Spatial Dynamics, Home Range, and Growth of Moapa dace
Authors: Mark Hereford, Mary Peacock
Year: 2013 (xlv)
Abstract
Moapa dace, Moapa coriacea, are an endangered thermophilic cyprinid endemic to the upper reaches of the Muddy River, Nevada. Threats to this fish include non-native species, loss of habitat, and water withdrawal. Currently the population is limited to three restored tributaries above a gabion barrier which is in place to prevent invasion of blue tilapia, Oreochromis aureus. A mark-recapture study was conducted between October 2009 and September 2012 to analyze the spatial dynamics and growth of Moapa dace adding to the current knowledge of this unique desert fish. Fish were captured bi-monthly using a random-stratified design throughout their current range using minnow traps. Captured dace were measured, weighed, and a small clip of their caudal fin was taken for genetic analysis. Using genetic microsatellite analysis of caudal fin tissue over 3,000 samples were successfully genotyped at 5 to 10 loci and over 1,500 individual fish were uniquely identified during the study period with a mean recapture rate per individual of 2.04 (SD = 1.78). Geographic Information Systems (GIS) software was used to analyze individual movements and home range, which increased during the study period. Home range density shifted from the upper reaches of two distinct tributaries in 2010 and 2011, to include more downstream reaches and tributary junctions in 2012. Growth rates were calculated and compared between years, seasons, and size classes and showed a drastic decline as fish become adults. Condition factors of individuals were also calculated and compared between size classes, seasons, and years using Fulton’s condition factor (K = W/L3) which demonstrated that mean K values appear to oscillate with seasonal changes in photoperiod. This study demonstrates the usefulness of genetic tagging when the study organism is too small or when traditional tagging techniques are not an option.