When Do Mountain Whitefish (Prosopium williamsoni) Spawn? A Comparison of Estimates Based on Gonadosomatic Indices and Spawner and Egg Counts

Abstract

Determining when fish spawn has major implications for effective fisheries management, particularly in dam-controlled rivers where reproductive potential may be affected by an altered hydrograph. Three methods for estimating spawn timing in riverine broadcast spawners were compared for their precision, effort and potential impact on a population of Mountain Whitefish in the regulated Lower Duncan River, Canada. The first method is based on the Gonadosomatic Index (GSI), which is a measure of the relative mass of an individual's gonads. The second method is based on counts of aggregating adults, while the third method is based on passive egg collection using egg mats. Analysis of the GSI data provided the most precise estimates. It estimated that spawning occurred between October 30th and November 26th in 2010 and between November 8th and November 27th in 2011. Collection of GSI data required moderate effort and had some impact due to the need for lethal harvest. Analysis of the spawner counts using a simple Bayesian Area-Under-the-Curve model provided less precise estimates of spawn timing but the method likely had negligible impact on the population and required only moderate effort. Deployment of egg mats required high effort and collected insufficient information to derive statistical estimates of spawn timing. We discuss how information from different methods could be combined together into a single integrated model to maximize the precision while minimizing the effort and impact.

Exposure Risk of Fish Downstream of a Hydropower Facility to Supersaturated Total Dissolved Gas

“…The timing of MW spawning tends to be population specific, driven largely by temperature (Benjamin et al., 2014) and varies according to altitude and longitude of the system (Boyer et al., 2017; Pettit & Wallace, 1975; Thompson & Davies, 1976; Wydoski, 2001). The main spawning season for MW in the Lower Columbia system, or those close by, occurs between late October and February with a peak in January (Ford et al., 1995; Irvine et al., 2017). Mountain whitefish were most often resident at Norns Creek, Kinnaird Rapids, and the Kootenay confluence areas in the winter, which have been identified as primary and secondary spawning locations in the system (Golder Associates Ltd., 2014).…”

Passive Integrated Transponder Tag Monitoring Reveals Complex Migration and Life History Patterns in Mountain Whitefish in Upper Columbia River Tributaries

“…Stock separation was based on assumed spawning location, as determined by movement into an area when spawning was expected to occur or out of an area after spawning was expected to have been completed. Spawning was considered to occur between early October and late November annually (Wydoski 2001;Boyer et al 2017;Irvine et al 2017). The application of these rules resulted in the identification of two Mountain Whitefish populations: Twisp River residents that remain in the Twisp River until spawning season has ended and Okanogan River migrants that exit the Twisp River in early summer and migrate to the Okanogan River for the spawning season.…”

“…When observed over sufficient duration, detections of fish movement via PIT tag technology may reveal life history complexities that are difficult to discern with single-record marking methods (e.g., coded wire tags) commonly used with semelparous salmonids. For Mountain Whitefish, spawning ground fidelity may be documented over many years using PIT tag technology if spawning behavior is sufficiently understood (e.g., Meyer et al 2009;Boyer et al 2017;Irvine et al 2017), such that passive observations can be confidently assumed to be spawning observations in lieu of direct confirmations common for semelparous salmonids (i.e., redds or carcasses).…”

Vendace (Coregonus albula) Disperse Their Eggs Widely during Spawning

“…Egg abundance monitoring of coregonids is used to study location of spawning areas (Amidon et al 2019), spawning time (Irvine et al 2017), egg density and mortality (Nissinen 1972, Viljanen 1980, Żuromska 1982, Ventligen-Schwank & Müller 1991, Müller 1992, and spawning stock size (Wahl & Löffler 2009). In coregonid spawning, eggs released by females and possibly fertilised by males sink towards the bottom sediment.…”