A heuristic framework for understanding and predicting the distribution and categorical abundance of species in stream communities is presented. The framework requires that species be described in terms of their functional relationships to habitat selective forces or their surrogates, which constitute "filters" occurring at hierarchical landscape scales (ranging from microhabitats to watersheds or basins). Large-scale filters are viewed as causative or mechanistic agents that constrain expression of local selective forces or biotic potential at lower scales. To join a local community, species in a regional pool must possess appropriate functional attributes (species traits) to "pass" through the nested filters. Biotic interactions are also a potential filter on local community composition, and they are invoked at the lower hierarchical levels, after species have passed through the physicochemical habitat filters. Potential landscape filters and their associated selective properties are identified, as are ...

Landscape filters and species traits: Towards mechanistic understanding and prediction in stream ecology

Traditionally lower and upper temperature tolerances of fishes have been quantified in the laboratory via three different experimental approaches: the Fry or incipient lethal temperature (ILT), critical thermal (CTM) and chronic lethal (CLM) methodologies. Although these three experimental laboratory approaches generate endpoints which are quantitatively expressed as a temperature, are determined experimentally with random samples of fish acclimated to specific temperatures, and involve both time and temperature as major test variables, they do not quantify the same response. All three approaches generate valuable, albeit different, information concerning the temperature tolerance of a species. In this review we have summarized published research concerning the tolerance of North American freshwater fishes to dynamic changes in temperature, i.e., tolerance is tested by methods that gradually change temperatures until biological stress is observed. We found more than 450 individual temperature tolerances listed in 80 publications which present original dynamic temperature tolerance data for 116 species, 7 subspecies and 7 hybrids from 19 families of North American freshwater fishes. This total represents about 1/3 of the families and 1/6 of the known North American freshwater species. Temperature tolerance data were partitioned by experimental approach, i.e., critical thermal method (CTM) and chronic lethal method (CLM), and direction of temperature change. Although both CTM and CLM expose fish to dynamic changes in water temperature, these two methods differ in temperature change rates and test endpoints, and hence measure different aspects of thermal stress. A majority of the 80 studies employed CTM to assess temperature tolerance, in particular determination of CTmaxima. One or more CTmaxima has been reported for 108 fishes. Twenty-two fishes have reported highest CTmaxima of 40°C or higher. Several species in the family Cyprinodontidae have generated some of the highest CTmaxima reported for any ectothermic vertebrate. For a variety of reasons, data concerning tolerance of low temperatures are less plentiful. Low temperature tolerance quantified as either CTminima or CLminima were found for a total of 37 fishes. Acclimation temperature exerts a major effect on the temperature tolerance of most North American fish species and it is usually strongly linearly related to both CTmaxima and CTminima. Although we uncovered dynamic temperature tolerance data for 130 fishes, only a single dynamic, temperature tolerance polygon has been published, that for the sheepshead minnow, Cyprinodon variegatus.

Temperature Tolerances of North American Freshwater Fishes Exposed to Dynamic Changes in Temperature

We reviewed 725 papers published since Cowles and Bogert's paper on thermal tolerance (R.B. Cowles and C.M. Bogert. 1944. Bull. Am. Mus. Nat. Hist. 83: 261–296) to create a data base of studies tha...

The critical thermal maximum: history and critique

The relative influence of geologic versus anthropogenic attributes of catchments on stream ecosystems was examined in 45 catchments of a river basin in central Michigan. Each catchment was characterized by land use, surficial geology, elevation, and hydrography, and summaries of these data were related to physical habitat characteristics that had the greatest influence on macroinvertebrate assemblages. Partial redundancy analysis revealed that geologic and land-use variables had similar magnitudes of influence on stream habitats. Of the geologic variables, catchment area, proportion of lacustrine clays, and glacial outwash materials had the strongest influence on physical habitat, particularly on channel dimensions. Row-crop agriculture and the presence of wetlands were the most important land-use variables, particularly influencing amounts of woody debris. Stream buffers (100 m) were more important than whole catchment data for predicting sediment-related habitat variables; however, channel morphology was more strongly related to whole catchments. Results suggest that catchment-wide geology and land-use characteristics may be more important than stream buffers for maintaining or restoring stream ecosystems. These techniques can be used to develop biologic signatures of catchment condition that discriminate causal factors influencing the biodiversity and health of stream ecosystems. Resume : Nous avons examine les influences respectives sur les ecosystemes des cours d'eau des attributs geologiques des bassins-versants en regard de leurs attributs anthropiques dans 45 aires d'alimentation d'un bassin fluvial du centre du Michigan (Etats-Unis). Nous avons caracterise chaque aire d'alimentation par l'utilisation du sol, la geologie de subsurface, l'elevation et l'hydrographie et nous avons rattache les sommaires des donnees ainsi obtenues aux caracteristiques de l'habitat physique qui exercaient la plus forte influence sur les communautes de macro-invertebres. L'analyse par redondance partielle a revele que les variables geologiques et les variables d'utilisation du sol exercaient sur les habitats une influence du meme ordre de grandeur. Pour ce qui est des variables geologiques, ce sont l'aire du bassin-versant ainsi que la proportion d'argiles lacustres et de materiaux stratifies fluvio-glaciaires qui ont agi le plus sur l'habitat physique, particulierement sur les dimensions du chenal. Les cultures en lignes et la presence de terres humides consituaient les plus importantes variables en matiere d'utilisation du sol, variables qui ont agi tout particulierement sur la quantite de debris ligneux. Les zones tampons (100 m) ont joue un plus grand role que les donnees sur les bassins-versants tout entiers dans la prevision des variables d'habitat relatives aux sediments; par contre, la morphologie du chenal se rattachait plus fortement aux bassins-versants tout entiers. Les resultats permettent de penser que la geologie du bassin-versant et les caracteristiques d'utilisation du sol font peut-etre plus que les zones tampons pour maintenir ou retablir les ecosystemes des cours d'eau. On peut recourir a ces techniques pour elaborer, au sujet de l'etat des bassins-versants, des signatures biologiques qui distinguent les facteurs causaux de la biodiversite et de la sante des ecosystemes des cours d'eau. (Traduit par la Redaction)

Landscape-scale influences on stream habitats and biota

The extensive development of surface and subsurface drainage systems to facilitate agricultural production throughout North America has significantly altered the hydrology of landscapes compared to historical conditions. Drainage has transformed nutrient and hydrologic dynamics, structure, function, quantity, and configuration of stream and wetland ecosystems. In many agricultural regions, more than 80% of some catchment basins may be drained by surface ditches and subsurface drain pipes (tiles). Natural channels have been straightened and deepened for surface drainage ditches with significant effects on channel morphology, instream habitats for aquatic organisms, floodplain and riparian connectivity, sediment dynamics, and nutrient cycling. The connection of formerly isolated wetland basins to extensive networks of surface drainage and the construction of main channel ditches through millions of acres of formerly low-lying marsh or wet prairie, where no defined channel may have previously existed, have r...

Effects of Agricultural Drainage on Aquatic Ecosystems: A Review

Riparian buffer zones serve several important roles in linking a stream to its watershed. A main function is controlling the dynamics of sedimentation. This paper documents how siltation impacts fish communities and how proper riparian management can mitigate the negative effects of sedimentation. Two studies examined the relation between stream siltation and fish community characteristics. Community responses to siltation were poorly described by common structural indices. Community level responses to varying siltation were most consistently described by changes in functional characteristics of the resident fish species using a guild-based analysis. Herbivores, benthic insectivores and simple lithophilous spawners were most sensitive to siltation while other guilds were not. These results were repeatable in both intraregional comparisons among sites of similar size and character, and in interregional comparisons of streams which varied in characteristics besides siltation. This suggests the index may be useful in separating the effects of siltation from other environmental variables. A discussion of bufferstrip characteristics important in mitigating against, or preventing, excess siltation is presented.

Effects of siltation on stream fishes and the potential mitigating role of the buffering riparian zone

We developed a reference base of relative hypoxia and hyperthermia tolerance rankings for many of the common fish species that inhabit small streams in Missouri. We also investigated the influences of geographic variation and of fish size on these tolerances. Fish collected from the wild were acclimated to laboratory conditions over a 63–160-d period. They were then exposed to either progressively increasing temperatures or to decreasing dissolved oxygen concentrations over a 4–6-h period. The temperature at which a fish lost equilibrium or the oxygen concentration at which it ceased ventilating was recorded as the end point. No significant differences in critical maximum temperatures (hyperthermia tolerance) or critical minimum oxygen concentrations (hypoxia tolerance) occurred in any of the five comparisons between fish of the same species collected from different locations in Missouri. Neither the hypoxia nor hyperthermia tolerance values varied with fish size for any species. Among the 35 spe...

Hypoxia and Hyperthermia Tolerances of Headwater Stream Fishes

Indices of hypoxia and hyperthermia tolerance for Missouri fish assemblages were based on laboratory measurements of lethal dissolved oxygen concentrations and temperatures, combined with field measures of the relative abundances of tolerant and sensitive species. Fish assemblages and extreme physicochemical conditions were monitored over 3–4 years at 18 sites on headwater streams in the Prairie, Ozark Border, and Ozark regions of Missouri. Oxygen minima ranged from 0.8 to 6.0 mg/L, and temperature maxima ranged from 19.6 to 30.7°C; oxygen minima at study sites were not correlated with temperature maxima. Hypoxia tolerances of fish assemblages were strongly correlated with minimum stream oxygen concentrations and varied concordantly with regional, longitudinal, and temporal gradients in stream oxygen minima. Hyperthermia tolerances of fish assemblages were not correlated with maximum stream temperatures, nor were regional, longitudinal, or temporal differences in hyperthermia tolerances concordan...

Martin A. Smale

Papers

Effects of siltation on stream fishes and the potential mitigating role of the buffering riparian zone

Hypoxia and Hyperthermia Tolerances of Headwater Stream Fishes

Influences of Hypoxia and Hyperthermia on Fish Species Composition in Headwater Streams