A new method for reporting and interpreting textural composition of spawning gravel.

Abstract

A new method has been developed for collecting, sorting, and interpreting gravel quality. Samples are collected with a tri-tube freeze-core device and dry-sorted using sieves based on the Wentworth scale. An index to the quality of gravel is obtained by dividing geometric mean particle size by the sorting coefficient (a measure of the distribution of grain sizes) of a sample. The resulting number is called the "fredle index" and is proposed as a standard for evaluating the reproductive potential of spawning gravel.

Yakima River Spring Chinook Enhancement Study, 1991 Final Report.

“…Linear regression analysis was used to determine if a correlation existed between eggto-fry survival rate and one the following indices of gravel quality: geometric mean particle diameter, percent fines co.85 mm, and the fredle index (Lotspeich and Everest 1981).…”

“…They observed a 60% survival rate for gravel mixtures with a fredle index of about 3.8. Lotspeich and Everest (1981) investigated steelhead (0ncorhynchus mykiss) survival ("swim up" fry to emerging fry) in laboratory gravel mixtures and found a survival rate of about 58% when the fredle index was 3.8 .…”

Evaluation of Fall Chinook and Chum Salmon Spawning Habitat near Ives and Pierce Islands in the Columbia River, Progress Report 1999-2001.

“…However, our methods did not allow us to make inferences about subsurface sediment composition, which may influence redd-site selection and subsequent fry survival. High amounts of fine sediments at 10-30 cm depth in the substrate, where salmonids typically deposit their eggs (Everest et al 1982), can decrease subsurface water flow, oxygen availability, and reduce fry emergence (Phillips 1975;Iwamoto et al 1978;Lotspeich and Everest 1981). This may explain why fish were observed spawning in distinct areas within our study area despite the availability of apparently similar habitats that were not used.…”

Measuring Rates and Effects of Dredging-Induced Sedimentation: Results From a Survey of Experts

“…Fredle number is an index of permeability that has been correlated with survival to emergence of salmon and trout (Lotspeich and Everest, 1981). Hinchey et al, (in review) chose effective overburden stress (kPa: bulk density and depth of burial, Richards et al, 1974) as a reliable measure of the force exerted on organisms by sediment burial because it combines burial thickness and porosity.…”

“…There is a need to determine relevant scales of sediment thickness and bulk characteristics prior to larval or egg settlement and deposition of sediment after attachment or settlement. The effects of increased sedimentation resuhing in "embeddedness" (fine sediment filling in gaps between gravel in streams) on hatching of salmonid eggs has been described (Waters 1995) and has resulted in guidelines based on percent fines and other variables (Lotspeich andEverest 1981 andCaux et al, 1997 Additional related information is available on the effects of both sediment transport and suspended sediment concentrations on the early life stages offish. Lisle and Lewis (1992) provide a useful model of salmonid embryo survival based on streamflow and sediment transport.…”