Session C7: An Evaluation of Eel Ladders as Traps for Migrating Sea Lampreys

Abstract: We tested if eel ladders with the right spacing of pegs on slanted ramps can selectively trap migrating sea lampreys. We compared entry of adult sea lampreys into eel ladder-style traps (ELST) with capture by funnel traps during three seasons in two Michigan rivers. Both funnel traps and ELST caught several thousand lampreys, but only the ELST perfectly retained trapped animals and had zero by-catch of finfish. Markrecapture experiments revealed significant trap happiness of ELST-caught lampreys. In one river, the ELST catch was strongly biased toward females. At the same site, the ELST caught lampreys with lower average weight and a lower female GSI. We analyzed via PIT tags and video observations of hundreds of nocturnal approaches and attempts to swim up the exposed part of the ramp. The rate of completion of climbs varied considerably between sites and years. Most of the failed attempts were aborted near the base of the ramp; those attempts appeared to be caused more often by a decision to turn around than a lack of stamina to swim all the way up. Manipulations of ramp angle and attraction/ ramp flow resulted in varying rates of attempt and completion: steeper ramp angle and more attraction flow lead to more successful passage over the ramp. We showed that eel ladder-style traps can selectively catch (or pass over obstacles) adult migrating sea lampreys. While we can’t explain the reason for the trap biases we observed, our observations underline that fish passage devices or traps that rely on complex behavior of the target animal will likely select for a subset of the target population. After further fine-tuning of the ramp parameters and flow, modified eel ladders could become a valuable tool for management of adult lampreys

Equivalence of the realized input and output oriented indirect effects metrics in ecological network analysis

A new understanding of the consequences of how ecosystem elements are interconnected is emerging from the development and application of Ecological Network Analysis. The relative importance of indirect effects is central to this understanding, and the ratio of indirect flow to direct flow (I/D) is one indicator of their importance. Two methods have been proposed for calculating this indicator. The unit approach shows what would happen if each system member had a unit input or output, while the realized technique determines the ratio using the observed system inputs or outputs. When using the unit method, the input oriented and output oriented ratios can be different, potentially leading to conflicting results. However, we show that the input and output oriented I/D ratios are identical using the realized method when the system is at steady state. This work is a step in the maturation of Ecological Network Analysis that will let it be more readily testable empirically and ultimately more useful for environmental assessment and management.Comment: 13 pages, 1 figure, 1 tabl

Throughflow centrality is a global indicator of the functional importance of species in ecosystems

To better understand and manage complex systems like ecosystems it is critical to know the relative contribution of system components to system functioning. Ecologists and social scientists have described many ways that individuals can be important; This paper makes two key contributions to this research area. First, it shows that throughflow, the total energy-matter entering or exiting a system component, is a global indicator of the relative contribution of the component to the whole system activity. It is global because it includes the direct and indirect exchanges among community members. Further, throughflow is a special case of Hubbell status as defined in social science. This recognition effectively joins the concepts, enabling ecologists to use and build on the broader centrality research in network science. Second, I characterize the distribution of throughflow in 45 empirically-based trophic ecosystem models. Consistent with expectations, this analysis shows that a small fraction of the system components are responsible for the majority of the system activity. In 73% of the ecosystem models, 20% or less of the nodes generate 80% or more of the total system throughflow. Four or fewer dominant nodes are required to account for 50% of the total system activity. 121 of the 130 dominant nodes in the 45 ecosystem models could be classified as primary producers, dead organic matter, or bacteria. Thus, throughflow centrality indicates the rank power of the ecosystems components and shows the power concentration in the primary production and decomposition cycle. Although these results are specific to ecosystems, these techniques build on flow analysis based on economic input-output analysis. Therefore these results should be useful for ecosystem ecology, industrial ecology, the study of urban metabolism, as well as other domains using input-output analysis.Comment: 7 figures, 2 table

Yellow Perch Population Assessment in Southwestern Lake Michigan, Including Evaluation of Sampling Techniques and Identification of factors that Determine Yellow Perch Year-Class Strength April 1, 2005 - March 31, 2006

Annual Report, Federal Aid Project F-123-R-12, April 1, 2005 - March 31, 2006Report issued on: June 2006INHS Technical Report prepared for Illinois Department of Natural Resources, Division of Fisherie

Irrigation Requirements for Salinity Management on Perennial Ryegrass (Lolium perenne L.) Turf

Irrigation scheduling based on reference evapotranspiration (ETo) multiplied by a crop coefficient (Kc) is an accepted approach for managing and conserving water applied to turfgrass. However, increasing use of recycled water that is often high in salinity warrants further examination of irrigation practices for turfgrass health and salinity management. A 2-yr study was conducted in Riverside, CA to evaluate the response of perennial ryegrass (Lolium perenne L. `SR 4550') turf to varying quality and quantity of irrigation water. A modified line-source gradient experiment was designed to alternate between distribution of potable and saline water to establish an irrigation salinity gradient (EC ~ 0.6 to 4.2 dS m-1) in between lines. Irrigation was scheduled in four separate irrigation zones perpendicular to the irrigation lines according to 80, 100, 120, and 140% ETo. Changes in turf quality (R2 = 0.30***), cover (R2 = 0.26***), and clipping yield (R2 = 0.08***) were primarily driven by the number of days that the area had been irrigated with saline water. When data were separated by irrigation amount, both time and water quality accounted for 54% and 46% of the variability (P < 0.001) in quality and cover, respectively at 80% ETo. Soil salinity (ECe), and sodium absorption ratio (SAR) were highly correlated with irrigation water quality, but not irrigation amount. Stepwise linear regression revealed that soil ECe at 20-30 cm (P < 0.05), and SAR at 10-20 cm (P < 0.001) and 20-30 cm (P < 0.01) accounted for 43% of the variability in quality and cover in August 2012. In September 2012, soil ECe at 10-20 cm (r = -0.62) and 0-30 cm (r = -0.60) had the highest correlation with turfgrass quality and cover. Regression results revealed that soil ECe at 10-20 cm (P < 0.001) and SAR at 10-20 cm (P < 0.05) accounted for 41% of the variability in quality and cover in September 2012. Our results suggest that perennial ryegrass requires irrigation scheduling above 120% ETo, irrigation water quality below ECw ~ 1.7 dS m-1, and soil salinity (ECe) below 3.8 dS m-1 to maintain acceptable quality and cover for over one year in Riverside, CA