Filipe Ritter

Nursery rearing of jundiá, Rhamdia quelen (Quoy & Gaimard) in cages: cage type, stocking density and stress response to confinement

Abstract The use of net cages allows the exploration of some water bodies, without usual aquacultural techniques for earthen ponds. Several advantages are proposed for the use of cages, however some disadvantages, as the higher possibility of stress and diseases are known. Growth parameters, survival rate and stress response of hatchery-bred Jundia ( Rhamdia quelen , Quoy & Gaimard) fry reared at different cage types and densities in net cages suspended in pond were evaluated. The first experiment compared fry reared at the circular and cubic-shaped cages at a density of 100 fry/m 3 . Fish held in cubic cages were heavier than the fish held in circular cages, presented higher weight gain and daily weight gain and a better food conversion. The survival rates were similar between fish raised in both types of cages. In the second experiment, cubic cages were stocked with 100, 200 and 300 fry/m 3 . Fish held in cages with lower density were heavier than the ones held at higher densities, presented higher weight gain and daily weight gain. Food conversion and survival rates were similar between different fish densities. According to the results presented in this study, the growth of jundia in cubic-shaped cages was density dependent. In terms of weight parameters, the most effective stocking density of jundia was 100 fry/m 3 that reaches 63.74±3.69 g of body weight. However, if the desirable weight was from 30 to 40 g, the density of 300 fry/m 3 is most effective because the fingerling production increases three times. In experiment 3, in all sample days, the serum cortisol levels were higher than the pre-stock and basal levels. The 80 days of cage confinement were not enough for adaptation of fingerlings to cage environment. The maintenance of high cortisol concentrations after 80 days of experimental period suggests the presence of typical chronic stress response that might have some detrimental effects over fish growth. Taken together, the data presented herein suggests that the improvement of rearing conditions (e.g. water quality, food quality, cage design, culture management, etc.) capable to minimize the stress response, may affect positively the growth performance in jundia during the nursery period.

Chronic exposure to sub-lethal concentration of a glyphosate-based herbicide alters hormone profiles and affects reproduction of female Jundiá (Rhamdia quelen).

This work was carried out to verify the effect of a glyphosate-based herbicide on Jundiá hormones (cortisol, 17β-estradiol and testosterone), oocyte and swim-up fry production. Earthen ponds containing Jundiá females were contaminated with glyphosate (3.6mg/L); blood samples were collected from eight females from each treatment immediately before, or at 1, 10, 20, 30 and 40 days following contamination. A typical post-stress rise in cortisol levels was observed at the 20th and 40th days following exposure to glyphosate. At the 40th day, 17β-estradiol was decreased in the exposed females. A similar number of oocytes were stripped out from females from both groups; however, a lower number of viable swim-up fry were obtained from the herbicide exposed females, which also had a higher liver-somatic index (LSI). The results indicate that the presence of glyphosate in water was deleterious to Rhamdia quelen reproduction, altering steroid profiles and egg viability.

Embryonic and larval development of Jundiá (Rhamdia quelen, Quoy & Gaimard, 1824, Pisces, Teleostei), a South American Catfish

The jundiá (Rhamdia quelen, Quoy and Gaimard) is an endemic South American fish species. Because this species supports cold winters and grows faster during warm months, it has begun to be viewed as an ideal species for fish production in southern South America. In the present study, jundiá oocytes used were obtained by extrusion from females after hormone injection. Soon after hydration, the eggs were transferred to 50 L conic glass incubators, with constant and controlled water influx. Samples of fertilized eggs were transferred to Petri dishes and, examined under a stereoscopic microscope, were spherical, demersal, and non-adhesive with defined perivitelline space and resistant chorion. Cleavage stages occurred during the first 3.5 h. After hatching, larvae were transferred to 200 L glass fiber incubators. First signs of embryo movement were observed 21 h after fertilization; larval eclosion occurred 30.5 h after fertilization. Present findings may provide a basis for studies aimed at determining the complete ontogeny of jundiá and may be useful in eco-toxicological studies.

The color of illumination affects the stress response of jundiá (Rhamdia quelen, Quoy & Gaimard, Heptapteridae)

This paper provides the first data about physiological responses to stress in jundia (Rhamdia quelen) exposed to different light colours. Jundia is a species for fish production in the southern part of South America - and suitable for any region with a temperate or subtropical climates. In order to develop a light management for jundia fingerlings during indoor maintenance and to understand the relationship between welfare and light colour in the jundia, fingerlings were exposed to white, blue and green light. At the 10th day of light exposure an acute stressor was imposed. One hour after the application of the stressor, fish were sampled. Stress was assessed by means of cortisol determination. Our results show that green light seems to be the worst alternative to illuminate jundia indoor experimentation facilities, or even fish transportation. The results also suggests that colour affects the stress response of jundia, and may be usefull for the management of this species.