Spawning Substrate Size, Shape, and Siltation Influence Walleye Egg Retention

Abstract

We compared Walleye Sander vitreus egg retention among varying rock treatments placed in a hydraulic flume to test the influence of spawning substrate shape and size on egg retention and the influence of substrate siltation on egg adhesiveness. Egg loss from suboptimal spawning substrates has been hypothesized as a substantial source of mortality during the incubation period. To investigate the influence of substrate size and shape on Walleye egg retention, known numbers of Walleye eggs were pipetted onto rock substrate in a hydraulic flume and exposed to flowing water conditions. Eggs scoured from the substrate during each trial were collected and enumerated. Egg retention was higher in angular crushed limestone than in round glacial till and greater in coarse gravel than in larger size‐classes, under all water velocity regimes. Angular coarse gravel had the highest egg retention rate (mean ± SD, 66.9 ± 3.7%), and round very coarse gravel had the lowest egg retention rate (47.0 ± 3.1%) of all the rock size and shape treatments. Substrate siltation significantly influenced egg adhesion. Clean rocks had a mean ± SD egg retention of 35.9 ± 36.6%, whereas fine‐sediment‐covered rocks did not retain any eggs throughout the course of the experiment. Differences in substrate size, shape, and siltation between Walleye spawning sites may contribute to variation in egg retention rates. Using angular gravel during the creation of Walleye spawning habitat and maintaining clean spawning substrates (through scouring effects and habitat restoration) may decrease mortality associated with egg entrainment and redistribution.Received June 13, 2012; accepted December 12, 2012

Portfolio theory as a management tool to guide conservation and restoration of multi‐stock fish populations

“…For example, the Maumee and Sandusky rivers flow through watersheds dominated by agricultural land use with low gradients and are subsequently highly responsive to regional temperature fluctuations and extreme precipitation events (Richards 1990;Pritt et al, unpublished manuscript). High variability in temperature and flow regimes in these systems can influence timing of production and larval survival (Mion et al 1998, Crane and Farrell 2013, Pritt et al 2013. The open-lake reef complex is located in relatively shallow water influenced by Maumee and Detroit River discharge, and is responsive to regional temperature fluctuations.…”

Influence of wind, wave, and water level dynamics on walleye eggs in a north temperate lake

“…It is likely that after losing their adhesiveness, eggs that settle into interstitial spaces in coarse substrates are additionally protected from wave transport owing to substrate roughness (Bozek et al 2011b). Crane and Farrell (2013) found a mean retention of nonadhesive walleye eggs of 57.5% at 95 cm·s −1 up to 59.8% at 55 cm·s −1 in various gravel mixtures and that coarse gravel (16-45 mm) retained walleye eggs at a higher rate than even very coarse gravel (23-90 mm), suggesting an optimal substrate size for egg retainment and survival. In addition, gravel matrices are more stable than sand because of higher C v values and multiple layers often mixed with other coarse substrates.…”

“…laboratory flume study, Crane and Farrell (2013) found clean coarse substrates could retain adhesive eggs at 65 cm·s −1 but that "silt-covered coarse substrates" could not. It is likely that after losing their adhesiveness, eggs that settle into interstitial spaces in coarse substrates are additionally protected from wave transport owing to substrate roughness (Bozek et al 2011b).…”

“…The percentage of data points that exceeded C v values would have been lower if we used the Humphrey et al (2012) C v values necessary to remove 90% of adhesive eggs. However, Humphrey et al (2012) and other flume studies (e.g., Crane and Farrell 2013) used consistent velocities in one horizontal direction. We recorded variable and high velocities in both horizontal and vertical directions, and it is possible that horizontal oscillations combined with vertical uplifting may be important in egg transport in both lakes and rivers.…”

Egg deposition by lithophilic-spawning fishes in the Detroit and Saint Clair Rivers, 2005–14

“…Interestingly, walleye eggs were never collected at the coal cinder pile in North Channel Saint Clair River-a presumably preferable substrate compared to sand and clay. It was noted that the creation of reefs in both rivers has shown no obvious impact on where walleye, lake whitefish, and suckers choose to spawn but has likely increased the survival of eggs deposited over them by decreasing rates of egg siltation, predation, or of being washed downstream (Crane and Farrell, 2013).…”