Photo by Bruce Molnia USGS Meanders of Shenandoah River, Virginia
On Wednesday we will be reading papers on appropriate spatial scales for conserving riverine resources. My lecture on Wednesday will focus on Population Ecology of Stream Fishes and the emphasis will be on the temporal variation in habitat and the tendency of stream fish populations and assemblages to maintain some semblance of stability in a temporally variable environment (no assigned reading).
Our discussion will complicate this picture by taking a realistic view of the spatial connectivity of habitats. The paper by Kurt Fausch and others is a thorough literature review which proposes a number of principles based on a few example studies that study fish populations in a spatial context. The other papers that have been assigned will provide us additional examples from darters, smallmouth bass, mountain suckers and charr. These papers describe complex studies and numerous types of data and data analysis and are long -- so do not leave your reading to the last minute, hours or day .
Pay close attention to principles described in Table 1 and bring your examples of your personal insights and examples of these premises. Or think about these principles and their applications as you read specific articles about spatial patterns in stream fishes.
This just in: About the Trends in Nutrients in Shenandoah River of Virginia. Here is an example of the spatial complexity of addressing a basic question about the trends in water quality over time.
"There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact." Mark Twain, Life on the Mississippi, 1883
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Faush et al. argue in their article “Landscapes to riverscapes: bridging the gap between research and conservation of stream fishes” that focusing on the landscape scale of stream and fisheries ecology to encompass the whole life history of fishes is the best way to forward science and to make meaningful contributions towards the conservation of stream fishes. The authors support this argument by pointing out the continued imperilment of stream fishes and the large-scale anthropogenic disturbances that necessitate understanding the linkages between scale, habitat heterogeneity and spatial connectivity of stream segments for appropriate management of aquatic resources. The authors are firm in their belief that an intermediate scale, spatially explicit, hierarchical understanding of stream fishes is the best, most informative for conservation of populations of stream fishes. The writers’ main purpose is to encourage fisheries ecologists to broaden their scope of study to that which fully addresses the scope of the life history of the organism so future studies can be used to address both current challenges in conservation as well as those which are bound to emerge in the future.
K.D. Faush, C.E Torgersen, C.V. Baxter and H.W. Li. 2002. Landscape to riverscapes: bridging the gap between research and conservation of stream fishes. Bioscience 52(6): 483-498.
Bult et al. (1998), in their journal article, “New technique describing spatial scaling and habitat selection in riverine habitats”, argue that since organisms are associated with their environment at a range of spatial and temporal scales, a comprehensive understanding of factors affecting the distribution and abundance of fish can only be achieved by studying factors affecting fish distributions at a range of scales, rather than one or even a few selected scales. They then propose a quantitative multi-scale technique based on frequency analysis and randomisation to study habitat selection by fish in riverine habitats. This method is then illustrated using both simulated fish distributions, as well as field data. In this method the authors employ the use of formulae and a computer program to determine fish-fish, group-group, habitat-habitat and fish-habitat relationships. These relationships are considered at different temporal and spatial scales. The authors readily admit that this method requires much computing time for analyses where density estimates are obtained by high resolution dummy positions. The authors’ main purpose is to introduce a mathematical technique that is suitable for studying fish in rivers, using a multi-scale approach.
Bult T.P., Haedrich R.L. and Schneider D.C. 1998. ‘New technique describing spatial scaling and habitat selection in riverine habitats’, Regulated Rivers: Research & Management, 14: 107–118.
Watson, Greg and Hillman T.W. “Factors Affecting the Distribution and Abundance of Bull Trout: An Investigation at Hierarchical Scales.” (1997) presents ideas that different characteristics may have different impacts on bull trout presence at different special scales, which need to be taken into consideration when planning restorations for their habitats, since bull trout populations have continually been declining in recent history. Watson and Hillman surveyed 1,057 randomly selected sites from 93 streams across 18 different drainages across the Pacific Northwest for the presence of bull trout under several physical and biotic settings and used logistic regression to assess the presence of salmonids. Of the 93 streams that were sampled, 31 of the streams contained bull trout and there showed to be significant differences between the preferences of the bull trout habitats, like substrate type, valley bottom type and riparian vegetation. Watson and Hillman present important factors to consider when preparing a restoration plan in order to make future restorations of bull trout habitats more successful and ensure ideal conditions for the bull trout to thrive. This article is intended for any managers or consultants that would be planning restorations of certain stretches of stream that contain bull trout, but depending on the special scale that is being restored, this article may appeal to different people.
Dauwalter et al. 2007 compare smallmouth bass densities along three scales in an article titled “Geomorphology and stream habitat relationships with smallmouth bass (Micropterus dolomieu) abundance at multiple spatial scales in eastern Oklahoma.” The three scales tested were watershed morphology, reach morphology, and channel-unit characteristics and these were compared among three mountain ecoregions. The authors found that no single scale had a greater influence on smallmouth bass density than the others, implying that each scale is linked to the others and the relationship between scales is very complex. For example, the high densities were found in shallow, wide channel units only when bedrock was found. Although the authors used Frissel et al. (1986) classification scheme to define scale, they did not address the segment scale in their analysis. The authors believe that understanding the effects of factors at multiple scales is important to understand how to best manage the smallmouth bass and give insight into how land use practices may influence this species.
Dauwalter, D.C., D.K. Splinter, W.L. Fisher, and R.A. Marston. 2007. Geomorphology and stream habitat relationships with smallmouth bass (Micropterus dolomieu) abundance at multiple spatial scales in eastern Oklahoma. Canadian Journal of Fisheries and Aquatic Science 64:1116-1129.
Fausch et. al (2002) uses empirical evidence and the dynamic landscape model for stream fish ecology proposed by Schlosser (1991) to introduce a better way of addressing stream issues for both researchers and managers. In a riverscape model, heterogeneity is important for fish to survive through their different life stages and is important in dispersal. The role of geomorphology in the selection of redds of trout in Montana, and the survival and dispersal of the Arkansas darter provide two empirical examples of the importance of selecting the proper scale for analysis to understand how the context of landscape is crucial for managing a species. The authors propose five principles to guide research and management in streams: 1) choosing an appropriate scale, 2) interaction occurs among scales, 3) unique features can have overriding effects, 4) consequences of habitat degradation occur in all directions, and 5) match research to scales that managers can use. The authors believe that using scale correctly will allow us to fix problems facing our stream fisheries at more than just the reach level.
K.D. Faush, C.E Torgersen, C.V. Baxter and H.W. Li. 2002. Landscape to riverscapes: bridging the gap between research and conservation of stream fishes. Bioscience 52: 483-498.
R.H. Hilderbrand and J.L. Kershner (2000) in “Conserving inland cutthroat trout in small streams: how much stream is enough?” discuss minimum stream lengths (MSL) to maintain cutthroat trout populations according to density. Barriers, serving as protection against introduced fishes, are an effective method to maintain viable cutthroat populations. High cutthroat abundance streams (n = 2500) showed a need for over 8 km stream length, with an adjusted 10% length of 9.3 km. Low cutthroat abundance streams (n=2500) needed lengths of 25 km, with an adjusted 10% length of 27.8 km. The higher the number of individuals in the isolated population, the more length of stream is needed to adequately sustain it based on density. Maintaining adequate population sizes of isolated populations of cutthroat trout with the influence of introduced salmonids and population loss is critical for sustainment.
Hilderbrand, R.H., and J.L. Kershner. 2000. Conserving inland cutthroat trout in small streams: how much stream is enough? North American Journal of Fisheries Management 20: 513-520.
In “Landscapes to riverscapes: bridging the gap between research and conservation of stream fishes,” K.D. Fausch et al (2002) address the need for landscape ecology to be applied to active management for stream fishes. Extinction and extirpation management, mainly due to anthropological influences, is a major need for research and conservation. Reach heterogeneity, multi-scale habitat understanding and assessment, and stream connectivity should all relate and influence management decisions. The authors outline five riverscape principles for carrying out research and management is regard to lotic fishes: 1) appropriate scale choice – don’t be afraid to implement or use multiple scales, 2) scale interactions exist and will influence each other, 3) unique feature effects – sometimes override and significantly affect habitats, 4) anthropogenic sources can hurt aquatic systems spatially and temporally, 5) Compare before and after conditions to assess improvement. In conclusion, many challenges due to anthropogenic effects still exist, for which research and management need to work together to solve. Increasing knowledge with an increase in research parameters may facilitate more applicable management practices.
Fausch, K.D., C.E. Torgersen, C.V. Baxter, and H.W. Li. 2002. Landscapes to riverscapes: bridging the gap between research and conservation of stream fishes. BioScience 52(6): 483-498.
Letcher et al 2007. Population Response to Habitat Fragmentation in a Stream-Dwelling Brook Trout Population.
The authors begin by describing some effects of habitat fragmentation on natural populations. They sought to estimate size-specific population variables for various fragmented metapopulations of brook trout. They found that isolated tributaries were genetically divergent from connected systems. They also found that reductions in tributary connectivity increased the probability of stream-wide extinction. They conclude that fragmentation increases extinction risk, and that frequent movement between patches is necessary to ensure local persistence.
In “Landscapes to riverscapes: bridging the gap between research and conservation of stream fishes” Fausch et al. argue that in order to adequately conserve and manage lotic fishes, researchers must focus on the “riverscape” scale of fisheries and stream ecology. The authors do this by exploring the common ground between landscape ecology and river ecology, considering empirical data that focuses on intermediate and spatial scales to examine a stream’s heterogeneous nature, and defining five principles for more effective research: 1) choose appropriate scales, 2) embrace the ecological complexity of lotic systems, 3) do not overlook rare or unique features, 4) understand that unintended consequences of habitat degradation will occur in all directions, and 5) conduct research at scales relevant to managers. The authors conclude in order to effectively conserve and manage stream fishes, researchers and managers will need to perform experiments and design management systems at scales that are relevant to the life history characteristics of the species that they are researching. The main purpose of this paper is to implore fisheries biologists to shift their methods of thinking and adapt their sampling methods to an intermediate scale to improve the understanding of stream fishes and lotic ecosystems.
Fausch, K. D., C.E Torgersen, C.V. Baxter and H.W. Li. 2002. Landscape to riverscapes: bridging the gap between research and conservation of stream fishes. Bioscience 52: 483-498.
Fausch et al suggest that a landscape level approach is necessary for a complete understand of the underpinnings of stream fish ecology. They address Schlosser’s work regarding the necessity of habitat heterogeneity to satisfy all fishes’ life history demand. They cite empirical studies that prove the necessity for a riverscape approach. They state that as many stream fishes exhibit high levels of dispersal, the necessity to manage populations within a large-scale perspective is necessary. They outline five principles to use when investigating stream ecosystems: 1) determining an appropriate scale, 2) interactions among scales, 3) features that have overriding effects, 4) the consequences of habitat degradation occur in all directions, and 5) research must match scales that managers are able to use in their own practices
The 2000 article “Metapopulations and salmonids: a synthesis of life history patterns and empirical observations” by Rieman and Dunham states that although many of the processes present in metapopulation theory can be applied to salmonid conservation, there is little empirical evidence to apply the metapopulation theory as a whole to salmonid conservation. In order to support this claim, the authors initially outline the basis of the metapopulation theory and then provide three salmonid, life-history examples (Bull trout (Salvelinus confluentus), Lahontan cutthroat trout (Oncorhynchus clarki henshawi), and Westslope cutthroat trout (Oncorhynchus clarki lewisi)) to determine the relevance and applicability of metapopulation theory to salmonid conservation. The authors conclude that there is no empirical evidence to support the use of a general metapopulation model to manage/conserve salmonid species; however, some basic elements of metapopulation theory (such as dispersal, life history, and patch-size requirements) are relevant and can be applied when studying salmonids. The goal of this paper is to encourage managers to conserve or restore key process that could possibly lead to a successful metapopulation rather than attempting to outline a metapopulation network.
Rieman, B. E., J. B. Dunham. 2000. Metapopulations and salmonids: a synthesis of life history patterns and empirical observations. Ecology of freshwater fish 9: 51-64.
Mattingly, H. T. and D. L. Galat. 2002. Distributional patterns of the threatened Niangua Dater, Etheostoam niagnuae, t tress spatial scales, with implications for species conservation. Copeia 2002 (3): 573-585.
Mattingly and Galat (2002) assume that presence of the Niangua dater in a given patch is the process of filtering at three successively nested spatial scales: stream (among streams in a system), reach and microhabitat. They used historical data to determine presences in a stream, surveyed reaches in streams historically occupied by darters, and measured microhabitats characteristics in occupied reaches. Accordingly, they measured appropriate characteristics that would differ among streams (measures of order and location in a drainage network), among reaches of give stream (direction of flow, gradient, instream cover, habitat type, etc,) and among microhabitats in a reach (depth, velocity, substrate, etc.). They found the Niangua dater occupied specific places in the drainage (typically larger streams and tributaries to those streams that were of similar stream order), reaches with intermediate elevation, intermediate gradient and intact banks, and in microhabitats with narrower range of depth, substrate, temperature, silt than available. The purpose of this article was to test the assumption that this dater has a hierarchically nested distribution, whether that was adequately answered remains to be debated; nevertheless, these finds provide insight to management.
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