Abstract The dorado (Salminus brasiliensis) has a relevant value for recreational fish ing in Argentina. In Córdoba province its presence has been reported in a limited number of aquatic environ ments, most of them belonging to la Plata River Basin. By 2016, in accordance with extraordinary floods, numer ous specimens were captured in the center-south region of Córdoba. The objective of this research is to report new occurrence localities, discuss the possible entry routes and describe water characteristics of the site with the highest abundance of fish recorded. Information about capture sites was collected for the period 2016-2020. Ichthyological surveys were carried out and parameters related to water quality were obtained in a shallow lake. Eight specimens were taxonomically studied presenting standard lengths between 235 and 323 mm and weights between 199 and 640 g. A total of 27 occurrence sites were recorded in the study area, of which 22 correspond to localities where their presence had not been reported before. The presence of S. brasiliensis in the region, and in these new sites could obey to episodical entrances with a synchronous condition of hydrological excess. This situation would be further enhanced by the current hydrological connectivity generated by artificial waterways in the region.

Resumen El dorado Salminus brasiliensis posee un valor relevante para las pesquerías recreacionales de la Argentina. En la provincia de Córdoba su presencia ha sido reportada en un limitado número de ambientes acuáticos, la mayoría de ellos pertenecientes a la cuenca del Plata. A partir del año 2016, en concordancia con inundaciones extraordinarias, se han producido cuantiosas capturas de ejemplares en la región centro-sur de la provincia. El objetivo de este trabajo es reportar nuevas localidades de ocurrencia, discutir las posibles rutas de ingreso y describir las características del agua del ambiente con mayor abundancia de peces registrada. Se recopiló información sobre sitios de captura en la región en el período 2016-2020. Se realizaron, además, relevamientos ictiológicos y se obtuvieron datos relacionados a la calidad del agua en una laguna. es tudiados taxonómicamente presentando longitudes estándar entre 235 y 323 mm, y pesos entre 199 y 640 g. Se registraron un total de 27 sitios de ocurrencia en el área estudiada, de los cuales 22 corresponden a puntos en donde su presencia no había sido reportada hasta el momento. La presencia de dorados en la región y en estos nuevos sitios obedecería a ingresos episódicos en sincronía con condiciones de exceso hídrico, situación que se vería favorecida por la actual conectividad hidrológica que generan las canalizaciones.

ABSTRACT The action of menthol on physiological and anesthesiological variables in rainbow trout was evaluated. Clinically healthy juvenile trout were used, of both sexes, formed in group A (n=20) of 201.4 ± 60.1 g of weight subjected to 100 ppm/L of menthol in water at pH 6.4 and in group B (n=20) of 187.3 ± 48.6 g of weight exposed to identical concentration of menthol with the water adjusted to pH 8.0 with sodium bicarbonate. The fish were placed in containers with water at 16.7 °C and electrical conductivity of 0.10 mScm -1. The work methodology was: 1) acclimatization of fish in a container without drug and recording of the basal respiratory rate (RR) after adopting a normal swimming behavior; 2) transfer to a second container with menthol and recording of times of loss of lateral balance and anesthesia; 3) transfer of anesthetized fish to a third container without drug and record of RR and its behavior during the recovery period. In group A, anesthesia was achieved in 127.7 ± 46.3 s with a strong reduction in baseline RR from 132.4 ± 12.6 to 40.4 ± 14.4 mov/min and total recovery occurred in 189.7 ± 64.2 s. In group B, anesthesia and recovery time were observed at 93.4 ± 34.3 and 181.7 ± 68.0 s, respectively, and a reduction in RR from 137 ± 14.3 to 43.6 ± 10.4 mov/min. The results indicate that menthol in water adjusted to pH 8.0 is a good alternative for rainbow trout fish farming practices.

RESUMEN Se evaluó la acción de mentol sobre variables fisiológicas y anestesiológicas en truchas arcoíris. Se trabajó con truchas juveniles clínicamente sanas, de ambos sexos, conformadas en grupo A (n= 20) de 201.4 ± 60.1 g de peso sometidas a 100 ppm/L de mentol en agua a pH 6.4 y en grupo B (n=20) de 187.3 ± 48.6 g de peso expuestos a idéntica concentración de mentol con el agua ajustada a pH 8.0 con bicarbonato de sodio. Los peces se ubicaron en recipientes con agua a 16.7 °C y conductividad eléctrica de 0.10 mS cm-1. La metodología de trabajo fue: 1) aclimatación de peces en un recipiente sin fármaco y registro de la frecuencia respiratoria basal (FR) tras adoptar un comportamiento normal de natación; 2) transferencia a un segundo recipiente con mentol y registro de tiempos de pérdida de equilibrio lateral y de anestesia; 3) traspaso de peces anestesiados al tercer recipiente sin fármaco y registro de FR y su comportamiento durante el periodo de recuperación. En el grupo A la anestesia se logró en 127.7 ± 46.3 s con fuerte reducción de la FR basal de 132.4 ± 12.6 a 40.4 ± 14.4 mov/min y la recuperación total se produjo en 189.7 ± 64.2 s. En el grupo B se observó tiempo de anestesia y recuperación a los 93.4 ± 34.3 y 181.7 ± 68.0 s, respectivamente, y reducción de la FR desde 137 ± 14.3 a 43.6 ± 10.4 mov/min. Los resultados indican que mentol en agua ajustado a pH 8.0 es una buena alternativa para las prácticas de piscicultura de truchas arcoíris.

Summary Background and aims: Solanum elaeagnifolium, morphologically variable, multiplies sexually and asexually and is invasive worldwide. In Argentina there are natural diploid, tetraploid and hexaploid populations. It presents three clearly separated genetic lineages, two in South America with polyploid populations and a third with only diploids in North America and invaded areas. Our aim is to detect relationships among ploidy levels, lineages and provenance with morphological features of the plants and climatic variables. M&M: Chromosomal preparations and measurements of epidermal, floral and seed features were made in 2x, 4x and 6x individuals from different lineages and geographic origin. The mean values obtained were compared by statistical tests and the global similarity assessed by multivariate analyses. Results: Only number of stomata and seed mass were significantly different between ploidy levels: the tetraploids have fewer stomata and heavier seeds. The remaining morphoanatomical variables contribute to the global differentiation of cytotypes, although the means did not vary proportionally with increasing ploidy. Mean annual rainfall contributes to the separation of cytotypes, the western distribution of tetraploids coinciding with the arid diagonal in Argentina. Conclusions: The differences in the tetraploids cannot be attributed to a polyploidization effect. The global pattern of data could be explained by multiple independent origins of polyploidy, phenotypic plasticity, and environmental pressures.

Urban lakes are frequently used for recreation and tourism, in addition to their aesthetic value. They are also important as a refuge for biodiversity. They are generally small and shallow, so they are strongly influenced by human activities. In Argentina, the ecology of urban lakes has not received much attention. The objective of this study was to identify the zooplankton and their relationships with environmental parameters in Dalcar (33° 06’S; 64° 22’W), an artificial lake of Río Cuarto City (Córdoba province). Seasonal samples were taken in 2017, when the lake had partial coverage of macrophytes and abundance of fish. The pH and conductivity were 8.97 (±0.19) and 0.81 mS/cm (±0.06), respectively. The water transparency was 0.72 m (±0.25), and the trophic status index was 64.73. Eight cladocerans, 3 copepods, and 25 rotifers were recorded. This high richness could be due to the reduced salinity, the presence of species associated with macrophytes and to the protection provided by these against predation. The dominance of rotifers, especially of the genera Brachionus, Keratella, and Lecane and the presence of cladocerans, such as Moina micrura and Bosmina longirostris are indicators of high trophic level. The zooplankton density was lower than that of other urban lakes in Central Argentina. Since Dalcar’s zooplankton is dominated by small organisms and predation would prevent large species with high grazing rates from thriving, in absence of any event that modifies the current characteristics of the lake, the influence of zooplankton on the amount of phytoplankton and water transparency is not expected to change.

Los lagos urbanos tienen importancia estética, como refugio para la biodiversidad y frecuentemente se utilizan para recreación y turismo. Como generalmente son pequeños y someros, están fuertemente influenciados por actividades humanas. En Argentina, su ecología no ha recibido mucha atención, por lo que el objetivo fue estudiar el zooplancton y las relaciones con parámetros ambientales en Dalcar (33° 06´S 64° 22´O), un lago artificial de Río Cuarto (Córdoba). Se tomaron muestras estacionales en 2017, cuando el lago tuvo parcial cobertura de macrófitas y gran abundancia de peces. El pH y la conductividad fueron 8,97 (±0,19) y 0,81 mS/cm (±0,06). La transparencia del agua fue 0,72 m (±0,25) y el índice de estado trófico fue 64,73. Se registraron 8 cladóceros, 3 copépodos y 25 rotíferos. La elevada riqueza podría deberse a la reducida salinidad, a la presencia de especies ligadas a las macrófitas y al refugio brindado por éstas contra la predación. El dominio de rotíferos, en especial de los géneros Brachionus, Keratella y Lecane y la presencia de cladóceros como Moina micrura y Bosmina longirostris son indicadores de un alto nivel trófico. La densidad zooplanctónica fue menor que la de otros lagos urbanos de Argentina. Como el zooplancton de Dalcar está dominado por organismos pequeños y la predación impediría que prosperaran especies grandes con alto pastoreo, en ausencia de algún evento particular que modifique las características actuales del lago, no es esperable que cambie la influencia del zooplancton sobre la cantidad de fitoplancton y la transparencia del agua.

Resumo Os copépodos parasitos da família Lernaeidae são frequentemente encontrados infestando peixes de água doce em todo o mundo, causando a lernaeose, uma doença que pode levar a graves efeitos patogênicos em seus hospedeiros. O lerneídeo mais comum é a Lernaea cyprinacea, que tem sido amplamente introduzida por meio da importação de peixes tropicais, tais como ciprinídeos. Na América do Sul, é um dos parasitos mais comuns em peixes selvagens, bem como em peixes de cultivo na região central argentina. Odontesthes bonariensis é um dos peixes mais importantes para a pesca esportiva na Argentina e um dos mais afetados pela lerneose. Um total de seis espécimes desses copépodes foram coletados de espécimes de 30 O. bonariensis capturados em um lago de pouca profundidade nos Pampas (33°25’28”S 62°53’56”W) em Córdoba (Argentina). O gene 28S rRNA de L. cyprinacea foi amplificado por PCR para obter a sequência do 28S rDNA. A sequência obtida desse parasito da Argentina mostrou alta similaridade genética com aquelas de outras origens geográficas. O presente estudo forneceu, pela primeira vez, uma caracterização molecular de L. cyprinacea na América do Sul.

Abstract Parasitic copepods of the family Lernaeidae are often found infesting freshwater fishes worldwide. They cause lernaeosis, a disease that can lead to serious pathogenic effects on their fish hosts. The most common lernaeid is the Lernaea cyprinacea, which has been widely introduced through importation of tropical fishes, e.g. cyprinids. In South America, it is one of the most common parasites both in wild and in farmed fish in the central region of Argentina. The silverside Odontesthes bonariensis is the most important fish of the sport fisheries of Argentina and one of the fish most affected by lernaeosis. Six specimens of copepods were collected from 30 specimens of O. bonariensis collected in a Pampean shallow lake (33°25'28”S 62°53'56”W) of Córdoba (Argentina). The 28S rRNA gene of L. cyprinacea was amplified by means of PCR to obtain the 28S rDNA sequence. The sequence obtained of this parasite from Argentina showed high genetic similarity with those from various geographical origins. The present study provided molecular characterization of L. cyprinacea in South America for the first time.

The Piedras Moras reservoir (32°10.13’S, 64°16.50’W) is the latest in a series of six that have been built over the basin of “Tercero” river, situated in Córdoba province. Hence, the present study was carried out to determine the physic-chemical characteristics of water and ichthyofauna in Piedras Moras. Water and fish samplings were taken seasonally. The fish were caught with trawl nets, gill nets and longlines. The water had low hardness and salinity (164 mg / L). The temperature, transparency, pH and dissolved oxygen did not show significant differences between sampling sites (P> 0.05), but did occur between seasons (P <0.01). Water temperature varied from 14.7 to 26.5 °C, while the values of dissolved oxygen were within the range of 5.7 and 9.3 ppm. There was a significant correlation between both variables (rs = -0.78, P <0.01). A total of twelve species of fish, belonging to five orders and eight families were captured. The presence of the genus Hypostomus was also confirmed. The largest family was the Characidae. The values of the Shannon-Wiener diversity index ranged from 1.45 to 2.01 bits. Catch per unit effort (CPUEp) of the fishery target species: Odontesthes bonariensis, varied from 0.74 to 3.24 kg / 20hs / gillnet. In the Piedras Moras reservoir there are only eleven of the 29 species recorded in the basin of “Tercero” river. The ichthyofauna at Piedras Moras had greater similarity to the ones in the reservoirs located in the same basin than those which are located in any other one.

El embalse Piedras Moras (32°10,13’S, 64°16,50’W) es el último de una serie de seis que se han construido sobre la cuenca del río Tercero en la provincia de Córdoba (Argentina). En el presente estudio se determinaron las principales características físico-químicas del agua y la composición de la ictiofauna del embalse Piedras Moras. Se realizaron muestreos estacionales con mediciones de agua in situ y en laboratorio. Los peces se capturaron con redes de arrastre, enmalle y espineles. El agua se caracterizó por su baja dureza y contenido de sales (164 mg/L). La temperatura, transparencia, pH y oxígeno disuelto no presentaron diferencias significativas entre sitios de muestreo (P>0,05), pero si entre épocas del año (P<0,01). Las temperaturas extremas del agua fueron 14,7 y 26,5 °C, mientras que los valores de oxígeno disuelto estuvieron dentro del rango de 5,7 y 9,3 ppm. Se observó una correlación significativa entre estas dos variables (rs= -0,78, P<0,01). Los peces capturados pertenecieron a doce especies distribuidas en cinco órdenes y ocho familias, se confirmó además la presencia del género Hypostomus. La familia más numerosa fue Characidae. Los valores del índice de diversidad de Shannon-Wiener estuvieron comprendidos entre 1,45 y 2,01 bits. La captura por unidad de esfuerzo de Odontesthes bonariensis (CPUEp), especie blanco de la pesquería, fue de 0,74 y 3,24 kg/20hs/red de enmalle. En el embalse Piedras Moras habitan sólo once de las 29 especies registradas en la cuenca del río Tercero. Al comparar la ictiofauna de seis reservorios de la provincia de Córdoba, Piedras Moras tuvo mayor similitud con los ubicados en la misma cuenca.

Aquatic ecosystems near urban areas suffer a steady deterioration caused by physical and chemical factors related to human activity, representing a danger to organisms that inhabit them, especially the fsh. These effects may be biomonitored by widely used techniques, such as the Micronucleus Test (Mn) and Nuclear Abnormalities (NA), among others. The aim of this study was to verify and compare the frequency of micronuclei and nuclear abnormalities in three fsh species collected in an urban lake, Cyprinus carpio, Astyanax eigenmanniorum and Cheirodon interruptus. After the capture and anesthesia of the fsh, weight and length were registered, and a blood sample was obtained from each individual. The samples were fxed and stained with 10% Giemsa, subsequently they were analyzed with the microscope (1000X) and photographed with a digital camera. The body con-dition index (K) was calculated for each fsh caught. A correlation analysis Spearman rank (rs) between frequency of Mn and NA vs. K was performed for each species. The Kruskal-Wallis test was applied to assess differences in Mn and NA between species. The results showed no statistically signifcant correlation (P> 0.05) between the frequencies of Mn and NA vs K. The frequencies of Mn between different species yielded no signifcant differences (P> 0.05), whereas NA (P <0.05) did. A. eigenmanniorum was the most sensitive species. NA preliminary differences between the species used, convert A. eigenmanniorum in a sort of "sentinel specie" and a possible biomonitor of xenobiotic agents.

Los ecosistemas acuáticos cercanos a las zonas urbanas sufren un deterioro constante ocasionado por diversos factores físico-químicos relacionados con la actividad antrópica, representando un riesgo para los organismos que los habitan, en especial los peces. Estos efectos pueden ser biomonitoreados mediante técnicas de amplia utilización, como el Test de Micronúcleos (Mn) y el de Anormalidades nucleares (AN), entre otros. El objetivo de este trabajo fue verifcar y comparar la frecuencia de micronúcleos y anormalidades nucleares en tres especies ícticas colectadas en un lago urbano, Cyprinus carpio, Astyanax eigenmanniorum y Cheirodon interruptus. Luego de la captura y anestesia de los peces, se extrajo de cada individuo una muestra de sangre y se registró el peso y la longitud total. Las muestras fueron fjadas y luego teñidas con Giemsa al 10%, posteriormente se las analizó con microscopio (1000X) y se les tomaron fotografías con cámara digital. Se calculó, además, el índice de condición corporal (K) para cada uno de los ejemplares capturados. Se aplicó un análisis de correlación de rangos de Spearman (rs) entre frecuencia de Mn y AN vs K para cada especie. La prueba de Kruskal-Wallis se aplicó para evaluar diferencias de Mn y AN entre las especies. Los resultados no mostraron una correlación estadísticamente signifcativa (P> 0,05) entre las frecuencias de Mn y AN vs K. Las frecuencias de Mn entre las diferentes especies no arrojaron diferencias signifcativas (P> 0,05), mientras que las AN sí (P< 0,05). Astyanax eigenmanniorum fue la especie que mayor sensibilidad presentó. Las diferencias preliminares de AN entre las especies utilizadas, convierten a A. eigenmanniorum en una especie "centinela" y posible biomonitor de agentes xenobióticos.

O peixe rei Odontesthes bonariensis é um peixe de água doce de grande importância na região central da Argentina. O objetivo deste trabalho foi descrever a sazonalidade do parasitismo de O. bonariensis no reservatrio La Viña (31º 17'S, 65º 01'W), província de Córdoba, Argentina. Durante os anos 1999 e 2002 foram capturados 573 peixes. Nestes se fez à avaliação da condição corporal usando como parâmetro o peso relativo e identificaram-se os seguintes parasitos: Lernaea cyprinacea (Crustacea), Contracaecum spp. (Nematoda) e Cangatiella macdonaghi (Cestoda). As prevalências e intensidades de Contracaecum spp. foram muito baixas. Houve diferenças nas prevalências de L. cyprinacea e C. macdonaghi na época do ano (P < 0,01), sendo maiores no verão e na primavera, respectivamente. Houve diferenças estacionais na intensidade de L. cyprinacea (P < 0,05) e na densidade de C. macdonaghi (P < 0,01), neste ultimo alcançou-se um valor máximo nas amostras de 32,0 (±22,5) parasitos por cm³ de conteúdo digestivo. Não houve associação entre o parasitismo e o peso relativo dos peixes. Embora haja certa sazonalidade, as diferentes cargas parasitárias encontradas nâo prejudicam a saúde de O. bonariensis enquanto sua condição corporal.

The pejerrey Odontesthes bonariensis is the most important freshwater fish of Argentina central region. The present study was conducted to describe the seasonal variation of parasitism in O. bonariensis from La Viña reservoir (31º 17'S, 65º 01'W), located in the province of Córdoba, Argentina. Between years 1999 and 2002, 573 fishes were caught, and their parasite infection and relative weight (Wr) were assesed. Three parasites were found, Lernaea cyprinacea (Crustacea), Contracaecum spp. larvae (Nematoda) and Cangatiella macdonaghi (Cestoda). Overall, Contracaecum spp. prevalence and intensity were very low. Lernaea cyprinacea and Cangatiella macdonaghi prevalences increased during summer and spring (P < 0.01), respectively. Lernaea cyprinacea infection showed also seasonal differences in intensity (P < 0.05), as well as C. macdonaghi regarding parasites density (P < 0.01). Cangatiella macdonaghi average parasites density was 32.0 (±22.5) cestodes per cm³ of digestive content. No association between parasitism and fish relative weight was found. Besides the seasonality variations observed, the parasite burden found did not compromise fish body condition.

The silverside Odontesthes bonariensis is the most important species in the fisheries of central Argentina. Cap¬ture per unit effort (CPUE), body condition, growth and feeding were studied for O. bonariensis in the Pampean shallow lake "Los Charos" (34º28´S, 64º23´W, 240 ha), located in Córdoba province. Four seasonal sampling procedures were carried out during 2002-2003. Floating gillnets and trawlnets were used to capture the fishes. Specimens captured (n= 2862) were ranged between 38 and 380 mm of standar length (StL). CPUE average was 74.3(±71,0) kg/20 hs/gillnets. The StL-weight relationship showed signifficant differences along the sea¬sons (P< 0,01). The body score indices were within the reffered limits for this species. Growth was calculated by StL(t)= 459,8*[1-exp(-0,3105*(t-0,175))]. The StL-Total length (TL) ratio was TL(mm)= 8,23+StL*1,14 (n= 283; R2= 0,99). For the young fishes the zooplankton constituted a secundary feeding source. In individuals older than 3 years of age, a marked canibalism was observed, which might explain partially their body condition. The shallow lake "Los Charos" shows an elevated production of O. bonariensis.

El pejerrey Odontesthes bonariensis es la especie más importante de las pesquerías del centro de Argentina. Se estudio la captura por unidad de esfuerzo (CPUE), la condición corporal, el crecimiento y la alimentación de O. bonariensis de la laguna pampeana Los Charos (34º28´S, 64º23´W, 240 ha), ubicada en la provincia de Córdoba. Se realizaron cuatro muestreos estacionales en el periodo 2002-2003. Para la captura de peces se utilizaron redes de arrastre y enmalle. Se capturaron 2862 ejemplares de un rango de talla comprendido entre 38 y 380 mm de longitud estándar (LSt). La CPUE promedio fue de 74,3(±71,0)kg/20 hs de tendido de red. La relación LSt-peso presentó diferencias significativas entre épocas del año (P< 0,01). Los índices de condición corporal estuvieron dentro de los límites de referencia de la especie. El crecimiento calculado fue: LSt(t)=459,8*[1-exp(-0,3105*(t-0,175))]. La relación LSt-Longitud total (LT) fue: LT(mm)=8,23+LSt*1,14 (n=283; R2=0,99). El zooplancton constituyó un ítem alimenticio secundario en los peces jóvenes. En los ejemplares de 3+ años de vida se observó un marcado canibalismo, situación que explicaría en parte su mejor condición corporal. La laguna Los Charos presenta una elevada producción de O. bonariensis.

Chocancharava River (Cuarto River) joints Tercero River to form Carcarañá River, an important affluent of Paraná River. The aim of this work was to evaluate bacteriological, phycological and physical-chemical variations of Chocancharava River along the year, in order to establish the potential risk for human and animal health. According to the effluents received by this environment, six sampling stations were selected. The abundance of total coliform and faecal coliform microorganisms showed variations along the year, exceeding admissible levels at stations located downstream the city discharges. A similar situation was observed for Streptococcus faecalis. Algal counting did not show similar values at the sampling stations evaluated along the year; however, genera belonging to the Bacillariophyceae were predominant. Physical parameters were found to be between admissible limits, except for sites receiving effluents. Considering their chemical characteristics, water was classified as hypohaline and sodic bicarbonated. According to the results obtained, three of the sampling stations (km 597, km 587 and Paso del Durazno) do not accomplish established limits of quality.

El río Chocancharava (río Cuarto) se une al río Tercero para formar el río Carcarañá, destacado afluente del río Paraná. El objetivo del presente trabajo fue evaluar las variaciones bacteriológicas, algales y físico-químicas del río Chocancharava, determinando el riesgo potencial para la salud humana y animal. Según los diversos aportes que recibe este ambiente, se establecieron seis estaciones de muestreo. La abundancia de microorganismos coliformes totales y coliformes fecales presentó variación a lo largo del año, superando las estaciones ubicadas río abajo de la descarga cloacal los límites admisibles. Similar situación se presentó para Streptococcus faecalis. El recuento de algas no presentó registros similares en las estaciones de muestreo evaluadas a lo largo del año; sin embargo, el predominio le correspondió a los géneros de la clase Bacillarophyceae. Los parámetros físicos se encontraron dentro de los límites admisibles, salvo para los sitios que reciben aportes o efluentes. Por sus características químicas, el agua fue clasificada como hipohalina y bicarbonatada sódica. De acuerdo a los resultados obtenidos, tres de las estaciones de muestreo (km 597, km 587 y Paso del Durazno) no cumplen con los límites guías e imperativos de las directivas de calidad para aguas recreacionales.