Number Of Macroinvertebrates Research Articles

Intensive removal of signal crayfish (Pacifastacus leniusculus) from rivers increases numbers and taxon richness of macroinvertebrate species

Invasive species are a major cause of species extinction in freshwater ecosystems, and crayfish species are particularly pervasive. The invasive American signal crayfish Pacifastacus leniusculus has impacts over a range of trophic levels, but particularly on benthic aquatic macroinvertebrates. Our study examined the effect on the macroinvertebrate community of removal trapping of signal crayfish from UK rivers. Crayfish were intensively trapped and removed from two tributaries of the River Thames to test the hypothesis that lowering signal crayfish densities would result in increases in macroinvertebrate numbers and taxon richness. We removed 6181 crayfish over four sessions, resulting in crayfish densities that decreased toward the center of the removal sections. Conversely in control sections (where crayfish were trapped and returned), crayfish density increased toward the center of the section. Macroinvertebrate numbers and taxon richness were inversely correlated with crayfish densities. Multivariate analysis of the abundance of each taxon yielded similar results and indicated that crayfish removals had positive impacts on macroinvertebrate numbers and taxon richness but did not alter the composition of the wider macroinvertebrate community. Synthesis and applications: Our results demonstrate that non-eradication-oriented crayfish removal programmes may lead to increases in the total number of macroinvertebrates living in the benthos. This represents the first evidence that removing signal crayfish from riparian systems, at intensities feasible during control attempts or commercial crayfishing, may be beneficial for a range of sympatric aquatic macroinvertebrates.

Influence of hydropower dams on the state of macroinvertebrates assemblages in the Virvyte river, Lithuania

AbstractMacroinvertebrate organization along the Virvytė River was examined to relate biological response in environmental changes. Benthic macroinvertebrates and a range of environmental variables were sampled from three study sections: control, HPP dams and below HPP dams. Total macroinvertebrate taxon number (NT = 28), EPT taxon number (NT = 13) and Shannon-Wiener diversity index (H′ = 3.85) were the highest in control sites of the river and the smallest in HPP dams (17, 5, 2.75, respectively). Taxon number and total abundance of macroinvertebrates declined significantly both in HPP dams and below them in comparison with the control sites. Total macroinvertebrate abundance in the control sites (698±41 ind.m−2) was significantly higher than in HPP dams and below them (430±21 ind.m−2 and 425±22 ind.m−2, respectively). The obtained data show that the investigated sections differed in terms of composition and relative abundance of different taxa of macroinvertebrates. Compared to reference conditions (cont...

Effects of crayfish on leaf litter breakdown and shredder prey: are native and introduced species functionally redundant?

Recent increases in biological invasions frequency may have important consequences on native communities. However, functional redundancy between invasive and native species could reduce non-native species effects on native ecosystems. Despite this, even small differences in functional traits between these species may still have unpredictable effects on colonized ecosystems. Invasive crayfish, as ecosystem engineers, potentially have wide and complex effects on recipient ecosystems, even when replacing a native counterpart. We used laboratory microcosms to test whether native (Astacusastacus) and invasive crayfish species (Orconectes limosus, Pacifastacusleniusculus and Procambarusclarkii) are actually functionally redundant in their effects on prey/shredder density and leaf litter breakdown. Results show that crayfish strongly influenced macroinvertebrate numbers and leaf litter breakdown and indicate that differences in direct (prey and leaf litter consumption) and indirect (prey habitat use and leaf litter breakdown) effects between crayfish species do exist. While the replacement of A. astacus by O. limosus may have induced only minor changes in freshwater ecosystems, invasions by the larger and more aggressive P. clarkii and P. leniusculus will likely have strong effects on invaded ecosystem. Overall, there seems to be no functional redundancy between these four species and outcomes of crayfish invasion will likely be species specific.

An exploratory analysis of benthic macroinvertebrates as indicators of the ecological status of the Upper Yellow and Yangtze Rivers

This study presents findings of the first systematic analysis of aquatic biotic assemblages in the source region of the Yellow and Yangtze Rivers. It provides an initial basis with which to select representative organisms as indicators to assess the aquatic ecological status of rivers in this region. Macroinvertebrates are considered to be good indicators of long-term environmental changes due to their restricted range and persistence over time. Field investigations of macroinvertebrates were conducted in August 2009 in the source region of the Yellow River, and in July 2010 in the source region of the Yangtze River. Altogether 68 taxa of macroinvertebrates belonging to 29 families and 59 genera were identified. Among them were 8 annelids, 5 mollusks, 54 arthropods and 1 other animal. In the source region of the Yellow River, taxa number, density and biomass of macroinvertebrates were 50, 329 individuals m−2 and 0.3966 g dry weight m−2, respectively. Equivalent figures for the source region of the Yangtze River were 29, 59 individuals m−2 and 0.0307 g dry weight m−2. The lower benthic animal resources in the source region of the Yangtze River are ascribed to higher altitude, higher sediment concentration and wetland degradation. Preliminary findings of this exploratory study indicate that hydroelectric power stations had a weak impact on benthic dwellers but wetland degradation caused by a series of human activities had a catastrophic impact on survival of macroinvertebrates. Ecological protection measures such as conservative grazing and vegetation management are required to minimize grassland degradation and desertification, and reduce soil erosion rate and river sediment discharge.

Aquatic Macroinvertebrate Communities and Water Quality at Buffered and Non-Buffered Wetland Sites on Federal Waterfowl Production Areas in the Rainwater Basin, Nebraska

Nebraska’s Rainwater Basin has an abundance of natural wetlands and is a focal point in the annual migration corridor used by millions of waterfowl and shorebirds. However, these wetlands are in a landscape dominated by agriculture and as a result, siltation and poor water quality are continual problems. We evaluated twelve wetland sites on federally managed Waterfowl Protection Areas from 2007 – 2009 for water quality, sediment quality, and macroinvertebrate diversity. Six of the sites received agricultural runoff directly via culverts and drainage ditches (non-buffered sites) and six sites were protected from agricultural runoff by a vegetated buffer (buffered sites). Mean total number of aquatic macroinvertebrates were significantly greater (p <0.001) for buffered sites (230 ± 44 standard error) than non-buffered sites (97 ± 24). Water from non-buffered sites had significantly greater turbidity, conductivity, and concentrations of chlorophyll α and atrazine than buffered sites in addition to consistently greater annual averages of total nitrogen and total phosphorus. Furthermore, sediments from non-buffered sites had significantly greater cadmium, potassium, sodium and zinc than buffered sites. Use of vegetative buffers to intercept direct row-crop runoff can improve water quality and aquatic macroinvertebrate diversity and abundance in Rainwater Basin wetlands.

Eco-hydraulics and eco-sedimentation studies in China

This paper reviews the state-of-the-art eco-hydraulic and eco-sedimentation studies in China, particularly focusing on the impact of hydropeaking, habitat suitability modelling, bio-invasion control strategies, sediment transport effects on river ecology, and ecological restoration. Field investigations found that macro-invertebrate species number reduced nearly to zero in a short reach downstream of a dam due to hydropeaking, resulting from a hydropower station. Habitat suitability modelling for the Chinese sturgeon indicated that the habitat suitability was reduced after the Three Gorges Dam began filling. Macro-invertebrate species number and fishery harvest reduced sharply after riparian lakes were cut-off from the Yangtze River. Invasion and dense attachment of mussels on water transfer tunnel walls have caused biofouling in many countries. An effective control strategy, using hydraulic control methods for the golden mussel invasion is proposed. Erosion, sediment transportation, and deposition create and change habitats for many macro-invertebrate species. The biodiversity and number density of individual invertebrates are high in stable streams, lower in incised streams and streams experiencing sedimentation, and lowest in streams with intensive sediment transport. In stable streams, macro-invertebrates colonized a layer of bed sediment up to 60 cm, in which different species preferred different depths. For incised streams, the ecosystem was restored with artificial step-pools, which stabilized the channel bed and created high-habitat diversity. The problems and studies presented in this paper indicate the growth points of the discipline of eco-hydraulics and eco-sedimentation.

Application of the Maximum Convex Sum Algorithm in Determining Environmental Variables that Affect Nigerian Highland Stream Benthic Communities

In this paper, we utilise the newly developed method K-Disjoint Maximum Convex Sum Problem (K-DMCSP) in a real-life application, which investigates the effects of land use changes on benthic stream communities in highland tropical streams of Nigeria. A collaboration between computer scientists and freshwater biologists was established to implement and examine the robustness of this approach compared to a traditional method that used rectangular shape in the K-Disjoint Maximum Sub-Array algorithm (K-DMSA). This novel approach uses the K- DMCSP, which utilises a convex shape as compared to a rectangular shape. In the above comparison the new approach using the convex shape optimises the sum and yields more accurate and precise results. This is because using the rectangular shape is limiting and is therefore not flexible enough to cover various sets of data distributions. The new approach was applied to data that were collated from 55 tropical highland streams on the Mambilla Plateau, Nigeria to investigate the interactions between substrate index or dissolved oxygen and temperature with number of macroinvertebrates (taxa). The K-DMCSP method located the K-maximum threshold values. This was achieved by defining the substrate index or dissolved oxygen associated most with the temperature by maximising the sum of elements of a selected portion of a two dimensional array. The K-DMCSP successfully detected the various temperatures between the different categories of the substrate index or dissolved oxygen, and how those variables affect numbers of macroinvertebrates. Furthermore, applying the algorithm revealed that the number of macroinvertebrates differs according to land use (e.g. forestry and agriculture). The new method used in this paper is encouraging in its capability to find the relationship between various environmental parameters and macroinvertebrate distribution and diversity. This method can potentially be applied to other real-life applications requiring finding associations between different parameters.

Macrophyte presence and growth form influence macroinvertebrate community structure

Multivariate analysis demonstrated that macroinvertebrate assemblages of macrophyte-dominated sub-habitats within a small eutrophic pond differed markedly from those of Bottom substrate and Open water habitats. Certain habitats (e.g. Nymphaea and Phragmites) appeared to be quite similar in their macroinvertebrate communities, whereas others appeared to be very distinct in terms of the species composition (e.g. Open water habitat). Analysis of functional feeding groups also revealed differences between habitats in terms of the community structure. Again, the Open water habitat exhibiting the most marked difference. Macrophyte growth form does not cause significant differences in macroinvertebrate species richness and diversity but it has a significant effect on macroinvertebrate abundance. Habitats consisting of highly branched and dissected macrophyte growth forms provide more food resources and microhabitats supporting larger numbers of macroinvertebrates than macrophytes with firm undissected stalks and leaves. This study highlights the importance of maintaining the ecological quality of small freshwater habitats in order to promote macrophyte growth and thus maintain a high level of species richness within such ecosystems.

Macroinvertebrate richness on flood defence walls of the tidal River Thames

The River Thames through central London has seen significant environmental recovery, particularly in regard to water quality, but a substantial barrier to further ecological improvement is the spatial restriction of riparian areas. Flood defence walls represent a potential habitat for ecological improvements to benefit biodiversity. However before restoration actions are considered, an understanding of the current biodiversity and ecological status of these structures is necessary. Physical habitat and macroinvertebrate richness of flood defence walls at 15, evenly spaced sites along a 32 Km reach in central London were evaluated. We found no longitudinal patterns in total macroinvertebrate richness among our 15 sites, but did find that richness was influenced by wall type. Specifically, we found the highest richness on brick walls and lowest richness on concrete walls. Further, wall sections with algal cover supported significantly higher numbers of macroinvertebrates than sections lacking algal cover. However, reaches of the river where the channel was constricted had fewer macroinvertebrates likely due to scouring flows. These results show that macroinvertebrates of the river walls are influenced by habitat availability (i.e., wall type) and localised river flows. This work suggests that appropriate management of river wall habitats has the potential to enhance the biodiversity of highly modified, urban rivers.

Effects of macrophyte heterogeneity and food availability on structural parameters of the macroinvertebrate community in a Pampean stream

Environmental heterogeneity in natural ecosystems influences several parameters at the population and community levels. In freshwater ecosystems, habitat heterogeneity can be provided by macrophyte species with different structural shapes. Previous studies suggest that aquatic plants with more complex architectures will support higher number, biomass, and taxon richness of macroinvertebrates than plants with simpler shape. We investigated the influence of macrophyte structural heterogeneity (quantified by fractal dimension) and food availability (represented by epiphytic biomass) on several parameters (number of individuals, biomass, body size distribution, taxon richness, and diversity) of the macroinvertebrate community in a Pampean stream. Four submerged macrophyte species (Egeria densa, Elodea ernstae, Ceratophyllum demersum, and Stuckenia striata) and associated macroinvertebrates were sampled in late spring, summer, and autumn. Plants were photographed and fractal dimension was estimated from the images by the box-counting method. Fractal dimension was independent of plant surface area per unit of macrophyte biomass and differed significantly among species. Mean fractal dimension varied between 1.29 and 1.62, and increased following the sequence E. densa → S. striata → E. ernstae → C. demersum. Macrophyte species with higher fractal dimension supported a greater abundance of macroinvertebrates, especially those of small body size (500–1,000 μm); but fractal dimension was unrelated to macroinvertebrate biomass, richness, and diversity. However, overall animal biomass was significantly associated to the epiphytic abundance. Consequently, macrophyte heterogeneity influences macroinvertebrate density and body size distribution, while animal biomass depends on epiphytic food resources provided by plants.

Vertical distribution of benthic macroinvertebrates in a meromictic lake (Lake Czarne, Drawieński National Park)

Abstract Investigations of the distribution of benthic macroinvertebrates in Lake Czarne were conducted in fall 2005 and spring 2006. Samples were taken in three transects (at a depth of 0.5 m and at 5 m intervals). It was noted that macrobenthos only inhabit depths to 10 m. Laminar sediments from 15 m to 29 m indicate that macrobenthos never inhabit the deepest part of the lake in spite of temporary oxygen abundance (between 15 and 20 m during the winter and spring mixing periods). The largest diversity and biomass of macrozoobenthos was observed in the littoral zone at a depth of 0.5 m. At a depth of 5 m in the characean stands and at a depth of 10 m the number and biomass of benthic macroinvertebrates were significantly smaller. The reason for the decrease of benthos density seems to be gradual oxygen depletion.

Macroinvertebrate community dynamics in a temperate European Atlantic river. Do they conform to general ecological theory?

Spatial and temporal dynamics of macroinvertebrate communities have usually been linked to several environmental and anthropic factors. The aim of this study is to elucidate how important are these factors in structuring macroinvertebrate communities from temperate regions. Regarding the macroinvertebrate number of taxa, the Habitat Template Model, the Dynamic Equilibrium Hypothesis and the Intermediate Disturbance Hypothesis will be tested in order to know how important the diversity of instream elements and the hydrological disturbance frequency are in defining the macroinvertebrate taxonomic richness. Thus, the structure and composition of macroinvertebrate communities were analysed in nine sites of the Pas River basin, a temperate Atlantic basin in northern Spain, during winter, spring, summer and autumn 2005, together with water physicochemical and environmental characteristics. Macroinvertebrate abundance increased downstream and during summer, probably favoured by lower hydraulic stress and water organic enrichment. As predicts the Habitat Template Model, the macroinvertebrate number of taxa was related to habitat heterogeneity. However, no clear relationship amongst macroinvertebrate richness and water quality was found. The macroinvertebrate taxonomic richness did not correspond exactly with the Dynamic Equilibrium Hypothesis and the Intermediate Disturbance Hypothesis because it was relatively high in the absence of hydrological disturbances (summer). Thus, disturbance events may play a secondary role in determining the seasonal dynamic of the number of taxa. However, hydrological disturbances can be considered the most important factors explaining the seasonal pattern of macroinvertebrate abundance. On the other hand, spatial patterns of macroinvertebrate community structure and composition were mainly determined by resource availability, hydraulic conditions, habitat heterogeneity and human alterations, whilst hydrological predictability and resource availability might play a major role in determining seasonal dynamics.

Short-term responses of macroinvertebrate drift following experimental sediment flushing in a Japanese headwater channel

We examined short-term responses of macroinvertebrate drift associated with experimental sediment flushing in a headwater. Increases in the drifting abundances of Ephemeroptera and Plecoptera coincided with increases in bed load yield rather than peaks in discharge or suspended sediment concentrations. The approach and arrival of a sediment wave may provide a physical cue that initiates the escape of benthic macroinvertebrates. Because fine bed load sediments, with diameters <4 mm, tended to accumulate on and in the substrate matrix, such sedimentation affected the benthic macroinvertebrates residing on and in the substrate, increasing the number of macroinvertebrates in the drift. Therefore, the decreases observed in the densities of most macroinvertebrate taxa following sediment flushing were probably associated with sediment deposition and the resulting escape of macroinvertebrates from benthic habitats. The magnitudes of the decreases in macroinvertebrate density were lower at sites located 200 m downstream from the sediment sources than at sites located 20 m downstream. The results from this experimental flushing study suggest that bed load movement and resulting sediment accumulation alter macroinvertebrate drift patterns and cause decreases in the abundances of benthic macroinvertebrates in headwater streams.

A Rapid Assessment of Macroinvertebrates Associated with &lt;i&gt;Salvinia molesta&lt;/i&gt; In Moremi Game Reserve, Okavango Delta

Salvinia molesta is an invasive species in the Okavango Delta. The plant forms monotypic covers in places where it occurs and thus affects macroinvertebrates diversity within them. Three habitats with low, moderate and heavy infestation by the weed were selected inside Moremi Game Reserve to study macroinvertebrates diversity within them. A total of 31 taxa were identified in the study area, with the highest number occurring in heavily infested habitat. An analysis of variance (ANOVA) indicated that the means for the number of individuals collected at each habitat were significantly different from each other. And the result from calculations of Shannon Wiener diversity index showed that heavy infestation by S. molesta is associated with high macroinvertebrates diversity. There were also more functional feeding groups (FFGs) in sites that were heavily infested by the weed. However, highest numbers of macroinvertebrates associated with low oxygen environments, particularly Hirudinae, occurred in places with heavy infestation by the weed. This was not surprising since S. molesta depletes oxygen from the water bodies as was indicated by the results on dissolved oxygen (DO) measurements from the study area. Therefore, S. molesta infestation in the Okavango Delta should be totally controlled to ensure a high DO environment typical of a freshwater wetland ecosystem, which would also result in a shift in the diversity of macroinvertebrates in the area. Keywords: Salvinia molesta, macroinvertebrates, invasive, functional feeding groups, Okavango DeltaTropical Freshwater Biology Vol. 17 (1) 2008: pp. 13-23

Effects of mooring management on submerged vegetation, sediments and macro-invertebrates in Lake Constance, Germany

Mooring areas are a common form of berthing in many of Germany’s inland waters for the growing number of sporting boats. A circular swinging zone around the anchor zone is formed, in which the submerged macrophyte vegetation is destroyed to a large extent, and the sediment surface is eroded. We investigated the effects of two types of buoy (conventional and so-called hook-buoys) in comparison with undisturbed reference sites nearby. The aim of the study was to identify possible harmful consequences of mooring sites to lake littoral habitats in Lake Constance-Untersee, and to provide information to managers to aid them in the formulation of mooring management plans with the least ecological impact. The study focused on submerged vegetation, surface sediments and macro-invertebrate colonisation. In the swinging circle of conventional buoys (87 m2) we observed a significant sediment matter erosion of 0.9 tonnes and a reduction of organic matter amount by 4.5% of the undisturbed reference. The vegetation free area increased by 122%, and the phytomass (mainly Chara div. spp.) was reduced by 14.6% per berth. The psammophilous macro-invertebrate numbers were not significantly affected (−3%) in contrast to the phytophilous taxa which were reduced by 12.7% per berth. The mayfly larvae were the most negatively affected taxon. Oligochaetes profited from the clearing of the sediment surface in the swinging circles. The ecological effects of the hook-buoys were more minor, mainly due to the smaller swinging circle (6 m2). We concluded that the detrimental effects of mooring can be significantly reduced by mooring systems, e. g. the hook-buoy system as it was used in this study, which reduce the area disturbed and cleared by the anchor chain. We argue that these results can be generalised to mooring areas with soft bottom and dense macrophyte vegetation in Lake Constance and other large lakes.

Indirect effects of the algivorous fishPlecoglossus altivelis altivelison the growth of two insectivorous benthic fish

Summary1. Animals exploiting different resources may nevertheless interact if one species indirectly alters the abundance and distribution of the food of the other. To analyse this indirect effect, we conducted experiments in artificial pools and in the field to investigate the influence of the algivorous fishPlecoglossus altivelis altivelis(known as the ayu) on two species of insectivorous benthic fish,Pseudogobio esocinus esocinusand the gobyGymnogobius petschiliensis.2. In the pool experiments, algal biomass was not correlated with the number of ayu, but the percentage of blue‐green bacteria rose as the number increased. The number of aquatic macroinvertebrates on the upper surface of ceramic tiles placed in the pool bed decreased as the number of ayu increased.3. Although ayu and the benthic species did not interact directly, the reduction in invertebrate abundance on the upper surface of tiles in the pool reduced the growth rate of the benthic insectivores.4. In field experiments, the introduction of ayu into habitats withP. esocinus esocinusorG. petschiliensisreduced the growth rate of these benthic fish. In the field experiment that was carried out over 5 years in theG. petschiliensishabitat, the population density of the goby decreased when ayu were stocked.5. The ayu is a strong interactor or bioengineer in streams, affecting not only benthic algae but also aquatic invertebrates and fishes. We conclude that to predict the outcome of interspecific interactions amongst fishes in streams with high algal production, possible indirect effects must be considered alongside better known direct effects.

Interaction between Macroinvertebrate Abundance and Habitat Use by Diving Ducks during Winter on Northeastern Lake Ontario

Although numbers of buffleheads ( Bucephala albeola), common goldeneyes ( Bucephala clangula) and long-tailed ducks ( Clangula hyemalis) over-wintering on Lake Ontario have increased substantially over the past two decades, factors influencing habitat use and the potential for competition have not been investigated. The purpose of this study was to determine the relationship between prey availability and community structure of diving ducks during winter on northeastern Lake Ontario. Benthic and nektonic samples collected during fall, winter, and spring 2002–2004 indicated that macroinvertebrate numbers differed by location but generally did not decline throughout winter. Large accumulations of macroinvertebrates, apparently moved by wave action and currents, were documented in nearshore areas. Surveys showed that diving ducks congregated in mixed species flocks within areas of higher food abundance. Mixed species flocks were common in nearshore areas, likely because energydense foods (Amphipoda and Chironomidae) were abundant in the narrow zone of shallow water, close to shore. Although macroinvertebrate numbers likely affected habitat use by diving ducks, birds did not greatly reduce abundance of macroinvertebrates. It is unlikely that exploitative competition was occurring and interference competition appeared below threshold levels that would cause species to spatially segregate. Overall, our results suggest that food availability is not a limiting factor for buffleheads, common goldeneyes, or long-tailed ducks wintering on northeastern Lake Ontario.

The Effect of Large Woody Debris on Macroinvertebrate Communities and Epilithon Detritus Composition in a Channelized Headwater Stream

ABSTRACT Large woody debris (LWD) was placed in a channelized second order reach of Cedar Creek, Michigan, to determine if its presence would alter substrate composition and macroinvertebrate community. Pre- and pos-treatment cores were analyzed for macroinvertebrate composition, substrate particle sue, epilithon, and detritus development. The addition of LWD in experimental sections increased the number of macroinvertebrates by 19% and total biomass by 10%. Species richness and the Shannon-Wiener diversity index increased. Inorganic substrate composition and epilithon development were not altered; however, course particulate organic matter retention was significantly increased in larger particle size classes (> 4 mm).

Effects of Porous Mesh Groynes on Macroinvertebrates of a Sandy Beach, Santa Rosa Island, Florida, U.S.A.

The use of porous mesh groynes to accrete sand and stop erosion is a relatively new method of beach nourishment. Five groyne, five intergroyne, and five control transects outside the groyne area on a beach near Destin, FL were sampled during the initial 3 mo after installment of groynes for Arenicola cristata (polychaete) burrow numbers, benthic macroinvertebrate numbers, and dry mass. Salinity, temperature, turbidity, and current velocity were measured at one location within the groyne site and control site. Current velocity was reduced and sand was accreted in the groyne site relative to the control site. Few significant changes or interactions (time X site) were found. Coquina (Donax), mole crab (Emerita), and several species of polychaete were not eliminated near groynes after installation of the groyne field. Arenicola cristata (polychaete) burrow numbers were higher near groynes. This is in contrast to dramatic changes often noted in the first few months after other types of beach nourishment techniques, such as sand pumping, where fauna can be completely eliminated.

Diet and feeding periodicity of Cox’s gudgeon Gobiomorphus coxii (Krefft) in a south‐eastern Australian stream

A 24 h study of stomach contents and simultaneous sampling of the drift and benthos was used to describe the diet and assess the prey selectivity of Cox’s gudgeon, Gobiomorphus coxii, within a small coastal stream in south‐eastern Australia. Prey items consisted entirely of macroinvertebrates with most being ephemeropterans and trichopterans. The greatest number and largest volume of macroinvertebrates were in the stomachs of fish collected just after sunset through until several hours after sunrise. Both the number of empty stomachs and proportion of digested material in the stomach contents peaked at mid‐day. Overall, it was concluded that G. coxii was a nocturnal feeder that specialized on benthos, although some evidence of opportunistic prey selection was apparent. Gobiomorphus coxii was also size selective, preferring relatively large prey from both the drift and benthos.