Research Outputs
EvaluaciĂ³n de la calidad de un tramo de rĂo urbano intervenido y selecciĂ³n de un paso para peces, RegiĂ³n del BiobĂo, Chile
En el presente estudio se evaluĂ³ la calidad de un tramo del sistema fluvial urbano Estero NonguĂ©n en la regiĂ³n del BiobĂo de Chile. Este estero ha sido encauzado en su rivera, con el objetivo de evitar futuros desbordes y afectar a las poblaciones aledañas a Ă©ste. Sin embargo, no han sido evaluadas las intervenciones al sistema fluvial para verificar y evitar que se altere el desplazamiento natural de la ictiofauna presente. Para esto, se analizĂ³ la presencia de barreras en un tramo del estero mediante indicadores de calidad y conectividad. Para recomendar una alternativa de paso de peces en un sitio identificado con una barrera, se utilizĂ³ el mĂ©todo de ponderaciĂ³n lineal. El tramo del rĂo analizado resultĂ³ ser de calidad moderada y la conectividad deficiente, lo que implicarĂa que existirĂan grupos de peces nativos que no se pueden desplazar aguas arriba ni aguas abajo de la barrera. Para restablecer la conectividad del sistema fluvial, se propone construir como paso un dispositivo de rampa de piedras, que es un sistema de bajo costo, de trĂ¡nsito sencillo y acorde al ambiente ribereño.
Critical swimming speed at different temperatures for small-bodied freshwater native riverine fish species
This study evaluated the efect of fsh total length (LT) and three water temperatures (10, 15 and 20 °C) on the critical swimming speed (Ucrit) of the species Percilia irwini (2.9–6.3 cm LT), Cheirodon galusdae (3.4–5.5 cm LT), and Trichomycterus areolatus (4.0–6.3 cm LT). An Ucrit estimation model was constructed for each species as a function of temperature and size. The results showed mean Ucrit for P. irwini of 44.56, 53.83 and 63.2 cm Âs−1 at 10, 15 and 20 °C, respectively: 55.34, 61.74 and 70.05 cm Âs−1 for C. galusdae and 56.18, 63.01 and 71.09 cm Âs−1 for T. areolatus. Critical velocity depended on the interaction between species, body length and water. The swimming performance increased signifcantly with rising temperature in all three species. The velocity also increased with greater fsh total length. After controlling for fsh total length, velocity also increased with higher temperature in the three species. This research is relevant to small fsh species that require conservation measures.
Settlement experiment of spat using three different collectors in two contrasting coastal sites from Chile (SE Pacific Ocean)
Most of the marine bivalve production comes from aquaculture and only 11% comes from the wild fishery. For example, mussel aquaculture still strongly relies on spat - the recently settled juveniles. Gaps of information on the recruitment and settlement of spat are important drawbacks for the development of mussel aquaculture in several geographic regions. We here study these processes using three collectors (Anchovy mesh, Rope and Raschel mesh) throughout one year in two coastal sites of Central Chile (Coliumo and Punta LoberĂa) at three depths (2, 4 and 6 m). Five spat species were settled in the collectors, i.e. Aulacomya atra, Choromytilus chorus, Mytilus chilensis, Mytilus galloprovincialis and Semimytilus algosus. Recruitment was consistently higher during summer and autumn at both sites. Different seasonal recruitment patterns were observed regarding the spat species. Spat collection of the former mytilid species occurs from spring to autumn with the exception of M. galloprovincialis in Coliumo and M. chilensis in Punta LoberĂa. M. galloprovincialis is settled mostly in autumn and summer, and M. chilensis during winter. There were also differences when considering the collector type, mostly due to A. atra and S. algosus which peaked in nylon rope. Spat collection of the commercial species M. chilensis should be preferentially carried out in nylon rope during autumn in Coliumo and summer and autumn in Punta LoberĂa. During summer and autumn, also S. algosus will be settled. These results will enable the implementation of management measures to promote mytilid culture on the coastal zone of the BiobĂo region.