Arthur V. Brown

Propensity to Drift Downstream among Various Species of Fish

ABSTRACT Seasonal and diel drift of fish were studied in the fifth order of the Illinois River, Arkansas during 1980–1982 to assess the inclination of the various species (ca. 60) in the community (and size groups within species) to drift and to determine their diel and seasonal periodicities of drift. Eighteen taxa were identified from the drift. Channel catfish (Ictalurus punctatus) and flathead catfish (Pylodictus olivaris) alevins represented 57% and 12% of the drift respectively. Slender madtom catfish (Noturus exilis) were abundant in the riffle studied but none were collected in the drift. Larval fish drifted from late April through late August with a peak on 23–24 June when an estimated 37,203 drifted through the study area. A distinct diel pattern was observed with peaks at 2300 and 0300 hours. Drifting larvae were more abundant near the surface and margins with catfish alevins on the deep side and cyprinids, sunfishes, and all prolarvae on the shallow side of the stream. Post-larval development ...

Impacts of Gravel Mining on Gravel Bed Streams

Abstract The impacts of gravel mining on physical habitat, fine-sediment dynamics, biofilm, invertebrates, and fish were studied in three Ozark Plateaus gravel bed streams. Intense studies were performed upstream, on site, and downstream from one large mine on each stream. Invertebrates and fish were also sampled in disturbed and reference riffles at 10 small mines. Gravel mining significantly altered the geomorphology, fine-particle dynamics, turbidity, and biotic communities. Stream channel form was altered by increased bank-full widths, lengthened pools, and decreased riffles in affected reaches. Fine particulate organic matter transported from riffles to pools was decreased. Biofilm organic content was decreased on flats and increased on remaining riffles. Density and biomass of large invertebrates and density of small invertebrates were reduced at the small, more frequently mined sites. Total densities of fish in pools and game fish in pools and riffles were reduced by the large mines. Silt-sensitive...

Riffle-pool geomorphology disrupts longitudinal patterns of stream benthos

An Ozark Plateau stream was studied to determine the influence of distinct pool and riffle geomorphology on the longitudinal zonation of macroinvertebrate species assemblages and functional group classification. All study sites were dominated by alluvial pool and riffle channel form and the first two orders became intermittent during summer months. Nine benthos samples were collected seasonally from riffles and pools at each of five sites using a vacuum benthos sampler. Diel temperature pulse and coarse particulate organic matter (CPOM) were measured at each site also. Water temperature was most variable in second order, and CPOM on riffles was not more abundant in upstream reaches. Annual average density and biomass of invertebrates were highest in third and fourth orders, respectively. Diversity was depressed in the intermittent headwaters sites. Macroinvertebrate functional groups did not exhibit strong longitudinal trends as predicted by the river continuum model, with species assemblages apparently more strongly affected by the segment-level physical template, although shredders were more abundant in the headwaters during fall and winter. This study indicates that a reach-level perspective based on channel form is a necessary complement to holistic stream ecosystem models, especially in alluvial gravel streams.

Distribution of Insects within Riffles of Streams

Extensive quantitative sampling of aquatic insects and factors known or suspected to affect their local distribution in streams was performed in three consecutive riffles in a hardwater stream of north central Texas, USA. This study revealed a strong upstream-biased distribution pattern of lotic insects within riffles. Twelve of sixteen taxonomic categories analyzed, representing 93.4% of the total numbers, showed a distinct pattern of distribution with greater abundance toward the heads of riffles. Density of insects was statistically correlated with several physical and chemical characteristics measured including quantity of coarse particulate organic matter on the substrate, quantity of fine particulate organic matter in transport, several substrate particle size classes, current, depth, dissolved oxygen and temperature. However, none of these variables were meaningfully correlated with distance from the heads of riffles, and therefore did not sufficiently explain distribution of the insect groups. Positive rheotaxis could have significant influence on distribution of insects in riffles. The observed distribution pattern indicates that filter-feeding riffle insects compete for high quality food items produced in upstream pools, and that density of macrobenthos within these riffles may be limited by the amount of high quality food available to them rather than by space.

A vacuum benthos sampler suitable for diverse habitats

The vacuum benthos sampler consists of a vacuum chamber equipped with a collecting net connected to the intake of a 12 volt pump, a battery, and a standpipe. Contents of the standpipe are vacuumed while substrate is removed and washed with the exhaust hose. The vacuum chamber is designed for rapid changing of nets during replicate sampling. This sampler is equally efficient in flowing and standing water. It was more effective than a modified Hess sampler for collecting a large variety of benthos from flowing (ca 0.25–0.75 m/s) riffles. Required operation time is variable, but 93% of invertebrates caught in 10 min were captured in the first 5 min during our tests, and there was a 94% mean recovery of released organisms during 10 min of subsequent operation. Advantages over previous suction samplers include interception of organisms before they pass through a pump, return of outlet water to the standpipe, capability of sampling in shallow (20–30 mm) water, and that it can be carried and operated by one person.

Diel Drift and Feeding of Channel Catfish Alevins in the Illinois River, Arkansas

Abstract The food habits of 317 channel catfish Ictalurus punctatus alevins (standard length 14–16 mm) collected from the Illinois River, Arkansas were investigated to determine if the drifting alevins were using drifting invertebrates as a food resource. Drift of alevins coincided with increases in fullness of their stomachs, but alevins had been feeding predominantly on chironomid larvae and pupae, which were rare in the drift and riffle substrate. Alevins apparently fed on chironomids in upstream pools and accidentally encountered swift currents that caused them to drift downstream. If so, drift was a consequence of feeding activity, not an aid to it.

Effects of Stocking Density and Cage Size on Growth, Feed Conversion, and Production of Rainbow Trout and Channel Catfish

Abstract Cages of 3.82 and 5.35 m³ were used in raising rainbow trout (Salmo gairdneri) and channel catfish (Ictalurus punctatus) in 24-ha Crystal Lake, Arkansas. Cages were stocked with 23.4-cm trout at densities of 183, 301, and 524/m³. Neither growth nor feed conversion were affected by cage size, but both were significantly better at stocking densities of 183 and 301/m³ than at 523/m³. Rainbow trout can be successfully raised in cages at initial stocking weights of up to 45 kg/m³. For channel catfish culture, cages were stocked with 14.8-cm fish at densities of 144, 235, and 366/m³. Apparently neither growth nor feed conversion were affected by either cage size or stocking density.

Responses of benthic macroinvertebrates in small intermittent streams to silvicultural practices

We examined macroinvertebrate communities in small(0.1-1.0 m2) pools of intermittent streams (alwayscontainingsome water but without perennial flow) with small watersheds(2-6 ha) subjected to five types of forest harvest to assesspotential impacts of the different harvest methods. Bufferstrips10 m wide were left on each side of the streams. Each harvesttreatment was coupled with a similar unharvested referencestand.An incomplete block design included three 0.05 m2 vacuumsamples from each treatment paired with three from theadjacentreferences. There was a high degree of similarity amongreferencesfor parameters other than taxonomic composition (e.g.macroinvertebrate density, number of species, Shannondiversity,functional groups, etc.). Statistically significantdifferenceswere found between references and treatments and among harvestmethods but the responses varied among response variables(density,Shannon-Weiner diversity, species composition), differentspeciesassemblages (all invertebrates, chironomids,Ephemeroptera-Plecoptera-Trichoptera [EPT], isopods), andfunctional group categories (shredders, collector-gatherers).Wecollected 56 taxa, 7–16 per site, with low communitysimilarity(mean Jaccard‘s = 0.18, mean Bray-Curtis percentdissimilarity = 81). The most severe harvest treatmentsresultedin the highest diversities of total invertebrates in thesesmallspring pool communities.

6 – LOWER MISSISSIPPI RIVER AND ITS TRIBUTARIES

The Mississippi River basin extends from 37°N to 29°N latitude, covers nearly 14% of the North American continent, and drains 41% to 42% of the area of the conterminous US. The Lower Mississippi River drains from three physiographic provinces, which are very distinct: Coastal Plain, Ouachita province, and Ozark Plateaus. The climate of this entire region ranges from temperate midcontinental in the northern and western portions to subtropical and very humid in the south. The mean annual temperature is about 16°C, with an annual range from 0°C to 35°C. Rainfall ranges from just over 100 cm/yr in the west to over 160 cm/yr in the warm, moist delta region of southern Louisiana. The lower Mississippi River valley is a highly productive land and has been cleared for intensive farming. The land also shows great biological diversity. Construction of levees, floodways, cutoffs, dikes, revetments, locks and dams, and tributary basin modifications by the US Army Corps of Engineers to control floods and allow shipping and barge traffic has altered the relative percentages of the different types of habitat and formed novel habitat types.

Influence of fine sediments on meiofauna colonization densities in artificial stream channels

Excessive fine sediments have been shown to adversely affect abundance and diversity of stream macroinvertebrates, but effects on meiofauna have been only minimally and indirectly assessed. We used 12 artificial channels in a 4 th order Ozark stream to investigate the influence of silt (particle diameter 63 μm to 2 mm) and gravel (particle diameter 2 to 16 mm) on meiofauna colonization. Four channels were filled with gravel, four with 1/2 gravel and 1/2 sand, and four with 1/3 gravel, 1/3 sand, and 1/3 topsoil, referred to as gravel, sand, and silt treatments, respectively. Substrate cores were taken from the natural and artificial channels for analysis of meiofauna (80 μm to 1 mm) and substrate composition. Rotifera, Copepoda, Chironomidae, Nematoda, Oligochaeta, and Mollusca (principally juvenile Corbicula fluminea) comprised the major meiofauna taxa. Total meiofauna density in the artificial channels differed significantly among treatments. Density was lower in the silt treatment than in gravel or sand treatments, but overall densities in the gravel and sand treatments did not differ. Responses to treatments varied among specific taxa; densities of rotifers, copepods, nematodes, and oligochaetes were lower in the silt than the gravel treatment, but chironomids and nematodes were equally abundant in gravel and sand treatments, while lower in the silt treatment. Total meiofauna density did not differ between the natural channel and the gravel treatment but was lower in the sand and silt treatments. Copepod density was higher in the gravel treatment, and nematode, oligochaete, and mollusk densities were lower for all three treatments compared to the natural channel. The lower density of total meiofauna associated with high concentrations of silt suggests that excessive silt reduces habitat space and/or quality for meiobenthic organisms, while a sand and gravel mix is suitable for some meiofauna taxa.