Search Results (123)

Global warming raises surface water temperatures, impacting fish alongside pollutants, such as ubiquitous xenoestrogens. Combined stressor effects are poorly studied but likely to worsen impacts and hinder biota adaptation, warranting further research. Unadapted fish face heightened risks. The liver is a vital metabolic organ, sensitive to temperature and xenoestrogens, eventually adjusting hepatocyte size and number to ensure survival, growth, and reproduction. This study assessed, for the first time, the impact of exposure (45 days) to thermal stress (29 °C versus 26 °C) and ethinylestradiol (EE2, 5 ng/L) on male guppies, primarily on body and quantitative liver morphology. Higher temperature reduced body mass (14%) and standard length (3.6%) gain. EE2 exposure reduced body mass increase (14%), hepatosomatic index (20%), and the volumes of the liver (32%), hepatocytes (16%), and their nuclei (17%). The nucleus-to-cytoplasm ratio and total hepatocyte number remained stable. No histopathological lesions existed. Guppies appear to have adapted to stressors by reducing hepatocyte size and utilizing lipid reserves, yet they exhibited deficits in body growth and hepatosomatic index. Gonadal maturation was unaffected. Only under EE2 at 29 °C did hepatocytes show minimal lipid droplet content (less vacuolation). This indicated exhausted reserves, reinforcing how heat and toxicants interact to exacerbate impacts. Full article

Understanding how fish communities respond to long-term environmental changes in regulated floodplain ecosystems is essential for managing biodiversity amid increasing anthropogenic and climatic pressures. This study evaluates the spatiotemporal dynamics of functional diversity in juvenile fish assemblages within the Dnipro-Orilskiy Nature Reserve (Ukraine) from 1997 to 2015. By employing a combination of extensive ichthyological field surveys and satellite-derived environmental indices (including NDVI, chlorophyll-a, turbidity, and spectral proxies for algal blooms), we assessed the impacts of eutrophication, hydrological alterations, and climate warming on functional structure. Our results reveal three key responses in fish functional diversity: (1) a decline in functional specialization and imbalance, indicating the loss of unique ecological roles and increased redundancy; (2) a rise in functional divergence, reflecting a shift toward species with outlying trait combinations; and (3) a complex pattern in functional richness, with trends varying by site and trait structure. These shifts are linked to increasing eutrophication and warming, particularly in floodplain areas. Remote sensing effectively captured spatial variation in eutrophication-related water quality and proved to be a powerful tool for linking environmental change to fish community dynamics, not least in inaccessible areas. Full article

The use of cellular energy allocation (CEA) as a physiological energetic biomarker is useful for detecting the sublethal effects of environmental contaminants. The CEA assesses the health and energy status of organisms, serving as a reliable indicator for monitoring the health of aquatic ecosystems. This study aimed to evaluate the impact of emerging contaminants already listed as a priority for monitoring in freshwater ecosystems, namely sulfamethoxazole (0.156–2.50 mg/L), trimethoprim (25.0–400 mg/L), 4-chloroaniline (5.21–20.0 mg/L), and 3,4-dichloroaniline (0.38–4.00 mg/L), on the CEA of D. rerio embryos. A standard fish embryo toxicity test was conducted, and an adaptation of the allometric scaling approach was developed through the relationship between the size and the fresh weight of the embryos. All the compounds affected the fractions of the energy reserves (total carbohydrate, lipid, and protein contents) differently, with carbohydrates being the predominant energy fraction and the most responsive indicator. Although the energy consumed showed no significant changes, the CEA was notably altered after exposure to all the contaminants, indicating a direct connection to shifts in the available energy. The CEA alterations may indicate a reallocation of energy toward detoxification, combating the stress of contaminant exposure. Energy allocation biomarkers provide a comprehensive assessment of an organism’s physiological state, which is essential for evaluating emerging contaminants’ impacts, safeguarding aquatic ecosystems, and shaping effective environmental policies. Full article

Nitrite is a common pollutant in aquaculture systems and can pose serious threats to fish health, especially under high-temperature conditions. This study aimed to investigate the impact of nitrite stress on the growth, glycolipid metabolism, and hepatic metabolomic profiles in the spotted seabass fry (Lateolabrax maculatus) under elevated temperature conditions at 33 °C. A total of 450 fish (28.52 ± 0.84 g) were randomly distributed into nine tanks and exposed to three nitrite concentrations (0, 8, and 16 mg/L), with samples collected on days 1, 3, 7, 14, 21, and 28. Results showed that higher nitrite levels significantly reduced final body weight, weight gain, survival rate, hepatosomatic index, and viscerosomatic index. Blood glucose and triglyceride levels, whole-body crude lipid, liver total cholesterol, and hepatic glycogen content also declined significantly under higher nitrite stress. In contrast, hepatic lactate and lactate dehydrogenase increased in the high-nitrite group. Gene expression analysis revealed suppressed lipid synthesis and enhanced lipolysis under nitrite exposure. Metabolomic analysis further demonstrated disruptions in key energy-related pathways, including the TCA cycle, pentose phosphate pathway, and insulin signaling. These findings indicate that nitrite stress impairs growth and energy metabolism in spotted seabass, which respond by mobilizing energy reserves to cope with combined stress of high temperature and nitrite. Full article

The wild resources of Spinibarbus caldwelli, once an important economic fish in southern China, have been drastically reduced in recent years due to environmental changes and human activities. The Liuxi River S. caldwelli National Aquatic Germplasm Reserve was established in Conghua District, Guangzhou city, and the release of S. caldwelli was carried out. However, traditional fishery resource survey methods yield less accurate results when the abundance of the surveyed species is low or when they are difficult to catch. As a non-destructive and non-invasive approach, environmental DNA (eDNA) is widely employed in aquatic species monitoring, though its detection efficiency may be affected by environmental conditions. Therefore, this study explored the eDNA monitoring methods of S. caldwelli in Liuxi River from the following four aspects: (1) the relationship between eDNA release and biomass/abundance; (2) the concentration and diffusion range of eDNA over time in a lentic ecosystem; (3) the diffusion range of eDNA in a lotic ecosystem; and (4) the effects of eDNA application in field monitoring. Our results showed a correlation between eDNA concentration and abundance/biomass of S. caldwelli. eDNA of S. caldwelli can diffuse up to 18 m in lentic ecosystems within 2 h and decreases with distance. eDNA of S. caldwelli released by 10 individuals in Liuxi River could be detected 900 m downstream. Field studies in Liuxi River showed that the eDNA method has high sensitivity in detecting the presence or absence of species and is highly consistent with the results of traditional methods. This study explored the application of environmental DNA technology in species monitoring in Liuxi River. Our aim was to evaluate the applicability and potential of eDNA in ecological monitoring of stream fishes. Full article

Coral reef and their ecological services of food production and shoreline protection are threatened by unsustainable use. To better understand their status, multiple approaches to estimating fisheries sustainability were compared, namely fisheries-independent stock biomass and recovery rates, fisheries-dependent landed catches, balanced harvest and gear use metrics, and fish length measurements. A community biomass recovery was established over a 45-year no-fishing stock recovery time series from seven fisheries reserves and compared to catch- and length-based estimates of sustainability. The logistic production rates (r = 0.09 ± 0.06 95% confidence interval (CI)) and maximum equilibrium total biomass (~150 ± 30 tons/km²) indicated a broad range of potential maximum sustainable yields, with a likely range of 1.1 to 3.9 (95% CI; mean = 3.8) tons/km²/year. In contrast, the mean annual linear biomass growth rates in reserves were lower but less variable than logistic surplus production estimates, ranging from 2.1 to 3.5 (mean = 2.8 tons/km²/year). Realized catches at landing sites were lower still, ranging from 1.43 to 1.52 (mean = 1.48 ± 0.2 tons/km²/y). Differences between production estimates and capture were largely attributable to changes in taxonomic composition and an imbalance in the estimated proportionality of production potential versus actual capture rates. Lost potential capture was likely due to differences in the vulnerability of taxa to fishing and a lack of compensatory increased production among fishing-resistant taxa. Large proportional losses of catch were measured among snappers, unicorn fish, sweetlips, goatfish, and soldierfish, while smaller proportional gains in the catch samples were found among resident herbivorous rabbitfish, parrotfish, and groupers. Many of these declining taxa have vulnerable schooling life histories that are likely to require special habitat and reserve characteristics. Evaluations of sustainability from length measurements found 17 or 7% of total and 12% of caught species had sample sizes minimally sufficient for evaluation (>30 individuals from 413 catches, 2284 captured individuals composed of 144 species) of length and spawning metrics of sustainability. Seven of these species met length-based and three met spawning potential ratio thresholds for sustainability. Consequently, length-based evaluations had poor species coverage and therefore we were unable to evaluate the sustainability of the larger fish community. Recommendations for future research include a better understanding of the consequences of variability in spillover and proportionality of production potential for sustainability. Management recommendations are to focus management on the recovery of species abundant in unfished locations but not contributing to fisheries yield. Full article

The Peruvian coast covers more than 3000 km along the Pacific Ocean, being one of the richest seas in terms of biodiversity, productivity, fishing, and renewable energy potential. Marine renewable energy (MRE) in both offshore and coastal environments of Peru is, currently, a huge reserve of practically unused renewable energy, with inexhaustible potential. In this context, renewable energies from hydroelectric, biomass, wind, and solar sources have been applied in the country, but geothermal, waves, tidal currents, and tidal range sources are currently underdeveloped. This article presents the enormous source of sustainable blue energy for generating electrical energy that exists in Peru from waves and tidal resource potential. In addition, this article presents the main opportunities, gaps, and key issues for the implementation of marine renewable energy (MRE), with emphasis on: (i) showing the available potential in the northern, central, and southern Pacific Ocean territories of Peru, (ii) characterizing the marine energy best available technologies to implement, (iii) the environmental and socio-economic impacts of marine renewable energy, and (iv) discussion of challenges, opportunities, and future directions for developments in the marine energy sector. Finally, the article concludes that the greatest possibilities for exploiting the abundant marine renewable energy (MRE) resource in Peru are large spaces in both offshore and coastal environments on the Pacific Ocean that can be considered for harvesting energy. These issues will depend strongly on the implementation of regulations and policies for the strategic use for planning of marine resources, encouraging research and development (R&D) for creating sustainable innovations, incentives for project finance mechanisms, and developing specialized local human capital, considering the sustainability of livelihoods of coastal communities and ecosystems. Full article

The Belostomatidae is a family of aquatic Heteropteran insects that normally inhabit swamps of tropical, subtropical and temperate regions where they naturally feed on a large range of prey, mainly fish, amphibians and reptiles. However, these arthropods can occasionally bite humans when provoked, causing pain. The only species of giant water bug known to be found in Europe is Lethocerus (L.) patruelis. We reported the finding of a specimen of female L. patruelis in Southern Italy. The arthropod was collected by a tourist on his body while he lying down on a beach close to a nature reserve. To finalize the giant water bug identification, both morphological and molecular tools were used for the first time in our country. Herein, information on cases of patients bitten by giant water bugs belonging to the Belostomatidae family are reported, and circumstances involving their contact with humans are also discussed. Full article

This study assessed the effects of thymol and yeast Saccharomyces cerevisiae on the growth performance, antioxidant capacity and immunological responses and gut immunological transcripts in rainbow trout, Oncorhynchus mykiss. Two hundred and seventy fish (6.62 ± 0.18 g) were distributed in 18 aquaria (15 fish per aquarium) as a 2 × 3 factorial design. The fish were fed on diets containing 0 and 1 × 10⁸ cfu/g of yeast and 0, 250 and 500 mg/kg of thymol for 60 days. The results showed that dietary yeast supplementation led to significantly improved fish weight gain and feed efficiency (p < 0.05). Thymol and yeast supplementation affected the hepatic antioxidant status, leading to lower lipid peroxidation and higher glutathione reserves (p < 0.05). Thymol and yeast supplementation led to significantly lowered plasma aspartate aminotransferase levels (p < 0.05). Dietary yeast supplementation led to significantly elevated plasma and mucus lysozyme, plasma alternative complement, immunoglobulin and mucus alkaline phosphatase levels. In contrast, thymol supplementation led to significantly increased plasma lysozyme and mucus alkaline phosphatase levels (p < 0.05), whereas it had no significant effects on other immunological parameters. The mucus bactericidal activities were improved by dietary yeast but both supplements enhanced the plasma bactericidal activity (p < 0.05). Thymol and yeast supplementation significantly up-regulated the expression of tumor necrosis factor-alpha, interleukin-1 beta, transforming growth factor-beta, beta-defensin and heat shock protein-70 in the hindgut (p < 0.05). In conclusion, dietary yeast supplementation was particularly effective in enhancing fish growth performance and non-specific immunity, while thymol supplementation primarily led to improved antioxidant capacity. Notably, a dietary dose of 250 mg/kg of thymol alone failed to affect the gut transcription as much as 500 mg/kg; however, the co-supplementation of 250 mg/kg of thymol and yeast led to comparable results. Full article

The European catfish (Silurus glanis Linnaeus, 1758) was introduced into the Ebro Basin in Spain in 1974 for recreational fishing. Since then, the species has spread throughout the country’s river basins, reaching the Iznájar Reservoir (Guadalquivir River Basin) in 2011. This area is of great ecological and economic relevance, especially as it includes the Doñana National Park, one of the most important nature reserves in Europe. Recently, the presence of catfish has been reported in the lower reaches of the river. In this work, we used non-invasive vertical and horizontal hydroacoustic surveys and environmental DNA river sampling to unravel the actual distribution and dispersal pattern of the species in the lower Guadalquivir River. The hydroacoustic profiles and the species-specific detections by real-time PCR (qPCR) and droplet digital PCR (ddPCR) showed that these non-invasive methods allow the detection and quantification of catfish and provide valuable information on the species’ presence. We have confirmed the presence of catfish in most of the study area, including downstream areas of the Guadalquivir Basin. The results suggest the possibility of other isolated introductions and/or human-mediated movements of specimens, and imply that a coordinated catfish prevention and mitigation strategy is therefore urgently needed. Full article

The tambaqui (Colossoma macropomum) is Brazil’s most farmed native species, playing a crucial role in aquaculture. This study aimed to evaluate growth, hematological, biochemical, and body condition (Kn) parameters of tambaqui under two stocking densities in a recirculating aquaculture system (RAS). A total of 240 tambaqui (12.2 ± 4.1 g; 6.63 ± 0.73 cm) were distributed across six experimental units in two treatments (SD1 = 140 fish m⁻³; SD2 = 180 fish m⁻³) with three replicates. After 45 days, no significant differences were observed in water quality or zootechnical performance (p > 0.05), with final productivities of 8.64 ± 1.85 kg m³ and 9.46 ± 1.95 kg m³ for SD1 and SD2, respectively. Elevated plasma glucose, cholesterol, and triglyceride levels indicated energy reserve mobilization, suggesting some physiological response to higher stocking densities. However, other hematological and body condition parameters, including condition factor (Kn), indicated no significant adverse effects. These findings suggest that tambaqui can tolerate these stocking densities in RAS without compromising body condition, supporting the species’ intensive farming potential in controlled systems. This study highlights the importance of balancing productivity and physiological conditions in aquaculture management. Full article

Managing fishery resources is crucial to ensure the marine environment continues to provide diverse goods and services. To overcome difficulties of classical methods used for fish stock management, molecular tools have shown potential to address this issue assessing both targeted and non-targeted species. This study aims to evaluate the spatiotemporal diversity of fish using 12S rRNA gene eDNA metabarcoding sequencing in the Berlengas archipelago and compare two seawater eDNA sampling sources: samples collected by fishermen during their activities and those collected by our research team. The results indicated that autumn presented the highest diversity and that the area around Berlenga Island was the richest area, increasing biodiversity across the region. Fisher-collected samples were generally less diverse than those by the research team but detected species typical of deeper and open-ocean habitats, validating this sampling method. Our study also highlighted eDNA’s role in monitoring fish species by detecting unexpected species for the region, such as Atlantic salmon (Salmo salar) and Atlantic cod (Gadus morhua), while cautioning against false positives like orange clownfish (Amphiprion percula) and blue tilapia (Oreochromis aureus). Future optimisation of our eDNA sampling methodology could better refine marine ecosystem dynamics around the UNESCO Biosphere Reserve of the Berlengas Archipelago, Portugal. Full article

The aim of this paper is to provide evidence of the species-specific export of adult fishes for some species or group of species from six well-enforced Mediterranean marine protected areas (MPAs): Cerbère-Banyuls and Carry-le-Rouet in France and Medes, Cabrera, Tabarca, and Cabo de Palos in Spain. We estimated the distance at which spillover of those individual or groups of species occur by directly assessing the existence of gradients of biomass across the MPA boundaries by means of underwater visual census, asuming that such gradients will be specifics in terms of structure (sharpness, slope, and intercept) for every species and group of species. A significant “reserve effect” was observed for biomass of some of the individual and grouped species in all MPAs. Decreasing gradients of biomass differ among taxons and are not related with the insular nature of the location. Different gradients of biomass resulted from the interaction between species characteristics and some ecological and structural drivers, and we did not find regular patterns for each taxa among MPAs, even though the same species can exhibit different gradient structure and/or spillover distances in the same MPA depending on the orientation. Habitat patch distribution and continuity seems the most important environmental factor explaining the existence and pattern of gradients at species level, interacting with fish home range and fishing pressure close to the limits of the MPAs. Managers should take in account the surrounding distribution of habitats in terms of complexity and quality in order to optimize the spillover capacity of the MPAs. Full article

The Punta Coles Natural Reserve (PCNR), located on the southern coast of the province of Ilo, Moquegua Region, Peru, houses an area rich in marine biodiversity which is composed of natural banks of benthic invertebrates, which constitute the potential and dynamic fishery of commercial interest for artisanal fishermen that impact the area. To mitigate this impact, all stakeholders need to know, understand, value, and balance the dependence of benthic biodiversity with the ecosystem for its preservation and the promotion of sustainable fishing. Along these lines, the components studied are bathymetry, lithology, and the tapestry of bioengineers that make up the reserve’s seabed. Mapping of the complexity of the benthic habitat of the seabed was developed on the basis of an integrated analysis of multibeam bathymetric data, geoscientific information associated with the antecedents of benthic biodiversity of the PCNR, sediment maps of the seabed, subtidal sedimentological texture, and photographic records. The characterization and granulometry of the sediments that make up the PCNR were determined according to the Udden–Wentworth classification criterion (Φ). The utility of the GPSMAP 178C multibeam echosounder for the interpretation of seabed sediments stands out. The kriging interpolation method was used to extrapolate the characteristics of the benthic habitat, which is suitable for large areas of the sea. As a result, three habitats were derived and mapped, and three structures (bioengineers), namely, “subtidal kelps” (Lessonia trabeculata), “mussels” (Aulacomya atra), and “red sea squirt” (Pyura chilensis), were associated mainly with sedimentary rock habitats and mixed substrates. In the sand substrate, these algae were found to a lesser extent. The results show that this study is a conceptual model that summarizes the understanding of ecology and prospects for the sustainability of profitable, ecoefficient fishing activities in the Moquegua Region, Peru. Full article

A two-eyed seeing approach considered Indigenous knowledge and Western science towards eco–health, reconciliation and land back with Fort William First Nation (FWFN) in Ontario, Canada. To map traditional land use, occupancy, and ecological knowledge, we interviewed 49 FWFN members about their hunting, fishing, trapping, plant harvesting, cultural sites, and sacred gatherings on their ancestral land. Their traditional land use and occupancy includes more than 7.5 million ha of their ancestral land. The FWFN members reported many industrial impacts on their reserve and ancestral land. We analyzed the normalized difference vegetation index (NDVI) change over time on FWFN’s ancestral land and the Thunder Bay Pulp and Paper Mill (TBPP)’s National Pollutant Release Inventory data to investigate the FWFN members’ ecohealth concerns. The NDVI analysis revealed large tracts of degraded FWFN’s ancestral land due to logging areas, mining claims, settlements, and paper mills. Mining claims and greenstone belts occupy a quarter of the FWFN members’ ancestral land. The TBPP mill dumped pollution into the Kaministiquia River upstream and upwind of the FWFN community, exposing FWFN members to kilotons of cancerous and other toxic chemicals each year for over a century. Resource extraction and pollution in Northwestern Ontario negatively impacted the human health and ecosystem integrity of FWFN, requiring reconciliation by restoring damaged land and preventing pollution as the starting point for land back. The first step to land back is ending the environmental racism of the TBPP’s pollution directed downstream and downwind of FWFN and protecting ancestral land against logging, mining, and other extractive industries. Full article