Integrity Of Fluvial Fish Communities Is Subject To Environmental Gradients In Mountain Streams, Sierra De Aroa, North Caribbean Coast, Venezuela

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Neotropical Ichthyology, 4(3):319-328, 2006

Copyright © 2006 Sociedade Brasileira de Ictiologia

Integrity of fluvial fish communities is subject to environmental gradients in

mountain streams, Sierra de Aroa, north Caribbean coast, Venezuela

Douglas Rodríguez-Olarte*, Ahyran Amaro*, Jorge Coronel*

and Donald C. Taphorn B.**

We examined physical habitat and fish assemblages in rivers of the Aroa Mountains (Venezuela) with different levels of

environmental protection due to the creation of Yurubí National Park within the drainage. We developed an Index of Biotic

Integrity (IBI) and evaluated it using principal components analysis (PCA) and canonical correspondence analysis (CCA).

Tributary rivers were divided into classes according to their origin (protected by the park) and physical characteristics of each,

including substrate. Fishes were captured using standardized electrofishing. Fish communities showed greater species richness

in heterogeneous habitat and protected rivers but overall abundance was higher in unprotected and impacted rivers. The

IBI was sensitive to these differences and the scores were higher in protected rivers. The IBI detected degree of disturbance

of fish communities without direct consideration of habitat parameters measured. The PCA revealed a gradient in substrate

heterogeneity. Similarly, CCA revealed differences in fish assemblage composition along the environmental gradient and that

varied with protection status of the river. The relationship between PCA and IBI scores was highly significant (r2 = 0.61, P <

0.0001). The PCA and CCA analysis moderately validated the structure and predictability of IBI; but it is still necessary to

refine the model and to extend its application for more time and over a wider area.

Foram avaliados o ambiente físico e as assembléias de peixes em rios das montanhas Aroa (Venezuela) com diferentes níveis de

proteção ambiental devido a criação do Parque Nacional Yurubí nesta drenagem. Foi desenvolvido um Índice de Integridade

Biótica (IBI), avaliado através da análise de componentes principais (PCA) e análise de correspondência canônica (CCA). Rios

tributários foram divididos em classes, de acordo com sua origem (proteção pelo Parque) e características físicas, incluindo o

substrato. Peixes foram capturados utilizando-se pesca-elétrica padronizada. As comunidades de peixes mostraram maior

riqueza de espécies em habitats heterogêneos e rios protegidos, porém a abundância foi maior em áreas não protegidas e rios

não impactados. O IBI foi sensível a estas diferenças e os escores foram mais elevados em rios protegidos. O IBI detectou o

grau de distúrbio nas comunidades de peixes sem a consiedração direta dos parâmetros de habitat medidos. O PCA revelou um

gradiente de heterogeneidade no substrato. De modo similar, a CCA revelou diferenças na composição da assembélia de peixes

ao longo do gradiente ambiental que variou com o estatus de proteção do rio. A relação entre os escores de PCA e IBI foi

altamente significativa (r2 = 0.61, P < 0.0001). As análises de PCA e CCA validaram moderadamente a estrutura e a previsibilidade

do IBI; porém, é necessário refinar o modelo e estender este aplicativo por mais tempo e área mais abrangente.

Key words: Index of Biotic Integrity, Habitat characterization, Multivariate analysis, National Park.

* Colección Regional de Peces. CPUCLA. Laboratorio de Ecología. Departamento de Ciencias Biológicas. Decanato de Agronomía.

Universidad Centroccidental Lisandro Alvarado, UCLA. Barquisimeto, Estado Lara, Venezuela. Dirección Actual: Museo Nacional de

Ciencias Naturales, CSIC. Departamento de Ecología Evolutiva. C/. José Gutiérrez Abascal, 2. ES-28066 Madrid. España. e-mail:

douglasrodriguez@ucla.edu.ve

**Museo de Ciencias Naturales Guanare. MCNG. Vice-Rectorado de Producción Agrícola. UNELLEZ. Mesa de Cavaca, Portuguesa.

Venezuela. e-mail: taphorn@gmail.com

Introduction

The conservation status of a watershed has direct and measurable

effects on the fluvial ecosystem and fish communities.

Colonization and residence of organisms are determined by a

physical and biological gradient in the hydrosystem continuum

and by local habitat conditions. The assemblage of species

that make up fish communities is attributed mostly to substrate

composition, water type and velocity, but also, the degree of

conservation and land use in the basin (Roth et al., 1996; Naiman

& Decamps, 1997; Johnson et al., 2005). In contrast to basins

with significant human activities, protected areas (such as na320

Integrity of fluvial fish communities

tional parks or riparian forest) are known to act as buffer regions

that reduce the entry of sediment into the channels,

provide allochthonous organic material and permit the persistence

of diverse communities (Berkman & Rabeli, 1987; Poff et

al., 1997; Lammert & Allan, 1999; Growns et al., 2003). Furthermore,

point disturbances (e.g. dredging, sand or gravel extraction,

etc.), even in pristine environments, can impede migration

corridors thus reducing populations of sensitive species.

These regional and local effects are considered the principal

forces influencing the biotic integrity of aquatic ecosystems.

The changes in species richness and composition of fish

communities in rivers with different levels of environmental

impact can be determined in multiple ways. Attributes of communities

(e.g. species richness and diversity) provide basic

information about qualitative changes (Magurran, 2003), but

the recognition of emergent attributes (structure, composition

and organization) permit better assessments of environmental

effects on communities (Karr, 1981). The combination

of these attributes is used to predict the biotic integrity of

aquatic ecosystems.

A pioneer model to estimate the health or biotic integrity is

the IBI (index of biotic integrity) proposed by Karr et al.,

(1986). The IBI considers variation in attributes of fish communities

in rivers with different degrees of perturbation relative to

a regional baseline or reference system with minimal exposure

to anthropogenic perturbations. This model was originally

developed in the midwestern United States and has been tested

successfully in different regions

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