Researchers are focused on the identity and habits of the coaster because if the fish are just common brook trout living large in a Great Lake, then one could argue there’s nothing endangered about them: there are millions of ordinary brook trout in Michigan and throughout the Great Lakes basin. “You have to keep in mind that this is a complex listing because it’s not the only brook trout in North America,” says Jack Dingledine, a Fish and Wildlife Service biologist working on the petition. “Part of what we are doing is determining whether coasters are a distinct population segment of brook trout.”
Note that Dingledine did not say “distinct species.” To gain endangered species protection, separate species status is not required. Considerations such as where and how the fish lives and its breeding habits all factor in. In fact, scientists agree that the coaster is almost certainly not a separate species, that the long-held assumption that the fish is a large brook trout is probably accurate.
Genetic science does, however, come into play, but it is not focused on, say, Is there a gene that makes the fish big? Or Is there a gene that makes the fish migrate? That would be beyond the reach of the data. But genetics can be useful in helping determine whether the Salmon Trout coasters are a distinct breeding population. Based on tissue samples that Baker and Huckins collected in August, Dr. Kim Scribner, at Michigan State University, has found there are large and significant differences at the genetic level between brook trout in the Salmon Trout river and brook trout from other Lake Superior streams. There is comparatively less genetic difference between coasters and the brook trout they live among in the Salmon Trout. There is also evidence of interbreeding among coasters and resident brook trout.
So, couldn’t biologists just dump regular brook trout in Lake Superior and just watch them grow huge? This was tried a number of times in the 20th century, but the coaster population continued to slide. Nature, it turns out, is more nuanced than that. Or, as Scribner says, “That is a naïve view of the world.” And it remains one of the other great mysteries of the coaster: what makes them grow big?
Biologists did take a more nuanced approach to coaster stocking when they planted coaster fry in five Upper Peninsula streams—not the Salmon Trout—each year from 1997 to 2002. One stocking strain was from Canada’s Nipigon River (the world’s most stable coaster population) and the other from Isle Royale. “They’d grow and go out to the lake, but we just didn’t see them coming back as spawners,” Huckins says. A few stocked coasters were found in other streams, but if they did establish new populations it is not evident.
At this point, stocking the Salmon Trout would be “crazy” for fear of damaging the genetics of the coaster community, according to Huckins. Fish populations can become adapted to a river over the years, selected to do well under the conditions in that river. “If we stock new fish over the top of the local population, we can swamp that local population with alleles that weren’t selected for, and you would reduce the population.”
Biologists at the FWS are not, by law, allowed to tip their hand on how they will decide on the listing petition. So I call Huron Mountain Club member and attorney Dykema. He fell in love with the coaster when he caught one as a teen and, over the years, has not only raised money for the fish, but also spent time in waders helping with research. Is the coaster’s a compelling case? “It seems to me the case is very strong, if not overwhelmingly strong. But I’m also hopeful that the new administration will enforce the endangered species act.” Wishful thinking?
Rewind to early evening, that first day of sampling on the Salmon Trout. Huckins has to check a monitoring device that records water flow and temperature at the river mouth, so we jostle down the forest-dark two-track to Salmon Trout Bay and walk a mile along the sandy shore. The August sky glows a cloudless robin’s egg blue. I stand at the river mouth and take in the arc of the bay and the shimmering cobalt beyond. Huron Island floats as a barely visible dark nub on the northwest horizon. East along the shore, the giant nest of a bald eagle bulges from a towering white pine. I hear a motor from a boat I cannot see, though I can see for miles.
This is the realm of the Salmon Trout coaster. And this interface between river and lake, now at my feet, is their threshold. Genetics might determine their size, but crossing from the safety of the river to the dangers of the big water is the act that defines the coasters, that earns them their name. They live on the coast. They swim along it, hence, coaster.
And so, the final curious thing that captivates me about the coaster: how its destiny is embedded in its name. The health of the coast, the future of the coast—the coaster habitat—is what will determine the fish’s existence, endangered species listing or not. And a good, healthy coast, well, that will take many committed coaster fans to make happen.