Last week more than 100 maturing pallid sturgeon made the trip from the U.S. Fish and Wildlife Service’s Gavins Point National Fish Hatchery (http://www.fws.gov/gavinspoint/) in Yankton, South Dakota to Columbia, Missouri. Nearly nine years ago, in the spring of 2002, these fish began their lives in the hatchery as embryos artificially spawned by biologists. Some of the embryos were raised and released as juveniles, and then released into the river to increase imperiled populations. Others were housed in very large tanks to be watchfully cultured in the hatchery for possible use as adult broodstock – a kind of insurance policy – in the event that wild, spawning pallid sturgeon could no longer be caught from the Missouri River. The work of hatchery professionals (in both the U.S. Fish and Wildlife Service and participating State agencies) have been so successful at artificially propagating the species that there are more fish produced in hatcheries than are needed to support populations in the wild. This creates unique and valuable opportunities for researchers working to understand a rare and endangered species like the pallid sturgeon.
The 100 pallid sturgeon that made the trip to Columbia are excess to the needs of the conservation propagation program and have found a new role supporting the recovery of the species. Pallid sturgeon take many years to reach reproductive maturity and spawn. At 9 years old, the reproductive organs of these sturgeon are maturing and preparing for reproduction. This is a particularly important time in their life cycle. Soon after arrival at the USGS Columbia Environmental Research Center (CERC), biologists examined the reproductive status of each individual sturgeon using an ultrasound and extracted blood samples to analyze hormones. The sturgeon were then released into specially constructed ponds where they will be exposed for up to 3 years to a compound called ethinyl estradiol, which is the active ingredient found in many commonly used birth control pills. Previous studies with the closely related shovelnose sturgeon in the Missouri River have documented an unusually high incidence of reproductive anomalies, including an intersex condition in 15 to 25% of male sturgeon. Sturgeon that show this intersex condition have reproductive organs that are both male and female. The high frequency of intersex in Missouri River sturgeon may be linked to compounds like ethinyl estradiol that enter the river from wastewater treatment facilities, and is an emerging concern for the reproductive health of pallid sturgeon in the river. This long-term study will follow sturgeon through an entire reproductive cycle and will help researchers understand what causes intersex in sturgeon.
Long-term studies with adult sturgeon are not easy. Pallid sturgeon are large and live near the bottom of rivers in the current. It takes a lot of moving water and space to grow and keep big sturgeon healthy. In 2010, the CERC began the process of reconstructing the extensive network of experimental ponds at the Center. The USGS, with the assistance of funds provided through the American Recovery & Reinvestment Act, completed a 1.6 million dollar redesign and reconstruction in the fall of 2011. Part of that construction project provided for a series of small ponds with sand and gravel bottoms that can be fitted with a partial central divider and circulators to create a continuous current. This produces conditions that are much like the habitats where pallid sturgeon are found. These new ponds were completed just in time for their residents from Yankton, South Dakota to move in and make themselves at home. This study represents a twelve-year investment that would not have been possible without the dedication of the hatchery staff to successfully raise these fish and the re-investment in infrastructure to adequately provide suitable conditions for these large fish.
By Aaron DeLonay and Dianna Papoulias