Diel changes in <i>Pterygoplichthys</i> excretion and gut content mass.

<p>Average <i>Pterygoplichthys</i> excretion and gut content mass during daytime (1000–1500 h) and nighttime hours (1900–0400 h). (A) <i>Pterygoplichthys</i> NH₄⁺-N excretion rates; (B) <i>Pterygoplichthys</i> total dissolved phosphorus excretion rates; (C) N:P of <i>Pterygoplichthys</i> excretion; (D) gut content dry mass per wet mass of <i>Pterygoplichthys</i>. Error bars represent ±1 SE.</p

Biogeochemical hotspots created by aggregations of <i>Pterygoplichthys.</i>

<p>Means of NH₄⁺-N and PO₄⁻³-P (±1 SE) samples taken from paired sites within and outside of loricariid aggregations in the Chacamax River in 2008 (n = 16 ambient sites, n = 16 aggregation sites) and 2010 (n = 16 ambient sites, n = 16 aggregation sites). Aggregations were defined as water samples taken within groups of <i>Pterygoplichthys</i> that had an area of at least 5 m² with at least 40 <i>Pterygoplichthys</i> per m². Ambient samples were collected from sites parallel to the aggregations without immediate upstream aggregations of loricariids.</p

Diel changes in ambient water chemistry and <i>Pterygoplichthys</i> behavior.

<p>Data were collected in 2008 and 2010 (±1 SE). (A) NH4+-N and PO4-3-P concentrations over time; (B) number of <i>Pterygoplichthys</i> counted in 1 m² quadrats near the stream bank (within 24 cm) over time. The shaded areas represent nighttime sampling hours.</p

<i>Pterygoplichthys</i> in the Chacamax River (N17°29’047” W91°58’430”).

<p>(A) Daytime aggregation of loricariids. The white line outlines the aggregation boundary. (B) Underwater photo of loricariid aggregation. Individual fish are marked with white numbers (1–35). (C) Loricariids spreading out from aggregation to begin evening feeding. Each dark spot (C) is at least one <i>Pterygoplichthys</i>. A small group of fishes (1–10) have been marked with individual numbers to demonstrate fish abundance. Photo credits: K. A. Capps.</p

Invasive Fishes Generate Biogeochemical Hotspots in a Nutrient-Limited System

<div><p>Fishes can play important functional roles in the nutrient dynamics of freshwater systems. Aggregating fishes have the potential to generate areas of increased biogeochemical activity, or hotspots, in streams and rivers. Many of the studies documenting the functional role of fishes in nutrient dynamics have focused on native fish species; however, introduced fishes may restructure nutrient storage and cycling freshwater systems as they can attain high population densities in novel environments. The purpose of this study was to examine the impact of a non-native catfish (Loricariidae: <em>Pterygoplichthys</em>) on nitrogen and phosphorus remineralization and estimate whether large aggregations of these fish generate measurable biogeochemical hotspots within nutrient-limited ecosystems. Loricariids formed large aggregations during daylight hours and dispersed throughout the stream during evening hours to graze benthic habitats. Excretion rates of phosphorus were twice as great during nighttime hours when fishes were actively feeding; however, there was no diel pattern in nitrogen excretion rates. Our results indicate that spatially heterogeneous aggregations of loricariids can significantly elevate dissolved nutrient concentrations via excretion relative to ambient nitrogen and phosphorus concentrations during daylight hours, creating biogeochemical hotspots and potentially altering nutrient dynamics in invaded systems.</p> </div

Is Mobility a Fixed Trait? Summer Movement Patterns of Catostomids using PIT Telemetry

<p>Fish populations are composed of a mixture of sedentary and mobile individuals, but it is not clear whether movement behavior is plastic or fixed for individuals and what proportion of the population exhibits mobile behavior. To investigate the mobility and movement patterns of two common species of suckers, the Sonora Sucker <i>Catostomus insignis</i> and the Desert Sucker <i>Catostomus clarkii</i>, in the Gila River of western New Mexico, we tracked 449 individuals over three summers using passive integrated transponder (PIT) telemetry. Both species were mobile and the typical linear home ranges for mobile individuals exceeded 150 m, but approximately 25% of individuals were detected only in a single habitat segment. We observed increased movement after spates caused by summer monsoon rains, and fish used areas of the stream differently under high- and low-flow conditions. Fish moved farther between years than within years, but a subset of individuals were found in the same locations from year to year. For the study species, movement behavior does not appear to be a fixed trait for individuals, and many individuals exhibited both stationary and mobile behavior among years. We also investigated whether sample size biased the estimates of movement parameters. We concluded that movement parameters would be underestimated by 20–50% if we had tracked fewer individuals, but the degree to which the parameters were biased varied from year to year.</p> <p>Received August 7, 2013; accepted January 23, 2014</p

Anderson et al telemetry data

This Excel file contains radiotelemetry data from 24 Colossoma macropomum individuals included in our field study (2004-2006

retain

This text file contains individual level gut retention time data for captive fish from 2005 and 2006. Each line of data represents an individual seed, and indicates the time (hour) at which the seed was defecated by a given fish. Multiple seeds were fed to captive fish in each gut retention trial. Status codes seeds as 1 when defecated. Censored seeds (undefecated) are coded with 0

Influence of canopy state on nitrogen excretion by <i>T. granifera</i> in three streams.

<p>Panels from top represent Ramdeen Stream (RAM), Aripo River (ARI), and Yarra River (YAR). Open and closed circles represent individual snails collected in open and closed canopy habitats, respectively. Solid lines represent trends in closed canopy habitats, and broken lines represent trends in closed canopy habitats. All data were log-transformed.</p

Simulation model results

This Excel file contains 5 sheets: one for each of the seed species included in the study. Each sheet has the results of the simulation models, needed to produce the dispersal kernel figures (Figure 1 and Appendix Figure S2). Each simulation model was run for 100,000 iterations. Included in each sheet are columns for : Seed dispersal distance bins, frequency of dispersal to suitable habitats, proportion of seeds dispersed to suitable habitats, frequency of dispersal to permanent bodies of water, and proportion of seeds dispersed to permanent bodies of water