Hard Structure Aging Precision and Length-At-Age Data from Two Northern Leatherside Chub Populations

Northern leatherside chub Lepidomeda copei are an imperiled cyprinid fish native to the upper Snake River and upper Bear River basins in Utah and Wyoming.  Age and growth rates have been documented for only a few populations and the precision of scale and otolith age estimates have never been described for the species.  In this study, we describe the precision of scale and otolith derived age estimates for the northern leatherside chub.  We also document scale-derived estimates of age and growth rates of two populations, Ham's Fork, Wyoming and Yellow Creek, Utah.  Ages determined using scales agreed with those determined using otoliths in 70.8% of fish and agreement declined with age.  Scale derived age estimates were on average younger than otolith derived estimates.  The maximum age of the fish collected from Ham's Fork and Yellow Creek was three years.   At the end of the growing season, captured age 1, 2, and 3 fish had an average (range) total length of 86 (73-100), 105 (99-115), and 124 (100-135) mm, in Yellow Creek and 86 (63-96), 99 (89-117), and 112 (100-123) mm in Ham's Fork.  Growth rates did not differ between sexes in Ham's Fork, but females in Yellow Creek tended to grow faster than males.  The data from our study increases our understanding of age and growth rates in northern leatherside chub and how these parameters vary among populations

Effect of Diluent Type, Diluent:Sperm Ratio and Extender Use on Rainbow and Cutthroat Trout Egg Fertilization

Premature sperm activation can reduce fertilization.  Sperm extenders are a potential remedy.  In Test 1, rainbow trout (Oncorhynchus mykiss) sperm motility and motility duration were compared among three diluent types, three milt:diluent dilutions and between extended and un-extended milt.  Dilutions  ? 1:1 were sufficient for complete activation of un-extended rainbow trout sperm with all three diluents.  For extended milt, complete activation was observed in 4 of 5 replicates at 1:2 and all replicates of 1:3, but not at 1:1.  Sperm motility lasted from 21 to 52 s and was unaffected by extender, diluent type, or dilution.  In another test using extended and un-extended sperm to fertilize eggs at high female to male ratios (4:1), no significant difference in percent fertilization was observed between 4:1 and 1:1 ratios or between extended and control sperm treatments.   For cutthroat trout (O. clarkii pleuriticus) eggs fertilized with extended sperm, there was no significant difference in survival to eye-up.  The data indicated extender requires three-fold dilution, but did not negatively affect fertilization or duration of motility when common activating solutions were used