Hernán Ortega

Freshwater fishes and aquatic habitats in Peru: Current knowledge and conservation

Peruvian freshwater fishes and their habitats were investigated by the Natural History Museum of San Marcos University (MHNSM) as part of a long-term project. Fishes were inventoried by sampling in main drainage basins, including coastal rivers, highland rivers, and Perus Amazonian waters. To date, the MHNSM fish collection has approximately 300,000 specimens comprising 1000 valid species in 168 families and 8 orders. The greatest diversity lies within the Ostariophysi (80% of all species) with the dominant orders being Characiformes and Siluriformes. Characidae is the most diverse family with 22.5% of all species. Protected areas (i.e. Parks, Reserved Zones or National Reserves) have been sampled intensively providing a reasonable estimates of their fish diversity. However, our knowledge is still poor for less accessible areas. More fieldwork is needed in all of the large river basins before we can have a fuller understanding of total fish diversity. As an example of ongoing efforts, we discuss specific fish inventories in both Peruvian coastal rivers and highlands and in river systems shared with neighboring countries. In addition to Peruvian fish diversity; we discuss the state of aquatic resources and habitats in Perus principal river basins, and current problems facing such aquatic systems (e.g. inland fisheries and extractive activities such as deforestation and gold mining). Near large cities, such as Iquitos and Pucallpa, fishing effort has increased considerably in the last decade, whereas catch per unit effort appears to have decreased considerably indicating that over-fishing has become locally problematic. An overview is presented of main conservation problems, including exotic species that confront aquatic ecosystems in Peru. Finally, an environmental education program is recommended to inform the general public about the value of freshwater fishes and aquatic ecosystems and the main problems such resources are facing.

A new species of Hemibrycon (Teleostei: Characiformes: Characidae) from the río Ucayali drainage, Sierra del Divisor, Peru

A new characid species, Hemibrycon divisorensis, is described from the rio Ucayali drainage, Loreto, Peru. The new species is distinguished from all Hemibrycon species by the presence of a wide black asymmetrical spot covering base of caudal-fin rays and extending along entire length of caudal-fin rays 9 to 12-13 (except from H. surinamensis), and a black band in the lower half of the caudal peduncle extending from the region above the last anal-fin rays to the caudal-fin base. Furthermore, it is distinguished from most species of the genus by the number of scale rows below the lateral line (4-5 vs 5-9), except H. jabonero, H. microformaa, H. orcesi, and H. surinamensis. It differs from these species by scale and fin ray counts and color pattern. The lack of a supraorbital in Hemibrycon species is discussed and confirmed. Uma nova especie de caracideo, Hemibrycon divisorensis, e descrita para a bacia do rio Ucayali, Loreto, Peru. A nova especie distingue-se das demais especies de Hemibrycon pela presenca de uma ampla mancha preta assimetrica na base dos raios da nadadeira caudal estendida ate a extremidade dos raios 9 a 12 ou 13 (exceto de H. surinamensis), e de uma faixa preta na metade inferior do pedunculo caudal desde a regiao acima dos ultimos raios da nadadeira anal ate a base da nadadeira caudal. Ela distingue-se da maioria das especies do genero pelo numero de escamas abaixo da linha lateral (4-5 vs 5-9), exceto de H. jabonero, H. microformaa, H. orcesi e H. surinamensis. Ela difere destas especies pela contagem de escamas, raios das nadadeiras e colorido padrao. Discute-se e confirma-se a ausencia do osso supraorbital em Hemibrycon.

The Introduction of Nonnative Fishes into Freshwater Systems of Peru

Since the 1930s, alien fishes (fishes not native to Peru) have been introduced into the freshwater systems of Peru for different purposes such as fish farming, the ornamental fish trade, public health applications, and sport fishing. The fish were introduced either deliberately or casually into the three hydrographic systems of the country (Amazon, Pacific coastal rivers, and Lake Titicaca). To date, 20 alien species have been found in the continental water systems of Peru: Aristichythys nobilis, Carassius auratus, Cichlasoma nigrofasciatum, Ctenopharyngodon idella, Cyprinus carpio, Gambusia cf. affinis, Hypophthalmichthys molitrix, Odonthestes bonariensis, Oncorhynchus mykiss, Oreochromis aureus, Oreochromis hornorum, Oreochromis mossambicus, Oreochromis niloticus, Oreochromis urolepis, Poecilia reticulata, Poecilia velifera, Tilapia rendalli, Trichogaster leerii, Xiphophorus helleri, and Xiphophorus maculatus. Nativespecies transfers have also occurred; seven Peruvian species have been transferred from lowland forest waters to water systems of both the highland forest and the coast (reservoirs): Arapaima gigas, Astronotus ocellatus, Brycon cephalus, Cichla monoculus, Colossoma macropomum, Piaractus brachypomus, and Prochilodus nigricans. Herein, we present an overview of the current situation of these species introductions and transfers in Peru based on both fieldwork and a review of the pertinent literature. We then focus on the three alien species most frequently found in natural environments but not previously evaluated for their impacts. Our surveys in the aquatic basins of the Parque Nacional Rı́o Abiseo (PNRA; high-altitude, Amazon River system) show that the alien Oncorhynchus mykiss (rainbow trout) is the dominant species and that the three native species usually common in Peruvian highland Andean river basins (Astroblepus spp.) are present only in low numbers. The other two alien species— Oreochromis niloticus (tilapia) and Poecilia reticulata (guppy)—are well established and widely distributed in both the Huallaga (highland forest, Amazon River system)

Revealing Hidden Diversity of the Underestimated Neotropical Ichthyofauna: DNA Barcoding in the Recently Described Genus Megaleporinus (Characiformes: Anostomidae)

Molecular studies have improved our knowledge on the neotropical ichthyofauna. DNA barcoding has successfully been used in fish species identification and in detecting cryptic diversity. Megaleporinus (Anostomidae) is a recently described freshwater fish genus within which taxonomic uncertainties remain. Here we assessed all nominal species of this genus using a DNA barcode approach (Cytochrome Oxidase subunit I) with a broad sampling to generate a reference library, characterize new molecular lineages, and test the hypothesis that some of the nominal species represent species complexes. The analyses identified 16 (ABGD and BIN) to 18 (ABGD, GMYC, and PTP) different molecular operational taxonomic units (MOTUs) within the 10 studied nominal species, indicating cryptic biodiversity and potential candidate species. Only Megaleporinus brinco, Megaleporinus garmani, and Megaleporinus elongatus showed correspondence between nominal species and MOTUs. Within six nominal species, a subdivision in two MOTUs was found, while Megaleporinus obtusidens was divided in three MOTUs, suggesting that DNA barcode is a very useful approach to identify the molecular lineages of Megaleporinus, even in the case of recent divergence (< 0.5 Ma). Our results thus provided molecular findings that can be used along with morphological traits to better define each species, including candidate new species. This is the most complete analysis of DNA barcode in this recently described genus, and considering its economic value, a precise species identification is quite desirable and fundamental for conservation of the whole biodiversity of this fish.

Fragmentation of Andes-to-Amazon connectivity by hydropower dams

Hydropower development in the Andean Amazon has been underestimated and will disrupt connected human and natural systems. Andes-to-Amazon river connectivity controls numerous natural and human systems in the greater Amazon. However, it is being rapidly altered by a wave of new hydropower development, the impacts of which have been previously underestimated. We document 142 dams existing or under construction and 160 proposed dams for rivers draining the Andean headwaters of the Amazon. Existing dams have fragmented the tributary networks of six of eight major Andean Amazon river basins. Proposed dams could result in significant losses in river connectivity in river mainstems of five of eight major systems—the Napo, Marañón, Ucayali, Beni, and Mamoré. With a newly reported 671 freshwater fish species inhabiting the Andean headwaters of the Amazon (>500 m), dams threaten previously unrecognized biodiversity, particularly among endemic and migratory species. Because Andean rivers contribute most of the sediment in the mainstem Amazon, losses in river connectivity translate to drastic alteration of river channel and floodplain geomorphology and associated ecosystem services.

Chrysobrycon eliasi, new species of stevardiine fish (Characiformes: Characidae) from the río Madre de Dios and upper río Manuripe basins, Peru

Chrysobrycon eliasi is described from several drainages of rio Madre de Dios and upper rio Manuripe basins, rio Madeira basin, Peru. The new species is distinguished from its congeners by the maxillary teeth, which are tricuspidate, bicuspidate and conical, and the terminal lateral-line tube developed between caudal-fin rays 10-11. Other characters that help to recognize C. eliasi are the possession of maxilla with 6-15 (usually 11) teeth occupying more than 70% of the length of the maxilla in adults, predorsal scales 18-22, dorsal-fin to hypural complex length 36.32-41.17% of standard length (SL), gill-gland length in males 3.57-5.05% SL, maxillary length 33.76-38.75% of head length, and branched anal-fin rays 24-30. The discovery of C. eliasi allows us to extend the geographic distribution of the genus to the southeast, into the rio Madeira basin.

Fishes from the Lower Urubamba river near Sepahua, Amazon Basin, Peru

We report results of an ichthyological survey of the Lower Urubamba river, a tributary of the Ucayali river located in the southwestern portion of the Amazon Basin in southeastern Peru. Collections were made at low water (July, 2009) from 280 - 310 m elevation, near the town of Sepahua within the Fitzcarrald Arch, an upland associated with Pliocene (c. 4 Ma) uplift of the Peruvian Andes. This is the second of four planned expeditions to the region with the goal of comparing ichthyofaunas across the headwaters of the largest tributary basins in the western Amazon (Jurua, Ucayali, Purus and Madre de Dios). Twenty-one sites were sampled using seine nets, hook lines, cast nets and dip nets. A total of 98 species in 22 families and eight orders were captured and identified. The most diverse families are Characidae (40 spp.) and Loricariidae (20 spp.), and 12 families are represented by a single species. These data suggest that the fish fauna of the Lower Urubamba river near Sepahua is distinct from, and less diverse than, adjacent areas of lowland Amazonia.

Chrysobrycon yoliae, a new species of stevardiin (Characiformes: Characidae) from the Ucayali basin, Peru

Chrysobrycon yoliae, new species, is described from a drainage flowing into the rio Yucamia basin, rio Ucayali basin, Peru. Chrysobrycon yoliaeis readily distinguished from its congeners by the anterior tip of pelvic bone situated anterior to the fifth rib (vs. situated posterior to the fifth rib), the presence of 20-26 dentary teeth (vs. 11-19), and the possession of a terminal lateral-line tube between caudal-fin rays 10 and 11 (vs. the absence of this tube, except in C. eliasi). The new species differs from C. eliasiand C. myersiby the presence of teeth on third pharyngobranchial (vs. the absence of teeth on this bone) and also differs from C. eliasiby the dorsal-fin origin situated at vertical through anal-fin rays 5 to 7 (vs. located at vertical through anal-fin rays 8 to 10), the posterior extent of the ventral process of quadrate reaching the vertical through posterior margin of symplectic (vs. not reaching the vertical through posterior margin of symplectic), the dorsal-fin to adipose-fin length 26.8-28.8% SL (vs. 23.9-26.8% SL), and the body depth at dorsal-fin origin 34.4-42.2% SL (vs. 24.1-34.5% SL). A key for the identification of Chrysobryconspecies is provided.

Fishes from the Las Piedras River, Madre de Dios basin, Peruvian Amazon

We report results of an ichthyological survey on the Las Piedras basin, a tributary of the Madre de Dios River located in the southwestern portion of the Amazon Basin in southeastern Peru. Collections were made at low water (June, 2011) from 180 - 270 m elevation, within the Fitzcarrald Arch. This is the last of four expeditions to the region with the goal of comparing the ichthyofaunas across the headwaters of the largest tributary basins in the western Amazon: Jurua, Ucayali, Purus and Madre de Dios rivers. Twenty-one sites along the Las Piedras River and its tributaries were sampled and a total of 144 species belonging to 32 families and seven orders were captured and identified. The most diverse families were Characidae (34 spp.), Loricariidae (23 spp.), and Pimelodidae (19 spp.).

Revision of Gymnotus (Gymnotiformes: Gymnotidae) from the Upper Madeira Basin of Bolivia and Peru, with descriptions of two new species

Banded Knifefishes (Gymnotus, Gymnotidae) comprise the most species-rich genus of Neotropical electric fishes, with 41 species currently described from throughout the humid Neotropics, from Mexico to Argentina. Despite substantial alpha-taxonomic work in recent years, the diversity of Gymnotus in some regions remains poorly understood. Here we describe the Gymnotus fauna of the Upper Madeira basin of Bolivia and Peru from examination of more than 240 adult specimens. Species are delimited and described using body proportions (traditional morphometrics), fin-ray, squamation and laterosensory-pore counts (meristics), quantitative shape differences (geometric morphometrics), osteological traits, and color patterns. Comparisons of standardized linear measures as well as multivariate statistical methods validate the presence in the Upper Madeira basin of three previously described species, two with wide-spread geographic distributions throughout Greater Amazonia (G. carapo and G. coropinae), and one (G. chaviro) endemic to southwestern Amazonia. We also diagnose and describe two new species that are endemic to the Upper Madeira basin: G. eyra n. sp., morphologically most similar to G. mamiraua from lowland Amazonia, and G. riberalta n. sp., morphologically most similar to G. pantanal from the Paraguay-Paraná basin. The five Gymnotus species from the Upper Madeira basin are not monophyletic, each species being more closely related to a different species from another region; i.e. the Gymnotus species from the Upper Madeira represents a polyphyletic assemblage. These descriptions to 43 the number of valid Gymnotus species.