Fish Conservation Research Articles

Ecological Status and Fish Diversity in the MahendratanayaRiver Srikakulam-Andhra Pradesh-India

Mahendatanaya is the link river between the two states Andhra Pradesh and Odessa. It is origin from Rayagada hills (Eastern Ghats) and travel through Odessa to Andhra Pradesh, finally join with the Bay of Bengal at Baruvakotturu in Srikakulam. It is not only agricultural resource but also one of the high biodiversity spots in the Srikakulam Wetlands. I studied biodiversity of Mahendratanaya River by the survey method use of fish boats and fish gears along with fisher men and local people. I was collected the different water samples from the different areas and send to laboratory for indention to the values of ph, turbidity, Nitrates and Oxygen levels. Different Ichthyofauna was collected from the 34 sites with the help of fishermen by the use of the boats, fish gears, Fish traps and nets, the catching fishes are preserve in the bamboo traps and ice boxes and identified by IUCN the study time between 2023-2024. In the 30 water samples collected and set to the laboratory identifying for water elements. I was identified 10 orders, 19 families, 38 genus, 58 species of the total collected fishes count more or less 4300, fish conservation, anthropogenic and biodiversity of Ichthyofauna in the MahendratanayaRiver. I calculated the Environmental Tolerance Index (ETI) of the 10 species from the 9 sites of the river and beta diversity. Diagram1. Sample collection from MahendratanayaRiverat the four sites(site.1,2,3,4,)

Pinniped response to diadromous fish restoration in the Penobscot River Estuary

Successful conservation of pinnipeds in the northwest Atlantic has led to increasing populations of harbor seals (Phoca vitulina) and gray seals (Halichoerus grypus) in the Gulf of Maine. Within this region, habitat restoration and diadromous fish conservation in the Penobscot River have also been top priorities for the past decade. To understand the overlap between the regional recovery of pinnipeds and the aggregative response of pinnipeds to increasing forage fish, we assessed how counts, distribution, and behavior of seals in the Penobscot River Estuary have changed over time from 2012 to 2020 and determined whether those changes were related to changes in fish biomass that are occurring as the result of diadromous fish restoration. We did not see increased counts of hauled-out seals, but consistent with regional harbor seal phenology, hauled out seal counts were highest in late spring and declined throughout the summer and into the fall. The number of swimming harbor and gray seals, analyzed as a proxy for changes in behavior, showed a stronger annual trend with an increase throughout the study period. Fish biomass was negatively associated with total number of hauled out seals and swimming gray seals but positively associated with swimming harbor seals. We also documented the potential displacement of harbor seals when gray seals are present. Together, these results begin to provide insights into how regional conservation and local restoration efforts interact to affect multiple trophic levels in an ecosystem. Continued monitoring of predator-prey interactions, along with diet and movement studies, will further elucidate seal aggregative response to increasing prey species in this system and the potential impact of recovering predator populations on restored prey populations. Knowledge gained regarding pinniped response to increasing fish biomass has important implications for other systems with ongoing conservation measures that aim to improve habitat, decrease exploitation, or recover protected species. Studies like these can be critical for finding paths forward to reconcile the potentially competing objectives of marine mammal protection and fish restoration.

From neglect toward enlightenment: the conservation of native fishes in the twenty-first century

From neglect toward enlightenment: the conservation of native fishes in the twenty-first century

Exploring the influence of gas extraction on fisheries' footprint in the Middle East: applying spatial econometrics.

The different stages of oil and gas extraction in the seabed are linked to water pollution and threaten fish reserves. This issue becomes more critical in the Middle East countries which are rich in natural resources and at the same time are facing water tensions. The purpose of this paper is to analyze the harmful impact of gas extraction on fisheries' footprint in the Middle East based on data from 1990 to 2021. In addition, as the destructive effects of gas extraction are not only limited to the extraction area but also affect the region widespread, then to examine the spreading characteristic of fishing ground footprint in the entire region of the Middle East, this study applies spatial econometrics. According to the results, local gas extraction has a considerable positive and significant effect on the home fishery's footprint. Each percent growth in local gas extraction leads to a significant increase of approximately 0.21 in the home fishing footprint index. In addition, spatial coefficients analysis reveals that a 1% growth in gas extraction in neighboring countries leads to a 4% increase in fisheries footprint inside a country. In addition, the driving force of fisheries footprint in the Middle East mainly came from gas extraction, accelerated economic development (GDP^2), and agricultural production of the country itself, as well as the urbanization, industrialization, and gas extraction of neighboring countries, respectively. Then, the catastrophe of fishing areas' demolition caused by gas extraction activities in the Middle East area is remarkable and fish conservation needs more intra- and cross-country prevention policies in the Middle East area.

Assessing scientific knowledge on Ecuadorian bony fishes from a scientometric perspective.

Bony fishes play a pivotal role in Ecuador's social, economic, and ecological aspects. However, the current state of scientific knowledge on this group remains poorly understood. This study aims to assess the scientific output related to Ecuadorian bony fishes, identifying both well-researched and understudied areas. A scientometric analysis was conducted using the Scopus database, evaluating 265 peer-reviewed publications on marine and freshwater bony fishes. The results revealed that 55.5% of studies focused on marine environments, 41.9% on freshwater ecosystems, and 2.6% on mixed environments. The earliest study was published more than 130 years ago, with a marked increase in research output since 2018. Geographic and regional disparities in research efforts were evident, with the Galapagos Islands hosting the highest number of studies at the provincial level and the coastal region leading in regional publications. Additionally, there has been a notable increase in the participation of women in research over time; however, it remains significantly below parity. English was the dominant language in these publications. On average, the delay between data collection and publication was 8.43 years, which may lead to outdated or ineffective management decisions. This underscores the importance of continually updating data to ensure the accuracy of conservation status assessments. Both marine and freshwater species that were endemic have been less studied compared to non-endemic species. Most of the studied species were categorized as "least concern," although a significant proportion of species classified as "data deficient" have started to be investigated by Ecuadorian researchers. The categories "endangered" and "near threatened" were the least studied, highlighting the urgent need for conservation initiatives targeting these vulnerable taxa. Biases in the number of studies among families, species, and geographic distribution indicate the need to expand research efforts to underrepresented taxa and regions. This analysis underscores the necessity of diversifying methodologies and broadening the research focus to more comprehensively address the challenges associated with the conservation and management of bony fishes in Ecuador.

Novel Efficient Genome-Wide STR Panels for the Conservation of the Endemic Catfishes of Western Ghats: Critically Endangered Hemibagrus punctatus Jerdon (1849) and Vulnerable Horabagrus brachysoma (Günther, 1864).

The IUCN classifies two-endemic fishes of the Western Ghats in Peninsular India: Nilgiri mystus Hemibagrus punctatus is critically endangered, and Yellow catfish Horabagrus brachysoma is vulnerable. These are threatened by habitat degradation, excess fishing, and dam construction. ICAR-NBFGR, the premier research organisation in India for fish conservation, aims to conserve these two species through captive propagation, stock identification, and stock-specific ranching programs. The information on this species' genetic diversity and population structure is crucial for the successful rehabilitation of the species. Microsatellite markers are considered suitable markers for genetic stock structure analyses. An attempt was made to identify microsatellite markers in H. brachysoma (n = 27) and H. punctatus (n = 31) using Illumina Sequencing technology. The preliminary studies show that markers are efficient enough to differentiate the genetic stocks of these conservation-important species across their range of natural distribution. Three genetic stocks are identified in H. brachysoma and two in H.punctatus using the developed markers.

Density and diversity of larval fish in some coastal bays in Sharm El-Sheikh, northern Red Sea, Egypt

This study was carried out to investigate the composition and the spatial and temporal distribution of coral reef fish larvae in Port Bay, Sharm El- Maya Bay and Naama bay located in Sharm El-Sheikh area on the Egyptian Red Sea coast. Ichthyoplankton samples were collected monthly for one year mostly in the morning just before and at sunrise. A net of 100 cm, and 0.5 mm mesh size was towed horizontally parallel to the reef for 5–10 min. Throughout the period of study, a total of 205 plankton samples resulted in a collection of 3678 larvae representing 46 taxa and 32 fish families. Although larvae occurred all the year round, the general pattern showed two peaks in summer and winter with their maximum density in August with 1030 individuals/1000 m3. The lowest density of fish larvae was observed in September with 12 individuals/1000 m3. Regarding the distribution in bays, Port Bay (PRT) recorded the highest larval density where 1476 individuals/1000 m3 were collected. On the other hand, the lowest density was recorded in Sharm El-Maya Bay (SMB) with an average density of 908 larvae/1000 m3. The highest density of fish larvae occurred in any sample was recorded in Naama bay in August with a density of 1824 individuals/1000 m3. In several cases the spawning seasons of these taxa as determined from the present work based on the seasonal occurrence of larvae coincides mostly with that obtained from the literature based on the reproductive biological studies. Results obtained during this work reflected the importance of fish eggs and larvae survey in the management and conservation of reef fish in the Red Sea.

Monitoring and Conservation of Freshwater and Marine Fishes: Synopsis

Monitoring and Conservation of Freshwater and Marine Fishes: Synopsis

Development of ovaries, spawning season, size at maturity, and fecundity of Periophthalmus variabilis in the Mekong Delta, Vietnam

Reproductive traits are essential for fish conservation, however, they remain undocumented for Periophthalmus variabilis in the Vietnamese Mekong Delta, a species with potential as an aquarium pet. This study was carried out to provide Ps. variabilis with such crucial information. A total of 558 females were collected monthly by hand in 2022 from Tra Vinh to Ca Mau provinces. The results of the analysis of the ovary maturity stages frequency and gonadosomatic index indicated that this species exhibited a multi-spawner behavior. It is able to spawn year-round, with peaks from June to December. This was also evidenced by the presence of varying developmental stages of oocytes in the ovary’s fourth stage throughout the year. Further, it showed sexual and spatial variation in length at first maturity, ranging from 6.9 to 7.6 cm. The batch fecundity ranged from 696 to 8,124 eggs/female, reaching a peak at Ca Mau (2,974 ± 363 eggs), followed by Tra Vinh (2,685 ± 412), Soc Trang (2,621 ± 372 eggs), and Bac Lieu (2,536 ± 372 eggs). Egg diameter ranged from 0.60 to 0.65 millimeter among the four study sites. Based on the present findings, it is recommended to capture Ps. variabilis at a size larger than 6.9 cm, while imposing a closing seasons for its capture between June and December for suitable exploitation of this fish resource.

Ornamental Fish Diversity in Some Selected Water Bodies of the Upper Brahmaputra Basin in Assam, India

The northeastern region of India is renowned for its rich repository of ornamental fish. Though the majority of them constitute a rich source of dietary protein, many of them are also sourced as ornamental fish from the region. Among different states in the region, Assam is blessed with a huge repository of ornamental fish resources that are found to occur naturally in a variety of freshwater habitats. The present investigation deals with the diversity of ornamental fishes in prominent fish assemblage areas of the state. A total of 49 ornamental fish species were recorded represented by 32 genera under 18 families and 8 orders from the studied water bodies. Among the water bodies, R. Dibru accounted for the highest number of species, i.e. 46 ornamental fishes belonging to 31genera under 18 families. Mer Beel and R. Burhidihing recorded the lowest number of species. The findings of the present investigation provide crucial information on diversity in the study area, which would be helpful in better management and conservation of ornamental fish in the region.

Deep Dive Into Noninvasive Biometrics: A Pilot Journey Using Stereo-Video in a Public Aquarium.

Accurate collection of biometric data is important for understanding the biology and conservation of marine organisms, including elasmobranch and teleost fish, both in nature and controlled environments where monitoring marine specimens' health is mandatory. Traditional methods involving specimen capture and handling are invasive, stressful, and disruptive. Some techniques like underwater visual census or laser photogrammetry have been used for noninvasive data collection, but they have limitations and biases. The application of stereo-video photogrammetry through the use of diver-operated stereo-video systems (stereo-DOV) is a noninvasive method that overcomes these challenges, providing highly accurate measurements. It has become popular for species monitoring, studying anthropogenic impacts, and assessing length distributions. However, this technique is still uncommon and barely reported in aquarium settings. This study describes an innovative pilot study targeting multiple species carried out in a Public Aquarium, using a low-cost house-made device. The results revealed that measuring more than 100 individuals in approximately 1 day's work is possible. Total and fork lengths were estimated using specific software for 31 teleost and 16 elasmobranch species and compared with real measurements for the available species. Despite technical limitations that must be reviewed for application in future studies that resulted in high root mean square (RMS) values (> 20 mm), differences between methodological approaches revealed a minimal discrepancy (1.37%-5% in large sharks and rays and 1.8%-5.5% in teleost fish). This technique has time and cost requirements, but might represent a major advance in husbandry and in the contribution to conservation that ex situ studies can provide.

Intestinal Tissue, Digestive Enzyme, and Antioxidant Enzyme Activities in the Early Development Stage of Endangered Brachymystax tsinlingensis.

This work explores the digestive system characteristics of Brachymystax tsinlingensis during early developmental stages and aims to solve the problem of high lethality of fry during the transgression period, which is crucial for the artificial propagation and population conservation of endangered fishes. This study was carried out on intestinal tissue, digestive enzymes, and antioxidant enzyme activities in the early development stage of Brachymystax tsinlingensis. Ten random samples during endogenous nutrition (7, 10, and 11 days after hatching), mixed nutrition (13 and 19 DAH), and exogenous nutrition (31, 33, 39, 45, and 73 DAH) were collected by histological and biochemical analysis methods. The results showed that the intestine of Brachymystax tsinlingensis already has four layers initially at 7 DAH, and the intestinal gland tissue is evident at 73 DAH. The contents of total protein (TP) and the activities of lipase (LPS) and trypsin (TPS) were maximal at 39 DAH, and the activities were 3.20 ± 0.26 mg/mL, 2.52 ± 0.69 U/g, and 2717.45 ± 295.26 U/mg, respectively. Catalase (CAT) and glutathione peroxidase (GSH-PX) activities both showed the lowest values at 39 DAH, which were 0.57 ± 0.11 U/mg and 3.35 ± 0.94 U/mg, respectively. The activity of amylase (AMS) and the content of malonaldehyde (MDA) increased, and the highest values were reached at 45 DAH (1.32 ± 0.41 U/mg) and 73 DAH (1.29 ± 0.43 nmoL/mg), respectively. Superoxide dismutase (SOD) and GSH-PX activities both showed a peak value at 7 DAH (126.58 ± 20.13 U/mg and 6.47 ± 1.86 U/mg). Overall, the changes in intestinal tissue, digestive enzymes, and antioxidant enzyme activities at 39 DAH of Brachymystax tsinlingensis are inseparable from different vegetative stages during the developmental period, and these results can provide a reference for the proliferation and cultivation of Brachymystax tsinlingensis resources.

Important fish diversity maintenance status of the tributaries in a hotspot fish conservation area in the upper Yangtze River revealed by eDNA metabarcoding

This study employed Environmental DNA (eDNA) barcoding technology to delve into the influence of the tributaries and mainstem on fish diversity and spatiotemporal distribution in a hotspot fish conservation area in the upper Yangtze River. A total of 123 fish species were detected, belonging to 7 orders, 19 families, and 77 genera. The composition of fish species in tributaries is similar to that in mainstem, with higher fish community diversity in tributaries during the spring and summer. Exploration of fish ecotypes revealed significant differences between mainstem and tributaries. The fish community is mainly influenced by key environmental factors such as water temperature, dissolved oxygen, electrical conductivity, and ammonia nitrogen, with a higher impact of these factors on tributaries than on mainstem. In conclusion, while tributaries and mainstem in the Jiangjin section exhibit similarities in fish community composition, there are notable differences in community structure and diversity. Therefore, the protection of not only mainstem but also tributaries and their associated fish habitats is crucial for promoting the overall health and sustainability.

Population dynamics of resident fish in a coastal lagoon under eutrophication-mediated habitat changes

Coastal lagoons, as transitional ecosystems, are crucial for providing ecosystem services and preserving fish communities, yet they face increasing pressures from anthropogenic activities. The Mar Menor coastal lagoon in the western Mediterranean exemplifies this challenge, as it suffers from severe eutrophication driven by agricultural and urban influences. In this study, we assess changes in the population dynamics of three resident fish species (Apricaphanius iberus, Pomatoschistus marmoratus, and Syngnathus abaster) in the context of human-induced impacts in the Mar Menor. Using long-term monitoring data (the reference period of 2002-2004 vs. the eutrophication period of 2015-2019), we analyze temporal variations in their population dynamics and their relationships with eutrophication-mediated structural changes in shallow waters. Our results suggest that these resident species, which are closely associated with shallow areas, show population dynamics that reflect habitat alterations, underscoring their potential as indicators of eutrophication impacts. This study enhances our understanding of the dynamics within transitional ecosystems and provides a basis for integrated management strategies aimed at promoting effective fish conservation.

Character-based Identification System (CBIS) for Authentication and Conservation of Fishes from the Thamirabarani River, Western Ghats of India

Background: Accurate identification of freshwater fish is essential to preserving freshwater fish diversity. BLOG uses a short DNA sequence taken from a portion of mitochondrial DNA called Cytochrome C Oxidase subunit I (COI), which varies by several percent, even between closely related species, so it can be used to identify the species of a particular individual. Methods: BLOG 2.0 is an advancement of logic data mining and can identify nucleotide positions that characterize DNA barcode sequences and classify species using logic formulas. This character-based identification method identifies specimens to species with the help of their logic rules and diagnostic nucleotides in the selected gene sequences. In this study, 30 species distributed in the Indian freshwater region were taken as the target group. A 30 -110 mtCOI sequences for each species were downloaded and modified. Results: With the help of BLOG.2.0 software, to identified specific diagnostic nucleotides for these freshwater species. Species-specific probes ranging from 18-22 base pairs were designed based on identified diagnostic nucleotide sites that could be useful in customized microarrays (DNA chips). This BLOG based CBIS will be a promising technique for obtaining quick, convenient, and extensive knowledge about the conservation of various freshwater fishes and their forensic applications.

Farm dams: A valuable interim step in small‐bodied threatened fish conservation

AbstractFreshwater fish are facing an extinction crisis on a global scale, with increasing demand for human water consumption driving the regulation and degradation of freshwater ecosystems. Flow regulation especially poses a threat to small‐bodied floodplain and creek specialist species through increasing population fragmentation and isolation, loss and degradation of habitats, and interactions with predators and competitors, resulting in reductions in species' range and abundance. Conserving and recovering many small‐bodied fish species will likely require translocation from wild habitats to refuge habitats to reduce extinction risk and provide buffers against catastrophic natural events (e.g., drought, bushfires). We assessed the value of semi‐artificial farm dams, an abundant feature in the Australian landscape, as interim refugia for the threatened southern pygmy perch Nannoperca australis (Percicthyidae). We compared the relative abundance, population size–structure and body condition of fish introduced (3–4 years prior) into three farm dams with those of three nearby creeks to assess the feasibility of farm dams as a resource to assist small‐bodied native fish conservation and recovery. Farm dams had higher abundance of fish, and equivalent size structure and body condition compared with creek populations, highlighting that suitable farm dams are a valuable and underutilized asset for threatened species' conservation globally.

Length in assessing status of freshwater fish populations: A review

AbstractObjectiveEffective policy formulation regarding the conservation of freshwater fish necessitates an understanding of water‐specific prevailing conditions and trends. Assessing fish populations in inland waters is difficult and expensive because there are many independent systems that need to be evaluated. Therefore, numerous freshwater systems are beset by insufficient data and the lack of systematic assessments of their status. To alleviate this deficiency, the objective of this study was to review length‐based metrics that may have utility in evaluating the well‐being of freshwater fish populations.MethodsLength measurements can serve as proxies for a range of ecological and population dynamics attributes that are essential for the effective management of fish and associated fisheries. A review of the historical development of length measurements in fish conservation is provided, along with an examination of the potential biases that may arise from the use of lengths in practical contexts. In addition, we examine techniques that enable the spatial and temporal visualization of length data sets, as well as a range of indices and metrics that can be computed using length measurements.ResultBuilding populations assessments around length may be a cost‐effective strategy that allows a first cut at managing a large number of waters. Length‐based assessments can signal if management intervention is necessary, if management policies are yielding the intended outcome, or if surveys beyond mere length are necessary.ConclusionOur review indicates that length offers a straightforward and efficient approach to evaluate the status of fish populations in inland systems. We encourage pursuing additional study and to this end propose specific areas for investigation.

Comparison Study of Hydrodynamic Characteristics in Different Swimming Modes of Carassius auratus

This study utilized particle image velocimetry (PIV) to analyze the kinematic and hydrodynamic characteristics of juvenile goldfish across three swimming modes: forward swimming, burst and coast, and turning. The results demonstrated that C-shaped turning exhibited the highest speed, enabling rapid and agile maneuvers for predator evasion. Meanwhile, forward swimming was optimal for sustained locomotion, and burst-and-coast swimming was suited for predatory behaviors. A vorticity analysis revealed that vorticity around the tail fin was the primary source of propulsive force, corroborating the correlation between vorticity magnitude and propulsion found in previous research. The findings emphasize the crucial role of the tail fin in swimming efficiency and performance. Future research should integrate ethology, biomechanics, and physiology to deepen the understanding of fish locomotion, potentially informing the design of efficient biomimetic underwater robots and contributing to fish conservation efforts.

Long‐term effects of tagging fishes with electronic tracking devices

AbstractTagging fishes with internal or external electronic tracking devices (acoustic, radio, satellite, or archival tags) is invaluable to behavioural, ecological, and welfare research, but may have adverse effects on the animals studied. While short‐term responses to tagging (e.g., days to weeks) have often been investigated, less information is available on longer‐term impacts (e.g., months to years) and the potential chronic effects of tagging on basic biological needs such as foraging and reproduction. Here, we synthesize existing knowledge from peer‐reviewed acoustic, radio, satellite, and archival tagging articles (n = 149) and anecdotal accounts (n = 72) from 36 researchers to assess the effects of tagging over prolonged periods. We identified a dearth of research that has specifically measured or quantified the impacts of tagging over a period longer than a few weeks or months (e.g., median experimental study duration = 33 days; n = 120 articles). Nevertheless, there was limited evidence to support a net negative long‐term impact from the implantation or attachment of electronic devices. Considerations and future research directions are discussed with the goal of generating guidance to the research community and minimizing potentially detrimental impacts to study animals. Given the global application and relevance of electronic tagging research to inform conservation and management of fishes, it is imperative for scientists to continue evaluating how tagging procedures affect animal welfare, fate, and the interpretation of tracking data.

The effect of hydrological variability on stepped fishways

River systems are highly dynamic, affecting all associated structures and their derived uses. This is particularly relevant for applications such as hydropower production and other water abstractions. This dynamic nature also extends to mitigation measures like fishways, which are vital for reducing the impact of river fragmentation on fish populations. Fishways must be designed to balance biological and hydraulic fish requirements, needing adaptability to varying boundary conditions. This study examines the effect of hydrological variability on fish passage through fishways, particularly for the Iberian barbel (Luciobarbus bocagei). We hypothesized that hydrological scenarios can significantly affect upstream fish passage. To test this, we conducted laboratory and field studies, assessing fish movement under different boundary conditions. We compared passage rates, time metrics, and their correlations with the evolution of fishway hydraulics, and employed survival analysis to determine biometric limits. Our findings show that hydrological changes markedly influenced fish passage rates and timings, producing fish size selection and highlighting the impact of factors such as maximum velocity and power dissipation in the studied metrics. These insights underline the necessity of incorporating hydrological variability into fishway design and management, enhancing their effectiveness for fish conservation in river ecosystems, particularly under growing climatic uncertainties. This research underscores and discusses the need for comprehensive, long-term hydrodynamic studies in fishway assessment and design, advocating for adaptive management strategies to accommodate environmental changes.