By Miles King
In the bottom of a lull in the Sacramento River, a young North American Green Sturgeon hatches. He is surrounded by hundreds of other sturgeons hatching with him. As he grows, the amount of food in the river is not enough to feed him and his companions. He must move to open waters where he will have enough to eat. Currently living in freshwater, he will need to transition to be able to survive in the salty ocean. He moves first into the brackish water of the San Francisco Bay where he begins to change. His gills start to transform to serve an entirely different purpose. Whereas in freshwater they were focused on keeping water out to maintain salt levels in his bodies high enough, in saltwater the gills’ focus shifts to keeping salt levels in his body lower than the salty environment. After spending much of his juvenile life acclimating to the dramatic changes in his environment, he is finally ready to move into the Pacific Ocean.
Once in the ocean, he can eat to his heart’s content. He is a benthic feeder, which means that he finds his food near the ocean floor. He especially enjoys shrimp, mollusks, arthropods (like hermit crabs), and small fish. He is very selective about what he eats, and has even developed special organs devoted solely to identifying possible food items. Named barbels, these two fleshy protuberances extend from the corners of the mouth. These barbels feel and taste the food before he decides whether it is up to his standards. If he approves, he will consume it by siphoning it, or sucking it up like a vacuum.
He will grow to be quite large, so he needs a lot of food. In fact, he may weigh upwards of 350 pounds by the time he has fully matured. Much of this weight is due to the armor-like protective “shell” that encompasses his body. Like something taken from the prehistoric era, these protective plates (called sclutes) keep him safe from the dangers of his environment, similar to a turtle’s shell. They work well, and he will probably live to be 70 years old and could even make it to 100.
Although seemingly indestructible, these fish are at risk of endangerment. They have a slow reproductive rate and take a long time to reach maturity, both characteristics of threatened species. Spawning and growing in the San Francisco Bay Area, they require the continued health of this ecosystem for their continued survival. However, this habitat faces many threats. Among these are dams, pollution, and fisheries. Dams block adequate water flow, which means that nutrients won’t be effectively cycled. Pollution from humans can accumulate over time, especially in the deep pools where they like to mate, and create toxic habitats. Finally, the Green Sturgeon is often accidentally caught by fish trawlers looking for salmon or white sturgeon.
The North American Green Sturgeon has remained genetically unchanged for hundreds of thousands of years. A living fossil, this fish faces an important turning point in its life. If we can successfully protect the Bay Area Watershed and keep it habitable, the Green Sturgeon will continue to thrive. If not, we may lose thousands of years of genetic evolution and progress to extinction. For the moment, however, our sturgeon continues to live happily in the Pacific Ocean. He’s starting to think about finding a mate and returning to the Sacramento River to create some living fossils of his own.
