auer and Dave Dempsey, 2013, Michigan State University Press. “Lake Sturgeon “Thunder” Research, Moira Harrington, University of Wisconson Sea Grant Institute, 2014.