downstream and killed by a major flood event.
Long-term data also exist for Piney Creek, a permanent upland stream in the Ozarks (Ross et al. 1985; Matthews 1986b; Matthews et al. 1988) that offers a more benign habitat (i.e., no dewatering and less temperature variation). Not surprisingly, Piney Creek fishes also showed high persistence; however, in contrast to Brier Creek, the fish fauna in Piney Creek also showed greater faunal stability, both overall and at the assemblage level. Piney Creek had a severe flood in 1982; however, immediately after the flood there were no major changes in rank abundance of the 10 most abundant species (Matthews 1986b). Less common species did show changes in abundance, so local assemblages were altered immediately postflood. Eight months after the flood, the overall fish fauna and the fauna at individual collecting stations had essentially recovered to preflood conditions, leading Matthews (1986b) to conclude that the Piney Creek fish fauna showed stability and persistence across years and across a range of flow conditions.
Although some studies have shown that fish assemblages rebound rather quickly from flooding, as discussed previously, and as documented also by Taylor et al. (1996) for mainstem and tributary sites in the upper Red River system of Oklahoma, other studies indicate that floods or droughts acted to change or reset assemblage structure. Matthews and Marsh-Matthews (unpublished data) have recently found that two severe droughts resulted in a substantial change in the Brier Creek fauna, which did not recover to its former state until 3–4 years postdrought. Another example of how fish assemblages are affected by perturbations emphasizes the significance of timing of the event. In Coweeta Creek, North Carolina, a severe drought resulted in three distinct assemblages over a 10-year period corresponding to predrought, drought, and postdrought conditions (Table 6.1) (Grossman and Ratajczak 1998; Grossman et al. 1998).
TABLE 6.1 Long-Term (≥ 2 years) Studies of North American Stream Fish Assemblages Organized from Low to High Levels of Stress and from Low to High Latitudes
For a downloadable PDF of all tables, go to ucpress.edu/go/northamericanfishes
TABLE 6.1 (continued)
TABLE 6.1 (continued)
In the Sierra Nevada mountains of California, a severe spring flood in Martis Creek shifted the assemblage from being dominated by native, spring spawning species, to domination by the nonindigenous, fall spawning Brown Trout (Salmo trutta) (Table 6.1) (Strange et al. 1992). The importance of timing of floods relative to life history is also shown by responses of a northwestern fish assemblage in the John Day drainage, Oregon. Fishes that spawned in late spring and summer, such as Speckled Dace and Bridgelip Sucker (Catostomus columbianus), showed high losses of young-of-year individuals to summer flooding, whereas early spring spawners, such as Rainbow Trout, were more susceptible to spring flooding when the developing embryos were still in the redds (gravel nests) (Pearsons et al. 1992). In addition, losses of fishes due to flooding were greater in stream sections with low habitat complexity, leading Pearsons et al. (1992) to suggest that complex habitats may act as sources of individuals for the colonization of structurally simple habitats.
Levels of Persistence and Stability in Lentic Systems
There are relatively few studies with suitable data for assessing the temporal persistence and stability of lakes and reservoirs (Table 6.2). However, in an analysis of nine long-term studies (median duration = 15 years; range 11–72) of lentic fish assemblages (eight natural lakes and one impoundment), the levels of persistence and stability were essentially the same as those for lotic systems (Figure 6.5C; Table 6.2). Reduced persistence or stability of assemblages tends to occur in altered habitats and/or in habitats impacted by nonnative plants or animals. In contrast to lotic systems, all but one of the lentic studies had suffered moderate or major human impacts, primarily through commercial fishing pressure, the introduction of nonnative plants and animals, and overall urbanization within the watershed.
Examples of Persistence and Stability in Lentic Systems
Numerous lakes exhibit evidence of negative impacts on persistence and stability. Lake Michigan has received considerable study because of heavy fishing pressure and the introduction of nonindigenous species such as Sea Lamprey (Petromyzon marinus), Alewife (Alosa pseudoharengus), Rainbow Smelt (Osmerus mordax), Coho Salmon, Chinook Salmon, Rainbow Trout, Brown Trout (Salmo trutta), and Brook Trout (Salvelinus fontinalis). Many native species such as Lake Trout, Bloater (Coregonus hoyi), and Cisco (C. artedi), have shown substantial declines and/or increases as numbers of nonindigenous fishes have fluctuated (see also Chapter 15). Although overfishing, Sea Lamprey predation on large fishes, and competitive interactions all contributed to the decline of indigenous fish species, another factor has been predation on early life-history stages (Stewart et al. 1981; Eck and Wells 1987; Miller et al. 1989). Major shifts in species composition of a small Michigan lake after the loss and then reintroduction of Largemouth Bass (Micropterus salmoides) have also been observed (Mittelbach et al. 1995). In Lake Mendota, Wisconsin, which has been impacted by extensive shoreline urbanization and introduction of nonnative vegetation, the fish fauna showed both low temporal persistence as well as low stability (Lyons 1989)
Lentic systems showing greater persistence and stability were generally, but not always, less impacted by habitat alteration or introduction of nonnative species (Table 6.2). In six small Michigan lakes, changes in the fish assemblages were generally low over a four-year period, as determined from a measure of community heterogeneity (based on the average percent dissimilarity over all possible pairs of seine sites within lakes) (Benson and Magnuson 1992). Somewhat surprisingly, heterogeneity among seine hauls within a site (33 m of shoreline) was of the same magnitude as heterogeneity among sites, thus suggesting that fishes were responding to small-scale patchiness of the environment.
In a 15-year study of two depauperate Arctic lakes, Johnson (1994) examined long-term stability of Arctic Char (Salvelinus alpinus) populations. Arctic Char was the sole species in one lake and one of two species in the other. After an initial period of moderate (one lake) and high (the other lake) fishing exploitation, the lakes were allowed to recover for several years. In both lakes, age and size structure of Arctic Char returned to the original condition, indicating population stability.
Using long-term data, Gido et al. (2000) examined stability and persistence of a pelagic reservoir fish assemblage over a 43-year period in Lake Texoma, a large impoundment on the Oklahoma-Texas border. Except for the introduction of two species within the study period, Striped Bass (Morone saxatilis) and Threadfin Shad (Dorosoma petenense), the fauna showed persistence and stability as determined from the rank order of species. Numbers of individuals of each species showed greater fluctuations, with coefficients of variation of the 11 most abundant species ranging from 11–108% over the years.
Persistence and Stability Summary
At the scale of the entire fish assemblage and across a wide range of systems, persistence is fairly common and stability somewhat less so, although both can be impacted by the timing, type, and magnitude of perturbations. Persistence and stability in lentic and lotic systems are generally reduced following severe human disturbances (see also Schlosser 1982; Matthews 1998), and such disturbances occur in both types of systems, although they are more common in lentic (89%) compared to lotic studies (28%). At the population level, rare species, and especially those with limited vagility, recover more slowly or not at all from perturbations, as shown by Albanese et al. (2009) for fishes in the James River drainage, Virginia. Although rare species have less
