Catch Me If You Can

An ultrasound is used to determine the reproductive condition of female pallid sturgeon.

Biologists from the USGS Columbia Environmental Research Center set out to recapture two pallid sturgeon implanted with transmitters near Ponca, Nebraska on Mar. 22. The two sturgeon, females PLS07-001 and PLS10-015, were relocated by biologists from Nebraska Game and Parks Commission (NGPC) during their river sweep the week before.   After drifting over the bottom of the river with their 120 foot long trammel nets, both tagged fish were recaptured.

Female sturgeon PLS07-001 was first captured and tagged 4 years ago in March of 2007.  At that time she was not reproductive, but she had accumulated a lot of the fat that she would need to produce eggs.  In the fall of 2007 she was tracked as she moved rapidly upstream more than 100 miles above her first capture location.  She was found again in May of 2008 during the spawning season in the Recreational River Reach less than 30 miles below Gavins Point Dam.  Biologists suspected that she may be ready to spawn, but needed to recapture her and examine her to determine if her long distance movement was indeed a spawning migration.  Unfortunately, shortly after she was found in May she did what many females do after spawning, she turned around and swam rapidly downstream back to where she started.  Biologists with their recapture nets finally caught up to her in late July of 2008.  Surgical examination of her ovaries showed that she had spawned that spring, probably not far from where she was found in May.

After tracking her movements for three years, PLS07-001 began moving upstream again in the fall of 2010.  This time USGS biologists were prepared and recaptured her on her way upstream in October.  Ultrasound imagery of her ovaries showed the presence of large developed eggs.  This was a positive indication that she will attempt to spawn in the Spring of 2011.   Fortunately biologists were able to capture her again.  Blood and eggs samples were collected to verify that she is gravid (reproductive) and to track her progress towards spawning.  Biologists will keep a close eye on her through the Spring to document her final spawning migration and hopefully pinpoint her precise spawning location.

The second fish recaptured, PLS10-015, was first captured nearly a year ago by NGPC and sent by truck to Missouri’s Blind Pony State Fish Hatchery.  There she was used in the captive propagation program to produce more baby pallid sturgeon to support population recovery.  Following spawning in the hatchery, she was implanted with a transmitter and released back into the Missouri River.  She has since returned to the original capture location where NGPC biologists first found her.  Not only has she regained the weight she lost during spawning, she gained 200 grams more.  An ultrasound revealed no eggs, but lots of fat.  Maybe she will spawn again next year.

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