Assemblage stability in stream fishes: A review

Abstract

ABSTRACT/We quantified the stability of nine stream fish assemblages by calculating coefficients of variation of population size for assemblage members. Coefficients of variation were high and averaged over 96%; indicating that most assemblages were quite variable. Coefficient of variation (CV) estimates were not significantly affected by: (1) years of study, (2) mean abundance, (3) familial classification, or (4) mean interval between collections. We also detected minor regional differences in CVs. The high variability exhibited by many stream fish assemblages suggests that it may be difficult to detect the effects of anthropogenic disturbances using population data alone. Consequently, we urge managers to exercise caution in the evaluation of the effects of these disturbances. More long-term studies of the ecological characteristics of undisturbed stream fish assemblages are needed to provide a benchmark against which disturbed systems can be compared.We suggest that CVs are a better estimator of population/assemblage stability, than either Kendall's W or the standard deviation of the logarithms of numerical censuses. This conclusion is based on the following reasons. First, CVs scale population variation by the mean and, hence, more accurately measure population variability. Second, this scaling permits the comparison of populations with different mean abundances. Finally, the interpretation of CV values is less ambiguous than either of the aforementioned metrics.Annual and season variations in flow regimes (i.e., droughts and floods) can produce substantial fluctuations in the physical environment of many lotic ecosystems. Because droughts and floods occur with a relatively high frequency, especially when compared to many other natural disturbances (e.g., E1 Nifio, hurricanes), iotic environments are excellent systems for tests of equilibrium and nonequilibrium ecological theories. Implicit tests of such theories occurred as early as 1951, when William Starrett (1951) observed large variations in species abundances in an Iowa riverine fish assemblage and attributed these variations to unpredictable hydrologic events. Similar results were obtained by later researchers (Larimore 1954, Metcalf 1959, Paloumupis 1958, Larimore and others 1959, John 1964, Lowe and others 1967, Rinne 1975, Harrell and others 1967, Harrell 1978, Mills and Mann 1985, Moyle and Li 1979.Prompted by the general ecological debate regarding the importance of equilibrium and nonequilibrium processes to assemblage dynamics, Grossman and others (1982) reviewed the literature on stream systems. This review, coupled with a reanalysis of assemblage structure data from an Indiana stream, led them to reiterate Starrett's hypothesis and suggest that hydrologic variability may facilitate coexistence in assemblages of many stream organisms. The proposed

Hydrologic connectivity driven natural stream fish assemblages in mountain streams in the Yangtze River basin: implications for stream fish conservation in monsoonal East Asia

“…Under natural conditions, patterns and processes observed in fish assemblages are strongly influenced by multiple factors operating over a range of spatial and temporal scales (Horwitz, 1978;Schlosser, 1987;Tonn, 1990;Oberdoff et al, 1995;Ostrand & Wilde, 2002;Hoeinghaus et al, 2007). On a local scale, physical and chemical factors appear to determine species richness in variable environments (Gorman & Karr, 1978;Rahel, 1986;Schlosser, 1991;Matthews, 1998;Bond & Lake, 2003;Gerhard et al, 2004), while biological ones are more important in stable environmental conditions (Ross et al, 1985;Grossman et al, 1990). On larger spatial scales, physical factors such as spatial position within the drainage network (Osborne & Wiley, 1992;Grenouillet et al, 2004;Smith & Kraft, 2005), river size (Livingstone et al, 1982;Hugueny, 1989), climate (Hughes & Gammon, 1987), along with historical factors (e.g., speciation and dispersal) (Oberdoff et al, 1995), co-determine the composition of available species from which local communities are assembled.…”

Fish assemblage structure is consistent through an annual hydrological cycle in habitats of a floodplain-lake in the Colombian Amazon

“…In contrast, unpredictable flash floods that frequently occur in temperate streams cause strong disturbances to aquatic communities (Junk et al, 1989;Poff & Allan, 1995), and the process of recovery after disturbance is very dynamic and complex (Grossman et al, 1990). Predictable and lasting aquatic and terrestrial phases permit more efficient use of resources (Junk et al, 1997b).…”

Variabilité à long terme des peuplements de poissons : résultats provenant de rivières françaises et ouest africaines

“…For instance, after analysing data from a survey of a stream fish community over a 16 years period, GROSSMAN et al (1982) concluded to the existence of stochastic stream fish assemblages in which species abundance rankings do not remain constant from year to year despite temporally stable habitat structure. This conclusion has been challenged on many grounds (see références in GROSSMAN et al [1990]) and most of the axes listed above have been involved in the debate.…”

“…(2) Selon la classification proposée par GROSSMAN et al (1990) basée sur le CV moyen de l'abondance des espèces, tous les peuplements étudiés rentrent dans la catégorie des peuplements à fortes fluctuations interannuelles. Cependant certaines populations (les salmonidés en Bretagne par exemple) présentent une faible variabilité de leur densité.…”

“…Thèse controversies have motivated similar studies on freshwater fish assemblages, reviewed by GROSSMAN et al (1990). However, ail such studies have been located in North America.…”