Minimally invasive implantation of spawning-event tags in sturgeon
April 22, 2021
By Aaron DeLonay and Kimberly Chojnack
The USGS Comprehensive Sturgeon Research Project and its partners have identified and mapped spawning habitats in the Lower Yellowstone River and the Lower Missouri River by intensively monitoring the movement of telemetry tagged pallid sturgeon and recapturing them at suspected spawning sites (see “Characterization of Pallid Sturgeon (Scaphirhynchus albus) Spawning Habitat in the Lower Missouri River”). The primary telemetry transmitters used in pallid sturgeon are surgically implanted in the abdomen of adult fish. They allow biologists to track and record location and movement of pallid sturgeon through the lifespan of the transmitter (3–5 years). Unfortunately, biologists cannot follow large numbers of tagged sturgeon continuously over hundreds of miles of river, and critical behaviors, such as spawning, are not readily detected in the swift, turbid water. Biologists need a way to remotely monitor if a female sturgeon has spawned and to precisely determine where spawning has occurred.
In 2019–2020 CSRP biologists conducted laboratory trials with shovelnose sturgeon to evaluate the use of small, secondary transmitters to use as a spawning-event tags. Spawning event tags are designed to aid in identifying the timing and location of sturgeon ovulation and deposition of eggs. Spawning-event tags are short-term tags (30-120 days) inserted into the oviduct using a minimally invasive procedure through the urogenital vent. Theses tags are designed to be released by the female during ovulation and spawning in or near a spawning patch.
Before spawning occurs, the biologists tracking a tagged female will detect the signals from both the primary tag and secondary, spawning-event tag. At spawning, the signals from both tags will appear to separate from one another as the spawn-event tag is deposited on the substrate of the spawning patch with the eggs. Separation of the tag from the female informs biologists tracking the female of her status and suggests that recapture to assess spawning success is advised. Location of a separated spawning-event tag at the river bed provides more precise definition of areas selected by sturgeon for spawning to focus mapping and habitat-characterization efforts. More precise definition of spawning events aids biologists in building conceptual models of spawning behavior and understanding the biomechanics of egg deposition and embryo survival (see “Physical characteristics and simulated transport of pallid sturgeon and shovelnose sturgeon eggs”). Spawning-event tags will be implanted in pallid sturgeon In the Missouri And Yellowstone Rivers for the first time in 2021.