Grazing Minnows, Piscivorous Bass, and Stream Algae: Dynamics of a Strong Interaction

Abstract

Striking differences in pool—to—pool distributions of an algae—grazing minnow (Campostoma anomalum), attached algae (predominantly Spirogyra sp. and Rhizoclonium sp.), and bass (Micropterus salmoides and M. punctulatus) are known to occur in some small Oklahoma streams. This study evaluates the complementarity of bass, Campostoma, and algae at different seasons, and uses in—stream experimental manipulations of bass and Campostoma to determine if the patterns resulted from strong interactions between predators, herbivores, and algae. In a 1—km reach of Brier Creek (south—central Oklahoma), bass and Campostoma distributions in 14 consecutive pools were inversely related in six of seven censuses conducted from 8 November 1982 to 5 September 1983. Bass and Campostoma co—ocurred in more than two pools only on two occasions, following the largest floods of the year. Campostoma and algal abundances were inversely related during late summer and in both autumns of this study. This relationship did not hold during the spring, when floods strongly affected algal distributions. During autumn of 1983, we removed bass from a pool, fenced it longtidinally, and added Campostomata to one side (1.4 individuals/m2). Over the next 5 wk, standing crop of algae decreased significantly on the Campostoma side but increased on the control side. In a nearby unmanipulated Campostoma pool, standing crop of algae was consistently low. We added three free—swimming bass to a Compostoma pool to evaluate presumptive predator—prey interactions. Within 3 h, the Campostoma moved from the deepest part of the pool to shallow areas. Over the next 5 wk, numbers of grazing Campostoma declined due to behavioral changes, emigration, and (presumably) predation. The standing crop of algae increased significantly 10—13 d after bass addition. In a second bass—addition experiment in June 1984, Campostoma responses were almost identical, and algal standing crop in deeper areas increased significantly after 1 wk. Collectively, our censuses and the experiments indicate that in Brier Creek, biotic interactions strongly influence the pool—to—pool distributions of Campostoma and algae, particularly during long periods of constant low discharge.

Why do juvenile fish utilise mangrove habitats?

“…These results differ to those for several other species in which the introduction of shelter had little or no effect on spatial distribution in the absence of predators (Werner et al, 1983a;Utne et al, 1993). However, there are many examples showing that in the presence of predators, aquatic fauna shift to areas offering improved shelter from predation (Stein, 1977;Stein and Magnuson, 1976;Sih, 1982;Vuorinen et al, 1983;Power et al, 1985;Utne et al, 1993). Thus, in terms of the hypothesis of predation risk, decreased risk of predation appears to be an important factor underpinning the preferred use of mangrove habitats by juvenile fish.…”

Invasive species cause large-scale loss of native California oyster habitat by disrupting trophic cascades

“…These observations could be the result of a trait-mediated cascade whereby native whelks hide rather than forage in the presence of crabs or relocate higher intertidally to avoid crabs and to consume barnacles instead of oysters. Similar reductions in foraging activity and behavioral shifts in habitat use are commonly displayed by prey in other systems (Gastreich 1999;Power et al 1985). In contrast, our survey and experimental results (Figs.…”

Environmental controls on food web regimes: A fluvial perspective

“…Smaller grazing minnows (when motivated by predator additions) could traverse these riffles. We found that emigration, rather than predation, accounted for about 50% of the reduction in minnow numbers following bass addition to a Campostoma pool (Power et al, 1985). This clear flowing river with its replicated pool habitats facilitated experiments that supported predictions from the trophic cascade model (Estes and Palmisano, 1974;Estes et al, 1978) and theory predicting the stabilizing effects of the differential mobility of predators versus prey through patchy environments (Huffaker, 1958;Hastings, 1977).…”

“…Each of these habitats partially delimit arenas for ecologically important interactions. The rough replication of habitat units (e.g., pools along channel reaches) can be useful for comparisons and manipulations (e.g., Power, 1984a;Power and Matthews, 1983;Power et al, 1985). Over time, discharge fluctuations of sufficient magnitude (e.g., bed scouring floods or dewatering) periodically remove organisms and reset river food webs, offering repeated opportunities to study food web assembly.…”