The Relative Contribution of Hudson River Tributaries to River Herring Spawning Dynamics
Quantifying the relative tributary contribution to anadromous fish spawning dynamics is irrefutably important when prioritizing habitat enhancement, restoration and management decisions (Everly and Boreman, 1999). Collecting sound baseline data becomes critical when seeking out the most significant contributors to spawning stock and flux. Sensitivity analyses can be employed to assess the range of uncertainty as it pertains to the estimation and application of these aforementioned contributors, however, hierarchical modeling, spatio-temporal visualization, and the cross validation of estimation methods provides a suitable means for addressing this uncertainty and the associated methods required for its reduction (Sullivan and Rudstam, 2016). With consistently measured baseline data collected and uncertainty fully characterized, one can utilize parametric optimization as a mechanism for inferring wide spread population phenomena from more localized estimates (Tam et al., 2002). Custom designed egg mats were deployed in Black Creek (Esopus, New York) and the Fall Kill (Poughkeepsie, New York) to obtain spawning river herring egg counts for abundance modeling and subsequent population estimation. Geographic coordinates (NAD 1983 UTM Zone 18N) were recorded at sites of egg collection, and kernel density based functions in GIS were used to visualize the spatial distribution and estimated counts of river herring throughout a given system. The sites of greatest egg deposition were ultimately viewed in conjunction with their relative proximity to the first impassable barrier to anadromous fish migration. The coordination of these activities serve to either refute or support the future augmentation of barriers to fish migration, management of habitat, prioritization of project management, and potential implementation of supplemental fish passage within tributaries of the Hudson River. Gravid female river herring were sampled from the main stem of the Hudson River through the use of haul seines for post-mortem ovary analysis. Auto-enumeration of ovary egg contents using an Epson Perfection V19 flatbed scanner and ImageJ software allowed for fecundity analysis. Standardized river herring standing egg crop (mean egg count per female) was multiplied by female river herring population estimates, obtained from Delta Vision HD underwater camera counts and Smith-Root SR-1601 potentiometric fish counts, in order to further estimate egg productivity within a system. Delta Vision HD underwater camera daily population estimates were compared against Smith-Root SR-1601 estimates to address issues of double counting, fiscal cost, cumbrous technology, and accuracy.
Statistics; Hierarchical Modeling; Hudson River; N mix; N-Mixture; River Herring; unmarked; Ecology; Aquatic sciences
Sullivan, Patrick J.
Sethi, Suresh Andrew
M.S., Natural Resources
Master of Science
dissertation or thesis