One Down, Several to Go

On May 7th, the CSRP sampling crew on the Missouri River in Nebraska reported the first free embryo capture of the season. Crews equipped with fine mesh nets have been sampling the Missouri and Platte Rivers for drifting embryos since April 15th in an effort to identify when and where sturgeon and paddlefish spawning naturally occurs (see, We’ve Only Just Begun).   Newly hatched sturgeon and paddlefish embryos are nearly indistinguishable, and it is unknown yet which species has been captured.  That distinction will be made using a microscope in the laboratory when the samples are returned to the Columbia Environmental Research Center at the end of the week.  Temperatures at the sampling location (14.5 degrees Celsius) were below temperatures where most sturgeon spawning occurs (16-22 degrees Celsius).  Based upon experience from previous years, it is likely that the free embryo captured is a paddlefish.  Paddlefish often spawn earlier and at cooler temperatures than shovelnose sturgeon or pallid sturgeon.  With no previous captures in the first three weeks of the sampling season, this signifies the first tangible confirmation that the spawning season in the Lower Missouri River above the Platte River is underway.

With contributions from Aaron DeLonay

Figure 1. A paddlefish or sturgeon embryo captured May 7th during larval sampling of the Lower Missouri River.

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