Safeguarding the Future of Sturgeon
From April until July, Michigan State University (MSU) AgBioResearch evolutionary ecologist Kim Scribner is more likely to be found wading with students in the evergreen-lined Black River of northern Michigan than in his campus office. The fisheries and wildlife professor studies lake sturgeon, a bottom-feeding Great Lakes fish species that can grow longer than 8 feet, weigh up to 300 pounds and live for nearly a century.
The Decline of Lake Sturgeon
Despite long lives, however, lake sturgeon populations have been in serious decline since the late 19th century. The U.S. Fish and Wildlife Service reports that in 1910, 80 percent of the species had disappeared from Lake Erie, and by 1929 the amount of sturgeon caught in Lake Michigan had dwindled from 3.8 million pounds to just 2,000. Numerous causes for the sturgeon decline are known. Scribner and his research team are trying to find a way to bring back the ancient fish.
“Sturgeon migrate from the Great Lakes to the rivers for spawning, which makes them an important part of that coupled ecosystem,” he said. “The species is a poster child for humans decreasing the population through overfishing and pollution, and we’re trying to help turn that around.”
Though female lake sturgeons lay thousands of eggs at a time, Scribner’s team has found that 95 to 98 percent never survive to hatching, and of those that do, 99 percent die in the larval stage. Those survivors must live 15 years before achieving sexual maturity and the ability to reproduce.
“Our primary focus is finding the factors that limit sturgeon survivability in the early stages of their life cycles,” Scribner said. “If we can identify the sources of mortality, we can create better management plans to help increase their numbers.”
Scribner and his team, in cooperation with the Michigan Department of Natural Resources (DNR), are in the 11th year of pursuing these answers. Though they employ a wide variety of experiments — from studying the organisms that prey on the young sturgeon to the microbial content of the stream and lake water they call home — accurate population estimates over time are absolutely essential to understanding the impact of those threats.
Tracking Sturgeon on the Black River
In the spring, when the sturgeon return from the lakes to their ancestral spawning grounds upstream, Scribner’s team is in the river daily, using nets to collect the fish and tagging them with an array of tracking devices. Some tags are simply colored markers, enabling the researchers to identify a specific fish on sight. Others are more complex, such as passive inducible transponders (PIT), which are implanted in the fish to detect their exact locations.
The ability to track and monitor Black River sturgeon has taken Scribner’s research to a new level of experimentation and analysis. His team has documented the genotype of the nearly 1,200 spawning lake sturgeons, allowing the researchers to identify the parents of newborn sturgeon and make predictions about which genetics are the most beneficial to the species’ survival. The technology has also allowed the team to discover which stream environments sturgeon spawn in, and how various environmental and water quality conditions affect the hatch time and the likelihood that a larval sturgeon will live to adulthood.
“Temperature has a definite effect on their growth rate and survival,” Scribner said. “Eggs laid in colder temperatures incubate longer, and the larva that emerges has a larger body size.”
Keeping tabs on the lake sturgeon population is crucial to understanding these fish and the threats they face.
“No two years are the same,” Scribner said. “You need long-term research when you’re studying a fish that can live over 100 years.”
Following the Spawning Sturgeon
Scribner’s lab has taken their work further, partnering with the MSU Quantitative Fisheries Center (QFC) to understand lake sturgeon populations in Lake Michigan where these same issues apply. Together, Scribner, a QFC associate researcher, and other QFC scientists are using genetic marker data from fish sampled in the lake, where different populations mix, to untangle the dynamics of populations spawning in different streams.
Without the ability to keep accurate records of lake sturgeon population levels, Scribner said this type of research would not be possible, and the future of lake sturgeon would continue to remain troubled.
Caption:A group of lake sturgeons wait to be fed in Kim Scribner’s Black River sturgeon hatchery. The bony ridges along the back and sides are very pronounced during its larval stage, but grow less prominent as the fish matures and eventually vanish in adulthood. problem.
Photo courtesy of Kim Scribner.
– from Futures, James Dau, AgBioResearch