Fish Age Research Articles

Trophic Structure and a Temporal Shift in Trophic Diversity of Mobile Consumers in a Subarctic Estuary

Quantifying trophic relationships within and between species in terms of trophic position, ontogeny and trophic diversity provides information on community-level structure and function. Little attention has been focused on examining the trophic structure and temporal changes of communities in freshwater-marine coupled systems in the subarctic and associated impacts of anthropogenic activity on trophic interactions. Therefore, the objective of this study was to quantify the trophic position of mobile consumers (15 species in total) within the lower Churchill River area (Churchill, Manitoba, Canada), examine trophic position variation in relation to ontogeny, and measure the trophic diversity of a fish assemblage before (1993–1995) and after (2019–2020) the installation of the Churchill River weir in the late 1990s. We used stable isotopes (δ13C and δ15N) to quantify individual and group-level variation in trophic position of thirteen fish species and two seal species and also assessed six community-level metrics of a three fish species assemblage between time periods. Overall, species that mainly foraged on freshwater resources occupied lower trophic positions than species that mainly consumed marine resources. Trophic position increased with fish age only in cisco, fourhorn sculpin, Greenland cod and northern pike. A temporal shift from a trophically diverse to a more trophically redundant fish assemblage occurred between 1993–1995 and 2019–2020. As a result, these predator species now play similar trophic roles. Information on the long-term change in trophic structure of this sub-Arctic estuarine system may help with understanding how anthropogenic activity and climate change have influenced the trophic diversity of a fish assemblage inhabiting this system.

Annotating otoliths with a deep generative model

Abstract Otoliths are a central information source for fish ecology and stock management, conveying important data about age and other life history for individual fish. Traditionally, interpretation of otoliths has required skilled expert readers, but recently deep learning classification and regression models have been trained to extract fish age from images of otoliths from a variety of species. Despite high accuracy in many cases, the adoption of such models in fisheries management has been slow. One reason may be that the underlying mechanisms the model uses to derive its results from the data are opaque, and this lack of legibility makes it challenging to build sufficient trust in the results. Here, we implement a deep learning model that instead of age predicts the location of annotation marks for each of the annuli. This allows an expert to evaluate the model’s performance in detail. The quality of the annotations was judged by a panel of four expert otolith readers in a double-blinded randomized survey. Using a scale from 1 to 5, the generated marks received an average quality score of 4.22, whereas expert annotations received an average score of 4.33. By counting the marks to determine fish age, we obtained an agreement between expert and model annotations of 64% on our test set, which running the model stochastically increased to 69%. Stochastic sampling yields further benefits, including an explicit measure of the model’s uncertainty, the post hoc likelihood of the different age classes for each otolith, and a set of alternative annotation sequences that highlight the structure of the annuli.

Size-based indicators for assessments of ecological status of coastal fish communities

Abstract Human impact does not only affect the abundances of fish, but also the age- and size-distributions. Indicators of fish age and size-structures can hence be useful tools for fisheries- and environmental management. Size-based indicators have been tested and proposed for large, homogenous marine ecosystems with high fishing mortality, but rarely for fine-scaled heterogeneous ecosystems in coastal zones. Here we analyse a suite of size indicators for coastal fish communities in the Baltic Sea, including mean and median length, 10th and 90th-percentile of the length distribution (L10, L90), mean length of the 10% largest fish (Lmax), large fish indices, size-spectra, and size-diversity. Results show good precision and accuracy of most indicators at realistic sample sizes, except for size-spectra and size-diversity, making them less suitable. Different indicators showed correlations among sites, indicating similar responses to environmental variation. Most size indicators responded positively to lower fishing pressure, especially indicators emphasizing the largest individuals in the population (e.g. L90 and Lmax), whereas eutrophication and physical disturbances had less impact. We conclude that size-based indicators aiming at describing the occurrence of larger fish, like L90 and Lmax, are useful for establishing management targets and assessing the status of coastal fish.

The Distribution of IgT mRNA+ Cells in the Gut of the Atlantic Salmon (Salmo salar L.).

The newly discovered IgT+ B cell is thought to play a dominant role in mucosal immunity, but limited studies have examined its distribution in fish species, hindering our understanding of its function. This study investigated IgT and poly Ig receptor (pIgR) mRNA+ cell distribution in Atlantic salmon (Salmo salar) gut using RNAscope in situ hybridization (ISH) and assessed the effects of vaccination. The pyloric caeca, mid-intestine (first and second parts), and posterior segment in two weight stages (Group 1: avg. 153 g, Group 2: avg. 1717 g) were examined in both vaccinated and unvaccinated fish. ISH revealed more IgT mRNA+ cells in the second part of the midgut compared to other intestinal segments, as well as a higher number of positive cells in Group 2 (older fish). In line with previous findings, intraperitoneal vaccination had no significant impact on the number of IgT+ transcripts. IgT mRNA+ cells were found mostly in the lamina propria and near capillaries, while pIgR was registered in both the lamina propria and mucosa. Interestingly, vaccinated fish presented adhesions and granulomatous tissue in the peritoneum, with both IgT and pIgR mRNA+ cells. Taken together, these results suggest that the distribution of IgT mRNA+ cells in the intestine of Atlantic salmon is region-specific and is not affected by intraperitoneal vaccination but varies with fish age.

Discrimination of Schizothorax grahami (Regan, 1904) Stocks Based on Otolith Morphology

Otoliths grow throughout a fish’s life and are important for identifying fish stocks and fish age. This study aims to differentiate different stocks of Schizothorax grahami (Regan, 1904) in the Chishui River, an upper reach of the Yangtze River, by otolith morphology. The otolith morphology of S. grahami from three different river sections was analyzed using the Shape Index, Fourier coefficients, and wavelet coefficients. The composite discrimination success rate of the Shape Index was 59.7%, and it was difficult to distinguish in the scatter plots. In contrast, canonical principal coordinate scatter plots clearly showed three distinguished stocks. The above results indicate that otolith morphology can discriminate between stocks in plateau endemic fish, and several S. grahami stocks may be separately managed in the Chishui River.

Fitting Time Series Models to Fisheries Data to Ascertain Age

The ability of government agencies to assign accurate ages of fish is important to fisheries management. Accurate ageing allows for most reliable age-based models to be used to support sustainability and maximize economic benefit. Assigning age relies on validating putative annual marks by evaluating accretional material laid down in patterns in fish ear bones, typically by marginal increment analysis. These patterns often take the shape of a sawtooth wave with an abrupt drop in accretion yearly to form an annual band and are typically validated qualitatively. Researchers have shown key interest in modeling marginal increments to verify the marks do, in fact, occur yearly. However, it has been challenging in finding the best model to predict this sawtooth wave pattern. We propose three new applications of time series models to validate the existence of the yearly sawtooth wave patterned data: autoregressive integrated moving average (ARIMA), unobserved component, and copula. These methods are expected to enable the identification of yearly patterns in accretion. ARIMA and unobserved components account for the dependence of observations and error, while copula incorporates a variety of marginal distributions and dependence structures. The unobserved component model produced the best results (AIC: −123.7, MSE 0.00626), followed by the time series model (AIC: −117.292, MSE: 0.0081), and then the copula model (AIC: −96.62, Kendall’s tau: −0.5503). The unobserved component model performed best due to the completeness of the dataset. In conclusion, all three models are effective tools to validate yearly accretional patterns in fish ear bones despite their differences in constraints and assumptions.

Age interpretation of cod otoliths using deep learning

Fish age estimation plays a crucial role in stock management and provides valuable information for biological studies. Fish age is typically estimated by experts that manually count annual increments in otoliths. This process is prone to age reader bias, which makes comparisons between readers and labs challenging, and requires considerable time and resources. In this study, we developed a machine learning framework for fish age prediction using 5150 images of otoliths from Barents Sea Atlantic cod (Gadus morhua) collected between 2012 and 2018. In contrast to previous studies that utilise models trained on otolith sections, we used images of broken otoliths that require no processing prior to imaging, and hence, could potentially facilitate at-sea age estimation. We trained convolutional neural networks (CNNs) based on two modern architectures (EfficientNetV1 and EfficientNetV2), which vary in model size (number of model parameters), and compared performance. Model average accuracy was 72.7% and mean-squared-error was 0.284 when compared with the human-read ages. The models' accuracy for one- and two-year-old individuals was over 90% and no systematic bias in the age predictions across age groups was detected. The best models were EfficientNet B4 and EfficientNet B6 using images taken with low exposure times. A maximum accuracy of 78.6% was achieved using an ensemble consisting of six models. Model predictions were also strongly correlated, limiting the utility of building large ensembles Model performance was compared to the results of an internal workshop where 100 independent images of broken otoliths were aged by a group of experts. Variations in percentage agreement between age classes showed a similar pattern (decreasing with age) in both CNN-based predictions and age estimates made by the expert group. While CNN-based percentage agreement was often lower than the expert estimates, it remained within or close to the range of percentage agreement observed across all readers. Our results demonstrate the potential of deep learning techniques for extracting age estimates from otolith images. When developing frameworks for age estimation using machine learning, we recommend EfficientNet B4 models are used as they are quicker to train than larger models and perform well. Ensemble approaches are also recommended if sufficient computational resources are available, as they can provide increased accuracy and lower variance of the predictions.

Hormonal (sGRnH) Doses Optimization with the Ages of Brood Fish in Induced Breeding of Mystus tengara (Hamilton, 1822)

The age of brood fish is an inevitable factor in induced breeding technology worldwide. This study aimed to determine the optimal age for M. tengara for induced breeding and identify the most suitable age based on hormonal doses. Three age groups (1, 1.5, and 2-year-old) of brood fishes were used as three different treatments (T1, T2, and T3), with 0.8 ml kg-1, 1 ml.kg-1, and 1.2 ml kg-1 body doses of Ovasis (sGRnH) as the replications (R1, R2, and R3) of each treatment. Results showed that the highest mean fertilization rate (77.5 ± 1.73 %) was achieved in T1R2 for 1-year-old fish, while 1 ml kg-1 dose was ideal for them. For 1.5-year-old M. tengara, the highest mean fertilization rate was observed in T2R1 (79.25 ± 2.99 %) with 0.8 ml kg-1 dose being the most suitable. Two-year-old fish had the highest mean fertilization rate in T3R1 and T3R2 (76.25 ± 5.5 %) in June. Based on the fertilization rate and hatching rate, 1 ml kg-1 dose was identified as ideal for 1-year-old, and 0.8 ml kg-1 was suitable for 1.5-year-old M. tengara. Among all the treatments, T2R1 (1.5 year age, 0.8 ml kg-1) showed the highest hatching rate (78.25 ± 2.36 %) and most successful breeding performance over the study period, and June was identified as the best time for induced breeding. This scientific evidence provides valuable insight into the optimal age and hormonal doses for M. tengara in induced breeding technology

Assessment of Age and Growth in Fishes

Fish are the largest and most diverse group of vertebrates [...]

Exploring morphometric frontiers: A comprehensive study of otolith growth patterns in brown comber Serranus hepatus (Linnaeus, 1758).

Otoliths are widely employed in marine sciences to gain insights into fish growth, age, migrations, and population structure. This study investigates the relationships between morphometric measurements, otolith characteristics, and length size patterns in the brown comber (Serranus hepatus) from the Gulf of Cádiz, a species discarded in artisanal trawl fisheries. Our findings reveal significant changes in otolith shape indices as fish grow, with symmetry observed between left and right otolith measurements. Otolith size is found to be related to fish size, supporting its use in estimating body length at different life stages. Otolith shape analysis has potential applications in stock identification, detecting catch misreporting, and studying marine predator diets. Combining otolith shape analysis with other data types can clarify relationships among taxa and inform spatial management strategies, contributing to the long-term sustainability of fish populations and the assessment of the impact of management strategies on fish size and growth. This study enhances our understanding of the broader implications of morphometric and otolith analyses in fisheries research and supports the development of more sustainable fisheries management practices.

The interactions between fishing mortality, age, condition and recruitment in exploited fish populations in the North Sea

A quantity of studies have documented how greater condition and older age of individual fish enhances reproductive success via a variety of processes from egg production to larval survival. If these relations translate into relationships between stock demography and recruitment, maintaining a “healthy” age composition may be a key step towards ensuring stock productivity. We examined the correlation between indicators of the age and size composition and the residual-variation from the stock-recruitment relationship (i.e. the variation not explained by the spawning stock biomass) in eleven commercially exploited fish stocks in the North Sea. We also analyzed to what extent spawner age and size composition responded to variations in fishing mortality. Before detrending to accommodate any temporal patterns, recruitment residuals correlated negatively with the relative age composition in all eleven stocks (plaice, whiting, and saithe being significant). However, after detrending the recruitment residuals, the correlations weakened and only nine out of eleven stocks correlated negatively. Lastly, we also conducted a delay difference analysis, which yielded a more or less even distribution between negative and positive correlations, and in addition two stocks (cod and Norway pout) came out showing significant positive correlations between recruitment residuals and age composition. In contrast, eight of the eleven stocks showed positive correlations between spawner weight and recruitment residuals and correlations were significant for plaice, cod, and saithe. After detrending the data, the significant correlations disappeared, but the overall tendency towards positive correlations between spawner weight and recruitment residuals prevailed. Overall, these results suggest that fish condition is more likely to show positive relationships with recruitment success than age composition. Lastly, it was found that the majority of stocks showed a strong link between fishing mortality and the two indicators of age composition, and when looking across stocks, the age composition appears to have returned to the same level as in the 1960 s. Conversely, spawner weight at age have not recovered, and considering the indications of a positive link between spawner weight and recruitment, recruitment success of the North Sea stocks may remain low in spite of the apparently successful rebuilding of the age composition.

Young Allis Shad Alosa alosa (Clupeidae) Would Not Be Euryphagous: An Assessment of Juvenile Diet and Prey Selectivity under Riverine-Type Conditions

Allis shad Alosa alosa hatches and develops in freshwater before migrating to the sea during its first months of life. Some field research works dedicated to the diet of the species in freshwater put forward that young stages of allis shad feed mainly on zooplankton, being opportunistic and euryphagous; their diet would diversify through ontogeny in relation to growth. However, these assumptions have never been confronted to the availability of prey, and the exact age of fish was unknown. In this work, we reared young allis shad under seminatural conditions, from 6 to 10 days posthatching until nearly 3 months old, in a trophic environment representative of a natural river. The rearing structures were designed as artificial rivers, supplied continuously by natural riverine water and zooplankton prey. Additional zooplankton was produced in separate basins and added daily in the structures. One artificial river was used to rear allis shad in 2018, and the experiment was conducted on two allis shad batches in 2019 (one batch per river). We described the nekton communities of potential prey available for allis shad in the rearing structures by sampling the water every week, and we compared these data with the stomach contents of fish captured at one and two months old posthatching to describe their diet and prey selectivity. Our results suggest that young allis shad should not be considered as opportunistic in their feeding, since clear selectivity was observed at both ages. One-month-old allis shad highly selected cladocerans, probably because they are easy to catch for fish at this age, when their swimming abilities are limited. Feeding selection at two months old drifted towards other prey taxa (dipteran larvae, ostracods, and/or copepods), whereas cladocerans were no longer preferred. Our results suggest that fish density and competition may entice two-month-old allis shad to enlarge their diet to other taxa, including benthic organisms, while one-month-old fish do not seem able to shift their diet and would fast in the absence of cladocerans. Thus, this highlights that the feeding of young allis shad may be highly challenging during their first month of growth.

An integrative perspective on fish health: Environmental and anthropogenic pathways affecting fish stress

Multifactorial studies assessing the cumulative effects of natural and anthropogenic stressors on individual stress response are crucial to understand how organisms and populations cope with environmental change. We tested direct and indirect causal pathways through which environmental stressors affect the stress response of wild gilthead seabream in Mediterranean costal lagoons using an integrative PLS-PM approach. We integrated information on 10 environmental variables and 36 physiological variables into seven latent variables reflecting lagoons features and fish health. These variables concerned fish lipid reserves, somatic structure, inorganic contaminant loads, and individual trophic and stress response levels. This modelling approach allowed explaining 30 % of the variance within these 46 variables considered. More importantly, 54 % of fish stress response was explained by the dependent lagoon features, fish age, fish diet, fish reserve, fish structure and fish contaminant load latent variables included in our model. This integrative study sheds light on how individuals deal with contrasting environments and multiple ecological pressures.

Population dynamics of thresher shark (Alopias pelagicus) landed at the Kutaraja fishing port, Banda Aceh

At the Kutaraja Fishing Port, the shark species Alopias pelagicus accounts for the vast majority of shark catches. The purpose of this research was to ascertain the length distribution of A. pelagicus, the length at which it was first captured, the sex ratio, the von Bertalanffy growth parameters and functions, the mortality rate, and the exploitation rate. This study was carried out in the Kutaraja Fishing Port from December 2021 to February 2022. The incidental sampling method was used to collect 406 samples in total. The FAO-ICLARM Stock Assessment Tools were utilized to analyze population dynamics parameters. The male, female, and combined length distributions of A. pelagicus ranged from 186-295cmTL, 205-304cmTL, and 186-305cmTL, respectively. The length of the first capture was 249.40 cmTL, 252.29 cmTL and 250.78 cmTL, sex ratio of males and females is 1:2.24, the asymptotic length (L∞) was 344.25 cmTL, fish age at length 0 (t0) was 0.066/year, with a growth rate (k) of 0.50/year, 0.36/year dan 0.19/year, 374.83 cmTL and 378.92 cmTL, 0.058/year dan 0.048/year. Natural mortality (M) was assessed to be 0.59/year, 0.47/year, and 0.31/year, fishing mortality (F) was 2.08/year, 2.47/year, and 2.20/year, and total mortality (Z) was 2.67/year, 2.94/year, and 2.51/year. The A. pelagicus exploitation rate (E) was 0.78/year, 0.84/year, and 0.88/year, demonstrating complete exploitation of the male, female, and combined populations.

Lake Trout population dynamics in the Northern Refuge of Lake Michigan: Importance of stocking rate

AbstractObjectiveThe Northern Refuge of Lake Michigan was established under the auspices of the Great Lakes Fishery Commission in 1985 as an additional step toward restoring a self‐sustaining Lake Trout Salvelinus namaycush population to the lake. The overall goal of our study was to assess progress toward Lake Trout rehabilitation in the Northern Refuge through 2021.MethodsWe conducted annual (1992–2021) gill‐net surveys in the fall to assess the adult population and beam trawl surveys in the spring to assess naturally reproduced age‐0 Lake Trout.ResultSpawner abundance averaged 45 fish • 305 m of gill net−1 • day−1 during 1992–1999, just 4 fish • 305 m of gill net−1 • day−1 during 2000–2014, and then 67 fish • 305 m of gill net−1 • day−1 during 2018–2021. Sea Lamprey Petromyzon marinus wounding rate decreased by nearly 90% between the 2000–2014 and 2015–2021 periods. The average annual mortality rate of adult Lake Trout decreased from 43% during the 1990s and 2000s to 22% during 2015–2021. All of these population dynamics were partly driven by changes in Lake Trout stocking rates, which declined by roughly 50% during 1994–1996 but then increased roughly twofold during 2006–2010 and remained at this higher level during 2010–2018. In 2021, early signs of natural recruitment of Lake Trout became evident. Beam trawling during June 2021 yielded a wild age‐0 Lake Trout, the first ever caught since the surveys began in 1992. In addition, 15 (4% of total catch) of the Lake Trout caught in the fall 2021 gill‐net survey were unclipped (wild) fish. Estimated ages of these wild fish indicated that natural recruitment had begun sometime around 2015.ConclusionWith Alewife Alosa pseudoharengus abundance in Lake Michigan at record low levels, Sea Lamprey wounding rate greatly reduced, and Lake Trout spawner abundance at relatively high levels, the outlook for Lake Trout rehabilitation in the Northern Refuge holds promise.

The flesh texture of teleost fish: Characteristics and interventional strategies

AbstractWith the growing demand of consumers for high‐quality aquatic products, controlling the harvest quality of farmed fish is becoming increasingly important in aquaculture industry. The texture is a sensory property that covers a group of attributes, such as firmness, tenderness, chewiness, adhesiveness, resilience, etc., which greatly determine consumers' perception and satisfaction for flesh products. Regarding texture quality, extensive research has been conducted in recent decades based on its related theories, influencing factors, and intervention strategies. However, the information available is largely scattered and disjointed. Essentially, flesh texture is mainly determined by the collective contribution of three major muscle components: muscle fibres, intramuscular connective tissue, and intramuscular fat. Therefore, changing these components in living animals through nutritional and management factors has the potential to modulate texture quality. Here, we briefly introduced the features and development of the three muscle components mentioned above, particularly their potential contributions to texture quality of fish flesh. Exciting promises to manipulate flesh texture through dietary intervention, feed restriction, and exercise training were also discussed. To ensure their applications in large‐scale aquaculture facilities, specific considerations of these regimens should be incorporated in experimental design parameters, including the species and age of fish, research system, experiment duration, and exercise intensity. Finally, the existing challenges and limitations of fish texture studies were presented, along with some viewpoints about current work and future directions of this field.

Diet Analysis of the Amur Sleeper (Perccottus glenii) from the Danube River Drainage Channel (Serbia)

The stomach content of 277 Amur sleeper individuals has been analyzed to present its feeding habits. Fish were sampled using electrofishing from July to November 2017 in the Danube River drainage channel near Veliko Gradište (Serbia). Fish age was estimated by otoliths examination. Ingested prey organisms were identified to the lowest reliable taxonomic level. The biotic indices: vacuity index (VI), frequency of occurrence (F), abundance (Cn), index of importance (PV), Shannon`s diversity index (H`), and equitability index (Eh) were calculated. A total of 18 prey categories and 1144 individual prey were identified in the fish diet, dominantly aquatic macroinvertebrates. There were no significant difference in diet composition between sampling months as well as 0+, 1+, and 2+ age groups (both 3+ and 4+ had one individual). Only eight individuals were found with empty intestines, thus VI was low (2.9). In average, each fish had 4.1 prey items in their intestines. For whole sample, H′ was 1.84 and Eh was 0.64. Trichoptera, Ephemeroptera, and Gastropoda were the most frequent, dominant, and abundant. The greatest diversity of prey items was recorded for fish sampled in October as well as for 2+ individuals, and the lowest for fish from August and 0+ individuals.

Parasite Diversity in a Freshwater Ecosystem.

Parasites are a significant component of biodiversity. They negatively affect fish appearance, growth, and reproduction. In this study, the prevalence of infection, diversity, and mean intensity of parasites were examined in 9 freshwater fish species (45 samples per fish species). Ecto-parasites were examined on the skin, gills, and fins with a hand lens. Wet mounts were prepared using mucosal scrapings from all the external and internal organs of the sampled fish. Microscopy, muscle compression, and the pepsin-HCL artificial digestion technique were also performed. In this study, 26 species of parasites were identified including three taxa belonging to 9 species of protozoan parasites, 11 treamtodes, and 6 monogenean parasites. The identified protozoan parasites were Entamoeba histolitica, Chilodonella sp., Coccidia sp., Costia sp., Cryptobia sp., Ichthyopthiris-multifilis, Microsporidia, Piscinoodinium sp., and Ichthyobodo necator. The identified trematode parasites were Fasciola gigantica, Echinostoma revolutum, Fasciola hepatica, Haplorchis pumilio, Brachylaima cribbi, Echinostoma cinetorchis, Neascus sp., Deropegus sp., Trematode Soldier, Centrocestus formosanus, and Clinostomum marginatum. The identified monogenean parasites were Dactylogyrus limipopoensis, Dactylogyrus anchoratus, Dactylogyrus myersi, Dactylogyrus vastator, Gyrodactylus salaris, and Ancyrocephalus. The diversity of parasites was maximum at the Okara site. The host's organs that were targeted for parasitic infection included the intestine, liver, gills, fins, skin, and kidneys. The majority of the parasites were identified in Labeo rohita followed by Hypophthalmichthys molitrix, Ctenopharyngodon idella, Oreochromis niloticus, Cyprinus carpio, and Wallagu attu. Two species appeared to be resistant species because none of the parasites were observed in Notopterus notopterus or Sperata seenghala. This study also concluded that the prevalence of parasites increased with increasing length, size, and age of fish.

Food Habits of Snakehead, Channa Striata (Bloch), in Aquatic Habitats: a Review Literature

Snakehead fish as a fish of high economic value is currently still caught through nature where cork maintenance has not been widely done. Snakehead fish contains high protein, good for health can also for recover damaged. This investigation intends to produce findings from earlier research into the feeding patterns of snakehead fish (Channa striata) in aquatic environments. Because it can serve as a resource for the public and other parties in terms of ecological and biological studies as well as serve as a guide for activities involving the farming of snakehead fish, this study literature is fascinating to address the feeding habits of snakehead fish (Channa striata). Fish fries are the principal diet for carnivorous snakehead fish. when zooplankton or other tiny crustaceans are more commonly consumed by snakehead fish larvae. This disparity in eating patterns is determined by things including fish kind, age, food availability, environment, and fish size. Due to the lack of food, the effects of the season, and the time spent searching for food, snakehead fish are found to have an empty stomach in both their larval and adult stages.

Elder fish means more microplastics? Alaska pollock microplastic story in the Bering Sea.

Marine microplastics are an increasingly big concern. We analyze the occurrence of microplastics in Alaska pollock (Gadus chalcogrammus) across 2+ to 12+ ages sampled from the Bering Sea. Results show that 85% of the fish have ingested microplastics and elder fish ingest more with over a third of microplastics in the 100- to 500-micrometer size range, indicating the prevalence of microplastics in Alaska pollock distributed in the Bering Sea. A positive linear relationship is obtained between fish age and microplastic size. Meanwhile, the number of polymer types increases in elder fish. The link between microplastic characteristics in Alaska pollock and the surrounding seawater suggests an extended spatial impact of microplastics. The impact of age-related microplastic ingestion on the population quality of Alaska pollock is still unknown. Therefore, we need to further investigate the potential impact of microplastics on marine organisms and the marine ecosystem, taking age as an important factor.