Abstract The Cautin river is located in the 137 years old Araucania region, Chile (38°S), and is characterized by alterations through human interference due agriculture and towns in its surrounding basin, the presence of salmonids, and by its mixed regime, originated from snow melting in summer and rains in winter. The aim of the present study was to make a review of the inventory and ecological role of the benthic inland water macroinvertebrates of the River Cautin, in order to understand their importance in the ecosystem of the river. The fauna of this river includes a fauna composed of endemic and introduced fish, which has, however, been only poorly studied until now. The literature revealed the presence of abundant populations of Diptera, Trichoptera and Ephemeroptera larval stages, and few crustaceans specifically amphipods and freshwater crabs along the river’s course. Many of these macroinvertebrates are prey for both introduced salmonids and native fishes. Similar results have been reported for other southern Argentinean and Chilean Patagonian rivers.

The Toltén river is located in the 137 years old Araucania region, Chile (38° S), and is characterized by low alterations through human interference due agriculture and towns in its surrounding basin, the presence of native fishes and salmonids, and by its lake effluent regime originated from Villarrica lake. The aim of the present study was to make a review of ecological role of the benthic inland water macroinvertebrates as preys for native fishes of the River Toltén, in order to understand their importance in the ecosystem of the river. The literature revealed that the main prey for native fishes are Chironomidae larvae, nevertheless there are not specific reports for Tolten river. The exposed results are similar with similar native species for Patagonia, and these native species would have prey for introduced salmonids, or these species would have prey competition with introduced salmonids in according to the literature descriptions for Argentinean and Chilean Patagonia.

Abstract.-This study aims to evaluate the effect of pH on embryonic survival of Galaxias maculatus. Embryos were incubated at 6 different pH levels in the water. One-way ANOVA was used to compare averages between treatments and Tukey test to determine post hoc differences. The Probit regression was used to estimate the embryonic and the hatching period. Embryos survive pH from 5 to 11 and die at pH extremes 3 and 13. The best average survival rates were obtained at neutral pH (78.7 ± 1.2) and as the pH decreases away from embryonic survival 7 embryonic survival decreases. In conclusion, pH is an important factor to consider for the production of larval G. maculatus.Key words: Pisciculture, embryos, incubation, pH tolerance INTRODUCCIÓNEn el cultivo de peces uno de los factores ambientales que afectan la supervivencia es el pH, valores por ejemplo que se alejan del neutro generalmente producen alteraciones fisiológicas y que dependiendo de lo extremo del valor y el tiempo expuesto del individuo suelen producir mortandad. Valores de pH entre 5,0 a 5,5 pueden ser dañinos para la reproducción de los peces, puesto que los huevos y los alevines son más sensibles al pH bajo que los peces juveniles y adultos (Hepher 2001).Peterson & Martin (1982) demostraron que la captación de agua para la formación del espacio perivitelino de las ovas de salmón del Atlántico (Salmo salar) a pH 4 y 4,5, decreció significativamente respecto de ovas colocadas en pH 5 y 6,8 y a pH 4 murieron dentro de las 8 h de exposición sugiriendo que las reducciones en la cantidad del fluido perivitelino a bajo pH podría aumentar la susceptibilidad de los huevos a lesiones físicas. Rombough & Jensen (1985), también encontraron que los huevos de Oncorhynchus mykiss absorbieron significativamente menos agua a pH 5,5 y fueron significativamente más sensibles a la deformación mecánica a pH 6,0 que los que estuvieron a pH 7,2.En cuanto al pH básico, existen pocos trabajos que especifiquen su efecto en la etapa embrionaria de peces. Meyer & Hansen (2002) determinaron que el contenido corporal de Na a pH 10 fue un 14% más bajo que los controles y que hubo una tendencia hacia un agotamiento más rápido de las larvas de Deltistes luxatus. Bergerhouse (1992) demostró que breves periodos de pH altos causan mortalidades significativas en alevines de walleye (Stizostedion vitreum). Del mismo modo Xuemin & Randall (1991) demostraron que la actividad natatoria de juveniles de Oncorhynchus mykiss fue afectada en pH ácidos y básicos. Actualmente no se cuenta con información respecto de la influencia del pH en embriones de puye Galaxias maculatus (Jenyns, 1842), por lo tanto en el presente trabajo se evaluó la influencia del pH en la supervivencia embrionaria, periodo embrionario y periodo de eclosión del puye sometidos a 6 niveles de pH del agua (3, 5, 7, 9, 11 y 13). La hipótesis de trabajo fue que los embriones de G. maculatus por habitar en ambientes estuarinos poseen la capacidad de tolerar y adaptarse a amplias variaciones de pH. MATERIALES Y MÉTODOS MUESTRA BIOLÓ...

RESUMEN.Se evaluó e l efecto de la salinidad en la supervivencia embrionaria, período embrionario y período de eclosión de puye, Galaxias maculatus. Se utilizaron ocho tratamientos, con salinidades de 0, 4, 8, 12, 16 y 20 obteniéndose supervivencias embrionarias promedios respectivas de 84,9; 84,0; 85,5; 86,1; 82,6 y 75,8%, sin diferencias significativas entre ellas, mientras que con salinidad de 24 se obtuvo sobrevivencia de 10,4%, significativamente diferente al resto de los tratamientos y con salinidad de 28 causó 100% de mortalidad. A diferencia del estado juvenil y adulto, el embrión es incapaz de resistir la salinidad marina y su umbral de tolerancia se encuentra entre salinidades de 24 y 28. Las mayores supervivencias promedios larvales a 10 días de vida fueron con salinidades intermedias de 8, 12 y 16 de 79,3; 80,3 y 74,6% respectivamente, sin diferencias significativas entre ellas, demostrando alta viabilidad del embrión post-eclosión. Los períodos embrionarios promedios (50%) más breves fueron a bajas salinidades 0, 4, 8, 12 con 28,7; 28,0; 29,7 y 29,7 días y los más extensos en los tratamientos con salinidades de 16 y 20, con 34,0 y 34,3 días, sin diferencias significativas entre ellos. Los períodos de eclosión promedio (50%) con salinidades de 0, 4, 8, 12, 16, 20 y 24 fueron de 5,0; 5,5; 7,5; 8,8; 13,0; 14,3 y 15,8 días respectivamente, sin diferencias significativas entre ellos. Palabras clave: Galaxias maculatus, puye, eclosión, incubación, tolerancia salina, acuicultura. Effect of salinity on survival of embryos of jollytailGalaxias maculatus (Jenyns, 1842)ABSTRACT. Eight different salinity effects on embryonic survival and embryonic and hatching phase time duration of jollytail (Galaxias maculatus) were assessed. Mean survival rates were higher at salinities values of 0, 4, 8, 12, 16 and 20 with 84.9, 84.0, 85.5, 86.1, 82.6 and 75.8% respectively with no significant differences between them; in contrast to salinity of 24 was obtained by 10.4%, significantly different from other treatments. Salinity of 28 caused 100% of mortality. According to results, the embryo is unable to resist ocean salinity and its tolerance limit is between 24 and 28. The highest larval survivals at 10 days after hatching occurred in those treatments in which embryos were performed to intermediate salinities of 8, 12 and 16 with 79.3, 80.3 and 74.6% respectively, with no significant differences between them. These results demonstrate high post-hatching viability. Embryonic time period (50%) were shorter at low salinities 0, 4, 8 and 12 with 28.7, 28.0, 29.7 and 29.7 days and the largest, in the treatments of salinities of 16 and 20 with 34.0 and 34.3 days. No significant differences were found between all of them. Regarding the average hatching time periods (50%) in the treatments of salinities of 0, 4, 8, 12, 16, 20 and 24 were 5.0, 5.5, 7.5, 8.8, 13, 0, 14.3 and 15.8 days respectively, without significant differences between them.

Efecto combinado de la temperatura y salinidad sobre la supervivencia embrionaria de Galaxias maculatus Abstract.-This study aims to evaluate the effect of temperature and salinity on Galaxias maculatus embryo survival. Embryos were incubated at 5, 10 and 15°C and 0, 10 and 30 psu. At 5°C all salinities induced 100% mortality. Furthermore, salinity of 30, regardless temperature, caused 100% mortality. In freshwater, embryos reached 74.7 and 69.3% survival at 10°C and 15°C, respectively. While, at 10 psu, the larvae survivals were higher, 88.7 and 80.0% with 10 and 15°C respectively. These findings suggest that there is not a temperature-salinity interaction effect on embryonic development of G. maculatus.In conclusion the embryonic development of this fish is only possible at fresh and brackish waters and it is not viable at salt w ater.