This study analyzed the structure of the gill rakers of Parapimelodus valenciennis and Parapimelodus nigribarbis (planktivorous), Serrasalmus maculatus and Hoplias malabaricus (piscivorous), Iheringichthys labrosus (benthophagous) and

This study evaluated the periods of time of anesthetic induction and recovery of Serrasalmus rhombeus exposed to essential oils (EOs) of Aloysia triphylla and Lippia alba and eugenol, as well as if these anesthetics can be used for transport of this species, through analysis of swimming behavior. Fish were placed in aquaria containing different concentrations of A. triphylla EO or L. alba EO or eugenol, and posteriorly were transferred to aquaria containing only water to evaluate the recovery time. In the second experiment, behavior was analyzed during exposure to A. triphylla EO, L. alba EO or eugenol at 5 or 10 µL L-1. The evaluations were carried out at 0, 1, 5, 10 and 15 min of exposure. Fish exposed to 150, 200 and 50 µL L-1 of A. triphylla EO, L. alba EO and eugenol, respectively, showed anesthetic induction time lower than 3 min and recovery time lower than 10 min. Concentrations of 50 µL L-1 of both EOs and 25 µL L-1 eugenol caused only sedation. Exposure to 5 and 10 µL L-1 EOs and eugenol decreased fish swimming time. Both EOs and eugenol were effective for anesthesia and can be used for transport of S. rhombeus.

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This study examined ammonia, urea, creatinine, protein, nitrite, nitrate, and phosphorus (P) excretion at different water hardness, humic acid, or pH levels in silver catfish (Rhamdia quelen) juveniles. The fish were exposed to different levels of water hardness (4, 24, 50, or 100 mg L(-1) CaCO3), humic acid (0, 2.5, or 5.0 mg L(-1)), or pH (5.0, 6.0, 7.0, 8.0, or 9.0) for 10 days. The overall measured nitrogen excretions were 88.1% (244-423 μmol kg(-1 )h(-1)) for ammonia, 10.9% (30-52 μmol kg(-1 )h(-1)) for creatinine, 0.02% (0.05-0.08 μmol kg(-1 )h(-1)) for protein, 0.001 % (0.002-0.004 μmol kg(-1 )h(-1)) for urea, 0.5% (0.64-3.6 μmol kg(-1 )h(-1)) for nitrite, and 0.5% (0.0-6.9 μmol kg(-1 )h(-1)) for nitrate, and these proportions were not affected by water hardness or humic acid levels. The overall P excretion in R. quelen was 0.14-2.97 μmol kg(-1) h(-1). Ammonia excretion in R. quelen usually was significantly higher in the first 12 h after feeding, and no clear effect of water hardness, humic acid levels, and pH on this daily pattern of ammonia excretion could be observed. Water hardness only affected the ammonia and P excretion of R. quelen juveniles in the initial and fifth days after transfer, respectively. The exposure of this species to humic acid increased ammonia excretion after 10 days of exposure but did not affect P excretion. An increase in pH decreased ammonia and increased creatinine excretion but did not change P excretion in R. quelen. Therefore, when there is any change on humic acid levels or pH in the culture of this species, nitrogenous compounds must be monitored because their excretion rates are variable. On the other hand, P excretion rates determined in the present study are applicable to a wide range of fish culture conditions.

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