Biological patterns of reproduction of the Brazilian sardine Sardinella brasiliensis in the purse seine fishery of Southwest Atlantic Ocean: A long-term assessment.

Recent estimates of the size at first maturity (L50) of Sardinella brasiliensis showed contradictory results with a decreasing in the fish stock biomass encompassed by increasing values of L50. The methodological approach used hereby allowed to separate sardines classified in the virginal maturity stage from those categorized in the recovery stage, and ready for one next spawning event. This study evaluated the hypothesis of the existence of separated stocks experiencing distinct environmental conditions and fishing pressures which may have altered L50 estimates using a robust dataset based on biological samples collected along the entire species distribution area in the southeast-south Brazilian coast [Rio de Janeiro (RJ), São Paulo (SP), Paraná (PR), Santa Catarina (SC) and Rio Grande do Sul (RS)] between 2000 and 2018. A reclassification of the gonadal maturity stages provided a more realistic estimate of L50. Combining biological, reproductive, fishing data and the mean temperature of the catch (MTC), the leave-one-out classification correctly re-assigned individuals with an overall accuracy of 85% [100% (RJ), 45% (SP), 99% (PR), 99% (SC) and 82% (RS)]. The connectivity between the local populations of S. brasiliensis off RJ (23°S) and the southern populations is limited, contrasting to spatial structured semi-discrete population-units found between SP and RS (24°S-30°S). The northern extreme population-unit (RJ, 22°S-23°S) showed an expressive reduction of L50, and a negative correlation was detected between the increasing MTC values and the abundance of early maturing individuals and recruits of the species. Stock specific L50 estimates seemed to act as indicators of long term environmental fluctuations.

Chelidonichthys lucerna (Linnaeus, 1758) Population Structure in the Northeast Atlantic Inferred from Landmark-Based Body Morphometry.

The study of geometric morphometrics among stocks has proven to be a valuable tool in delineating fish spatial distributions and discriminating distinct population units. Variations in fish body morphology can be linked to genetic factors or to phenotypic adaptability in response to environmental variables. The tub gurnard (Chelidonichthys lucerna) is a demersal species that usually lives in the bottom of the continental shelf, being widely distributed along the northeast Atlantic, Mediterranean and Black seas. Worldwide interest in the species has increased since 2006, when ICES recognized its potential for commercial exploitation. However, despite its broad geographic occurrence, to date, research on C. lucerna population structure at large spatial scales is still lacking. In this paper, body geometric morphometrics, using a landmark-based truss network, was applied in order to discriminate C. lucerna populations caught in three different fishery grounds areas along the northeast Atlantic: Conwy Bay (United Kingdom), Biscay Bay (Spain) and Matosinhos (Portugal). The results obtained in this study revealed a high overall relocation success (95%) of samples to their original locations, thus demonstrating the existence of significant regional differences and indicating that we are dealing with different fish population units. Moreover, the data revealed a partial overlap between individuals from Spain and United Kingdom, suggesting that in geographically distant areas these populations may inhabit similar environments. However, to corroborate these findings, future works using a holistic approach with alternative and complimentary stock assessment tools (e.g., genetic and phenotypic natural tags) are highly recommended.

Genetic diversity and population structure of the blue jack mackerel Trachurus picturatus across its western distribution.

Blue jack mackerel Trachurus picturatus collected at six sampling locations of the north-east Atlantic Ocean (Azores, Madeira, Canaries, and Matosinhos, Peniche and Portimão, mainland Portugal) and one location in the Mediterranean (Sicily), were used to examine the genetic structure of this species. Three mitochondrial gene regions (cytochrome c oxidase subunit I, cytochrome b and control region) were used to study the genetic structure of the species in Macaronesia, as well as to compare the genetic diversity of this region with published results from its eastern distribution. All markers indicated the absence of genetic structure among populations, with high indices of genetic diversity. These results suggest that the species went through a bottleneck event, followed by a recent population expansion. Moreover, the comparison with previously published results from the T. picturatus Mediterranean distribution suggests the existence of a single panmictic population throughout the species' full range. This was, however, an unexpected result since other methodologies have shown the presence of, at least, three different population-units in the NE Atlantic Ocean.

Toxicity of erythromycin to Oncorhynchus mykiss at different biochemical levels: detoxification metabolism, energetic balance, and neurological impairment.

During the last decades, the presence of antibiotics in different aquatic compartments has raised increasing interest and concern, since these compounds are usually persistent and bioactive pseudo pollutants. Erythromycin (ERY) is a macrolide antibiotic, prescribed for human and veterinary medicines but also used in aquaculture and livestock production. Taking into account the recorded environmental levels of ERY, its toxicity to non-target organisms has become a still poorly studied issue, particularly in fish. In this sense, this study investigated the acute and chronic effects of realistic levels of ERY on Oncorhynchus mykiss (rainbow trout), namely, through the quantification of the activity of enzymes involved in different biochemical pathways, such as detoxification (phase I-7-ethoxyresorufin O-deethylase (EROD); phase II-glutathione S-transferases (GSTs), uridine-diphosphate-glucuronosyltransferases (UGTs)), neurotransmission (acetylcholinesterase (AChE)), and energy production (lactate dehydrogenase (LDH)). Both types of exposure caused significant increases in EROD activity in liver of O. mykiss; an increase in GST activity in gills after chronic exposure was also observed. UGT branchial activity was significantly depressed, following the long-term exposure. Thus, EROD, GST, and UGT enzymatic forms seem to be involved in the biotransformation of ERY. In terms of neurotransmission and preferential pathway of energy homeostasis, the exposed organisms appear not to have been affected, as there were no significant alterations in terms of AChE and LDH activities, respectively. The here-obtained data suggest that the observed alterations in terms of detoxification enzymes may have prevented the establishment of a set of toxic responses, namely, neurotoxic and metabolic disorders.

Assessment of toxic effects of the antibiotic erythromycin on the marine fish gilthead seabream (Sparus aurata L.) by a multi-biomarker approach.

Erythromycin (ERY) is one of the most common antibiotics used in human and veterinary practices, leading to ubiquitous environmental distribution and possible toxicity to non-target organisms. The purpose of this study was to determine sub-lethal effects of ERY towards the marine fish Sparus aurata (gilthead seabream). S. aurata were acutely (0.3-323 µg/L, 96 h) and chronically (0.7-8.8 µg/L, 28 d) exposed to ERY. Detoxification [7-ethoxyresorufin O-deethylase (EROD), glutathione S-transferases (GSTs), uridine-diphosphate-glucuronosyltransferase (UGT)], oxidative stress [catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GRed)], lipid peroxidation [thiobarbituric acid reactive substances - (TBARS)], genotoxicity [genetic damage index (GDI) and erythrocytic nuclear abnormalities (ENAs)], neurotransmission [acetylcholinesterase (AChE)] and energy metabolism [lactate dehydrogenase (LDH)] biomarkers were evaluated. Results showed that ERY did not promote significant effects in detoxification biomarkers, but induced slight pro-oxidative effects (decrease of GPx activity in the liver after acute exposure and an increase in gills after chronic exposure; and an increase of hepatic GRed activity following chronic exposure). There was a significant decrease in TBARS after chronic exposure, which contradicts a full scenario of oxidative stress. In terms of genotoxicity, both ERY exposures caused only a significant increase of GDI. Neurotransmission and energy metabolism were not also affected by ERY. Although few toxic effects of ERY have been previously documented (involving different metabolic pathways, as tested in this work), these were mainly observed for freshwater species. These findings suggest low vulnerability of S. aurata to ERY at levels close to the ones found in the wild.

Rainbow trout (Oncorhynchus mykiss) pro-oxidant and genotoxic responses following acute and chronic exposure to the antibiotic oxytetracycline.

Oxytetracycline (OTC), an antibacterial agent, is extensively used in aquaculture practices all over the world, but also in human and veterinary medicines. Because of its intensive use, low rates of absorption by treated animals, inadequate disposal, and low efficiency of removal in wastewater treatment plants, the potential harmful effects on aquatic organisms are of great concern. This work aimed to assess the effects of this antibiotic in rainbow trout, following both acute and chronic exposures. Catalase (CAT), total glutathione peroxidase (GPx), glutathione reductase (GRed) activities and lipid peroxidation (TBARS levels) were quantified as oxidative stress biomarkers, in gills and liver. Genotoxic endpoints, reflecting different types of genetic damage in blood cells, were also determined, by analysis of genetic damage (determination of the genetic damage index, GDI, measured by comet assay) and erythrocytic nuclear abnormalities (ENAs). The obtained results showed a mild pattern of antioxidant response, with modifications in CAT and GPx activities in gills, and lipid peroxidation in liver. These results suggest that despite the occurrence of oxidative effects, a full scenario of oxidative stress is not likely. However, exposure to OTC resulted in the establishment of genotoxic alterations with the induction of DNA strand breaks in blood cells (increase of GDI), and of chromosome breakage and/or segregational abnormalities (increase of ENAs). Considering that the oxidative response was not totally devisable, other mechanisms may be involved in the genotoxic effects reported.

Alterations in gills of Lepomis gibbosus, after acute exposure to several xenobiotics (pesticide, detergent and pharmaceuticals): morphometric and biochemical evaluation.

In recent decades, scientific research about the effects of anthropogenic xenobiotics on non-target organisms has increased. Among the likely effects, some studies reported the evaluation of biochemical and morphological changes in specific tissues or organs of fishes, such as gills, which are key organs for the direct action of pollutants in the aquatic environment. This work intended to assess biochemical [oxidative stress/phase II conjugation isoenzymes glutathione S-transferase (GSTs)] and morphological [secondary lamellar length (SLL), secondary lamellar width (SLW), interlamellar distance (ID), basal epithelial thickness (BET) and proportion of the secondary lamellae available for gas exchange (PAGE)] changes in gills, after acute exposure to the pesticide chlorfenvinphos, the detergent sodium dodecylsulphate (SDS) and to the anticholinesterasic pharmaceuticals (neostigmine and pyridostigmine). Our results point to a significant, eventually hormetic, effect in the activity of GSTs following exposure to chlorfenvinphos that significantly increased the activity of GSTs at concentration of 0.2 mg/L. The activity of GSTs increased significantly after exposure to 100 mg/L of neostigmine. Considering the morphometric analysis of the gills, the data obtained showed that chlorfenvinphos exerted mainly minor architectural alterations in gills, with the exception of the highest tested concentration of chlorfenvinphos that produced also a slight decrease of the PAGE. The overall conclusions point to a null or negligible toxicity of the selected toxicants towards L. gibbosus, which may be reverted if exposure is withdrawn.