READING
Albanese, B. W., P. L. Angermeier, and C. Gowan. 2003. Designing mark-recapture studies to reduce effects of distance weighting on movement distance distributions of stream fishes. Transactions of the American Fisheries Society 132:925–39. Explores the role of changing capture probabilities with distance from the release point in estimates of fish movement.
Belyea, L. R., and J. Lancaster. 1999. Assembly rules within a contingent ecology. Oikos 86:402–16. An overview of the literature on community assembly.
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 52:483–98. Emphasizes the need to view streams and rivers as complex landscapes and the importance of access to these varied habitats by fishes.
Gowan, C., M. K. Young, K. D. Fausch, and S. C. Riley. 1994. Restricted movement in resident stream salmonids: A paradigm lost? Canadian Journal of Fisheries and Aquatic Sciences 51:2626–37. A reanalysis and counter argument to the restricted movement paradigm.
Mandrak, N. E., and E. J. Crossman. 1992. Postglacial dispersal of freshwater fishes into Ontario. Canadian Journal of Zoology 70:2247–59. An important paper on the glacial refugial origins of Ontario freshwater fishes.
Taylor, C. M. 1996. Abundance and distribution within a guild of benthic stream fishes: Local processes and regional patterns. Freshwater Biology 36:385–96. Uses field collections and manipulative studies to test predictions of hypotheses regarding the abundance and distribution of fishes.
SIX
Persistence of Fish Assemblages in Space and Time
CONTENTS
Responses to Environmental Perturbations
Dealing with Environmental Change
Levels of Persistence and Stability in Lotic Systems
Examples of Persistence and Stability in Lotic Systems
Levels of Persistence and Stability in Lentic Systems
Examples of Persistence and Stability in Lentic Systems
Persistence and Stability Summary
Persistence and Stability of Local Associations
Persistence, Stability, and Control of Fish Assemblages
THE FIRST TWO CHAPTERS in Part 2 examined how fish species and assemblages are affected by broadscale landscape features, how various models relate assemblages to the environmental variables, how fish assemblages are formed, and the role that movement plays over different life-history stages in allowing fishes to access new habitats and to move among habitats so that their fitness is maximized. This chapter focuses primarily on the temporal and spatial dynamics of fish assemblages, or how fish populations and assemblages cope with relatively short-term physical and biotic challenges.
Understanding the type, frequency, and magnitude of variability in fish assemblages is important for several reasons (e.g., Grossman et al. 1990; Matthews 1998). First, assessing the impact of anthropogenic environmental changes requires knowing the background level of natural variation in assemblages. Second, the degree to which assemblages are resistant to changes over space and time is related to the strengths of control mechanisms operative within the assemblage. Although assemblages generally are structured and not random collections of species from a regional species pool (Chapter 5), once established, they may be acted upon by external or internal processes. With some exceptions (Strong 1983), assemblages showing high variation in species composition and abundances may primarily be governed by external, stochastic (i.e., random) processes such as floods, droughts, or other major events. These events can control such processes as species persistence, colonizations, or even extinctions. In communities with strong stochastic influences, the importance of biotic interactions (i.e., competition or predation) in affecting community structure is considered to be lessened because of the frequent changes in species composition. In contrast, assemblages that show little variation may be controlled primarily by deterministic processes, such that the characteristics of the environment result in a particular suite of species (e.g., the landscape filters described in Chapter 4). In assemblages that show little variation in species composition, the possibility of well-developed biotic interactions is considered to be greater (Grossman et al. 1982; Lepori and Malmqvist 2009). Importantly, processes controlling communities should not be viewed in an either-or situation. Stochastic and deterministic processes can act hierarchically (i.e., stochastic processes influence the species on which deterministic processes act). The relative importance of stochastic versus deterministic controls varies with disturbance levels, although not necessarily monotonically (Lepori and Malmqvist 2009).
RESPONSES TO ENVIRONMENTAL PERTURBATIONS
Types of Perturbations
Natural perturbations have shaped the evolution of fish populations and, in the case of severe events, have resulted in the local extirpation of populations or the total extinction of species. For instance, large-scale Cenozoic climatic changes resulted in the extinction of numerous western North American fishes at the end of the Miocene and also the early Pleistocene (G. R. Smith 1981). Natural perturbations include droughts, floods, fires within the watershed, climatic changes, and biotic changes (such as the addition or loss of a predator). Human-induced changes might include chemical spills or piscicide applications; changes in land use, such as mining, agriculture, or timber harvesting resulting in flooding, increased water temperature, nutrient or herbicide runoff, and erosion; major barriers to fish movement as a result of dams or water diversions; stream channelization; and the introduction of nonindigenous species.
One way to view both natural and human-caused disturbances is by their extent. Events that persist longer than the life spans of the species in an assemblage and impact large spatial areas are referred to as press disturbances, in contrast to
