Resumo A cultura da ostra tem como problema de produção o organismo incrustante, neste contexto, avaliou como controle biológico contra organismos incrustantes e sedimentos a introdução do gastrópode Tegula atra (Lesson, 1830) em culturas de ostras chilenas (Triostrea chilensis Phillippi, 1844) em condições de presença e ausência de fome, localizadas em gaiolas flutuantes e culturas de fundo. A predação e o efeito mecânico no pastejo de T. atra geraram uma diminuição em sete dias de 19,8% e 13,7% dos organismos incrustantes na cultura em gaiola e nos sedimentos de fundo, por efeito de gastrópodes sem fome, respectivamente. Considerando que houve decréscimo de 12,6% e 11,4% dos organismos incrustantes na cultura em gaiola e nos sedimentos de fundo pelos efeitos dos gastrópodes com fome respectivamente. Os organismos incrustantes removidos eram principalmente algas, ascídias coloniais, poliquetas, briozoários e pequenos crustáceos.

Abstract The oyster culture has the incrusting organism as problem for production, in this context, it evaluated as biological control against incrusting organism and sediments the introduction of gastropod Tegula atra (Lesson, 1830) in Chilean oysters (Triostrea chilensis Phillippi, 1844) cultures in conditions of starvation presence and absence located in floating cages and bottom cultures. The predation and mechanic effect on T. atra grazing generated a decreasing in seven days of 19.8% and 13.7% of incrusting organisms in cage culture and bottom sediments by effects of gastropods without starvation respectively. Whereas it had a decrease of 12.6% and 11.4% of incrusting organisms in cage culture and bottom sediments by effects of gastropods with starvation respectively. The incrusting organism removed were mainly algae, colonial ascidia, polychaeta, bryozoan and small crustaceans.

The use of antifungals was assessed to improve embryo survival of Galaxias maculatus. Three treatments using formalin dose of 250 ppm, iodine dose of 100 ppm, and sea salt in doses of 30 ups were designed, and a control treatment under 10 of salinity water. For each treatment and control, 15 replicates were used, with 100 embryos in each replicate. Embryos were immersed into each treatment solution for one hour every two days. Larval survival after 15 days old was assessed. Higher embryonic and larval survival was obtained in sea salt treatment improving by 27.4 and 11.6% (P < 0.05) respectively over control results. Formalin treatment resulted in embryonic and larval survival of 9.8 and 4.0% respectively more than control (P < 0.05) and in the case of iodine embryonic survival, 2.6% more than control (P > 0.05) and larval survival of 16.4% lower than the control (P < 0.05). In conclusion, sea salt shows greater effectiveness as a prophylactic treatment to improve the embryonic survival of G. maculatus.

Se evaluó el uso de antifúngicos para mejorar la supervivencia embrionaria de Galaxias maculatus. Se diseñaron tres tratamientos utilizando formalina en dosis de 250 ppm; yodo en dosis de 100 ppm y sal de mar en dosis de 30 ups y un tratamiento control. Para cada tratamiento y el control se utilizaron 15 réplicas con 100 embriones por réplica. El tratamiento correspondió a sumergir los embriones en un baño profiláctico por una hora cada dos días y el control sólo en agua de salinidad 10. Posteriormente se evaluó la supervivencia larval de cada tratamiento y control a los 15 días de vida. En el tratamiento con sal se obtuvo la mayor supervivencia embrionaria y larval, mejorando en un 27,4 y 11,6% (P < 0,05) por sobre el control. En el tratamiento con formalina se obtuvo supervivencia embrionaria y larval de 9,8 y 4,0% respectivamente sobre el control (P < 0,05) y en el caso del yodo se obtuvo una supervivencia embrionaria de 2,6% por sobre el control (P > 0,05) y supervivencia larval de un 16,4% menor al control (P < 0,05). En conclusión la sal muestra mayor efectividad como tratamiento profiláctico para mejorar la supervivencia embrionaria de G. maculatus.

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.

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.

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.

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 water.