Parasitism by argulids (Crustacea: Branchiura) in piranhas (Osteichthyes: Serrasalmidae) captured in the Caiçara bays, upper Paraguay River, Pantanal, Mato Grosso State, Brazil

In this study, 446 fishes were analyzed: 190 Pygocentrus nattereri, 193 Serrasalmus maculatus, and 63 S. marginatus.They were captured in two bays, upper and lower Caiçara, in the upper Paraguay River basin, during one hydrological cycle from May 2008 to April 2009. Six species of Branchiura were found: Dolops bidentata, D. longicauda, Dolops sp., Argulus multicolor, A. chicomendesi, and Dipteropeltis hirundo. All fish species were infested by more than one species of Branchiura and the overall prevalence was 33.4%. The following prevalences were observed: 52.6% in P. nattereri; 20.3% in S. maculatus, and 15.8% in S. marginatus. The relative condition factor (Kn) differed significantly between parasitized and non parasitized individuals only in P. nattereri and S. maculatus. There was no correlation between Kn and abundance of parasites nor between body length (Ls) and intensity of infestation, in all three host species. © 2012 Sociedade Brasileira de Ictiologia

Individual, spatial and inter-sex variation in somatic growth: A study of Piaractus mesopotamicus (Characiformes: Serrasalmidae), a long-distance freshwater Neotropical migratory fish

Growth is a fundamental biological process, driven by multiple endogenous (intra-individual) and exogenous (environmental) factors that maintain individual fitness and population stability. The current study aims to assess whether individual, spatial (headwaters and floodplains) and inter-sex variation occurs in the growth of Piaractus mesopotamicus in the Cuiabá River basin. Samples were collected monthly from July 2006 to July 2007, at two areas in the Cuiabá River basin (headwaters and floodplain). Three growth models (individuals; individuals and sex factors; individuals and areas factors) were developed and compared the fish growth parameters using Akaike information criterion (AIC). The best fit to the length-at-age data was obtained by a model that considered individual variation and sex. The theoretical maximum average length (L∞) was 64.99 cm for females, and 63.23 cm for males. Females showed a growth rate (k) of 0.230 yr-1and males of 0.196 yr-1. Thus, could be concluded that individual variability and sex were the main sources of variation in P. mesopotamicus somatic growth parameters. © 2017 Sociedade Brasileira de Ictiologia. All rights reserved

Metabotropic glutamate receptor 1 blockade impairs acquisition and retention in a spatial Water maze task

Metabotropic glutamate receptors, including the mGlu1 receptor, have received considerable attention as potential targets for anxiolytic, antidepressant, antipsychotic and antinociceptive drugs. mGlu1 receptors have also been suggested to play a role in the modulation of cognitive processes, but knowledge is still very limited. In the present study the effects of the selective mGlu1 receptor antagonist 3,4-dihydro-2H-pyrano[2,3]beta-quinolin-7-yl)(cis-4-methoxycyclohexyl)methanone (JNJ16259685, 0.63-10 mg/kg s.c.) on more or less spatially demanding learning and spatial memory (retention and re-acquisition) were investigated in mice performing in a water maze. Selective mGlu1 receptor blockade with JNJ16259685 impaired spatial acquisition processes, irrespective of spatial load, as well as spatial re-acquisition, already at the lowest dose tested (0.63 mg/kg). In contrast, effects on spatial retention performance were relatively mild in mice that had learned to locate the position of the escape platform prior to treatment. Thigmotaxic behaviour and locomotor activity appeared to be unaffected by JNJ16259685. These data suggest that blockade of the mGlu1 receptor primarily affects learning of new information, but leaves retention of spatial information relatively unaffected. Blockade of the mGlu5 receptor with MPEP also impaired spatial learning, although only at the highest dose tested (10 mg/kg). An ex vivo receptor occupancy study in rats revealed that MPEP occupied central mGlu5 receptors with an ED(50) of 2.0 mg/kg one hour after subcutaneous administration. This is 50-150 times higher than the ED(50) reported for JNJ16259685 at central mGlu1 receptors and suggests that one reason why the two compounds cause cognitive effects at different doses might be due to differences in central mGlu receptor occupancy, rather than fundamentally different roles of mGlu1 and mGlu5 receptors in the modulation of cognitive function

Environmental and ecological indicators of fish mass-mortality phenomena in mediterranean reservoirs.

Reservoirs are the preferred locations for anglers in Mediterranean regions. However, such ecosystems are impaired by a set of characteristics and phenomena that can constrain the suitable management and exploitation of related goods and services, especially in the current climate change context. In these reservoirs, eutrophication is one of the main water quality problem. These systems are often affected by large nutrient inputs and accentuated water-level fluctuations, especially during summer, that lead to a decrease in habitat availability and quality. Fish density tends to increase which, together with a low oxygen concentration, contributes for massive fish mortalities, compromising a valuable resource for recreational fisheries. Knowledge about the environmental and ecological factors that are directly related with fish biomass increases in these ecosystems, is extremely important to promptly identify this environmental risk and minimize its occurrence. This study, developed for the project “GAMEFISH - Management of Mediterranean reservoirs for the promotion of recreational fishing activities”, aims to identify the main environmental and ecological indicators of fish mass-mortality phenomena in southern Portuguese reservoirs, by evaluating: i) which are the fish species, and respective biomass thresholds, that contribute more to this phenomenon; and ii) which environmental variables are related with population changes and can be used to predict the probability of occurrence of fish mass mortalities. During one-year, monthly fish sampling campaigns were conducted in five reservoirs from the south of Portugal (Póvoa e Meadas, Penedrão, Serpa, Tourega and Divor), using a mix array of electrofishing and multi-mesh gill nets. Several environmental variables were collected for each reservoir-sampling campaign combination, including average depth, Secchi-Disk, water temperature and dissolved oxygen (both continuously registered at 15-min intervals) and water samples for the analysis of quality parameters (e.g. chlorophyll-a, CBO5, phosphorus, nitrates, bacteria). Complementarily to the in situ characterization, each reservoir was also monitored through Sentinel-2 (S2) satellite image products, which provide high-resolution optical imagery for land services. Obtained results reveal significant differences between the monitored reservoirs concerning the temporal variability of their fish assemblage composition, abundance and biomass, as well as their abiotic characteristics, particularly dissolved oxygen, which in some cases (i.e. Tourega and Divor) drastically diminished into values below the limit for fish survival (<3 mg/L) during summer. In some of the studied reservoirs, significant biomass increases and subsequent fish mass-mortality were detected (August-October 2017), which caused accentuated changes in the abundance and biomass of some species, less tolerant to environmental degradation, such as the non-indigenous largemouth bass and bleak, and native Iberian nase. During the study, two of the monitored reservoirs (i.e. Penedrão and Divor) were subjected to a national plan of fish removal, with distinct impacts in the respective communities, which also allowed to evaluate the effectiveness of such management effort. Outcomes from this study will provide owners and managers of these reservoirs with monitoring information capable of promoting a timely prediction and avoidance of massive fish mortality phenomena

LIFE Agueda—Gaining Habitat for Migratory Fish in the Vouga River Basin

Habitat loss and overfishing are the most significant threats to diadromous fish, most of them of high socioeconomic and conservationist importance, such as Alosa alosa, Alosa fallax, Petromyzon marinus and Anguilla anguilla. The main objective of the LIFE Águeda project (LIFE16 ENV/PT/000411) is the removal of hydro-morphological pressures towards the reestablishment of conditions for a good ecological status, as required by the Water Framework Directive (WFD) and associated River Basin Management Plans. Actions to achieve the project’s objectives include the restoration of river morphology through the construction of nature-like fish passes, removal of river obstacles and re-naturalization of the riverbed. Aside from these interventions, the project also contemplates riparian habitat restoration, design and operation of a pilot translocation program directed to European eel juveniles, management of recreational and commercial fisheries, and stakeholders’ engagement, safeguarding compatibility of ecosystem uses. To reestablish longitudinal connectivity in rivers Agueda and Alfusqueiro, a total of five fish passes (two modular and temporary vertical-slot and three nature-like fish passes) will be installed in obstacles where current uses need to be secured and removal is not an option. Obsolete or illegally built obstacles are to be completely or partially removed, in a total of eight interventions in both rivers. By placing PIT antennas in the most upstream fishways planned to be built in both rivers, and by monitoring the movements of tagged fish from target species, the efficiency of these habitat restoration actions, and the reestablishment of longitudinal connectivity, will be assessed