The days are getting shorter and cooler, and researchers are already beginning to think about the next spring’s spawning migrations. But, they may not be the only ones. Female pallid sturgeon PLS11-007 was initially captured and implanted with telemetry devices on April 5, 2011. She was not in reproductive condition at that time, but small white eggs were visible in the ultrasound and through a small incision during surgery. Tracking crews relocated her 12 different times between April 5 and September 13, 2011. Over the five-month observation period this female spent her time within just 0.6 miles of river.
With fall approaching, USGS Comprehensive Sturgeon Research Project field crews targeted this female for recapture. They wanted to see if her eggs had developed to the point where they can confidently predict that she will spawn in the spring of 2012. This female pallid sturgeon was successfully located and recaptured in a drifted trammel net on September 16. A minimally invasive ultrasound scan conducted on the boat showed the presence of large, maturing eggs. The verdict was in – PLS11-007 will be ready to spawn next spring.
Perhaps PLS11-007 was listening when the results of the ultrasound scan were announced because she began moving upstream almost immediately. Since the time of her recapture and ultrasound evaluation until October 7, the female pallid sturgeon has moved upstream more than 16 miles and into the Lisbon chute, near Arrowrock, Missouri. By October 14, only a week later, she had navigated an additional 5 miles upstream of the Lisbon chute. Ten days later tracking crews found she had swum 30 miles farther upstream and had passed the Grand River. After another week, crews found her upstream an additional 24 miles. From mid-September to Halloween, PLS11-007 had moved steadily upstream 75 miles. Biologists tracking her are left wondering if she has decided to get a head start on her spring spawning migration and how far might she go before the cold and ice of winter settles in. What makes some adult sturgeon start their spawning migrations in fall, while others wait until spring? Do they have a specific destination in mind? Do they know how far they need to go? Only time will tell.
Completed with contributions by Aaron DeLonay