Lenise Vargas Flores da Silva

Transport of silver catfish (Rhamdia quelen) fingerlings at different times, load densities, and temperatures

Abstract Silver catfish (Rhamdia quelen) fingerlings (5–10 cm) were caught from a fish culture pond and placed in a tank for stomach emptying for 24 h. Fingerlings were then weighed and placed in plastic bags (5 l) with 1.5 l water and oxygen, which were kept at temperatures of 15, 20, and 25 °C. The load densities tested were 50, 67, 87, and 168 g l−1. When bags were opened after 6, 12, or 24 h, mortality, dissolved oxygen, pH, total ammonia, non-ionized ammonia, total hardness, nitrite, total alkalinity, and carbon dioxide levels were determined. There was fingerling mortality only at the load density of 168 g l−1 after 24 h of transport at 20 and 25 °C, suggesting that mortality increased with temperature and time of transport. The dissolved oxygen levels in the water were reduced throughout 24 h of transport in the load density of 168 g l−1 at 20 and 25 °C, but remained unchanged at the other load densities. The pH decreased significantly at all load densities and temperatures throughout 24 h. Total alkalinity, total ammonia, and carbon dioxide levels increased significantly up to 24 h of transport in all treatments. Non-ionized ammonia and nitrite levels were below 0.02 and 0.06 mg l−1, respectively. Total hardness ranged from 20 to 48 mg l−1 CaCO3. The best temperature for transporting fingerlings of this species in plastic bags is 15 °C, because up to 24 h there was no significant mortality even at the load density of 168 g l−1, dissolved oxygen levels were still high, and total ammonia and carbon dioxide presented the lowest increase. Transport at 25 °C and a load density of 168 g l−1 must not exceed 6 h due to the high levels of ammonia and carbon dioxide and low dissolved oxygen levels in the water.

Survival and growth of silver catfish larvae exposed to different water pH

The objective of this study was to determine the influence ofwater pH (5.5, 6.0, 7.0, 8.0, and 8.5) on survival and growth ofsilver catfsh (Rhamdia quelen) larvae. Larvae were obtained frominduced spawning in November and maintained under controlledconditions of 25 (1) °C using a water re-use system incontinuously aerated 40 L polyethylene tanks (350 larvae/tank).Larvae were fed until satiation six times a day. At days 0, 7, 14,and 21 and after yolk absorption, 10 larvae from each group wererandomly chosen to evaluate length, weight, and specific growthrate (SGR). Length, weight, survival, and biomass at the end of 21days were significantly higher at pH 8.0 and 8.5. As expected,specific growth rate decreased with time. These results suggest that 8.0–8.5 isthe best pH range for survival and growth of the larvae of thisspecies.

Growth and survival of Rhamdia quelen (Siluriformes, Pimelodidae) larvae exposed to different levels of water hardness

Abstract The response to water hardness increase varies from species to species. The purpose of this study was to verify the survival and growth of larvae of silver catfish, Rhamdia quelen , in water with different levels of water hardness. Larvae (2.75 mg and 5.00±0.05 mm) were randomly allotted to experimental units (three replicates per treatment) and kept in 44-l boxes (400 larvae/box). Larvae were exposed to five water hardness values (30, 70, 150, 300, and 600 mg l −1 CaCO 3 ) at pH 8.25. Samples of larvae were collected on days 0, 7, 14, and 21, and the length, weight, and specific growth rate (SGR) were determined for each collection. Survival and biomass were calculated on day 21. Higher larvae growth, survival, and biomass were obtained at 30 and 70 mg l −1 CaCO 3 . Therefore, this is the recommended hardness range for growth and survival of silver catfish larvae.

Incubation of silver catfish, Rhamdia quelen (Pimelodidae), eggs at different calcium and magnesium concentrations

Abstract Ca 2+ and Mg 2+ are important for ionic regulation of freshwater fish because both ions influence the permeability of biological membranes, preventing diffusive flow and high ionic loss to water. The objective of this study was to analyze the hatchery rate and post-hatch survival of silver catfish ( Rhamdia quelen ) eggs at different Ca 2+ and Mg 2+ concentrations. Eggs were incubated in continuously aerated 4-l polyethylene bottles (600 eggs/bottle) at 24 °C and randomly divided into five treatments (three replicates per treatment) with different concentrations of Ca 2+ and Mg 2+ at hardness values of 70 and 150 mg l −1 CaCO 3 . There were also two control groups with hardness of values 20 mg l −1 CaCO 3 . Dissolved oxygen, pH, temperature, total alkalinity and nonionized ammonia levels in water were always satisfactory for fish culture throughout the experiments. The increase of water hardness to 70 mg l −1 CaCO 3 (all treatments) increased hatch rate, but the highest Ca 2+ level reduced post-hatch survival. However, the eggs incubated at water hardness of 150 mg l −1 CaCO 3 presented the lowest hatch rates and post-hatch survival values at higher Ca 2+ concentrations. These results suggest that the increase of water hardness to 70 mg l −1 CaCO 3 using either Ca 2+ or Mg 2+ improved hatch rate, but the increase of waterborne Ca +2 above 20 mg l −1 , irrespective of water hardness, is not indicated for incubation of silver catfish eggs because it reduces post-hatch survival.

Efficacy of Different Salt (NaCl) Concentrations in the Treatment of Ichthyophthirius multifiliis-Infected Silver Catfish, Rhamdia quelen, Fingerlings

ABSTRACT The objective of this study was to evaluate different salt concentrations in the treatment of Ichthyophthirius multifiliis. Silver catfish, Rhamdia quelen, fingerlings infected with I. multifiliis were submitted to four sodium chloride concentrations (g/L): 0,1,2, and 4 for 23 days. In a second experiment, fingerlings were maintained with 4 g/L salt, but for 45 days. Treatments with 2 and 4 g/L salt significantly increased fingerling survival compared with 0 and 1 g/L, and survival was significantly correlated with salt concentrations. In the second experiment, fish maintained at 4 g/L salt showed a gradual reduction of “white spots” and survival was 100%. Therefore, salt offers an alternative for treatment of silver catfish fingerlings infected with I. multifiliis.

Physiological responses of Rhamdia quelen (Siluriformes: Heptapteridae) to anesthesia with essential oils from two different chemotypes of Lippia alba

The aim of this study was to evaluate if Lippia alba has different chemotypes according to the chemical composition of the essential oil (EO) considering collection site, and if the EO may have different effects on blood and plasma parameters in silver catfish, Rhamdia quelen, during and immediately after anesthesia. The citral (EO-C) and linalool (EO-L) chemotypes were identified, and both presented similar anesthetic effects for silver catfish. Fish were exposed to two concentrations of each EO, which induced slow and fast anesthesia (100 and 300 µL L-1, respectively). Blood ions did not change at any time of anesthesia induction and recovery and, therefore, the electrolyte balance was not altered. Blood gases oscillated through all exposure and recovery times, but there was an increase in pO2 after 10 min recovery in fish anesthetized with EO-C. Glucose increased in fish exposed to both EOs when compared with the control group. Overall, exposure to both EOs (except 100 µL L-1 EO-L at most times) reduced plasma cortisol levels compared to the control and/or ethanol groups. However, as plasma creatinine levels in fish anesthetized with EO-C were higher than control fish, the use of EO-L is preferable.

Anesthesia of tambaqui Colossoma macropomum (Characiformes: Serrasalmidae) with the essential oils of Aniba rosaeodora and Aniba parviflora and their major compound, linalool

The aim of this study was to determine the anesthetic efficacy of the essential oils (EOs) of Aniba rosaeodora (EOAR) and Aniba parviflora (EOAP) and one of their main compounds, linalool, in two forms: synthetic and extracted from EOAR (linalool-AR) in tambaqui (Colossoma macropomum). In the first experiment, the anesthetic induction and recovery of juveniles exposed to 25200 μL L-1 of EOAR or 50300 μL L-1 of EOAP or synthetic linalool or linalool-AR was evaluated. The second experiment observed the behavioral effects of long-term exposure (12h) of these EOs and linalools (5 and 10 μL L-1). Fish exposed to 50200 μL L-1 of EOAR and 100-300 μL L-1 of EOAP and both linalools reached deep anesthesia between 1-10 min. Induction time for all anesthesia stages decreased with the increasing concentration of the anesthetics. Linalool-AR showed lengthier time for anesthesia induction in some stages and for recovery at 100 and 200 μL L-1 in comparison to synthetic linalool. Normal equilibrium and swimming behavior was observed in fish exposed to the EOs and linalools throughout the 12 h of exposure. In conclusion, both EOs and linalools can be used as anesthetics and sedatives in tambaqui.