Effects of size and sex on swimming performance and metabolism of invasive mosquitofish Gambusia holbrooki

In freshwater ecosystems, abiotic factors such as flow regime and water quality are considered important predictors of ecosystem invasibility. The aim of this study was to investigate the critical swimming capacity and metabolism of the eastern mosquitofish, Gambusia holbrooki, focusing on sex and size effects, to evaluate the influence of water flow on its invasive success. Specimens of mosquitofish were captured from the Ter Vell lagoon (L'Estartit, north‐eastern Spain) in July 2014, and we measured the critical swimming speed (U_crit) and oxygen consumption of individual fish (30 females and 30 males) using a mini swim tunnel. The mean U_crit of this poeciliid fish was estimated at 14.11 cm·s^?1 (range = 4.85–22.26), which is lower than that of many other fishes of similar size and confirms that this species is limnophilic and its invasive success might be partially explained by hydrologic alterations. However, the U_crit and maximal metabolic rate vary markedly with fish size and sex, with males having much higher values for the same body mass, and thus probably being more resistant to strong water flows. Multiple regression models illustrate that multivariate analyses might increase the predictive power and understanding of swimming performance and metabolic traits, compared to results from conventional simple regressions.     

A new strategy proposal to monitor ray fins landings in south‐east Brazil

1. Statistical fisheries data are usually obtained during landings, through rapid fish classification and their categorization under the trade names given to species or groups of species. However, species classification is often difficult, particularly concerning elasmobranchs whose fins and heads have been removed, leading to labelling errors.
2. The aim of this paper is to identify the ray species composition landed in south‐east Brazil, providing identification strategies to support a plan for more efficient labelling and management.
3. Samples were obtained from artisanal fleet landings, between November 2012 and May 2014. For taxonomic identification of whole or processed animals (n = 279, belonging to 10 species), morphological, metric, and molecular techniques were employed. The common name used by fishermen was more related to the location where they lived than the fishing gear used.
4. Morphometric analyses resulted in pectoral fin to length and weight conversion equations of whole individuals for each species, and 10 variables were found to be diagnostic of each genus.
5. A genetic identification, based on sequencing of the mitochondrial genes cytochrome b and cytochrome oxidase I, was applied to verify morphological identification. A dichotomous key that allowed ray identification at the species level from pectoral fin morphology was developed. The approach was field tested and deemed adequate, leading to a robust monitoring strategy for estimating the biomass of specific landed rays.

     

Historical perspective of artisanal encircling gillnet use at the Brazilian coast: Changes in fishing behaviour is mirrored by dwindling stocks

Managing coastal resources sometimes requires looking into the past, as this provides a baseline against which present conditions may be gauged. The present study evaluated the circumstances that led Brazilian coastal fishers to modify their use of encircling gillnets. Other stressors (i.e. water pollution and habitat degradation) acted synergistically on the fisheries dynamic between 1950 and 2016. Declining catches of several species were observed through fishers' historical perception and through fisheries landing records. Three notable trends in net handling were associated with distinct historical periods. Specifically, pressures from modern fishery practices and gear (e.g. monofilament nets), the adoption of spiral setting arrangements and the increasing use of trammel nets appear responsible for the decline of many stocks. Mullet, seabass, jack and pilchard stocks decreased over time and were associated the changes witnessed in the encircling net operations. These changes occurred in response to overexploitation of fish stocks, to exploit the dwindling fisheries resources. The study also discusses the reasons leading fishers to accept how encircling gillnets ought to be used, their interpretation of such changes and the implications these changes have for fisheries management.     

Use of Artemia supplemented with exogenous digestive enzymes as sole live food increased survival and growth during the larviculture of the longsnout seahorse Hippocampus reidi

This study evaluated the effect of exogenous digestive enzymes on the survival, growth performance and morphology of the digestive tract of juveniles of the longsnout seahorse Hippocampus reidi fed exclusively with Artemia and supplemented with five different concentrations of porcine pancreatin (PP) (0, 5, 25, 50 and 75 mg/L from birth until 30 days after release). The results found in the present study clearly show that there was a significant increase in survival and growth as well as substantial changes in the morphology of intestinal villi in seahorses fed exclusively with Artemia supplemented with 75 mg/L PP. Therefore, the use of digestive enzyme supplementation constitutes an important advance for the establishment of a more efficient and practical feeding protocol (exclusive use of Artemia) for juveniles of the longsnout seahorse.     

Yeast extract on growth,nutrient utilization and haemato‐immunological responses of Nile tilapia

Dietary supplementation (0, 10, 20, 40, 60, 80 g kg^?1) of a nucleotide source (NuPro^®) was evaluated on growth, nutrient utilization, haemato‐immunological responses and resistance to experimental infection of Nile tilapia. Fish (2.63 ± 0.63 g) were fed experimental diets to satiation three times a day for 75 days. Feed intake increased linearly with increasing levels of NuPro^® promoting higher weight gain (P < 0.05). Survival, feed conversion and protein retention were not affected. Following the growth trial, fish were challenged with Aeromonas hydrophila by intraperitoneal injection. Survival and innate immune responses (phagocytosis and lysozyme activity) were not significantly affected. However, among the haematological variables, thrombocyte, leucocyte and monocyte counts increased linearly (P < 0.05). The indirect measurement of digestibility in juvenile Nile tilapia (122.32 ± 11 g) indicated a linear decrease in protein (1.41%), dry matter (5.72%) and energy (4.10%) digestibility coefficients as dietary supplementation increased (P < 0.05). NuPro^® showed to be a beneficial additive to be supplemented in diets for juvenile Nile tilapia, providing 32.8% increase in feed intake and 28.8% in weight gain, as well as in thrombocyte, leucocyte and monocyte counts in blood, possibly indicating a more efficient defence response in the highest dietary supplementation levels tested.     

Microbiological quality of Litopenaeus vannamei culture using conventional and biofloc systems

Shrimp farming is a fast‐expanding activity that has supported the growth in the supply of these crustaceans to consumers around the world. However, the end product is vulnerable to contamination at all stages of the process, including the rearing tanks, where current practices prioritize to raise stocking densities and the minimization of water renewal. It is thus important to evaluate the potential of these systems for the proliferation of undesirable microorganisms, which may render the product unfit for human consumption. In the present study, the presence of coagulase‐positive Staphylococcus, Salmonella spp., Vibrio spp., and total and thermotolerant coliforms was verified in biofloc tank and conventional pond systems used for the rearing of Litopenaeus vannamei in Pernambuco, Brazil, and the results were compared with the legislation regulating the marketing of fresh shrimp. Samples were collected from two biofloc tanks with a density of 375 shrimp m^?2, and two conventional ponds with 12 shrimp m^?2. None of the samples tested positive for either Salmonella spp. or coagulase‐positive Staphylococcus, which is consistent with the legislation. While no standards are defined legally for Vibrio spp. or coliforms, very low concentrations were recorded in both systems, in comparison with other studies. While some variation in bacterial contamination was observed over the rearing process, the end product of both systems was fit for human consumption. The results of the study indicate that, while the water is not renewed in the biofloc system, the development of undesirable microorganisms can be controlled, with no adverse effects for the end product.     

Dietary Supplementation with Butyrate and Polyhydroxybutyrate on the Performance of Pacific White Shrimp in Biofloc Systems

This study aimed to evaluate the effects of dietary supplementation with sodium butyrate or polyhydroxybutyrate (PHB) on growth performance, as well as changes in intestinal microbiota and hemato‐immunological parameters, of Litopenaeus vannamei reared under a superintensive biofloc system. Twelve 800‐L tanks were each stocked with 250 shrimp/m³ (3.96 ± 0.04 g mean initial weight) and reared over a 6‐wk period. The basal diet and two test diets supplemented with 2% of each feed additive. At the conclusion of the growth trial shrimp fed with the butyrate‐supplemented diet, as compared with the control shrimp, showed higher survival and productivity and lower total bacterial and Thiosulfate‐citrate‐bile salts‐sucrose Agar (TCBS) counts in the intestine. However, no differences were observed in other performance parameters analyzed. Shrimp fed with both supplementation regimens also showed an increase in total and granular hemocytes, as well as an increase in serum agglutination titer. Shrimp offered diets supplemented with sodium butyrate had higher counts of hyaline cells. Thus, for L. vannamei reared in a superintensive biofloc system, it can be concluded that dietary supplementation of sodium butyrate, more so than PHB, acted as an immune system modulator by reducing the concentration of pathogenic bacteria in shrimp gut, thereby increasing survival and productivity.     

Fullerene and omega-3 and omega-6 fatty acids on fish brain antioxidant status

The carbon nanomaterial fullerene (C(60)) can act as anti or pro-oxidant. The aim of this study was to evaluate, in cell suspensions of carp brains (Cyprinus carpio, Cyprinidae), the effect of C(60) after a pre-treatment with polyunsaturated fatty acid (PUFAs) such as omega-3 (docosahexaenoic acid, DHA) and omega-6 (linoleic acid, LA). Assays consisted of a pre-treatment with PUFA (48?h) and then exposure to C(60) (2?h). Cell viability and total anti-oxidant capacity did not differ (p?>?0.05). A reduction (p?相似文献   

Evaluation of the oestrogenic potential of oestrone and bisphenol-A on the reproduction of Astyanax bimaculatus males after subacute exposure

Fish Physiology and Biochemistry - In the last decades, oestrogenic compounds have often been reported in environmentally relevant concentrations in aquatic environments around the world. Most...