Author: ries.83

Ohio’s Living Fossils

Sturgeon are a group of around twenty-five fish species that are in the family Acipenseridae. They are found all over the world, from Europe to Asia to right here in North America. In the United States, they are native to the Great Lakes, the St. Lawrence, Missouri, and Mississippi Rivers, and can be found on both the east and west coast and in the Gulf of Mexico. Interestingly enough, there are no known native populations of sturgeon that exist south of the Equator (Fishbase 2017). This group of fish has been found in the fossil record as early as 245 million years ago, making them the oldest of the ray-finned fishes. However, what makes them “living fossils” is that they have not evolved much in the last 240 million years; the sturgeons that exist today are very similar to the sturgeons that lived during the same time of the dinosaurs (Gardiner 1984). The image below shows a tree of the relationships between modern fish groups. The placement of the sturgeon in relation to the teleosts (which contains 96% of all modern fish diversity) demonstrates its status as a “relict” fish, a living fossil, along with the gar, bowfins, and birchirs.

Image taken from the lectures of Dr. Suzanne Gray, The Ohio State University

 

The Life of a Sturgeon

Sturgeon primarily are benthic feeders, which means that they feed on the bottom of rivers and lakes. They usually feed on snails and mussels, but have also been known to eat fish and plants (ODNR Lake 2012). To have babies, sturgeon move into rivers to spawn. When this happens, females can lay thousands of eggs at a time into the water column that are then fertilized by the males’ sperm. This process is called “broadcast spawning.” However, very few of these eggs to adulthood. The baby sturgeon are slow-growing and can take a long time to reach sexual maturity (20-25 years in the case of Ohio’s own lake sturgeon). Unlike salmon, sturgeon can spawn multiple times throughout their life, but do not spawn every year, sometimes going multiple years between spawning events (lake sturgeon typically spawn every four to seven years). While they may take a long time to mature, sturgeon are incredibly long-lived. Their average life-span is 60 years, but some species, like the lake sturgeon, can live longer than a century (ODNR Lake 2012).

 

Now that you know a little bit more about sturgeon in general, let’s take a look at the two species that call the waters of Ohio home:

Lake Sturgeon (Acipenser fulvescens)

Photo by the Tennessee Aquarium

 

The lake sturgeon is native to the waters of Lake Erie and the Ohio River, as well as in some of the larger inland rivers that feed into these water bodies. A large fish, this sturgeon measures 6-8 feet in length and usually weighs around 100 pounds (Trautman 1981). The largest specimen recorded was caught in 1929, weighing 216 pounds (ODNR Lake 2012) The Lake Sturgeon is “sharply bicolored” meaning that the dorsal (top) half of its body is one color (in this case olive-yellow, grey, or bluish), and its underside is a different color (in this case milky/yellow-white). These fish have a series of bony plates that run along their back and sides, forming ridges on their body. While these plates are sharp in juveniles, they dull as the sturgeon ages, becoming blunt by the time they reach adulthood (Trautman 1981).

Shovelnose Sturgeon (Scaphirhynchus platorynchus)

Photo by Ohio Division of Wildlife

 

The other native Ohio species of sturgeon, the shovelnose sturgeon, is the smallest sturgeon species in North America, reaching lengths of about 2.5 feet long and weighing usually 1-5 pounds. However, the largest specimen recorded in Ohio was 32 inches long and weighed 10 pounds. The shovelnose can be easily distinguished from the lake sturgeon by its wide, flat snout that gives this species its name. It also is bicolored like the lake sturgeon, but the shovelnose is usually brown, olive, or grey dorsally, and whitish underneath. The shovelnose has a long, thin caudal peduncle completely covered in bony plates, whereas the lake sturgeon’s is much wider and only has plates on the side. The bony plates covering the caudal peduncle are also sharp in both juveniles and adults, and do not dull over time like the Lake Sturgeon. In Ohio, the shovelnose sturgeon is native to the waters of the Ohio River and its tributaries, having also been caught in the Scioto and Muskingum Rivers (Trautman 1981). Interestingly, while lake sturgeons have been reportedly able to live to be 150 years old, shovelnose sturgeon live much shorter lives, rarely living past the age of 12, and spawn fewer times in their lifetime (ODNR Shovelnose 2012).

 

Conservation

While sturgeon are incredibly interesting as living fossils, populations of sturgeon species worldwide have been in decline. Both the lake sturgeon and shovelnose sturgeon are listed as “Endangered” in the state of Ohio. Information from the International Union for Conservation of Nature (IUCN) suggests that sturgeon are one of the most imperiled groups on the planet, with 85% of the species worldwide at risk for extinction (IUCN 2010). Two important human-induced factors leading to their declines are shown below: dams and caviar.

Left image from AS Food Studio, Right image from Popular Mechanics

 

While dams may be beneficial to us, they play havoc with a sturgeon’s life cycle. Many sturgeon species have migration routes and preferred spawning grounds. The construction of dams blocks a sturgeon’s ability to follow these routes or get to their spawning grounds, affecting their reproduction. Sturgeon are also harvested for their eggs, which are sold as caviar at high prices. In recent years, the market for this product has grown considerably, so more and more sturgeon have been harvested, both legally and illegally, to meet this demand (WWF 2017). Because it takes so long for sturgeon to reach maturity, and because they do not spawn every year, they are incredibly susceptible to overfishing, which has been shown in their species declines over the last few decades. Although they have been around for millions of years, unless action is taken to reduce sturgeon population declines, these living relics could potentially disappear into the fossil record for good.

 

Works Cited

Fishbase. 2016. Family: Acipenseridae. Fishbase. Online. Retrieved November 2^nd, 2017 from http://www.fishbase.us/identification/SpeciesList.php?famcode=32&areacode=&spines=&fins=.

IUCN. 2010. Sturgeon more critically endangered than any other group of species. IUCN. Online. Retrieved November 2^nd, 2017 from https://www.iucn.org/content/sturgeon-more-critically-endangered-any-other-group-species.

Gardiner, B.G. 1984. Sturgeons as living fossils. Pg. 148-152 in Living Fossils, Eldredge, N., and Stanley, S.M. Springer-Verlag, New York.

ODNR. 2012. Lake Sturgeon. ODNR Division of Wildlife. Online. Retrieved on November 2^nd, 2017 from http://wildlife.ohiodnr.gov/species-and-habitats/species-guide-index/fish/lake-sturgeon.

ODNR. 2012. Shovelnose Sturgeon. ODNR Division of Wildlife. Online. Retrieved on November 2^nd, 2017 from http://wildlife.ohiodnr.gov/species-and-habitats/species-guide-index/fish/lake-sturgeon.

Trautman, M.B. 1981. The Fishes of Ohio. Ohio State University Press, Columbus, OH.

WWF. 2017. Sturgeon. World Wildlife Foundation. Online. Retrieved November 2^nd, 2017 from http://wwf.panda.org/what_we_do/endangered_species/sturgeon/.

Photo by T. Lawrence, GLFC

Although this creature may look like something dreamt up for use in a horror movie, these fish are very real and have their own sort of horror story in the Great Lakes. The Sea Lamprey (Petromyzon marinus) is a jawless fish that resembles an eel in appearance. Able to live in both marine and freshwater habitats, the sea lamprey’s home range includes the Mediterranean Sea, the Atlantic coasts of Europe and the United States, and freshwater habitats in Europe and the US (USGS NAS 2016). This fish gained notoriety when it expanded its range into the Great Lakes ecosystem, causing devastation.

How did the sea lamprey get into the Great Lakes?

Researchers are unsure as to whether the sea lamprey is native to Lake Ontario, or whether it was introduced after the completion of the Erie Canal (USGS NAS 2016). However, the lamprey is not native to the rest of the Great Lakes, where it is now found today. When the Welland Canal was completed in 1829, linking Lake Ontario with Lake Erie, it provided a corridor through which the sea lamprey was able to invade, but it took over a century for the first sea lamprey to be found in Lake Erie. This happened in 1921 (Trautman 1981). However, within thirty years, the fish had established populations in the remaining three Great Lakes: Lake Michigan, Lake Huron, and Lake Superior (USGS NAS 2016). The sea lamprey had successfully invaded the largest freshwater lake system on Earth.

What impact did the sea lamprey’s introduction have on the Great Lakes?

The sea lamprey is a parasite, meaning that it lives on another organism (its host) to get its nutrients, to the detriment of the host. The sea lamprey uses its teeth to attach to a fish, grind through their scales and skin, and feed on the fish’s blood and other bodily fluids. The following is an image of sea lampreys attached to a trout.

Photo by US Fish and Wildlife

This parasitism can result in the death of the host fish, either due to loss of blood or due to infection (NY Department of Environmental Conservation). One sea lamprey is able to kill as much as forty pounds of fish in one year (National Ocean Service 2016). Sea lampreys prey on large sporting fish, including trout, pike, salmon, walleye, and sturgeon which are commercially fished in the Great Lakes (NY Department of Environmental Conservation). In 1940, as the sea lampreys were in the process of becoming established in the Great Lakes, these fisheries were valued at $5.5 million dollars. After the sea lamprey was introduced, these fisheries collapsed. From 1938-1959, the lake trout fishery in Lake Huron went from producing 2268 tons of fish to a complete crash. In Lake Michigan, lake trout catches went from 2948 tons to 1181kg in ten years (Smith and Tibbles 1980). Not only did the sea lamprey invasion have severe impacts on the fish already living in the lakes, it had a negative financial impact as well.

What can be done to control sea lamprey populations?

When trying to combat the sea lamprey, wildlife managers tried using barriers to prevent the sea lampreys from breeding in streams. Physical barriers such as dams were designed prevent lampreys from passing through, while still allowing other “good” fish to pass. Electrical barriers were put in place to prevent lampreys from entering rivers to lay their eggs. While these barriers were somewhat effective and are still in place today, they were not able eliminate the problem of the sea lamprey (Great Lakes Fishery Commission 2000; Smith and Tibbles 1980). In 1958, managers started using a chemical called 3-trifluromethyl-4-nitrophenol, commonly abbreviated as TFM, to control lamprey populations. TFM is a lampricide, a chemical designed to kill lamprey in their breeding streams when they are still young. This prevents them from growing up and doing damage to fish populations. The lampricide proved to be effective, greatly reducing population sizes of the sea lamprey (Smith and Tibbles 1980). This has allowed some fish populations decimated by the lamprey to increase, but it will take more time for the fisheries to fully recover (USGS NAS 2016). However, treatments with TFM are ongoing to prevent the sea lampreys from ever reaching their 1950s numbers. Researchers are continuing to search for other treatments that reduce sea lamprey numbers to reduce dependence on TFM, which could have negative effects on other fish living in areas where lampricide has been used (Birceanu et al. 2014; USGS NAS 2016). Researchers at the Hammond Bay Biological Station, a partner of Michigan State University, are examining how pheromones (chemicals that animals release into the environment) can be used to alter movements of sea lamprey and to lure them into areas where they can be easily captured or killed (USGS Great Lakes Science Center 2016).

To end, MSU researchers have also begun studying how odors from dead sea lampreys can affect the behavior of living individuals. This is another avenue with which managers can control sea lamprey behavior to eliminate them or prevent them from doing more damage (USGS Great Lakes Science Center 2016). They have recorded the alarm response of living sea lampreys when exposed to these odors, and published them at the following links for your enjoyment:
View from above the water: https://www.youtube.com/watch?v=BxvorkIBbOo
View from below the water: https://www.youtube.com/watch?v=PBvYCBk_ZHM

Works Cited:
Birceanu, O., Sorenson, L.A., Henry, M., McClelland, G.B., Wang, Y.S., and Wilkie, M.P. 2014. The effects of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) on fuel stores and ion balance in a non-target fish, the rainbow troug (Oncorhynchus mykiss). Comparative Biochemistry and Physiology 160: 30-41. https://doi.org/10.1016/j.cbpc.2013.10.002

Great Lakes Fishery Comission. 2000. Sea lamprey barriers: New technologies help solve an old problem. Great Lakes Fishery Commission. Online. Retrieved September 28, 2017 from http://www.glfc.org/pubs/FACT_5.pdf.

Great Lakes Science Center USGS. 2016. Hammond Bay Biological Station. USGS Great Lakes Science Center. Online. Retrieved on September 28, 2017 from https://www.glsc.usgs.gov/sites/default/files/infosheets/HBBS20150818.pdf.

National Ocean Service. 2016. What is a sea lamprey? National Oceanic and Atmospheric Administration. Online. Retrieved September 28, 2017 from https://oceanservice.noaa.gov/facts/sea-lamprey.html.

NY Department of Environmental Conservation. Sea Lamprey Biology. New York State Department of Environmental Conservation. Online. Retrieved September 28, 2017 from http://www.dec.ny.gov/animals/7242.html.

Smith, B.R., and J.J. Tibbles. 1980. Sea lamprey (Petromyzon marinus) in Lakes Huron, Michigan, and Superior: history of invasion and control, 1936-78. Canadian Journal of Fisheries and Aquatic Sciences 37(11):1780-1801.

Trautman, M.B. 1981. The Fishes of Ohio. Ohio State University Press, Columbus, OH.
USGS NAS. 2016. Petromyzon marinus. USGS Nonindigenous Aquatic Species. Online. Retrieved September 28, 2017 from https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=836.