Management Of Fish Populations Research Articles

Combining Local Ecological Knowledge (LEK) and Conventional Scientific Knowledge (CSK) for Exploring Nursery Grounds and Spawning Biology of Yellowtail Catfish Pangasius pangasius in the Meghna River Estuary, Bangladesh

ABSTRACTThe yellowtail catfish (Pangasius pangasius) population in Bangladesh is facing imminent threats that led to endangered status. We used conventional scientific knowledge (CSK) and local ecological knowledge (LEK) of fishers (n = 155) to identify nursery grounds and spawning seasons of yellowtail catfish in the Meghna river estuary. Nineteen nursery grounds were pinpointed using fishers' LEK (confluence/influent zone, current, depth, catch data, and turbidity) and later validated by CPUE data. The peak spawning season was identified in July–September based on GSI (gonadosomatic index) and LEK (58.06% of fishers identified the spawning season). Fecundity (810,980 ± 455,679) and condition factor (0.94–1.52) were quantified with CSK. Using CSK and LEK to delineate nursery grounds and spawning season underscores the value of LEK as a tool for fish population management that deserves policy recommendation and wider application.

A Fish Target Identification and Counting Method Based on DIDSON Sonar and YOLOv5 Model

In order to more accurately and quickly identify and count underwater fish targets, and to address the issues of excessive reliance on manual processes and low processing efficiency in the identification and counting of fish targets using sonar data, a method based on DIDSON and YOLOv5 for fish target identification and counting is proposed. This study is based on YOLOv5, which trains a recognition model by identifying fish targets in each frame of DIDSON images and uses the DeepSort algorithm to track and count fish targets. Field data collection was conducted at Chenhang Reservoir in Shanghai, and this method was used to process and verify the results. The accuracy of random sampling was 83.56%, and the average accuracy of survey line detection was 84.28%. Compared with the traditional method of using Echoview to process sonar data, the YOLOv5 based method replaces the step that requires manual participation, significantly reducing the time required for data processing while maintaining the same accuracy, providing faster and more effective technical support for monitoring and managing fish populations.

Predicting fish spawning phenology for adaptive management: Integrating thermal drivers and fishery constraints

Climate warming is causing shifts in reproductive phenology, a crucial life history trait determining offspring survival and population productivity. Evaluating these impacts on exploited marine resources is essential for implementing adaptive measures from an ecosystemic approach. This study introduces a statistical model designed to predict fish spawning phenology from sea surface temperature profiles, integrating mortality-corrected hatch-date distributions inferred from fishery-dependent samplings, along with the gonadosomatic index of adult individuals. When applied to different dolphinfish (Coryphaena hippurus) populations across a broad latitudinal range, the model reasonably predicts the spawning phenology across its extensive thermal ranges, elucidating a direct relationship between mean annual temperature and the breadth of the spawning season. Despite the varying thermal profiles, results show a consistent timing of spawning peaks approximately 49 days before the peak in temperature. Importantly, these findings account for the impact of fishery constraints, such as seasonal closures or different sampling schedules, offering a robust tool for adjusting management practices in response to inter-annual temperature variations. These insights are critical for both short-term fishery management, including the strategic planning of seasonal closures, and long-term projections of spawning phenology shifts under changing thermal regimes. By enhancing our ability to predict spawning times, this research contributes significantly to the sustainable management of fish populations and the adaptive response to environmental changes.

A problem for the ages: Achieving reliable fish age information through quality management

Age information is central to assessment and management of fish populations. Age information must be reliable to have value, which depends on its quality. Quality assurance (QA) and quality control (QC) are processes often applied to some aspects of producing age information (e.g., annulus validation). However, we advocate for a more holistic approach which leverages QA/QC measures across all phases of the age information-generating process. Systematic implementation of QA/QC measures in a repetitive process is common in the manufacturing industry where it is known as a quality management system (QMS) but this framework is not well described in the fisheries literature. We designed and implemented a QMS that incorporates QA/QC measures across all phases of fish age information development: Collection, Interpretation, and Distribution. These measures are guided by six principles: Train, Simplify, Validate, Compare, Record, and Improve. In our QMS, the Train, Simplify, and Validate principles are largely guidance for QA measures, while Compare, Record, and Improve guide QC measures. We provide examples of common errors (or sources of error) in each phase, and how the guiding principles in our QMS address these errors. This is a QMS crafted as a holistic approach to managing the quality of fish age information; however, it has broad application as a conceptual framework for other repetitive processes in fisheries.

Morphometrics and Truss-networking distances among three species of croaker (Johnius borneensis, Johnius argentatus and Johnius belangerii) from Bangladesh coast of the Bay of Bengal

Morphometric features are efficiently used for the differentiation of species and long-term management of fish populations. Truss analysis is a frequently used taxonomic method as well as a stock identification tool to dissimilitude the morphologically similar species. Using landmark-based truss networking techniques following 18 morphometric lengths, 10 meristic counts, and 23 truss-network distance, the morphological variation of three croaker species viz. Johnius borneensis, Johnius argentatus, and Johnius belangerii were examined from Bangladesh coast. Data were analyzed and visualized through univariate ANOVA, canonical discriminate function analysis (DFA), and principal component analysis (PCA). Results found that the first DFA was responsible for 80.6% & 81.1%, whereas the second DFA was responsible for 19.4% & 18.9% variations among three species for the morphometric and truss-distances, respectively. In addition, 14 out of 18 morphometric and 12 out of 23 truss-network measurements were significantly different (p < 0.05) among means of three species. 1st PCA found 70.76% & 64.49% explained variations and 2nd PCA displayed 12.8% & 11.5% explained variations respectively for morphometric and truss distances. The findings of the study demonstrates that J. borneensis and J. belangerii are highly morphologically similar and J. argentatus is completely distinct which might be due to their physiological and genetic variations. The present study might be helpful in differentiating species and managing existing stocks of marine fish. Further studies regarding the molecular characterization of the Cytochrome c oxidase subunit I (COI) gene could confirm the genetic variations among these species. Bangladesh J. Zool. 51(3): 233-251, 2023

Pengembangan Sistem Kontrol Populasi Ikan Berbasis Arduino Uno dengan Sensor Ultrasonik

Fish populations are one of the important assets in maintaining the balance of aquatic ecosystems. To manage fish populations effectively, an innovative and automated approach is needed. This research aims to develop an Arduino Uno-based fish population control system with ultrasonic sensors as an environmentally friendly and efficient solution. The developed system uses ultrasonic sensors to detect the presence of fish in a pond or water container. The detection data from the ultrasonic sensor is then processed by the Arduino Uno microcontroller. The system can identify the number of fish in aquatic containers and take appropriate action to control fish populations. This research integrates ultrasonic sensor technology with Arduino Uno control capabilities to provide an accurate and automated solution in controlling fish populations. In trials, this system succeeded in identifying and controlling fish populations well, maintaining the balance of aquatic ecosystems without the need for direct human intervention The results of this research have great potential in fish farming applications, environmental research, and natural resource conservation. With the proposed automated approach, it is expected to make a positive contribution in maintaining the balance of aquatic ecosystems and supporting environmental sustainability

Population Size Structure and Length–Weight Relationships of Selected Pelagic Fishes From The Gambian Waters (West Africa)

The population size structure and length–weight relationships (LWRs) are fundamental tools in fishery science, providing valuable insights into the health, dynamics, and management of fish populations and contributing to the sustainable use of aquatic resources. The data used in this study were estimates from the main small pelagic fishes exploited in the Gambia. They were collected using surface and bottom gillnets between November 2020 and October 2021 during scientific fishing operations. The main small pelagic fish size composition showed a modal class of 20 cm for Ethmalosa fimbriata, 21 cm for Sardinella aurita, 22 cm for Sardinella maderensis, and 30 cm for Trachurus trecae. The parameter b value of these fish species ranged from 1.6831 to 2.9461, and the correlation coefficient ranged from 0.81 to 0.95. Statistical LWRs for all species were very significant. Information obtained is essential in reviewing and establishing basic management measures for depleted shared pelagic stocks in the Gambian fisheries and the sub‐region. In the context of poor data fisheries, such results also encourage the Gambian government and intergovernmental subregional organizations to support data collection in the long term.

Aquaculture and Fisheries Science Sustainable Practices in Marine and Freshwater Systems

This article delves into the evolving realm of Aquaculture and Fisheries Science, with a focus on sustainable practices in both marine and freshwater systems. It presents a comprehensive overview of the current state of these industries, including their global impact, economic significance, and the crucial role they play in ensuring food security. The challenges faced by these sectors, particularly in the context of sustainability, are thoroughly examined. These challenges encompass overfishing, environmental degradation, and the effects of climate change on aquatic ecosystems. The article highlights innovative and eco-friendly practices being adopted in aquaculture, such as integrated multi-trophic aquaculture, advancements in breeding, and efficient feed management. In the realm of fisheries, it discusses the implementation of effective management strategies like quota systems and the establishment of marine protected areas. The role of modern technology in enhancing sustainability is also explored, showcasing the potential of AI, satellite monitoring, and advanced tracking systems in improving fish population management and ecosystem conservation. Furthermore, the socio-economic dimensions of sustainable aquaculture and fisheries are analyzed, emphasizing the importance of policy, governance, and community involvement.

Dynamics of sustainable fisheries: a mathematical approach using Lotka-Volterra equations

This study delves into the intricate dynamics of sustainable fisheries through the lens of mathematical modeling, specifically employing the Lotka-Volterra equa-tions. The Lotka-Volterra equations, originally conceived to understand predator-prey interactions, offer a potent framework to model and predict fish population dynamics within aquatic ecosystems. The aim of this research is to demonstrate the applicability and efficacy of the Lotka-Volterra equations in understanding the delicate balance of fish populations and aiding sustainable fisheries man-agement. Through this mathematical approach, we seek to provide a structured methodology and present results that showcase the potential of this model in pre-dicting and managing fish populations. In our analysis, we adjust the parameters of the Lotka-Volterra equations to simulate various scenarios, enabling a compre-hensive understanding of sustainable fishing practices. Our findings underscore the significance of mathematical models, particularly the Lotka-Volterra equa-tions, in informing strategies to maintain fish populations in a sustainable and ecologically balanced manner, thereby ensuring the longevity of marine ecosys-tems and the fisheries that rely upon them.Keywords: Runge-Kutta, Two-step, Exponentially-fitted, Periodic; Oscillatory;

Digital twins for land-based aquaculture: A case study for rainbow trout (Oncorhynchus mykiss)

The virtual, digital counterpart of a physical object, referred as digital twin, derives from the Internet of Things (IoT), and involves real-time acquisition and processing of large data sets. A fully implemented system ultimately enables real-time and remote management, as well as the reproduction of real and forecasted scenarios. Under the emerging framework of Precision Fish Farming, which brings control-engineering principles to fish production, we set up digital twin prototypes for land-based finfish farms. The digital twin is aimed at supporting producers in optimizing feeding practices, oxygen supply and fish population management with respect to 1) fish growth performances; 2) fish welfare, and 3) environmental loads. It relies on integrated mathematical models which are fed with data from in-situ sensors and from external sources, and simulate several dynamic processes, allowing the estimation of key parameters describing the ambient environment and the fishes. A conceptual application targeted at rearing cycles of rainbow trout (Oncorhynchus mykiss) in an operational in-land aquafarm in Italy is presented. The digital twin takes into account the disparate levels of automation and control that are found within this farm, and considerations are made on preferential directions for future developments. In spite of its potential, and not only in the aquaculture sector, the development of digital twins is still at its early stage. Furthermore, Precision Fish Farming applications in land-based systems as well as targeted at rainbow trout are novel developments.

Accurate, non-destructive, and high-throughput age estimation for Golden perch (Macquaria ambigua spp.) using DNA methylation

Age structure information of animal populations is fundamental to their conservation and management. In fisheries, age is routinely obtained by counting daily or annual increments in calcified structures (e.g., otoliths) which requires lethal sampling. Recently, DNA methylation has been shown to estimate age using DNA extracted from fin tissue without the need to kill the fish. In this study we used conserved known age-associated sites from the zebrafish (Danio rerio) genome to predict the age of golden perch (Macquaria ambigua), a large-bodied native fish from eastern Australia. Individuals aged using validated otolith techniques from across the species’ distribution were used to calibrate three epigenetic clocks. One clock was calibrated using daily (daily clock) and another with annual (annual clock) otolith increment counts, respectively. A third used both daily and annual increments (universal clock). We found a high correlation between the otolith and epigenetic age (Pearson correlation > 0.94) across all clocks. The median absolute error was 2.4 days in the daily clock, 184.6 days in the annual clock, and 74.5 days in the universal clock. Our study demonstrates the emerging utility of epigenetic clocks as non-lethal and high-throughput tools for obtaining age estimates to support the management of fish populations and fisheries.

Insight into the trophic niche and prey contribution in the diet of Lutjanus griseus (Linnaeus, 1758) captured by artisanal fishing fleet in the central and southwest Gulf of Mexico

Lutjanus griseus is a common species for fisheries of the Gulf of Mexico, and it is an effective vehicle to transport energy from low to top trophic levels in the ecosystem. The management of fish populations is based on the modeling and prediction of abundances. To accomplish this, trophic ecology results allow the understanding of habitat use and population expansions. To increase the knowledge in the trophic ecology of L. griseus, this study described its trophic niche, diet composition, and the prey contribution in the formation of muscle tissue. Results showed that the trophic niche in Veracruz was wider than in Campeche, this related to the consumption of prey in different habitats, coral reefs areas in Veracruz and seagrass beds in Campeche. According to the δ13C y δ15N values, in both regions the crustaceans were the most important group in the contribution of muscle tissue, however, it contrasted with the stomach content results, which suggested that the diet in Campeche was mainly composed of crustaceans, and in Veracruz of fishes. This difference could be related to the snapper’s movements, as they can be found in sea bottoms covered with seagrass, with high abundance of crustaceans, and sea bottoms composed of coral reefs with high diversity of fishes and other preys. Results highlight the generalist and opportunistic feeding strategy of L. griseus, this strategy allowed its population expansion to the north, consuming the available food source in the different habitats it occupied.

Balancing Physical Channel Stability and Aquatic Ecological Function through River Restoration

Vortex rock weirs (VRW) are often used in natural channel design applications to maintain channel form and function, provide physical channel stability, and enhance aquatic habitats. A balanced approach is required to address (often) conflicting goals of VRWs, which include providing erosion protection and grade control while facilitating fish passage for target species. This research evaluated a sequence of modified VRWs in a small-scale watercourse in Southern Ontario, Canada. To determine passage suitability for the target fish species, the water level, water temperature, and channel geometries at 10 VRWs and 11 adjacent pools were monitored under different water level conditions. The structural dimensions and velocity at each VRW were compared to the burst swim speed of local small-bodied fish species to determine fish passage suitability and identify the best practices for VRW design and construction. The results concluded that VRWs provided suitable passage for small-bodied fish species through gap and over-weir flow pathways, particularly during low water level conditions. Further, appropriate design considerations based on the VRW gradient, VRW width, keystone size, and pool length contributed to 100% fish ‘passability’ under all water level conditions. The methodology is provided for predicting the velocity and small-bodied fish passage suitability through VRWs, informing the best practices for VRW design and construction while balancing the requirements for channel stability and fish passage, and contributing to fish population management strategies.

Relative Condition Parameters for Fishes of Montana, USA

Body condition indices are commonly used in the management of fish populations and are a surrogate to physiological attributes such as tissue-energy reserves. Relative condition factor (Kn) describes the condition of species relative to populations in a geographic area. We developed models to allow for the calculation of Kn in Montana, USA by using the weight–length data collected by Montana Fish, Wildlife & Parks. We generated log10weight–log10length relationships to obtain Montana specific parameter estimates for relative condition equations (W′) for 51 species and three subspecies. We developed separate models by water type (e.g., lotic and lentic) and sex for five species due to varying growth based on sexual dimorphism and varying ecosystem types. Relative condition offers the advantage of describing body condition relative to species in Montana, provides a condition index for species that do not have standard-weight models developed for relative weight (Wr), and affords more information for the global database on weight–length relationships of fishes.

Thermal performance of the electron transport system Complex III in seven Alabama fishes.

Management of fish populations for conservation in thermally variable systems requires an understanding of the fish's underlying physiology and responses to thermal stress. Physiological research at the organismal level provides information on the overall effects of stressors such as extreme temperature fluctuations. While experiments with whole organisms provide information as to the overall effects of temperature fluctuations, biochemical assays of thermal stress provide direct results of exposure that are both sensitive and specific. Electron transport system (ETS;Complex III) assays quantify a rate-limiting step of respiratory enzymes. Parameters that can be estimated via this approach include optimum thermal temperature (Topt ) and optimal breadth of thermal performance (Tbreadth ), which can both be related to organismal-level temperature thresholds. We exposed enzymes of seven fish species (native fish chosen to represent a typical community in Alabama streams) to temperatures in the range 11-44°C. The resultant enzymatic thermal performance curves showed that Topt , the lower temperature for enzyme optimal thermal performance (Tlow ), the upper temperature for enzyme optimal thermal performance (Tup ), and Tbreadth differed among species. Relationships between enzymatic activity and temperature for all fish followed a pattern of steadily increasing enzyme activity to Topt before gradually decreasing with increasing temperature. A comparison of our enzyme optimum and upper-temperature limit results versus published critical thermal maxima values supports that ETS Complex III assays may be useful for assessing organismal-level thermal tolerance.

Rotenone encapsulated in pH-responsive alginate-based microspheres reduces toxicity to zebrafish

Rotenone is a botanical pesticide and has long been used for control of insect pests and also as a natural piscicide for management of fish populations in many countries. Field application for pest control, however, often encounters the movement of rotenone into surface water due to spray drift or surface runoff after rainfall, which could potentially result in water pollution and unexpected death of fishes. To minimize its effect on freshwater and the problem of fish dying, one solution was to encapsulate rotenone in specific microspheres, limiting its release and reducing its toxicity since rotenone can be quickly degraded under sunlight. In this study, pH-responsive alginate-based microspheres were synthesized to encapsulating rotenone, which were designated as rotenone beads. The rotenone beads, along with alginate beads (devoid of rotenone) were characterized and evaluated for their responses to pH and effects on zebrafish. Results showed that the microspheres had high loading efficiency (4.41%, w/w) for rotenone, and rotenone beads well responded to solution pH levels. The cumulative release rates of rotenone from the beads were 27.91%, 42.72%, and 90.24% at pH 5.5, 7.0, and 9.0, respectively. Under acidic conditions, the rotenone release rate was lower due to hydrogen bonding. On the contrary, rotenone became more quickly released at the high pH due to intermolecular repulsion. The toxicity of rotenone beads to zebrafish and fish embryos at a pH of 5.5 was reduced by 2- and 4-fold than chemical rotenone. Since pH levels in most freshwater lakes, ponds, and streams vary from 6 to 8, rotenone release from the beads in such freshwater could be limited. Thus, the synthesized rotenone beads could be relatively safely used for pest control with limited effects on freshwater fishers.

Effects of capture depth on walleye hooking mortality during ice fishing

Lyon CA, Davis JL, Fincel MJ, Chipps SR. 2022. Effects of capture depth on walleye hooking mortality during ice fishing. Lake Reserv Manage. XX:XXX–XXX. Length-based regulations are a common tool used to limit fishing mortality by controlling the size of fish harvested. While such regulations are helpful in managing fish populations, mortality associated with catch-and-release fishing may negatively impact a fishery. We evaluated factors affecting hooking mortality of walleye (Sander vitreus) in 2 mainstem Missouri River reservoirs in South Dakota. Winter walleye hooking mortality was evaluated during the ice fishing season in February and March 2020. After capture, walleye (n = 55) were placed into holding pens for 12 to 72 h to monitor postrelease mortality. Hooking mortality was found to be 20% following angling. Capture depth, landing time, and time in pen were the most influential variables on probability of hooking mortality (pm ). We observed a sharp increase in pm for walleye captured at depths from 10 to 12 m, where the probability of mortality for fish increased appreciably from 5 to 37%, respectively. Our findings indicate that hooking mortality during the ice fishing season can be substantial in lakes where walleye angling occurs at depths greater than 10 m.

The behavioural ecology toolkit for fish management and conservation

AbstractFishes include some of the most threatened vertebrate species globally. As such, efforts to effectively conserve and manage fish populations and their habitats are vast. Here, we present conceptual tools from behavioural ecology to establish a framework for studies of fish conservation and management, connecting questions relevant to managers and practitioners with behavioural theories and methodologies. We apply predictions developed from a theory to diet choice, patch use, habitat selection, movement, and social behaviours. We present questions and issues in fisheries management and conservation for which theory, hypotheses, and methodologies would be both novel and complementary to current assessment strategies or conservation efficacy studies. In each case, theory approaches the ecological trade‐offs associated with a given behavioural trait through the lens of adaptations and fitness implications—the foundational principles of behavioural ecology. We show key methodologies used to effectively apply behavioural theory to specific hypotheses relevant to a given management question. We then compile the conceptual and methodological approaches to assemble a toolkit through which fisheries managers may assess, for example, habitat selection behaviours via novel study designs and/or new ways of interpreting commonly collected data (e.g., distribution and abundance relative to habitat type). Finally, we propose training of aquatic and marine natural resource specialists and conservation agency fish biologists be complemented with behavioural ecology theories and methodologies.

Evidence of flow and low genetic structure between populations of the Gulf of Mexico and the Mexican Pacific of white mullet, Mugil curema (Pisces) inferred from single nucleotide polymorphisms

Population genomics methodologies offer new tools for fine structure identification and contemporary connectivity, providing valuable information for the conservation and management of fish populations. NextRAD sequencing was used for obtaining single nucleotide polymorphisms (SNPs) throughout the Mugil curema genome, a species of fish of great ecological and commercial importance, with a wide genetic dissimilarity between its populations throughout its distribution. The population structure, connectivity, and genomic diversity of 95 individuals from three locations in the Gulf of Mexico (GoM) and six in the Mexican Pacific (MP) were evaluated with a set of 14, 172 SNPs. The spatial analyses identified three genetic groups with incipient divergence (FST= 0.1–0.513), low nucleotide diversity (π = 0.019–0.200), and moderate gene flow among populations (2.4–12.8 %). The first group included two localities of the GoM (Madre and Alvarado lagoons) connected with two of the MP (Huave System (HU) and Puerto Escondido (PE)), which presented a moderate exchange of genotypes of 10.5–11.1 % between both slopes, which could be due to the connection between sub-basins or tributaries of the Gulf of Tehuantepec region; the second connected the six localities of the MP; and the third only to individuals from Celestun (CE), a population that could be under a recent divergence process, due to the accumulation of their ecological, environmental and genetic differences. The results reflect a low contemporaneous population genomic structure and connectivity of Mugil curema in the GoM and MP, in addition, they do not support the mitochondrial hypotheses of the cryptic species Mugil curema “T2″ from the Atlantic and Mugil sp. "O" of the Pacific.

Improving trophic niche and diet resolution of the salmonid community of Lake Ontario using three stable isotopes and multiple tissues

Salmonids are ecologically and economically important fishes in Lake Ontario but declines in Alewife (Alosa pseudoharengus), recently the primary prey item, may cause shifts in salmonid diets. Improving our understanding of salmonid trophic niches and diets and whether these have changed over time will provide insight into salmonid foraging patterns, ecology, and management. Using three stable isotopes (δ13C, δ15N and δ34S) and Bayesian models, we estimated core trophic niches, niche overlaps among species, and diets for six salmonid species from Lake Ontario sampled during 2018. We used fin and muscle tissue with different temporal assimilation periods to assess seasonal variability in diet, and investigated salmonid trophic niches and diets among three major spatial units (East, Central, West). Overall, core trophic niches overlapped across all species, except Lake Trout (Salvelinus namaycush). Consistent with previous lake-wide analyses of Lake Ontario salmonid diets, Alewife were the preferred prey fish, although Lake Trout and Atlantic Salmon (Salmo salar) had more varied diets, particularly based on white muscle. Fin-based isotope mixing models predicted greater consumption of shallow (< 30 m depth) Round Goby (Neogobius melanostomus) for Lake Trout, Brown Trout (Salmo trutta), and Rainbow Trout (Oncorhynchus mykiss) than other salmonids, indicating seasonal variation in diets. Lake Trout and Brown Trout also varied across spatial units with greater Round Goby consumption in western Lake Ontario. Spatially distinct diets suggest that Brown Trout and Lake Trout populations should be monitored regionally. Understanding prey consumption trends are important to effectively manage fish populations, especially considering on-going ecological changes in the Great Lakes.