Effects of coupled natural and anthropogenic factors on the community structure of diadromous fish and shrimp species in tropical island streams

Abstract

1. Overlapping river and road networks provide a framework for studying the complex interactions between natural and human systems, with river-road intersections as focal areas of study. Roads can alter the morphology of stream channels, pose barriers to freshwater fauna, provide easy access to streams for humans and non-native species and accelerate the expansion of urban development. 2. We determined what variables control the structure of diadromous fish and shrimp communities and assessed whether particular road crossings altered community structure in north-eastern Puerto Rico. We identified 24 sites that represented a range of river and road sizes across two catchments that drain El Yunque National Forest in Puerto Rico. 3. The location of natural barriers and the size of stream pools were the most important variables for predicting six of fifteen fish and shrimp distributions. Predatory fishes were predicted to be limited to areas in the river network below large, steep waterfalls, whereas adult shrimp Atya lanipes (Atyidae) were predicted to be present above these waterfalls. The fish Awaous banana was predicted to be present in pools >11.6 m wide, whereas the shrimp Xiphocaris elongata was predicted to be present in pools <10.4 m wide. The distributions of nine species were predicted poorly, but three of these species were common and three were rare. 4. Although urban and agricultural land covers were among the top three predictors of five species distributions, they were probably good predictors because they were correlated with the natural gradient. Further study is necessary to disentangle natural and anthropogenic gradients. 5. Road crossings, 10 of which were culverts, were not dispersal barriers for fishes or shrimps. On average, species were present both upstream and downstream from road crossings at 68% of sites where they occurred. Absences upstream or downstream from road crossings occurred at 16% of sites each and likely resulted from a failure to detect species.

Amphidromy in shrimps: a life cycle between rivers and the sea

“…A major benefit for freshwater shrimps in the headwaters of streams on mountainous tropical islands is that there are few or no fish predators there (e.g., Covich et al, 2009;Blob et al, 2010;Hein et al, 2011). Covich et al (2009) (2007) suggested that an overall escape from predation by marine and estuarine fishes may have been an initial selective pressure favoring invasion of fresh water by groups that were capable of moving upstream.…”

A mixed-methods analysis of social-ecological feedbacks between urbanization and forest persistence

“…Decision and classification trees are a nonparametric approach to exploring complex systems (Davidson et al 2009, Hein et al 2011) and provide an alternative to generalized linear models (GLM) because of their ability to characterize hierarchical and nonlinear relationships and expose interactions among predictor variables (Michaelsen et al 1994). …”

Gorgona, Baudó y Darién (Chocó Biogeográfico, Colombia): ecorregiones modelo para los estudios ecológicos de comunidades de quebradas costeras

“…Por ejemplo, varias especies de camarones Macrobrachium spp. y Potimirin glabra, y peces (A. monticola, S. plumieri, A. tajasica) encontradas en quebradas y ríos costeros del Caribe centroamericano (Lorion, Kennedy & Braatne, 2011) y Las Antillas (Fievet, Doledec & Lim, 2001;Hein et al, 2011) han sido encontradas en muestreos en la ecorregión Darién (Álvarez-León, 1991; Agudelo-Zamora et al, 2010; C. Escobar-Sierra & J. F. Blanco, observ. pers.)…”

“…producción primaria) (Pringle, 1997;Ramírez & Hernández-Cruz, 2004;Hein et al, 2011). Debido a que la distribución de esta fauna diádroma es controlada principalmente por la presencia de cascadas y tramos de alta pendiente, la abundancia, biomasa y riqueza de insectos y camarones presentan discontinuidades aguas arriba y aguas debajo de estas geoformas (Pringle, 1997;Ramírez & Hernández-Cruz, 2004;Hein et al, 2011).…”