Primeros estadios del ciclo de vida de peces nativos del Río San Pedro (Cuenca del Rio Valdivia, Chile) First stages of the life cycle in native fish from the San Pedro River (Valdivia River Basin, Chile)

Los estadios de huevos, larvas y juveniles de los peces de agua dulce nativos de Chile son prácticamente desconocidos. Conocer su estacionalidad, morfología y uso de hábitat es relevante para comprender su biología y permitir la conservación de esta ictiofauna altamente amenazada. Asimismo, los primeros estadíos del ciclo de vida de los peces determinan la persistencia de las poblaciones en el tiempo. Dado esto, el objetivo del presente trabajo fue dar a conocer y describir los resultados de intensivos muestreos (465 días) destinados a encontrar los primeros estadíos de las 14 especies nativas que habitan el río San Pedro (cuenca del Valdivia). Los muestreos se efectuaron desde octubre de 2005 a marzo de 2008. Se encontraron huevos, larvas y juveniles de Galaxias maculatus, Basilichthys australis y Percilia gillissi; larvas y juveniles de Geotria australis y Trichomycterus areolatus, y juveniles de Diplomystes camposensis, Percichthys trucha y Cheirodon australe. En cada caso se describe la época y hábitat de ocurrencia, así como sus características morfológicas generales, lo cual para P. gillissi constituye la primera descripción de sus estadíos de desarrollo embrional y larvario. En general, se aprecia una segregación espaciotemporal de las épocas de desove y crianza de larvas marcada por el uso de las planicies de inundación como sitios de crianza. La extensión temporal de este estudio a escala de ambientes ribereños sugeriría que los esfuerzos de búsqueda de aquellos primeros estadíos no detectados podrían enfocarse en ambientes más profundos o correntosos.<br>Eggs, larvae and juveniles stages of the Chilean native freshwater fish are practically unknown. To know their seasonality, morphology and habitat use is relevant to understand their biology and to allow the conservation of this highly threatened ichthyofauna. Likewise, the early stages of fish's life cycle are highly labile and their success determines the persistence of the populations over time. For this reason the aims of this work is to report and describe the results of intensive samplings performed to find the early stages of the 14 native species that inhabit in the San Pedro River (Valdivia river Basin). Samplings were done during 465 days along the river, from October 2005 to March 2008. We found eggs, larvae and juveniles of Galaxias maculatus, Basilichthys australis and Percilia gillissi, larvae and juveniles of Geotria australis and Trichomycterus areolatus; and juveniles only of Diplomystes camposensis, Percichthys trucha and Cheirodon australe. We describe the season and habitat of occurrence, as well as their general morphological characteristics. This is the first description of embryonic and larval development stages for P. gillissi. A spatial-temporal segregation of the spawning and larvae rearing is observed, mainly marked by the use of the floodplain as rearing sites. The temporal extention of this study at riparian scale suggests than efforts in search of early stages of knowless species would be focus in deeper and/or rushing environments

Patrones de desplazamiento de peces nativos en el Río San Pedro (cuenca del Río Valdivia, Chile) Movement patterns of the native fish fauna of the San Pedro River (Valdivia River Basin, Chile)

Los peces nativos chilenos se caracterizan por ser de tamaño pequeño (<30 cm). Por ello, generalmente se les menciona como de baja capacidad de natación y desplazamiento. Sin embargo, no existen estudios empíricos que lo demuestren. En este estudio describimos los patrones de movimiento de seis especies nativas en el río San Pedro (Aplochiton taeniatus, Galaxias maculatus, Galaxias platei, Diplomystes camposensis, Basilichthys australis, Percilia gillissi y Percichthys trucha), utilizando técnicas de marcaje-recaptura mediante pinturas elastoméricas y Pit-tags. Nuestros resultados sugieren que la mayor parte de las especies presentan desplazamientos pasivos, recorriendo distancias de hasta aproximadamente 40 km en el sentido de la corriente. También fueron frecuentes los movimientos entre riberas, aún en zonas de alta turbulencia en el río. No se evidenciaron claros movimientos activos hacia aguas arriba, pero el análisis de los resultados en conjunto con información de la estructura genética, abundancias y distribución de las especies en la cuenca, nos permite concluir que los patrones de desplazamiento de todas las especies estudiadas son relevantes para la mantención de su dinámica metapoblacional.<br>The Chilean native fish are characterized for having small sizes (< 30 cm). Due to this, they are generally described with a low swimming capacity and movement; nevertheless, there is no empirical study to show it. In this study we describe the movement patterns of six native species in the San Pedro River (Aplochiton taeniatus, Galaxias maculatus, Galaxias platei, Diplomystes camposensis, Basilichthys australis y Percilia gillissi) by using marking-recapture techniques with elastomeric inks and Pit tags. Our results suggest that most of the species show passive movements, crossing distances up to about 40 km in the flow direction. Movements between river banks were also frequent, even in zones of high turbulence of the river. Active movements upstream were note clear, but the analysis of the results altogether with information of the genetic structure, abundances and distribution of the species in the watershed, allows us to conclude that the movement patterns of all species studied are relevant for the maintenance of their metapopulation dynamics

Movement patterns and home range in Diplomystes camposensis (Siluriformes: Diplomystidae), an endemic and threatened species from Chile

ABSTRACT We document movement patterns and home range of Diplomystes camposensis, an endemic and threatened freshwater catfish from Chile. We tracked the movements of seven individuals of different body size (13.5 to 19 cm SL) using portable radio telemetry equipment to investigate movement patterns in relation to day/night activity and habitat use in the San Pedro River (Valdivia Basin). Tracked movements and model-based analyses revealed that D. camposensis has a large home range and high mobility. The average home range was 0.068163 ± 0.033313 km2, and the average area of higher activity was 0.005646 ± 0.011386 km2. The mean linear home range was 387.4 m. The results also showed that movements were longer during the night, supporting nocturnal habits. Movements tended to be in an upstream direction for some individuals, although these differences were not significant when data was pooled. Large home range and movements suggest that the species may require large river areas to meet ecological demands, an aspect that could be severely affected by fragmentation. These results, along with previously published genetic data, suggest that the conservation of D. camposensis would be seriously threatened by hydromorphological alterations (e.g. lack of connectivity), such as those resulting from dam building