This study investigated the efficacy of essential oils of Lippia alba (EOLA) citral chemotype and Lippia origanoides (EOLO) and their effects on ventilatory frequency (VF) of silver catfish, Rhamdia quelen. Fish were exposed to 50-300 µL L −1 of EOLA and 25-300 µL L −1 of EOLO to determine induction times to sedation, anesthesia, and recovery. Moreover, VF was determined in fish exposed to 5 or 10 µL L −1 of EOLA and of EOLO for 8 h. The increasing concentration of essential oils proportionally decreased sedation and anesthesia induction times. The highest EOLA concentration increased VF of fish from the control group at 1 h of exposure, but VF decreased at both EOLO concentrations after 2 h. The EOLA citral chemotype and EOLO were effective sedatives and anesthetics for silver catfish. However, EOLO was the most suitable sedative for additional studies regarding fish transport as it reduced VF and did not induce VF increase in silver catfish. The EOLA citral chemotype and EOLO are effective sedatives and anesthetics for silver catfish. Moreover, the EOLO is recommended for transport of silver catfish, because it maintains the ventilatory frequency constant, avoiding a possible metabolic stress.

This study investigated the anesthetic potential of the essential oil (EO) of Aloysia polystachya in juveniles of dusky grouper (Epinephelus marginatus). Fish were exposed to different concentrations of EO of A. polystachya to evaluate time of induction and recovery from anesthesia. In the second experiment, fish were divided into four groups: control, ethanol and 50 or 300 µL L −1 EO of A. polystachya, and each group was submitted to induction for 3.5 min and recovery for 5 or 10 min. The blood gases and glucose levels showed alterations as a function of the recovery times, but Na + and K + levels did not show any alteration. In conclusion, the EO from leaves of A. polystachya is an effective anesthetic for dusky grouper, because anesthesia was reached within the recommended time at EO concentrations of 300 and 400 µL L −1 . However, most evaluated blood parameters showed compensatory responses due to EO exposure.

No abstract

Bycatch in gillnet fisheries is one of the main threats to several penguin species. Magellanic penguins (Spheniscus magellanicus) are caught by gillnets during their wintering in southern Brazil. However, current information is based only on a small number of sets observed during a single fishing trip. This study assesses bycatch rates of bottom and drift gillnets operating in southern Brazil, and describes the sex and age classes of individuals captured. In 80 bottom gillnet sets, 33 penguins were captured (85% adults), 14 were sexed of which 13 were females. In 41 drift gillnet sets, four penguins were captured, three of which were juveniles. The mean bycatch rates, measured as number of penguins km−2 of net and number of penguins km−2 h−1, were significantly higher for the drift gillnets. Despite the lower bycatch rates, owing to the higher fishing effort in terms of number of boats, net length, net area, soak time and fishing season, the magnitude of penguin bycatch in the bottom gillnet fishery cannot be ignored. Despite based on small sample size, the predominance of adult and female Magellanic penguins as bycatch in gillnet fisheries in southern Brazil agrees with previous studies suggesting that females displace further north than males. In addition, such evidence contributes to the male‐biased sex ratio in breeding grounds, and the long‐term decline of major Patagonian colonies owing to higher female mortality during winter.

An understanding of the effects of fishing on marine ecosystems relies on information about the conserved state of these environments. Non-conventional approaches such as the use of historical data and local ecological knowledge can provide information and help adjust our references of changes in the environment. Also, the combination of different types of data can indicate a fisheries trend that would be undetectable when evaluated separately. Here we investigated changes in fisher’s perceptions regarding overexploited and new target species in artisanal fisheries in a secular fishing village of the subtropical, southeastern Brazilian coast. We identified temporal changes in landings and in the mean trophic level (MTL) of high trophic level species (≥ 3.5 and >4) over 16 years. Fishers’ knowledge revealed shifts in perception associated with years of fishing practice. More experienced fishers recognized a greater number of overexploited and new target species than fishers in the beginning of their careers. Landing data has revealed declining trends of 72% for five mesopredators species. Due to the overfishing of mesopredators, there was a shift in target species, towards fish that were previously discarded. Temporal changes in landings and in the MTL metric are concordant with previous reports on the overexploitation of species caught by local fishers. Our work reveals that multiple sources of information can be combined to establish historical baselines and improve the detection of change in marine ecosystems.