The Amazon rainforest has experienced rapid land-use changes over the last few decades, including extensive deforestation that can affect riparian habitats and streams. The aim of this study was to assess responses of stream fish assemblages to deforestation and land cover change in the eastern Amazon. We expected that percentage of forest in the catchment is correlated with local habitat complexity, which in turn determines fish assemblage composition and structure. We sampled 71 streams in areas with different land uses and tested for relationships between stream fish assemblages and local habitat and landscape variables while controlling for the effect of inter site distance. Fish assemblage composition and structure were correlated with forest coverage, but local habitat variables explained more of the variation in both assemblage composition and structure than landscape variables.Inter site distance contributed to variance explained by local habitat and landscape variables, and the percentage of variance explained by the unique contribution of local habitat was approximately equivalent to the shared variance explained by all three factors in the model. In these streams of the eastern Amazon, fish assemblages were most strongly influenced by features of instream and riparian habitats, yet indirect effects of deforestation on fish assemblage composition and structure were observed even though intact riparian zones were present at most sites. Long-term monitoring of the hydrographic basin, instream habitat and aquatic fauna is needed to test for potential legacy effects and time lags, as well as assess species responses to continuing deforestation and land-use changes in the Amazon. Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for PROCAD/ CAPES funding (project no 88881.068425/2014-01), the graduate scholarship for TOB and senior internship scholarship for LFAM to conduct research at Texas A&M University (process 88881.119097/2016-1). The manuscript was improved during the review process by addressing the thoughtful comments from Philip Kaufmann and an anonymous reviewer.

Revista Mexicana de Biodiversidad 89 (Suplem. 2018): S118 -S130 Suplemento Peces nativos y pesca artesanal en la cuenca Usumacinta, GuatemalaNative fish fauna and artisanal fisheries in the Usumacinta basin, ResumenLa ictiofauna nativa de la cuenca del río Usumacinta se documentó en el noroeste de Guatemala para conocer la composición de los peces nativos en 20 sitios y su importancia en la pesca artesanal. El estudio incluyó recolecta de las especies con diversas artes de pesca, evaluación de abundancia de las especies mediante muestreos en transectos e identificación de las mismas en los mercados de venta, y en entrevistas con pescadores. Se identificó un total de 54 especies, 38 géneros, 18 familias y 8 órdenes. Las familias más abundantes fueron Characidae (3 especies), Poeciliidae (12 especies) y Cichlidae (22 especies), y en términos de riqueza el 68% de las especies corresponden a las familias Cichlidae y Poeciliidae. Al menos 38 especies nativas y 7 exóticas fueron identificadas en la pesca artesanal, de las cuales Centropomus undecimalis., Megalops atlanticus y Atractosteus tropicus son de alto valor comercial. Entre las 7 especies exóticas identificadas solo las especies del género Pterygoplichthys no son parte de la pesca artesanal. Los peces del área se dividen en 2 grandes grupos, uno en las zonas bajas de Petén y otro en las zonas altas de Las Verapaces y la pesca artesanal varía de acuerdo con este patrón. Según el estudio, a pesar de las especies exóticas, la pesca en la cuenca del Usumacinta está basada principalmente en especies nativas. Se requieren medidas de control del pez diablo exótico Pterygoplichthys spp. para evitar la propagación de sus poblaciones y mitigar los efectos negativos en la comunidad íctica nativa. AbstractThe native fish fauna was characterized in 20 sites along three drainage areas of the Usumacinta river basin in northwestern Guatemala to understand the native fish fauna contribution and its importance to artisanal fisheries.

High-flow pulses affect river ecosystem dynamics in many important ways including by forming connections between the channel and oxbow lakes. This study assessed the influence of discharge on fish assemblage structure and diversity in the channel and oxbows of the Guadalupe River, Texas. Local assemblages of two oxbows and two channel sites were surveyed using standardized methods to test four hypotheses: (1) assemblage structure in oxbow lakes differs from those in the river channel, (2) α diversity decreases during extended periods of low discharge, (3) β diversity decreases during high discharge and increases during extended periods of low discharge, and (4) species turnover and assemblage nestedness decline during periods of high discharge. We found evidence to support the first three hypotheses. Unsurprisingly, lotic-adapted fishes were observed more frequently in the river channel, whereas lentic-adapted species generally were more common in the oxbow lakes. Species richness declined during periods of low discharge possibly due to harsher environmental conditions or stronger species interactions (e.g., predation). Discharge was inversely associated with both β diversity and species turnover, suggesting a stronger mass effect during high-flow pulses, and stronger species sorting during low-flow conditions. Contrary to our fourth hypothesis, assemblage nestedness increased during periods of high discharge. Finally, we also found evidence to support the hypothesis that species turnover decreased as discharge declined. The results of this study demonstrate the importance of flow pulses for maintaining fish diversity and assemblage structure in floodplain river systems. With additional research involving more sites and longer time series, it should be feasible to define and identify thresholds for flow regime changes that alter assemblage structure and species diversity.

Black bass Micropterus spp. support popular freshwater sport fisheries in North America. Bass anglers commonly adopt catch and release as a conservation practice, and frequently over 75% of angled black bass are released back into the water. If fish survive the angling event, the practice of catch and release as an alternative to harvest reduces direct mortality, but it has the potential to affect the postrelease feeding behavior and survival of the fish. The act of lifting black bass for handling, hook removal, and photograph opportunities may cause stress and injury, and the degree of injury sustained could be influenced by fish size. Holding fish in a tilted grip by the jaw has raised concern among anglers about potential damage to jaw musculature and tendons, as they may not support the fish's body weight out of water, particularly for trophy bass. We conducted an experiment with Florida Largemouth Bass M. salmoides floridanus to evaluate the relative differences in survival, jaw mechanics, and feeding success after the use of three common handling treatments: (1) a vertical hold using a lip‐grip device (vertical treatment); (2) a tilted, one‐handed grip using only the lower jaw (horizontal treatment); and (3) two‐handed support to the lower jaw and body (support treatment). The time taken by fish to regain equilibrium and resume normal swimming behavior after handling differed among the three treatments; the recovery period was shortest for fish in the support treatment (mean ± SD = 7 ± 10 s; vertical treatment: 33 ± 74 s; horizontal treatment: 12 ± 16 s). Minor injuries (e.g., abrasions and sores) and diseases (e.g., tumors and fungus) tended to increase after handling across the entire sample. Results suggested no evidence of handling‐specific differences in fish feeding behavior, jaw adjustments, and mortality after release. However, based on our results, we recommend that anglers use two‐handed support to handle Florida Largemouth Bass, thus minimizing the mean amount of time for an individual fish to regain equilibrium after an angling event. Received February 22, 2016; accepted October 7, 2016 Published online February 22, 2017

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