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

A new species, Rivulus sape, is described from two tributaries of the upper Paragua River, Caroní River drainage, of the Guyana Shield in Venezuela. It is a small (all specimens examined less than 50 mm SL), apparently non-annual species that is distinguished from congeners in having the dorsal, anal, and pelvic fins short; adult males with a truncate caudal fin with the upper and lower borders black; and an iridescent blue, ovate spot on sides of the body above the pectoral fins. Neither adults nor juveniles have an ocellus at the dorsal junction of the caudal peduncle and caudal fin. Only one contact organ per scale on some scales along the sides of the body was observed.

Hemibrycon guejarensis, new species, is described from the Güejar River, La Macarena mountain range, upper Guaviare River drainage, Colombia. The new species is distinguished from most cis-Andean congeners (H. jabonero Lake Maracaibo and adjacent Caribbean drainages, H. metae which is found in the Guavio River, some Orinoco and Caribbean River drainages in Venezuela, and H. taeniurus from Trinidad and adjacent mainland drainages in Venezuela) in having ii, 7, i dorsal-fin rays (vs. ii, 8). H. guejarensis is further distinguished from H. taeniurus and H. jabonero, in having a wider second pigment layer in the humeral spot (covering 3 vs. 2 scale widths). H. guejarensis is very similar to H. metae (an allopatric species also present in streams of the Orinoco River Basin in Venezuela and Colombia and some Venezuelan Caribbean drainages). Hemibrycon guejarensis is distinguishedby the orientation of the dorsal lateral-line canal which crosses the ventral part of the humeral spot transversely vs. horizontally across dorsal part of spot in the holotype of H. metae and Orinoco and Caribbean populations. H. guejarensis differs from H. metae in having the tip of the pectoral fin passing the pelvic-fin insertions (vs. pectoral fin tip not reaching pelvic-fin insertions). We identify populations previously considered as Hemibrycon metae from Venezuelan Orinoco River Basin piedmont streams and Caribbean drainages to be instead H. jabonero and H. taeniurus. Careful analysis of these populations indicated that all of them differ from the H. metae holotype and topotypic specimens in pelvic fin and postorbital lengths.

Apareiodon agmatos, new species, is described from the upper Mazaruni River and its tributaries, Essequibo Basin, in western Guyana. The new species is distinguishable from all other species of Parodontidae by having an incomplete lateral line. The scales of A. agmatos are more numerous than in any previously described parodontid. It has five incisorlike pedunculate teeth on the premaxilla aligned in a straight row, each with a large central spatulate cusp bordered on each side by a minute lateral cusp. The maxilla has two or infrequently three incisors. It shares an unusual pigmentation pattern of one dorsomedial and four lateral black stripes with A. gransabana, which was described from the neighboring upper Río Caroní drainage, Orinoco Basin. Apareiodon agmatos also shares with A. gransabana and Parodon guyanensis a higher number (5 versus 4) of teeth than other members of the genus in the premaxillary. Apareiodon agmatos and A. gransabana may also share an absence of thickening of the anterior pleural ribs noted by Starnes & Schindler (1993) for A. gransabana. While beyond the scope of this work, these features may prove sufficient to diagnose this group of species from the genus Apareiodon as currently recognized.