Final Report pdf file

Abstract

Reproductive timing in the native freshwater mussel genera Anodonta, Gonidea, and Margaritifera was investigated in the lower Pit River watershed, California, from April through November 2004 and February 2005 through April 2006. This information is necessary for assessing potential impacts of seasonal pulsed flow releases from hydroelectric facilities on mussel reproduction.

Spawning and glochidial release in Anodonta occurred throughout most of the 2004 and 2005–06 field seasons, except from August through early October; in Gonidea from late March/early April through mid July in 2004 and 2005, and beginning in late April in 2006; and in Margaritifera for periods of less than 4 weeks beginning in April, June, or July in 2004 and 2005, depending on location. In 2005–06, Anodonta and Gonidea glochidia were observed on fish collected in the Pit River throughout and not more than 2 weeks after the adult gravid periods. Margaritifera glochidia were not observed on any of the fish collected during this study.

In a freshwater aquaria experiment that extended from April through September 2005, Anodonta juveniles were collected during April through late July and Gonidea juveniles were collected during June and July from the bottom of aquarium tanks containing naturally infected Pit River fish separated by species. Anodonta juveniles were collected from tanks containing native hardhead, Sacramento pikeminnow, tule perch, Pit sculpin, and non-native green sunfish. Gonidea juveniles were collected from tanks containing native hardhead, tule perch, and Pit sculpin.

One of the sampling sites at Hat Creek	One of the sampling sites at Pit 4 reach
Fish electroshocking and collection at Pit 1 Bypass	Electroshocked fish recovered in the bucket
One of the potential hosts for Anodonta and Gonidea	Mussel collection at Pit 1 Bypass of Pit River
Measurement of the collected mussels	Gonadal sampling from a gravid mussel
Removing the fish gills for glochidial examination	Examination of fish gills for encysted glochidia
Some encysted fish were kept in aquaria	Subsequent water collection for examination of excysted glochidia development

Photo credit: Cincin Young
(Please request permission from psyoung@ucdavis.edu
and maria@springrivers.com for use of pictures)