By Kimberly Chojnacki, Justin Haas (Nebraska Game and Parks Commission), and Aaron DeLonay
Comprehensive Sturgeon Research Project (CSRP) scientists have documented that some tributaries may have significant value to the endangered pallid sturgeon (see previous posts “Where Are You When I’m Not Looking”, and “A Fork in the Road”). The spring of 2014 is providing additional insights for collaborating Nebraska Game and Parks Commission and U.S. Geological Survey research crews. From late April through May, four telemetered pallid sturgeon were found in the Platte River, two males and two females. The two male pallid sturgeon were located between 1 and 5 miles upstream in the Platte River during late May (Figure 1).
Female PLS10-29 was recaptured during the fall of 2013 and determined to be likely to spawn during the spring of 2014. She stayed in the Missouri River through mid-April before moving into the Platte River. During late April and early May PLS10-029 was located one to two miles up the Platte River and has since gone missing (Figure 1). Scientists believed that female pallid sturgeon PLS11-015 should also have been ready to spawn this spring, but she swam upstream into the Platte River before she could be captured and assessed. Since entering the tributary mouth she has been located on three occasions in the Platte River; the last time more than 30 miles upstream, near its confluence with the Elk Horn River, during late May (Figure 1). Both of the female pallid sturgeon that were found in the Platte River this spring are believed to have previously spawned there during 2011 (PLS11-015) and 2012 (PLS10-029). The Platte River is very difficult for fish tracking using acoustic telemetry tags because it is very shallow with braided sandbar complexes, so it is not uncommon to lose track of the tagged fish. Luckily, scientists have another way to determine whether they have spawned in the Platte River. CSRP scientists will attempt to recapture both of the females as soon as they emerge from the Platte River to determine if they have released their eggs and to recover the data storage tag that records temperature and depth data to find out (see previous post “Where Are You When I’m Not Looking”). In 2011, the temperature and depth data provided indirect, but strong, evidence that the fish had spawning in the Platte River. From these long-term tracking datasets, scientists have learned that female pallid sturgeon in the Lower Missouri River can spawn every 2 to 3 years, and that females attempting to spawn in the Platte River will return to the Platte River on subsequent spawning migrations.