The Effects of Stressful Broodstock Handling on Hormonal Profiles and Reproductive Performance of Rhamdia quelen (Quoy & Gaimard) Females

Abstract.— A stressful environment induces cortisol that might affect fish breeding and reproduction. In the present work, which aimed to mimic aquacultural conditions of the jundia (Rhamdia quelen) hatcheries in southern South America, females were submitted to normal or stressful handling and the effects of cortisol on serum levels of 17β‐estradiol (E2) and testosterone (T) were determined. In addition, the effect of stress on reproductive parameters such as eggs and swim‐up fry production was also measured. Eight females from a group submitted to stressful handling (SH) conditions and eight females from a group with normal handling (NH) conditions were captured for blood sampling at D 0 and at D 1, 10, 20, 30, and 40 of the experiment. A typical cortisol response was observed in the SH females group in that they presented higher cortisol level in contrast to the NH female group, in all days sampled, except at D 0. In the 10th and 20th d, the E2 levels were lower in SH females, but cortisol levels were higher, suggesting an effect of cortisol on E2 production and/or release. Stressful handling appeared to affect both the number and the quality of the gametes because a lower number of oocytes was stripped from SH females, and from SH fertilized eggs, a lower number of viable swim‐up fry was obtained to be transferred to earthen larviculture ponds. Taken together, the results indicated that stressful handling of broodstock impairs R. quelen reproduction.     

Economic evaluation of the commercial production between Brazilian samphire and whiteleg shrimp in an aquaponics system

The implementation of aquaponics systems has significantly increased in the last two decades, and several studies have reported on the technical, socioeconomic, and environmental ramifications in order to achieve sustainability in food production. The present study, however, aimed to perform a commercial-scale economic evaluation, using a model marine aquaponics production system with the halophyte Sarcocornia ambigua and the shrimp Litopenaeus vannamei cultivated in nutrient film technology (NFT) and biofloc technology (BFT) systems, respectively. To calculate phytotechnical and zootechnical indexes, we used recent studies available in the literature. Indicators of operational costs (total cost of production—TCP) and financial viability were calculated based on a cash flow horizon of 10 years. The proposed study estimated an initial investment of US$ 474,253.07, with annual TCPs around US$ 192,220.50, US$ 247,740.52, and US$ 223,482.65 years 1, 2 to 9, and 10, the different periods studied. Within these respective periods, the annual production of halophyte was 17,017, 23,286, and 18,808 kg, while marine shrimp production was 10,659, 14,586, and 11,781 kg. Based on these annual production numbers, the TCPs were US$ 4.75, US$ 4.03, and US$ 4.67 kg^?1 for halophyte and US$ 10.45, US$ 14.43, and US$ 11.52 kg^?1 for shrimp. Three sales prices were estimated per kilogram of halophyte produced and one fixed price per kilogram of shrimp produced. Only the highest selling price showed favorable indexes after testing sensitivities. Based on the above parameters, halophyte TCP was below sales value, i.e., reference price, with the possibility of increasing the price to “premium” level, indicating that this marine aquaponics production system was feasible for implementation in Brazil.     

The tetrasporophyte of Asparagopsis armata as a novel seaweed biofilter

The red seaweed Asparagopsis armata (Harvey; Rhodophytae, Bonnemaisoniaceae) produces biologically active secondary metabolites that are valuable natural ingredients for cosmetics and medicine and its cultivation may therefore be a profitable venture. The tetrasporophyte of this species (“Falkenbergia rufolanosa”) was successfully tank-cultivated as a continuous biofilter for the effluent of a commercial fish farm in southern Portugal. Optimal stocking density for highest biomass yield and a low level of other algal species in winter and late spring was 5×g centrifuged fresh weight l^− 1. The effect of total ammonia nitrogen supply (TAN flux) on biofiltration and biomass yield was investigated in winter and spring. Results revealed that A. armata is currently the seaweed-biofilter with the highest TAN removal of up to 90 μmol l^− 1 h^− 1 at a TAN flux of about 500 μmol l^− 1 h^− 1. In the tanks used, this is equivalent to a removal of up to 14.5 g TAN m^− 2 day^− 1. At a lower TAN flux of about 40 μmol l^− 1 h^− 1, TAN removal by A. armata is more than double to what is reported at this flux for another successful seaweed biofilter, the genus Ulva. Monthly variation of A. armata biomass yield peaked in May and was lowest in January. At TAN fluxes between 300 and 400 μmol l^− 1 h^− 1, an average water temperature of 21.7 °C and a total daily photon flux density of 47 Mol m^− 2, seaweed yield was over 100 g DW m^− 2 day^− 1 with a recorded maximum of 119 g. During spring, autumn and early summer, the biomass of A. armata within the experimental tanks doubled every week. A model for the up scaling of this finfish integrated aquaculture of A. armata varies the investment in biofilter surface area and estimates the return in biofiltration and biomass yield. Highest TAN removal efficiencies will only be possible at low TAN fluxes and a very large biofilter area, resulting in a low production of biomass per unit area. To remove 50% of TAN from the effluent (1 mt Sparus aurata; 21 °C), 28 m² of biofilter, designed to support a water turnover rate of 0.8 Vol h^− 1 would be necessary. This system produces 6.1 kg FW (1.5 kg DW) of A. armata per day and has the potential to turn biofiltration into an economically sustained, beneficial side effect.     

Introduction of jundia Rhamdia quelen (Quoy & Gaimard) and Nile tilapia Oreochromis niloticus (Linnaeus) increases the productivity of carp polyculture in southern Brazil

Fish polyculture is based on the assumption that each species has its own feeding niche and may increase the maximum standing crop of a pond by exploring a wider range of available food and ecological niches. In order to identify the better species ratio and to introduce jundia (JN) (Rhamdia quelen Quoy & Gaimard) and Nile tilapia (NT) (Oreochromis niloticus Linnaeus) in to the carp polyculture practiced in South Brazil, a 162‐day experiment was conducted, in 12 250‐m² earthen ponds (1.2 m deep). Treatment I (T‐I) contained 35% common carp, Cyprinus carpio (L.) (CC); 35% grass carp, Ctenopharyngodon idella Valenciennes (GC); 15% silver carp, Hypophthalmichthys molitrix Valenciennes (SC); and 15% bighead carp, Aristichthys nobilis Richardson (BC). Treatment II (T‐II) consisted of three ponds stocked at the following ratio: 17.5% CC, 35% GC, 15% SC, 15% BC and 17.5% JN. Treatment III (T‐III) consisted of three ponds with 35% CC, 35% GC, 7.5% SC, 7.5% BC and 15% NT. Treatment IV (T‐IV) consisted of three ponds with 17.5% CC, 35% GC, 7.5% SC, 7.5% BC%, 17.5% JN and 15% NT. No significant correlation was found between the treatments with different species ratio and water quality parameters. The final weight of different species, in different treatments, was statistically different. The major result was the clear positive effect on growth parameters observed by the introduction of JN and/or NT in to the carp polyculture. The yield per hectare was 2083.33±183 kg ha^?1 for polyculture with carp species; 2476.67±139.88 kg ha^?1 following the introduction of JN only; 2801.67±111.42 kg ha^?1 for isolated introduction of NT; and 2506.67±422.31 kg ha^?1 for simultaneous introduction of JN and NT. The introduction of JN and/or NT had a positive effect on growth parameters when compared with carp‐only polyculture. The reduction in CC ratio also had a positive effect on growth parameters.     

Cytogenetic studies of Atlantic mojarras (Perciformes – Gerreidae): chromosomal mapping of 5S and 18S ribosomal genes using double FISH

Fish of the family Gerreidae, mainly species of the genera Diapterus and Eugerres, have high potential for cultivation, because of their saline tolerance. A detailed cytogenetic analysis of Diapterus auratus, Diapterus rhombeus and Eugerres brasilianus was conducted using conventional staining, C‐banding, Ag‐NOR, AT/GC‐specific fluorochrome staining and mapping of ribosomal sequences with 5S and 18S rDNA probes. All the species exhibited symmetrical karyotype, 2n = 48 acrocentric chromosomes. Ag‐NORs and 18S rDNA are present in the interstitial position on pair 1 (genus Diapterus) and pair 6 in Eugerres brasilianus. The 5S rDNA sites, located in the interstitial position (pair 11), are conserved in the three species. Heterochromatic regions are similar in the Diapterus species, showing a pattern of reduced and centromeric bands, differing from E. brasilianus, where, in addition to these, more prominent interstitial bands were observed. GC‐rich regions are located at ribosomal sites. Karyotypic comparison between Diapterus and Eugerres reveals similarity in chromosomal macrostructure, differing in C‐positive heterochromatin distribution and position of 18S sites, indicating the occurrence of structural microrearrangements. Although complementary analyses are needed, the similarities observed for these and other species suggest the possibility of breaking postzygotic barriers and their potential use, through induced interspecific or intergeneric hybridizations.     

Two epizootic Perkinsus spp. events in commercial oyster farms at Santa Catarina,Brazil

Perkinsus spp. have been detected in various bivalve species from north‐east Brazil. Santa Catarina is a South Brasil state with the highest national oyster production. Considering the pathogenicity of some Perkinsus spp., a study was carried out to survey perkinsosis in two oyster species cultured in this State, the mangrove oyster Crassostrea gasar and the Pacific oyster Crassostrea gigas. Sampling involved eight sites along the state coast, and oyster sampling was collected during the period between January 2013 and December 2014. For the detection of Perkinsus, Ray's fluid thioglycollate medium (RFTM) and histology were used, and for the identification of the species, PCR and DNA sequencing were used. Perkinsus spp. was found by RFTM in C. gigas and C. gasar from São Francisco do Sul. This pathology was also detected in C. gasar from Balneário Barra do Sul both, by RFTM and histology. Perkinsus marinus was identified in C. gigas and C. gasar from São Francisco do Sul and Perkinsus beihaiensis in C. gasar from Balneário Barra do Sul. This is the first report of P. marinus in C. gigas from South America. Results of this preliminary study suggest that both oyster species tolerate the species of Perkinsus identified, without suffering heavy lesions.     

A general model of temporary aquatic habitat use: Water phenology as a life history filter

Temporary aquatic habitats are not widely appreciated fish habitat. However, fish navigate the transient waters of intertidal zones, floodplains, intermittent and ephemeral streams, lake margins, seasonally frozen lakes and streams, and anthropogenic aquatic habitats across the globe to access important resources. The selective pressures imposed by water impermanence (i.e., freezing, drying, tidal fluctuations), however, operate similarly across taxa and ecosystems. These similarities are formalized into a conceptual model relating habitat use to surface water phenology. Whereas all necessary life history functions (spawning, foraging, refuge, and dispersal) can be accomplished in temporary habitats, the timing, duration, and predictability of water act as a “life history filter” to which habitats can be used and for what purpose. Habitats wet from minutes to months may all be important—albeit in different ways, for different species. If life history needs co‐occur with accessibility, temporary habitats can contribute substantially to individual fitness, overall production and important metapopulation processes. This heuristic is intended to promote research, recognition and conservation of these frequently overlooked habitats that can be disproportionately important relative to their size or brevity of existence. There is a pressing need to quantify how use of temporary aquatic habitats translates to individual fitness benefits, population size and temporal stability, and ecosystem‐level consequences. Temporary aquatic habitats are being impacted at an alarming rate by anthropogenic activities altering their existence, phenology, and connectivity. It is timely that scientists, managers and policymakers consider the role these habitats play in global fish production.     

Soil microbiome biomass,activity, composition and CO2 emissions in a long-term organic and conventional farming systems

The implementation of environmentally friendly agricultural policies has increased the need to compare agricultural aspects of conventional (CON) and organic farming (ORG) systems. The objective of the present work was to compare the effects of an organic and conventional long-term experiment on bacterial and fungal biomass and activity, as well as soil CO₂ emission and readily available nitrogen forms in a soil cultivated with Helianthus annuus L. The microbial biomass was more active and abundant in ORG as well as soil CO₂ emission. Despite being less abundant, fungi were more active than bacteria in both ORG and CON experiments. 16S rRNA gene sequencing showed that the ORG treatment had a significantly greater bacterial richness than CON. Cyanobacteria, Actinobacteria and Proteobacteria were the most abundant phyla contributing more than others to the differences between the two systems. Moreover, the soil ${\mathit{NH}}_4^{+}$ and ${\mathit{NO}}_2^{-}$ content was not significantly different between ORG and CON, while ${\mathit{NO}}_3^{-}$ was less in ORG. ORG sunflower yield was significantly less compared with CON. While much remains to be discovered about the effects of these agricultural practices on soil chemical properties and microbial diversity, our findings may contribute to this type of investigation.