Composition and Diversity of Ichthyofauna In
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Composition and diversity of ichthyofauna in La Viña reservoir (Córdoba, Argentina) Mancini, M.a*, Haro, G.b, Bucco, C.c, Salinas, V.a and Miquelarena, A.d aAcuicultura, Facultad de Agronomía y Veterinaria, Universidad Nacional de Río Cuarto – UNRC, Ruta Nac. 36, Km 601, CP 5800, Río Cuarto, Argentina bCátedra de Diversidad Animal II y Museo de Zoología, Universidad Nacional de Córdoba – UNC, Vélez Sársfield, 299, CP 5000, Córdoba, Argentina cGuardafauna de la provincia de Córdoba, Argentina dDivisión Zoología Vertebrados, Museo de La Plata, Universidad Nacional de La Plata – UNLP, Paseo del Bosque, s/n, CP 1900, La Plata, Argentina *e-mail: [email protected] Received June 15, 2007 – Accepted July 11, 2007 – Distributed February 28, 2009 (With 4 figures) Abstract Several dams have been built in central and north Argentina. There are more than 20 reservoirs in Córdoba province, with a total estimated surface area of around 15,000 ha. Although construction of dams continues, some aspects about the richness, abundance and diversity of ichthyofauna in many of these environments are unknown, which prevents adequate management of fish resources. The goal of this work was to evaluate specific richness and diversity of ich- thyofauna in La Viña reservoir (31° 47’ S and 65° 01’ W, 1,050 ha, 846 m asl), one of the major reservoirs in Córdoba. Fifteen seasonal samplings were made in 1999-2002 using trawl nets and gillnets. A total of 3,242 specimens belong- ing to 7 species distributed in 5 orders and 5 families were caught. The tetra Astyanax eigenmanniorum (52.9%) and the silverside Odontesthes bonariensis (29.3%) were the most abundant species; the latter is the main target species for lake fishing and had greatest biomass (63.8%). Average diversity for all samples was H’T = 1.63 (95% confidence interval 1.49 to 1.77). Shannon-Wiener and Simpson diversity indexes values were generally intermediate. Specific richness of La Viña reservoir was moderate compared with other impoundments in central and north Argentina. Keywords: freshwater fish, diversity, reservoirs, Argentina. Composição e diversidade da ictiofauna do reservatório La Viña (Córdoba, Argentina) Resumo Na área central e norte da Argentina há uma importante quantidade de represas. Na província de Córdoba, existem, na atualidade, mais de 20 reservatórios que ocupam uma superfície aproximada de 15.000 ha. Embora a construção de represas continue em uma grande quantidade de ambientes, não se conhecem alguns aspectos da riqueza, abundância e diversidade da ictiofauna, dificultando a gestão e manejo dos recursos pesqueiros. O objetivo do trabalho foi avaliar a riqueza específica e a diversidade da ictiofauna do reservatório La Viña (31° 47’ S e 65° 01’ W, 1.050 ha, 846 msnm), um dos mais importantes de Córdoba. No período entre 1999-2002, realizaram-se 15 amostragens estacionais, uti- lizando-se redes de arrasto e de espera. Coletaram-se 3.242 indivíduos de 7 espécies distribuídas em 5 ordens e 5 famílias. Em função do número total de espécies, as de maior abundância foram lambari Astyanax eigenmanniorum (52,9%) e peixe-rei Odontesthes bonariensis (29,3%), sendo esta última espécie o objetivo da pescaria do lago e a que alcançou a maior biomassa (63,8%). Considerando o total da amostragem, a diversidade média foi de H’T = 1,63, com um intervalo de confiança (95%) de 1,49 a 1,77. No geral, os índices de diversidade de Shannon-Wiener e Simpson foram médios. Comparando com outros reservatórios da área central e norte da Argentina, a riqueza específica do reservatório La Viña é moderada. Palavras-chave: peixes, diversidade, reservatórios, Argentina. Braz. J. Biol., 69(1): 49-55, 2009 49 Mancini, M. et al. 1. Introduction N Reservoirs are artificial lakes of various sizes cre- W E 31° 47’ S Los Sauces river ated by the construction of dams for diverse purposes. S The number of dams has increased during recent years, South La Viña and this situation has contributed to the increase in the America reservoir volume of lentic environments on the planet during the 1,050 ha 20th century, one of the greatest man-made modifica- tions to hydrological basins (Cole, 1988; Locascio de Pacific 65° 01’ W Ocean Mitrovich et al., 1997). Argentina Los Sauces river Several dams have been built in central and north Argentina. The discrepancy between natural precipita- Atlantic 0 2.5 5 km La Viña II tion regimes and the human demand for water was one Ocean Villa Dolores city dam of the factors that prompted Córdoba to be among the first provinces to regulate hydrological resources in Figure 1. Geographical location of La Viña reservoir. Argentina. This province has more than 20 impound- ments, comprising an approximate surface area of 15,000 ha (Di.P.A.S., 2000). Some of the major uses are energy generation, buffering and control of irregular a drinkable water supply, as well as being a signifi- river flows, water supply, recreation and fishing, among cant touristic asset. It is one of the most visited sites in others. Fish resources are extremely valuable as sport Córdoba province for recreational fishing of the silver- fishing items, general environmental indicators, as well side Odontesthes bonariensis, a species that was first in- as fish captured for both consumption and recreation. In troduced in 1944 using specimens from the Río Tercero addition, the biological conditions of a fish community reservoir. Odontesthes bonariensis is the main target spe- are sensitive indicators of the “health” of an aquatic eco- cies for sport fisheries in central Argentina (Baigún and system and reflect environmental conditions of the wa- Delfino, 1994). ter body (Smith and Berrella, 2000; López et al., 2001; The climate in the area is mild, dry semi-arid, Schulz and Martins-Junior, 2001). with precipitation deficit during most of the year, and Given that fish species play relevant ecosystemic and mean annual temperatures varying from mild to warm. social roles, fish resources should be approached by the Monthly minimum and maximum temperatures are different parties that exploit the system from a general 10.3 and 25.0 °C and occur in July and January respec- perspective of sustainable use. Although several works tively (Servicio Meteorológico Nacional, 1992). Mean on various ichthyological aspects have been carried out annual precipitation is 650 mm (Di.P.A.S., 2000). in Córdoba province (Haro and Bistoni, 1996), there In recent years this reservoir has been classified are still numerous environments whose faunal richness as eutrophic, especially during the warmer months, remains undescribed. This lack of knowledge hinders a with occurrence of dinoflagellate florations, low wa- proper and sustainable management of these resources. ter transparency and occasional massive fish mortality The goal of this work was to assess the composition and (Rodriguez et al., 2005). diversity of ichthyofauna in La Viña reservoir. 2.2. Study and analysis of the ichthyofauna A total of 15 seasonal samplings were carried out 2. Materials and Methods between 1999 and 2002, with reservoir levels always above 95 m. Active and passive fishing methods were 2.1. Study area used (Scasso, 1999): La Viña reservoir (31° 47’ S and 65° 01’ W), also a) Trawl nets dragged toward the coast, 20 m long, known as Ingeniero Medina Allende dam, is located in with 3.5 m codend (mesh size 5 mm). Traslasierra valley, Córdoba province, west of the Sierras b) Three multifilament nylon floating gillnet sets for Grandes (Argentina). The homonymous compensating experimental fishing, with mesh sizes 15, 19, 22, dam is located downstream from La Viña (Figure 1). The 25, 30, 33, 38 and 40 mm from knot to knot (total La Viña reservoir is formed by a box-shaped basin with length 68.75 m). These nets were put in place at high-slope margins, with a surface area of 1,050 ha (at sunset-night and collected the following morning. maximum reservoir level) and a volumetric capacity of A minimum of two gillnet sets, placed in parallel 242 hm3; its altitude is 846 m asl (Di.P.A.S., 2000). The and perpendicularly to the coast, were used each impoundment is located within an endorrheic basin, and night. its main water supply is provided by Los Sauces river. The specimens were identified according to The steeply-inclined recharge area comprises 878 km2, Ringuelet et al. (1967) and Fernández (1994), and the and its potential irrigation capacity is 22,000 ha. systematic scheme follows López et al. (2003). For La Viña reservoir represents an important hydro- biomass measurements, all specimens were weighed to logical store destined to the production of energy and 0.1 g accuracy. 50 Braz. J. Biol., 69(1): 49-55, 2009 Ichthyofauna of La Viña reservoir (Argentina) Alpha diversity was evaluated by means of the The most abundant species was the tetra Astyanax Shannon-Wiener index: H = –Σ (pi) (log2 pi), where pi eigenmanniorum (52.9%), the second most abundant was is the proportion of the total sample corresponding to the the silverside Odontesthes bonariensis (29.3%) and the i species (Krebs, 1995). The following scale was used third most abundant was the pike characin Oligosarcus for interpretation of results: 0 to 1 bits – low diversity; jenynsii (13,6%). O. bonariensis was the most im- 1-2 bits – moderate diversity; and 2 or more bits – high portant in terms of biomass, with 63.8%, followed by diversity. The following indexes were also used: A. eigenmanniorum with 26.0% (Figure 2). A total of 952 silversides were caught, 36.9 of which were caught • Evenness index (Pielou’s index), E = H/log2 S, where S is the number of species in the sample. by trawl net and 63.1% by gillnet.