We examine evidence for the structuring of fish communities from stream and lake systems and the roles of biotic, abiotic, and spatial factors in determining the species composition. Piscivory by fish is a dominant factor in both stream and lake systems whereas evidence for the importance of competition appears less convincing. Within small streams or lakes, the impact of predation may exclude other species, thereby leading to mutually exclusive distributions and strong differences in community composition. Within a geographic region, abiotic effects frequently dictate the rel - ative importance of piscivory, thereby indirectly influencing the composition of prey species present. The spatial scale of studies influences our perceived importance of biotic versus abiotic factors, with small-scale studies indicating a greater importance of competition and large-scale studies emphasizing abiotic controls. The scale of the individual sites considered is critical because smaller systems have higher variability and wider extremes of conditions than larger lakes and rivers. The stability of physical systems and degree of spatial connectivity contribute to increased diversity in both larger stream and larger lake systems. We identify challenges and needs that must be addressed both to advance the field of fish community ecology and to face the problems associated with human-induced changes.

What controls who is where in freshwater fish communities — the roles of biotic, abiotic, and

We examine evidence for the structuring of fish communities from stream and lake systems and the roles of biotic, abiotic, and spatial factors in determining the species composition. Piscivory by fish is a dominant factor in both stream and lake systems whereas evidence for the importance of competition appears less convincing. Within small streams or lakes, the impact of predation may exclude other species, thereby leading to mutually exclusive distributions and strong differences in community composition. Within a geographic region, abiotic effects frequently dictate the relative importance of piscivory, thereby indirectly influencing the composition of prey species present. The spatial scale of studies influences our perceived importance of biotic versus abiotic factors, with small-scale studies indicating a greater importance of competition and large-scale studies emphasizing abiotic controls. The scale of the individual sites considered is critical because smaller systems have higher variability and ...

What controls who is where in freshwater fish communities the roles of biotic, abiotic, and spatial factors

The concept of process domains is proposed as an alternative to the River Continuum Concept for the influence of geomorphic processes on aquatic ecosystems. Broadly defined, the Process Domain Concept is a multi-scale hypothesis that spatial variability in geomorphic processes governs temporal patterns of disturbances that influence ecosystem structure and dynamics. At a coarse scale, regional climate, geolog vegetation, and topography control the suite of geomorphic processes that are distributed over a landscape. Within the broad context so defined, stream channel classification can guide identification of functionally similar portions of a channel network, but the response of otherwise similar reaches can depend upon their geologic and geomorphic context. Within geomorphic provinces defined by differences in topography, climate history, and tectonic setting, areas with generally similar geology and topography define lithotopo units, which are useful for stratifying different suites of dominant geomorphic processes. Process domains are spatially identifiable areas characterized by distinct suites of geomorphic processes, and the Process Domain Concept implies that channel networks can be divided into discrete regions in which community structure and dynamics respond to distinctly different disturbance regimes. The concepts of process domains and lithotopo units provide both a framework for the application of patch dynamics concepts to complex landscapes and a context for addressing the effects of watershed processes on the ecology of mountain drainage basins.

Process domains and the River Continuum

Fishes suspended in water are subject to the complex nature of three-dimensional flows. Often, these flows are the result of abiotic and biotic sources that alter otherwise uniform flows, which then have the potential to perturb the swimming motions of fishes. The goal of this review is to highlight key studies that have contributed to a mechanistic and behavioural understanding of how perturbing flows affect fish. Most of our understanding of fish behaviour in turbulence comes from observations of natural conditions in the field and laboratory studies employing controlled perturbations, such as vortices generated in the wake behind simple geometric objects. Laboratory studies have employed motion analysis, flow visualization, electromyography, respirometry and sensory deprecation techniques to evaluate the mechanisms and physiological costs of swimming in altered flows. Studies show that flows which display chaotic and wide fluctuations in velocity can repel fishes, while flows that have a component of predictability can attract fishes. The ability to maintain stability in three-dimensional flows, either actively with powered movements or passively using the posture and intrinsic compliance of the body and fins, plays a large role in whether fish seek out or avoid turbulence. Fish in schools or current-swept habitats can benefit from altered flows using two distinct though not mutually exclusive mechanisms: flow refuging (exploiting regions of reduced flow relative to the earth frame of reference) and vortex capture (harnessing the energy of environmental vortices). Integrating how the physical environment affects organismal biomechanics with the more complex issue of behavioural choice requires consideration beyond simple body motions or metabolic costs. A fundamental link between these two ways of thinking about animal behaviour is how organisms sense and process information from the environment, which determines when locomotor behaviour is initiated and modulated. New data are presented here which show that behaviour changes in altered flows when either the lateral line or vision is blocked, showing that fish rely on multi-modal sensory inputs to negotiate complex flow environments. Integrating biomechanics and sensory biology to understand how fish swim in turbulent flow at the organismal level is necessary to better address population-level questions in the fields of fisheries management and ecology.

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A review of fish swimming mechanics and behaviour in altered flows

1. Physical habitat is the living space of instream biota; it is a spatially and temporally dynamic entity determined by the interaction of the structural features of the channel and the hydrological regime.
2. This paper reviews the need for physical habitat assessment and the range of physical habitat assessment methods that have been developed in recent years. These methods are needed for assessing improvements made by fishery enhancement and river restoration procedures, and as an intrinsic element of setting environmental flows using instream flow methods. Consequently, the assessment methods must be able to evaluate physical habitat over a range of scales varying from broad river segment scale (up to hundreds of kilometres) down to the microhabitat level (a few centimetres).
3. Rapid assessment methods involve reconnaissance level surveys (such as the habitat mapping approach) identifying, mapping and measuring key habitat features over long stretches of river in a relatively short space of time. More complex appraisals, such as the Physical Habitat Simulation System (PHABSIM), require more detailed information on microhabitat variations with flow.
4. Key research issues relating to physical habitat evaluation lie in deciding which levels of detail are appropriate for worthwhile yet cost-effective assessment, and in determining those features that are biologically important and hence can be considered habitat features rather than simple geomorphic features.
5. The development of new technologies particularly relating to survey methods should help improve the speed and level of detail attainable by physical habitat assessments. These methods will provide the necessary information required for the development of the two-and three-dimensional physical and hydraulic habitat models.
6. A better understanding of the ways in which the spatial and temporal dynamics of physical habitat determine stream health, and how these elements can be incorporated into assessment methods, remains a key research goal.

The Importance of Physical Habitat Assessment for Evaluating River Health

We constructed an energetic model to determine the optimal focal point current velocity (i.e., microhabitat) for rainbow trout (Oncorhynchus mykiss) and rosyside dace (Clinostomus funduloides) in Coweeta Creek, a fifth-order stream in North Carolina, USA. Energetic costs were evaluated by quantifying the metabolic expenditure associated with swimming at a given velocity. We estimated benefits by measuring potential energetic gains of feeding at a given velocity. This included estimates of the ability of the fish to capture prey at different current velocities as well as estimates of the frequency and the energy content of drifting prey at various velocities. We derived separate models for small (53-70 mm SL (standard length)) and medium (71-125 mm SL) trout, and medium (47- 52 mm SL) and large (53-70 mm SL) dace for all seasons, deriving net energy gain as a function of current velocity. We predicted fishes would occupy velocities at which net energy gain was maximized. Predicted velocities were compared with those utilized by fishes inhabiting Coweeta Creek. Optimal velocities predicted by energetic models ranged from 7.7 to 22.1 cm/s, and closely matched actual velocity use (average deviation = 2.6 cm/s). Prey capture success appeared to be the most important component in the models. Consequently, we constructed models based solely upon aspects of capture success; the average deviation from velocity use with these models was only 1.8 cm/s. Thus, the ability of dace and trout to capture prey at varying velocities appears to be the dominant factor affecting microhabitat selection in these species.

https://www.jstor.org/stable/info/1940796

An Energetic Model of Microhabitat Use for Rainbow Trout and Rosyside Dace

We estimated home ranges of three fish species inhabiting a fourth order stream in the Blue Ridge Mountains of North Carolina. Individuals were uniquely marked with a subcutaneous injection of acrylic paint. Cottus bairdi, Rhinichthys cataractae and Clinostomusfunduloides moved an average of 12.9, 13.4, and 19.3 m respectively, between captures. Mean time interval between captures was 128 d; 86% of recaptures were in the stream section of previous capture. Individuals may not have moved throughout the entire section length (mean length 10.4 m); thus, these values likely overestimate actual movements.

Home range estimates for three North American stream fishes

We monitored fish populations at three sites in a southern Appalachian stream system during a 40-mo study. Assemblages at two sites, consisting of four and five resident species, were persistent in terms of relative species abundances and production. This persistence was related to low variation in abundance of the two numerically dominant fishes, mottled sculpins (Cottus bairdi) and longnose dace (Rhinichthys cataractae). Less abundant residents, rosyside dace (Clinostomus funduloides), rainbow trout (Salmo gairdneri), and greenside darters (Etheostoma blennioides), displayed lower levels of persistence. We also observed pronounced annual variation in either young-of-the-year recruitment and/or subsequent year-class strength of four resident species, possibly resulting from a severe drought during the third year of study. Abundance and production of rosyside dace and trout were greatly affected by fluctuations in recruitment and year-class strength, suggesting that environmental variability strongly infl...

Fish Assemblage Stability in a Southern Appalachian Stream

In this paper we attempt to synthesize a variety of developments in the fields of landscape and population ecology and apply these ideas to the physical and biological characteristics of lotic systems. First, most attempts to manage evolutionarily significant units (ESUs) are based on the notion that the physical characteristics of lotic habitats are stable. Yet, data from three permanent 100-m reaches in the Coweeta drainage of North Carolina indicated that these reaches possessed substantial annual variability with respect to both substratum composition and flow rates. In addition, substratum data demonstrated that these reaches were patchy environments, and that a landscape-based approach might facilitate the management of species in this system. Second, a simple landscape-driven difference equation model of population dynamics based on biological characteristics common to many fishes indicated that the critical habitat for population maintenance may not always be the area in which the species is most abundant. Finally, two tests for habitat selection by stream fishes indicated that more biologically realistic models (e.g., a landscape-based model that included prey abundance) and a model that included explicit tests for the mechanism of selection itself (e.g., energy gain) may greatly increase our ability to identify and manage habitats that are crucial for survival of ESUs. At present we are at a crossroads with respect to nized that most habitats are embedded within a preservation of the earth's genetic resources. In- larger landscape that may influence many of the creasing population growth combined with ques- ecological processes occurring in discrete habitat tionable economic and management practices have patches (Forman and Godron 1986; Pringle et al. driven us to a point at which the loss of biological 1988). For example, research on energy transforma- diversity is occurring at an exponential rate, a rate tions in eastern woodland streams has shown that previously unknown in modern times. Such losses these systems depend upon the surrounding decid- dramatically increase our need for innovative man- uous forest for most of their organic energy inputs agement strategies for the conservation of evolu- (Minshall 1967). Studies of anthropogenic distur- tionarily significant units (ESUs). (We will use the bances such as logging also demonstrate that activ- term ESUs to refer to species, subspecies, or pop- ities occurring in habitats far from the streambank ulations with extremely low abundances.) In this can have substantial deleterious effects on both fish paper, we will attempt to synthesize a variety of and invertebrate populations in lotic systems (Mor- developments in the fields of landscape and popu- ing 1975; Salo and Cundy 1987). Consequently, our lation ecology (Johnston and Naiman 1987; Pringle understanding of rivers and streams from both a et al. 1988; Johnston et al. 1990; Schlosser 1991) basic and applied perspective may be enhanced by and apply these ideas to the physical environment the application of a landscape perspective to studies of lotic systems, as well as to both population dy- of these systems. namics and habitat selection by lotic animals. We The field of landscape ecology is relatively recent; focus our observations on the speciose stream fish a text book on the subject was published in 1986 assemblages of the eastern and midwestern United (Forman and Godron 1986) and the specialized States, rather than on the depauperate western journal Landscape Ecology began in 1987. Many of fauna.

Observations on Habitat Structure, Population Regulation, and Habitat Use with Respect to Evolutionarily Significant Units: A Landscape Perspective for Lotic Systems

Jennifer Hill

Papers

An Energetic Model of Microhabitat Use for Rainbow Trout and Rosyside Dace

Home range estimates for three North American stream fishes

Fish Assemblage Stability in a Southern Appalachian Stream

Observations on Habitat Structure, Population Regulation, and Habitat Use with Respect to Evolutionarily Significant Units: A Landscape Perspective for Lotic Systems

Effects of subcutaneous marking on stream fishes