Sometimes you get lucky, finding yourself in the right place at the right place. Of course it helps having the awareness of a naturalist, knowing how to look. And so it went last Thursday when I found myself in the right place at the right time looking in just the right way!
(Warning: be forewarned that there’s a closeup image below of a lamprey’s mouth that my wife informs me is rather unpleasant, even disturbing).
Rock Suckers
About 6 years ago I was down at Salmon snorkeling in the low-water rapids of the Winooski River when I came across three snake-like fish huddled in a small crevice. The fish, sea lamprey (Petromyzon marinus), were using their round suction-cup mouths to scoop out surprisingly large rocks to create a protected nest for spawning. Their genus name, Petromyzon, comes from the Greek petro (πέτρα), for rock, and myzo (μυζώ), the Greek verb for suck.
Our “sea” lamprey are a special case for the species, isolated in the Lake Champlain watershed, they spend their entire lives in freshwater. Like their marine brethren (their species name, marinus, comes from the Greek for sea), our lamprey spend a year and a half to two years in open water before migrating up Lake Champlain’s tributaries to spawn. While they’re the demons of the deep, parasitized many a fish (with a penchant for scale-less or thin scaled fish), it is once they get up to the shallow rocky bottomed spawning grounds that the tables are turned and life becomes quite trecherous for amorous lamprey.
A deadly migration
The glut of lamprey on their spawning grounds is quickly followed by predators ready for the hunt. As I arrived down at the Winooski River last Thursday, I saw a great blue heron standing up at the top of the rapids. I rarely see heron in the rapids here, so I stopped to watch the heron hunt (it’s possible they’re unusual here because anglers are often fishing for trout in the rapids; the fishing season at Salmon Hole hadn’t opened yet).
After about 5 minutes the heron stabbed it’s beak into the water and pulled out a writhing 18″ lamprey! It struggled with the lamprey for a few minutes before flying off. The heron returned about 30 minutes later, caught a lamprey, struggled with it for a few minutes, and then flew off once again with the live lamprey in its beak. Over the two hours I spent at the rapids, I watched this happen four times. Just as I was about to leave, I saw an osprey fly off with a lamprey in its talons.
I went back on Saturday, the first day that fishing was opened back up below the dam on the Winooski River (a protection for spawning sturgeon), and I talked to someone trout fishing at the top of the rapids. He said he saw a lamprey wriggling upstream and just scooped it up in its net. Lamprey are typically more active at night (source), but that relates primarily to when they’re seeking for hosts. During the breeding season, male lampreys build out the nests in gravelly substrate and then release pheromones to attract females (source), making them more susceptible to predation. It’s no surprise that the sex ratio of male to female lamprey declines significantly over the course of the breeding season (source). All better judgment evaporates during the breeding season.
