SAULT STE. MARIE – A Lake Superior State University graduate has published findings in the Journal of Great Lakes Research that answer the question many anglers have been asking for years: Are Atlantic salmon reproducing in the Great Lakes?
According to Stefan Tucker, Belmont, Mich., yes, they are – at least in the St. Mary’s River.
Tucker, who graduated from LSSU in 2012 with a degree in fisheries and wildlife management, found wild Atlantic salmon fry in the St. Mary’s River while conducting research on lake sturgeon as part of his undergraduate senior thesis, a requirement for students in the sciences and other fields at LSSU. He published his findings with LSSU biology professors Dr. Ashley Moerke and Dr. Geoffrey Steinhart, and LSSU Aquatic Research Laboratory Manager Roger Greil in the October issue of JGLR.
The discovery is not only exciting for those at LSSU, the Michigan Dept. of Natural Resources, and others who have been involved with stocking Atlantic salmon in the upper Great Lakes for more than two decades, but also to anyone who follows the changing dynamics of the Great Lakes, especially in relation to lake trout and salmonids.
“We were conducting research for my sturgeon thesis when we found the Atlantic salmon fry,” said Tucker. “It was very exciting to everyone who was a part of my research to imagine what we had just stumbled upon.
“While sorting through my samples at the lab with Roger (Greil), we began to ID the salmonids and Roger had a suspicion that they were Atlantics,” he added. “We caught wild Atlantics in our next two sampling events, so we wanted to confirm our ID and we sent a few to Dr. Gerald Smith at University of Michigan, who confirmed the identification. So, while sampling for several days catching what we believed to be Atlantic salmon was exciting, it was even more so to get confirmation from a reputable, professional taxonomist.”
Atlantic salmon (Salmo salar) are native to Lake Ontario; but their populations severely declined by the late 1800s, according to Tucker’s abstract. During the early to mid-1900s, Atlantic salmon were stocked throughout the Great Lakes in effort to reestablish them into Lake Ontario and introduce the species into the upper Great Lakes. However, these efforts had minimal success.
In 1987, LSSU, in cooperation with MDNR Fisheries, began stocking Atlantic salmon in the St. Mary’s River. While the effort has resulted in a very successful recreational fishery along with an excellent educational experience for students, it appeared that Atlantics were still not reproducing naturally even though they would return to the river spawning grounds every year. Biologists wondered if competition from other salmonids spawning in the St. Mary’s in greater numbers – including chinook and pink salmon – was keeping Atlantics from thriving.
While this is the first documentation of natural reproduction of Atlantic salmon in the upper Great Lakes, Tucker’s study concludes that “the extent of natural reproduction and mechanisms influencing reproductive success are unclear and warrant further attention.”
Tucker said unclipped yearlings have been captured in the past, and while they could potentially be naturally produced fish, it is not likely. His study says it is suspected that thiamine deficiency has been a possible factor contributing to the limited success of natural reproduction and survival of salmon, including wild Atlantic salmon in the Great Lakes.
It was another LSSU study led by Dr. Marshall Werner and his students in 2006 that confirmed that thiamine deficiency – also known as early mortality syndrome (EMS) – was probably affecting wild salmonids in the upper Great Lakes. Werner’s study noted that the deficiency results from the presence of thiaminase, an enzyme that degrades thiamine (vitamin B1) and is found at high levels in common prey fish, including alewives.
“EMS is detrimental to the embryonic and larval stages of salmonids within the Great Lakes basin because it reduces their ability to convert carbohydrates into energy,” Tucker said. “For over a decade, EMS has been successfully treated in hatchery settings via thiamine baths, but treatment of naturally spawned embryos has not been possible.”
After the crash of the Lake Huron alewife population more than 10 years ago, thiamine concentrations in eggs of salmonids and lake trout were found to be much higher.
Tucker’s study noted, “A direct correlation between increased egg thiamine levels and decreased alewife abundance has supported an increase of spawning success for Atlantic salmon and lake trout (Salvelinus namaycush). The patterns observed in Atlantic salmon and lake trout suggest that these species may be experiencing the removal of long-standing reproduction impediments and show that low alewife abundance is a vital pre-requisite for natural reproduction.”
In addition, with the crash of the alewife population in Lake Huron, the chinook salmon population followed suit, possibly reducing competition for spawning areas.
“Stefan’s research is a fantastic example of unexpected scientific discovery that is leading to new questions and hypotheses about the life history of Atlantic salmon in the upper Great Lakes,” said Moerke, who is co-director of the LSSU Aquatic Research Laboratory. “Undergraduate students can contribute to and advance our scientific understanding, and Stefan’s publication illustrates that our students at LSSU are doing so. It’s an impressive accomplishment to be published in a peer-reviewed scientific journal, but even more so to do it as an undergraduate.”
Tucker’s senior thesis was “Verification of natural lake sturgeon reproduction in the St. Mary’s River, Michigan.” It expanded upon a growing body of data collected on lake sturgeon by LSSU students and faculty since the mid-1990s. Tucker was awarded an LSSU undergraduate research award to conduct the study, and he won the Best Student Field-based Thesis Award for his research from the LSSU School of Biological Sciences in 2012.
“So, in addition to writing my original thesis, I took on writing the Atlantic salmon paper as lead author,” Tucker said. “It was a great honor and learning experience to do so. Roger, along with Dr. Steinhart (former LSSU ARL co-director) and Dr. Moerke played a huge role with the technical aspect in some of the writing and their assistance after graduating has been incredible.”
Tucker’s research is timely as the MDNR has recently expanded its Atlantic salmon stocking program in the state and is hoping to see these salmon step in for the once abundant chinook salmon, which were highly sought by anglers in Lake Huron.