400
hotspots hold promise for coping with multiple taxa
in ecological assessments in a spatially explicit
way; however, criteria and procedures for identifying these phenomena remain poorly developed.
Given the diverse scales of life history and ecological response exhibited across aquatic taxa from
microbes to fishes, birds, and mammals (Townsend
and Hildrew, 1994), it remains unclear how coherent these phenomena might be among various taxonomic groups. Clearly, however, refugia, hotspots, and hostile ecological barriers often possess
distinct physical attributes that set them boldly
apart from the remaining matrix of aquatic habitat.
Physical scientists should help to address the ways
these physical attributes are manifested across the
range of biotically relevant spatial and temporal
scales. The developing, general paradigm in stream
ecology of deviation from a posited, locally normative dynamic state or regime (Richter et aI.,
1996; Stanford et aI., 1996; Poff et aI., 1997) holds
promise in facilitating the physical description of
these attributes in a new and holistic way.
Many opportunities for accurate and meaningful
biological assessment and effective decision making are missed because scientists and managers
have devoted insufficient attention to comparing
the inherent strengths and weakness of the many
approaches that have evolved over time. Assessment methods are often chosen based on habit, local tradition, available expertise, or apparent convenience and cost of application. Little critical
evaluation is directed toward the empirical, analytic, and conceptual consequences of the choice
and potential alternatives. In fact, because assessment methods vary in conceptual foundations, emphases, and assumptions, they can lead to markedly
different management implications, even using the
same set of empirical data. In many cases, the methods used do not adequately address the specific
management issue at stake; administrative appeals,
litigation, or unrealized expectations can then
vastly compound the difficulty and time necessary
to reach a technically defensible and socially acceptable resolution to a management problem.
More deliberate consideration of methodological
criteria, including taxonomic resolution, data requirements, and spatial and temporal scale of analyses, would contribute to more accurate, concise,
and cost-effective scientific assessments of aquatic
biota.
The past decade has seen major conceptual
advances in the understanding of aquatic ecosystem organization and response to environmental
change. Simultaneously, the globally precarious
status of aquatic biological resources is becoming
Assessment of Biotic Patterns in Freshwater Ecosystems
widely recognized. Past approaches and methods
of aquatic ecological assessment are beginning to
be reexamined in light of both these developments.
The next decade promises a revolution in the theory and application of ecological science in the
management and conservation of aquatic ecosystems and their biodiversity.
26.6 References
Allan, J. D.; Flecker, A. S. 1993. Biodiversity conservation in running waters. BioScience 43:32--43.
Allan, J. D.; Erickson, D. L.; Fay, J. 1997. The influence
of catchment land use on stream integrity across multiple spatial scales. Freshwater Bioi. 37:149-162.
Allendorf, F. W.; Bayles, D.; Bottom, D. L.; Currens, K.
P.; Frissell, C. A.; Hankin, D.; Lichatowich, J. A.;
Nehlsen, W.; Trotter, P. c.; Williams, T. H. 1997. Prioritizing Pacific salmon stocks for conservation. Conservo Bioi. 11:140-152.
Amoros, C.; Rostan, J. c.; Pautou, G.; Bravard, J. P.
1987a. The reversible process concept applied to the
environmental management of fluvial hydrosystems.
Environ. Manage. 11:607-617.
Amoros, c.; Roux, L.; Reygrobellet, J. L.; Bravard,
J. P.; Pautou, G. 1987b. A method for applied ecological studies of fluvial hydrosystems. Regul. River.
1:17-36.
Baxter, C. Y.; Frissell, C. A.; Hauer, F. R. 1999. Geomorphology, logging roads, and the distribution of bull
trout (Salvelinus confluentus) spawning in a forested
river basin: implications for management and conservation. Trans. Amer. Fisheries Soc. 128(5):854-867.
Biggs, B. J. F. 1995. The contribution of flood disturbance, catchment geology, and land use to the habitat
template of periphyton in stream ecosystems. Freshwater Bioi. 33:419--438.
Bravard, J. P.; Arnoros, C.; Pautou, G. 1986. Impact of
civil engineering works on the successions of communities in a fluvial system. Oikis 47:92-111.
Bryce, S. A.; Clarke, S. E. 1997. Landscape-level ecological regions: linking state-level ecological frameworks with stream habitat. Environ. Manage. 20:297311.
Carpenter, S. R.; Kitchell, J. F.; Hodgson, J. R. 1985.
Cascading trophic interactions and lake productivity.
BioScience 35:634-639.
Corkum, L. D. 1989. Patterns of benthic invertebrate assemblages in rivers of northwestern North America.
Freshwater Bioi. 21:191-205.
Corkum, L. D. 1990. Intrabiome distributional patterns
of lotic macroinvertebrate assemblages. Can. J. Fisheries Aquat. Sci. 47:2147-2157.
Culp, J. M.; Davies, R. W. 1982. Analysis of longitudinal zonation and the River Continuum Concept in the
Oldman-South Saskatchewan River system. Can. J.
Fisheries Aquat. Sci. 39:1258-1265.
Decamps, H.; Fortune, M.; Gazelle, F.; Pautou, G. 1988.
hotspots hold promise for coping with multiple taxa
in ecological assessments in a spatially explicit
way; however, criteria and procedures for identifying these phenomena remain poorly developed.
Given the diverse scales of life history and ecological response exhibited across aquatic taxa from
microbes to fishes, birds, and mammals (Townsend
and Hildrew, 1994), it remains unclear how coherent these phenomena might be among various taxonomic groups. Clearly, however, refugia, hotspots, and hostile ecological barriers often possess
distinct physical attributes that set them boldly
apart from the remaining matrix of aquatic habitat.
Physical scientists should help to address the ways
these physical attributes are manifested across the
range of biotically relevant spatial and temporal
scales. The developing, general paradigm in stream
ecology of deviation from a posited, locally normative dynamic state or regime (Richter et aI.,
1996; Stanford et aI., 1996; Poff et aI., 1997) holds
promise in facilitating the physical description of
these attributes in a new and holistic way.
Many opportunities for accurate and meaningful
biological assessment and effective decision making are missed because scientists and managers
have devoted insufficient attention to comparing
the inherent strengths and weakness of the many
approaches that have evolved over time. Assessment methods are often chosen based on habit, local tradition, available expertise, or apparent convenience and cost of application. Little critical
evaluation is directed toward the empirical, analytic, and conceptual consequences of the choice
and potential alternatives. In fact, because assessment methods vary in conceptual foundations, emphases, and assumptions, they can lead to markedly
different management implications, even using the
same set of empirical data. In many cases, the methods used do not adequately address the specific
management issue at stake; administrative appeals,
litigation, or unrealized expectations can then
vastly compound the difficulty and time necessary
to reach a technically defensible and socially acceptable resolution to a management problem.
More deliberate consideration of methodological
criteria, including taxonomic resolution, data requirements, and spatial and temporal scale of analyses, would contribute to more accurate, concise,
and cost-effective scientific assessments of aquatic
biota.
The past decade has seen major conceptual
advances in the understanding of aquatic ecosystem organization and response to environmental
change. Simultaneously, the globally precarious
status of aquatic biological resources is becoming
Assessment of Biotic Patterns in Freshwater Ecosystems
widely recognized. Past approaches and methods
of aquatic ecological assessment are beginning to
be reexamined in light of both these developments.
The next decade promises a revolution in the theory and application of ecological science in the
management and conservation of aquatic ecosystems and their biodiversity.
26.6 References
Allan, J. D.; Flecker, A. S. 1993. Biodiversity conservation in running waters. BioScience 43:32--43.
Allan, J. D.; Erickson, D. L.; Fay, J. 1997. The influence
of catchment land use on stream integrity across multiple spatial scales. Freshwater Bioi. 37:149-162.
Allendorf, F. W.; Bayles, D.; Bottom, D. L.; Currens, K.
P.; Frissell, C. A.; Hankin, D.; Lichatowich, J. A.;
Nehlsen, W.; Trotter, P. c.; Williams, T. H. 1997. Prioritizing Pacific salmon stocks for conservation. Conservo Bioi. 11:140-152.
Amoros, C.; Rostan, J. c.; Pautou, G.; Bravard, J. P.
1987a. The reversible process concept applied to the
environmental management of fluvial hydrosystems.
Environ. Manage. 11:607-617.
Amoros, c.; Roux, L.; Reygrobellet, J. L.; Bravard,
J. P.; Pautou, G. 1987b. A method for applied ecological studies of fluvial hydrosystems. Regul. River.
1:17-36.
Baxter, C. Y.; Frissell, C. A.; Hauer, F. R. 1999. Geomorphology, logging roads, and the distribution of bull
trout (Salvelinus confluentus) spawning in a forested
river basin: implications for management and conservation. Trans. Amer. Fisheries Soc. 128(5):854-867.
Biggs, B. J. F. 1995. The contribution of flood disturbance, catchment geology, and land use to the habitat
template of periphyton in stream ecosystems. Freshwater Bioi. 33:419--438.
Bravard, J. P.; Arnoros, C.; Pautou, G. 1986. Impact of
civil engineering works on the successions of communities in a fluvial system. Oikis 47:92-111.
Bryce, S. A.; Clarke, S. E. 1997. Landscape-level ecological regions: linking state-level ecological frameworks with stream habitat. Environ. Manage. 20:297311.
Carpenter, S. R.; Kitchell, J. F.; Hodgson, J. R. 1985.
Cascading trophic interactions and lake productivity.
BioScience 35:634-639.
Corkum, L. D. 1989. Patterns of benthic invertebrate assemblages in rivers of northwestern North America.
Freshwater Bioi. 21:191-205.
Corkum, L. D. 1990. Intrabiome distributional patterns
of lotic macroinvertebrate assemblages. Can. J. Fisheries Aquat. Sci. 47:2147-2157.
Culp, J. M.; Davies, R. W. 1982. Analysis of longitudinal zonation and the River Continuum Concept in the
Oldman-South Saskatchewan River system. Can. J.
Fisheries Aquat. Sci. 39:1258-1265.
Decamps, H.; Fortune, M.; Gazelle, F.; Pautou, G. 1988.