Search Results (100)

Climate change is projected to significantly alter hydrological conditions across the Northern Hemisphere, with increased precipitation variability, more intense rainfall events, and earlier, rain-driven spring floods in regions like northern Sweden. These changes will affect both natural ecosystems and hydropower-regulated rivers, particularly during ecologically sensitive periods such as the grayling spawning season in late spring. This study examines the impact of extreme spring flow conditions on grayling spawning habitats by analyzing historical runoff data and simulating high-flow events using a 2D hydraulic model in Delft3D FM. Results show that previously suitable spawning areas became too deep or experienced flow velocities beyond ecological thresholds, rendering them unsuitable. These hydrodynamic shifts could have cascading effects on aquatic vegetation and food availability, ultimately threatening the survival and reproductive success of grayling populations. The findings underscore the importance of integrating ecological considerations into future water management and hydropower operation strategies in the face of climate-driven flow variability. Full article

To investigate the group behavioral characteristics of Schizothorax wangchiachii during the spawning period, we used acoustic telemetry to track 10 mature individuals (4 females, 12 males) in a semi-controlled stream section (28.1 m × 5.8 m) simulating natural spawning microhabitats from 23 to 26 January 2024. By integrating trajectory similarity analysis and wavelet transform, we examined the aggregation patterns and activity rhythms during natural spawning events. The population formed two relatively stable subgroups, with significantly shorter inter-individual distances during the day (1.69 ± 0.72 m) than at night (2.54 ± 0.85 m, p < 0.01). Aggregation behavior exhibited a dominant ultradian rhythm of 16.5 h, with stable clustering between 09:00 and 16:00 (spawning window: 13:40–14:20) and dispersal from 19:00 to 00:00. Group activity followed a decreasing-then-increasing trend, with higher nighttime activity. Males were more active than females (F = 51.89, p < 0.01); female activity peaked on the spawning day and was influenced by reproductive progression, while male activity was mainly driven by diel rhythms (p < 0.01). A weak positive correlation was found between active time and inter-individual distance in both sexes (r = 0.32, p < 0.05), indicating reduced activity when aggregated. These findings provide insight into the temporal coordination and spatial regulation of reproductive behavior under semi-controlled conditions. However, due to the short monitoring period and experimental setup, caution is warranted when generalizing to the full reproductive season or fully natural habitats. Full article

As power grids scale and aging assets edge toward obsolescence, grounding grid corrosion has become a critical vulnerability. Conventional diagnosis must fit high-dimensional electrical data to a physical model, typically yielding a nonlinear under-determined system fraught with computational burden and uncertainty. We propose the Enhanced Biomimetic Hippopotamus Optimization (EBOHO) algorithm, which distills the river-dwelling hippo’s ecological wisdom into three synergistic strategies: a beta-function herd seeding that replicates the genetic diversity of juvenile hippos diffusing through wetlands, an elite–mean cooperative foraging rule that echoes the way dominant bulls steer the herd toward nutrient-rich pastures, and a lens imaging opposition maneuver inspired by moonlit water reflections that spawn mirror candidates to avert premature convergence. Benchmarks on the CEC 2017 suite and four classical design problems show EBOHO’s superior global search, robustness, and convergence speed over numerous state-of-the-art meta-heuristics, including prior hippo variants. An industrial case study on grounding grid corrosion further confirms that EBOHO swiftly resolves the under-determined equations and pinpoints corrosion sites with high precision, underscoring its promise as a nature-inspired diagnostic engine for aging power system infrastructure. Full article

To investigate the species composition, reproductive dynamics, and hydrological drivers of fish resources in the early stage in the Guiping section of the Xunjiang River, we conducted a two-year survey (2022–2023) downstream of the Datengxia Dam. A total of 22,464 fish eggs and larvae were collected, representing 6 orders, 17 families, and 67 species, with Cyprinidae (58.2%) as the dominant family. Dominant species included Squaliobarbus curriculus, Gobiidae, Hemiculter leucisculus, and Culter, exhibiting significant interannual variation in abundance. The breeding season peaked from May to September, accounting for 94.6% of annual recruitment. Hydrological conditions strongly influenced reproductive output: the multiple flood pulse periods in 2022 (peak discharge: 29,000 m³/s) yielded 34.997 billion eggs and larvae, whereas reduced flows in 2023 (peak discharge: 12,200 m³/s) led to a 75.4% decline (8.620 billion). Redundancy analysis (RDA) revealed that discharge, water temperature, natural hydrological data, and dissolved oxygen were the primary environmental drivers, explaining 46.11% of variability in larval abundance (p < 0.001). Notably, the proportion of important economic fish, “four major Chinese carps”, plummeted from 4.9% (2022) to less than 0.1% (2023), indicating spawning ground function degradation. Our results demonstrate that flood pulses are essential for sustaining fish recruitment, particularly for pelagic spawning riverine fish like the four major Chinese carps. Their proportion plummeted to less than 0.1% in 2023, highlighting the urgent need for eco-hydrological management in the Xunjiang River. Full article

Overexploitation is the main anthropogenic threat to groupers (Epinephelidae) that aggregate to spawn. Fishing negatively affects their reproductive success and indirectly harms fishery economic yield. In the southern Gulf of Mexico, grouper catches, which include thirteen species, are in decline. A lack of biological information on each exploited species prevents optimising fishery management. Using histological examination of the gonads, the reproductive traits of red hind Epinephelus guttatus and yellowfin grouper Mycteroperca venenosa were studied from January 2008 to October 2009. Collections were made at two reef systems (Alacranes Reef and Bajos del Norte) on the continental shelf of the Yucatan Peninsula, Mexico, where these species form transient spawning aggregations. The results confirmed that previously identified spawning aggregation sites at both reefs constitute productive seasonal and perennial “hotspots” for both groupers; they spawn annually between January and April. Females of these protogynous hermaphroditic species exhibit a reproductive strategy characterised by asynchronous ovarian development organisation and ovulation. Sex ratios and maximum sizes at each reef suggest that populations of both groupers had a good conservation status as of the late 2000s. Both reefs are now marine protected areas, and a discussion is made of the consequent possible benefits to grouper population conservation and sustainability in the southern Gulf of Mexico. Full article

The marine ornamental species trade relies heavily on wild-caught specimens, including the Vermiculated angelfish (Chaetodontoplus mesoleucus). Captive breeding of this species faces challenges with limited detailed knowledge available beyond 2 days post-hatch (dph) regarding the influence of environmental factors. This study provides a detailed characterization of C. mesoleucus from early development to 381 dph. Under controlled laboratory conditions, the effect of temperature (22–37 °C) on hatching rate, deformity rate, hatching period duration, time to 50% hatch, and survival rate is investigated. Additionally, the influence of different salinities (0–38 psu) on hatching rates and larval deformity rates was also examined. The optimal incubation temperatures for high hatching rate and minimal larval deformities are found to be within 25–28 °C. A lower salinity threshold of 10 psu was established for successful hatching, and the optimal salinity range for minimizing larval deformities was 33–36 psu. These findings provide crucial baseline data and practical recommendations for optimizing hatchery protocols for C. mesoleucus, contributing to enhanced larval survival and the potential for sustainable aquaculture production, thereby reducing the pressure on wild populations. Full article

The Peruvian grunt, Anisotremus scapularis, is a commercially valuable coastal fish in the southeastern Pacific that is facing overexploitation. To support its aquaculture development, this study evaluated the spontaneous reproductive dynamics of a captive broodstock held under natural photoperiod and temperature conditions in a flow-through system. Eleven wild adult specimens (3 females and 8 males) with an average size of 34.9 ± 5.4 cm and a weight of 986 ± 470 g were housed in a 9 m³ tank and monitored over five consecutive spawning seasons (2016–2021). Fish were fed a semi-moist, animal-protein-based diet (37% protein and 6.6% lipid) at 2% body weight/day. A total of 214 spontaneous spawning events produced over 83 million eggs. The highest reproductive output occurred in the first season (2016–2017) with 94 spawnings and 23.3 million eggs. Fertilization, hatching, and larval survival rates averaged 94.7%, 89.7%, and 75%, respectively, but declined in later years. Spawning showed marked seasonality from October to May, with a major reproductive pause in late January. The temperature (16–20 °C) and photoperiod (>12 h daylight) appeared to influence reproductive timing, alongside diet and broodstock handling. The findings reported herein are observational in nature and provide valuable baseline data for future experimental designs aimed at optimizing broodstock management in A. scapularis aquaculture. Full article

Pakistan’s marine fishing industry is crucial to the country’s economy, generating employment opportunities and foreign revenue. It produces 80% of the country’s total fish production. Otolithes ruber is a commercially important fish on the Makran coast of Pakistan, contributing significantly to the region’s croaker fisheries. This study is the first to apply three length-based approaches for assessing the stock status of O. ruber in the Makran coast: (1) TropFishR to estimate the mortality, growth parameters, and current exploitation status, reference points based on the yield per recruitment model, (2) the length-based Bayesian biomass method (LBB) to calculate stock biomass, and (3) the length-based spawning potential ratio (LBSPR) to estimate the spawning potential ratio. The length–weight relationship of Otolithes ruber was a positive allometric pattern (b = 3.28; R² = 0.94). Growth parameters for Otolithes ruber were L_∞ = 55.47 cm, K = 0.50 year⁻¹. The calculated total mortality rate (Z), natural mortality (M), and fishing mortality (F) were 2.27 year⁻¹, 0.67 year⁻¹, and 1.6 year⁻¹, respectively. The exploitation rate (E) was 0.70, indicating severe overexploitation. The current length at first capture (Lc₅₀) = 27.37 cm was lower than that at first maturity (Lm₅₀) = 30.75 cm, indicating growth overfishing. The current spawning potential ratio (8%) was lower than the optimal value (40%), indicating recruitment overfishing. The current biomass, concerning virgin biomass B/B_o, was also 8%, resulting in a 92% stock decline. We recommend reducing the exploitation pressure by limiting the commercial catch to an optimum length range of 34.5–42.2 cm and reducing fishing pressure by 40% to ensure sustainable fishery management. Full article

The visual system has served as an expeditious entry point for discerning the mechanism of action of many brain systems, spearheading multiple fields of neuroscience in the process. It has additionally launched the careers of countless scientists, as we have crafted new means to understand neuronal structures and their functions, leading to advances in many areas of the sciences. Indeed, one can readily mark the onset of the scientific examination of the visual system with the 1851 invention of the ophthalmoscope by Hermann von Helmholtz, and the trichromatic theory of color vision in 1802. The Young–Helmholtz understanding the red–green–blue nature of color vision became the foundation to understanding sensory system function that visual artists and also contemporary flat panel displays rely on. It is fascinating to realize that the paintings of Georges Seurat and an iPhone display share a commonality of this application of the trichromatic theory. While it was not until 1956 that the existence of cells responsive to three different ranges of wavelengths was proven with the work of Gunnar Svaetichin, this proof in many ways marked the advancement of tools to visualize at a microscopic level, a full century after the Young–Helmholtz theory was developed. Just a decade later, in 1966, the person widely considered as the founder of modern neuroscience, Stephen Kuffler, founded the Harvard neurobiology department. It was from Kuffler’s work with his post-doctoral students that many new fields of study were created and from whom many of the neuroscience programs across the US were founded. In terms of the visual system, Kuffler and his team were key in detailing areas of retinal neuroanatomy, neurochemistry, neurophysiology, and developmental neurobiology. This paper traces areas in visual system research that provide our understanding of the disparate areas of brain sciences. As such, there are six categories that are evaluated, each of which spawned work in multiple areas that have become mainstays in neuroscience. These range from fields that were dominant a half century ago to ones that have their origins in this decade. The commonality is that all of these owe their origin to Helmholtz and Kuffler, polymaths of the nineteenth and twentieth centuries. We will examine the impact of vision research across the following fields of neuroscience: sensory system function, neuroanatomy, neurochemistry, neurophysiology, developmental neurobiology, and neurological health and disease. Full article

Artificial diets applied in the mass-rearing propagation of H. axyridis can improve reproductive ability by optimizing the feeding formula. This study used transcriptome data to investigate the effects of various artificial diets on the growth and development of H. axyridis. Results indicate that spawning increased with the low-fat and JH III-supplemented artificial diet (Diet 3). Furthermore, the highest glycogen content found in Diet 3 was significantly different from the other two groups. Triglyceride content decreased as adult feeding time increased in the three artificial diet groups, with the fastest decrease observed in the low-fat diet (Diet 2). Protein content increased gradually in the high-fat diet (Diet 1) group compared to the other treatment groups. The adults reared on low-fat artificial diets, when compared to those on artificial diets supplemented with juvenile hormones at the transcriptome level, were found to have upregulated genes enriched in ubiquitin-mediated proteolysis, ribosome biogenesis, and the hedgehog signaling pathway. In contrast, the genes upregulated in the latter group were enriched in oxidative phosphorylation, amino acid biosynthesis, and the metabolism of other amino acids. The results suggest that nutritional status significantly affects the growth and development of H. axyridis and has practical implications for the artificial feeding of natural pest enemies. Full article

Mystus gulio and Mystus cavasius are small indigenous fish species (SIFs) found throughout the year at the various stretches of the river Ganga and contribute significantly to the commercial fishery. The current study was conducted with a total of 609 specimens of M. gulio with a total length ranging from 84 to 190 mm and 377 specimens of M. cavasius with a total length ranging from 51 to 232 mm, collected from eight selected sites of lower stretches of the river Ganga between July 2018 and October 2019 to analyse their growth, mortality, and exploitation status. The sample specimens’ length-frequency distribution, primarily taken from bag nets and set barrier nets used in artisanal fisheries, was assessed using the FiSAT II programme. For M. gulio, the estimated asymptotic length (L_∞), growth coefficient (K), and initial condition factor (t₀) were 183.23 mm, 0.31 yr⁻¹, and −0.486 years, and for M. cavasius, these values were 246.23 mm, 0.19 yr⁻¹, and −0.302 years, respectively. The estimates for the total (Z), natural (M), and fishing (F) mortality rates were 1.78, 0.49, and 1.29 yr⁻¹ for M. gulio and 0.68, 0.33, and 0.35 yr⁻¹ for M. cavasius, respectively. Both M. gulio (May to July) and M. cavasius (June to August) experienced a single spawning peak. The estimated exploitation ratio (E) for M. gulio was 0.72, which is higher than the optimal level of exploitation (E_opt) and the maximum level of exploitation (E_max). On the other hand, the E value for M. cavasius was 0.52, which means that it was exploited at the right level. The fishing pressure was found to be slightly excessive for the current stocks of M. gulio, which should be considered for proper management of the fishery in the river Ganga. The present study, the first of its kind, highlights the stock status of these two commercially important species and the management measures taken to revive the stock along the lower stretches of the Ganga in India. The environmental parameters of the lower stretches of the river Ganga show favourable conditions for the optimum growth of M. gulio and M. cavasius. Full article

Geoduck aquaculture is becoming a key component in meeting international market demand, given the natural and regulatory restrictions on wild geoduck supply. Geoduck clams are not sexually dimorphic, making it practically unfeasible to distinguish between males and females prior to a spawning event. To facilitate increased production of geoduck, a better understanding of reproductive biology and associated targeted bio-markers is required. In this study, metabolomics was utilised as a research tool to distinguish between metabolites related to male and female New Zealand geoduck (Panopea zelandica), gill and muscle samples collected from broodstock individuals housed in an experimental hatchery. A total of 17 metabolites were detected, showing significant differences between sexes. The findings indicate that metabolites associated with lipid biosynthesis were increased in female clams to support reproductive functions. An increase in carbohydrate-linked metabolic pathways was detected in male geoduck, arguably to sustain sperm production. Taurine has been reported as a biomarker to distinguish between male and female bivalves in other studies and is confirmed within this study, with significant elevation in male adductor muscle tissue. Moreover, male geoduck had increased purine and pyrimidine biosynthesis, supporting energy needs. This study provides useful sex biomarkers for future breeding strategies of P. zelandica. Full article

Scomber japonicus, commonly known as chub mackerel, is a fish species of economic significance in Korea, China, and Japan, whose natural abundance has reduced dramatically due to overfishing and environmental changes. To investigate the genetic differentiation and population structure of S. japonicus, a 359 base pair segment of the mitochondrial DNA (mtDNA) control region sequence was analyzed in 96 individuals sampled from three locations in Korean waters. Sixty-six haplotypes were recognized, of which 61 (92.42%) were population specific, whereas only five haplotypes were shared by multiple populations (8%). Two clades were revealed with low support values, and no specific genealogical branches were recognized according to geographical locations. Significant genetic differentiations, however, were detected among the three populations, with F_ST values (p < 0.05). These results indicate that populations of S. japonicus in Korean waters are genetically subdivided. Migration patterns, spawning site fidelity, and current temperature could be the possible causes of this subdivision. Consequently, it is thought that each of the genetically unique S. japonicus stocks found in Korean waters requires a different approach to management. Full article

The grooved carpet shell clam (Ruditapes decussatus), widely found along Morocco’s coasts and estuaries, is a key economic resource due to its high market value. However, clam production has declined over recent decades, largely due to the overexploitation of natural beds, and recruitment failures, leading to a limited wild spat availability. This study examined how the broodstock collection season (winter vs. summer) and origin (South Atlantic vs. North Mediterranean) affect broodstock performances in hatcheries. The maturity development (condition index (CI) and gonadal condition index (GCI)), histological examination, and reproductive output were evaluated. The results showed that Mediterranean clams achieved a higher maturity during winter conditioning (CI = 13.60 ± 1.02, GCI = 6.01 ± 0.90) than the Atlantic population (CI = 11.51 ± 1.50, GCI = 5.31 ± 1.14). Moreover, Mediterranean clams produced more oocytes per female (2.34 million), despite the lower spawning rate (42%), compared to the Atlantic clams (1.68 million) with a 69% spawning rate by the end of the winter conditioning. These findings highlight the importance of selecting broodstock by geographic origin to optimize shellfish hatchery production. Full article

According to EuroStat data, the recorded landings of fisheries products from European waters were estimated at about 6 million tons in 2001, down to 3.2 million tons in 2022. This gradual decline slowed after the entering into force of the reform of the European Common Fisheries Policy (CFP) at the end of 2013, but was followed by a steeper decline after 2018. This is reflected in the last assessment of the Scientific Technical and Economic Committee for Fisheries (STEPF), noting that despite progress in the NE Atlantic management, 41% of the assessed stocks in 2022 were outside safe biological limits, down from 80% in 2003. Improvements in the Mediterranean are significantly slower. A warming ocean provokes the measurable poleward migration of species and adds stress to predator–prey relations in all European seas. Within this general picture, the broad-brush landscape is influenced by policy applications more in favour of industrial exploitation and regulatory and market environments, making it very hard for many small-scale fishers (SSFs) to remain in business, let alone attract younger successors for generational transition. In crowded marine spaces, it is a challenge to allocate access rights fairly between fisheries, exclusion zones for resource and habitat protection and much-needed ecosystem recovery, platforms for fossil exploitation, wind farms, underwater cables and recreational uses. Two examples of local initiatives with faunal recovery potential in the Mediterranean are briefly presented as a bottom-up complement to more top-down management approaches. They are spearheaded by artisanal fishers, who seek to restore spawning grounds and other coastal habitats as a way to procure enough fish and other complementary activities to secure their livelihoods in the future. They are supported by local scientists and nature conservation organisations. While promising, this is still rather the exception. Here, it is argued that trust-building between artisanal fishers, conservationists and scientists, and greater systemic support to SSFs by governments, increase chances for the urgently needed structural shifts that deliver the reversal in the ongoing decline in biodiversity and ocean productivity that all aspire to, to ensure sustained social and economic benefits. Full article