The researchers collected 340 Japanese seabass monthly from January through December 2020 in the southwestern waters of Korea, including the western Korea Strait. Most specimens were between 30 and 60 cm in total length, and the full sample ranged from 26.0 to 97.6 cm. Longline, gillnet and handline fishing conducted through routine commercial operations supplied the fish, so the study involved no additional experimental procedures or animal-handling protocol.

After capture, specimens were transported on ice to a laboratory, where total length was measured to the nearest 1.0 mm and body weight to the nearest 1.0 g. All 310 stomachs examined were removed, and their contents were preserved in 5% buffered formalin for at least 24 hours. Prey were identified under a dissecting microscope to the lowest feasible taxonomic level, with some poorly digested specimens assigned to family or order. Of the 310 stomachs, 134 were empty, an empty-stomach ratio of 43.2%, leaving 176 containing food for dietary analysis.

Among identified fish prey, Engraulis japonicus contributed the greatest wet-weight share at 42.6%. It was followed by Trachurus japonicus at 20.5% and Thryssa kammalensis at 7.3%. Caridean shrimps ranked second as a prey group, with an index of relative importance of 6.8%, and included Crangon affinis and Penaeus chinensis. Brachyuran crabs, euphausiids, stomatopods and cephalopods were also consumed, but each had an index of relative importance below 0.2%. The estimated trophic level based on the TROPH calculation was 4.42 ± 0.79.

Diet composition changed markedly across body-size classes. Teleosts accounted for 54.6% of prey biomass among fish shorter than 40 cm and 98.1% among those longer than 80 cm. In the opposite direction, Caridea contributed 44.6% of biomass in the smallest class and declined to 3.2% in the 60–80 cm class. Estimated trophic level also rose with size, from 4.10 ± 0.51 for fish below 40 cm to 4.48 ± 0.79 for those above 80 cm. These observations support an ontogenetic transition from greater reliance on shrimps among smaller fish to predominantly piscivorous diets among larger fish.

Reproductive period was associated with both prey composition and stomach fullness. Teleosts represented 85.2% of prey biomass during the non-spawning period from April through September and 96.2% during the spawning period from October through March, while Caridea represented 12.3% and 3.6%, respectively. The stomach content index, calculated as stomach-content weight relative to body weight, was lower during spawning, decreasing from 0.64 ± 0.12 in the non-spawning period to 0.35 ± 0.06 in the spawning period. This difference was significant in a one-way analysis of variance (F = 5.76, P < 0.05).

Stomach fullness also differed significantly among size classes (F = 7.14, P < 0.05). Mean values increased from 0.20 ± 0.06 in fish below 40 cm to 0.42 ± 0.08 at 40–60 cm, 0.92 ± 0.20 at 60–80 cm and 1.21 ± 0.63 in fish of at least 80 cm. Because the study was observational, the results associate larger body size and the spawning period with different feeding measures; they do not directly establish why those differences occurred.

Distance-based linear modelling found that diet composition was significantly associated with size class, total length, reproductive season and month, while sex had no significant independent contribution (P = 0.222). A conditional model containing all five predictors explained only 19.1% of the variation in diet, leaving most of the multivariate variation unexplained. A graphical analysis of prey-specific weight abundance and frequency of occurrence indicated a predominantly generalized population-level strategy. Teleosts had a prey-specific weight abundance of 98.3% and an occurrence frequency of 70.5%, while the clustering of other prey near the left axis indicated substantial among-individual variation in resource use.

The analysis provides a one-year baseline for Japanese seabass feeding in the surveyed part of southwestern Korea, but its scope and design limit broader conclusions. The fish came from commercial fishing rather than a controlled experiment, 43.2% of examined stomachs were empty, and dietary analysis was based on 176 non-empty stomachs. The study covered one annual cycle and a defined geographic area, and the explanatory model accounted for less than one-fifth of dietary variation. Within those limits, the findings show a predominantly fish-eating population with size- and season-associated changes in diet, feeding intensity and estimated trophic position, providing baseline information for assessing trophic relationships in Korean coastal waters.

Subject of Research: Feeding ecology, diet composition and trophic position of Japanese seabass in southwestern Korean waters

Article Title: Feeding ecology and strategy of Japanese seabass, Lateolabrax japonicus ( Actinopterygii , Acropomatiformes , Lateolabracidae ), in the southern waters off Korean peninsula

Article References: Kang, D. Y., Park, J. M., Moon, S. Y., & Baeck, G. W. (2026). Feeding ecology and strategy of Japanese seabass, Lateolabrax japonicus (Actinopterygii, Acropomatiformes, Lateolabracidae), in the southern waters off Korean peninsula. Acta Ichthyologica et Piscatoria, 56, 167-176. https://doi.org/10.3897/aiep.56.187895

Image Credits: AI Generated

DOI: 10.3897/aiep.56.187895

Keywords: Japanese seabass, Lateolabrax japonicus, feeding ecology, diet composition, piscivory, ontogenetic shift, reproductive season, stomach contents, trophic level, Korean coastal waters, Feeding, ecology

Grasshoppers are not merely background players in grassland ecosystems. In China, they compete with domestic livestock for forage and are ranked alongside droughts and floods as major natural disasters affecting agricultural and livestock production. Understanding what these insects actually eat in the wild, and how their diets vary between sexes and individuals, is therefore a matter of practical urgency. The research team, led by scientists working in the Bozhou region of Xinjiang, set out to fill a conspicuous gap: although similar studies had been conducted in Inner Mongolia, Gansu, and Zhejiang, Xinjiang, home to roughly one-sixth of all known grasshopper species in China, remained largely unstudied.

The researchers focused on seven dominant species spanning two families and three subfamilies: Oedaleus decorus, Oedipoda caerulescens, and Bryodema gebleri from the Oedipodinae; Calliptamus coelesyriensis and Calliptamus barbarus from the Calliptaminae; Notostaurus albicornis from the Gomphocerinae; and Dericorys annulata from the family Dericorythidae. In July 2018, the team collected adult grasshoppers from six natural, unmanaged grassland sites, swinging a net 100 times in each of the four cardinal directions at each plot. Ten females and ten males of each species were randomly selected for dietary analysis, ensuring a balanced sample across the sexes.

The method at the heart of the study, microscopic analysis of crop contents, or MACC, is prized for its precision, efficiency, low cost, and simplicity. Each grasshopper was killed in 75 percent ethanol immediately after collection, and the plant fragments inside its crop, the storage organ of the digestive tract, were compared microscopically with voucher specimens of plants gathered from the same study area. This approach captures what the insects actually chose to eat in their natural environment, avoiding a key weakness of earlier caging studies, which can record artificial forced feeding rather than independent food selection. The researchers calculated a relative feeding frequency for each plant, classifying feeding as high-preference, preference, seldom, or occasional, and then applied Levin’s measure of niche breadth and Schoene’s measure of niche overlap to quantify dietary specialization and potential competition.

Across the seven species, the team identified 33 distinct plant species in the grasshoppers’ diets. Notostaurus albicornis proved to be the most adventurous eater, consuming 15 plant species, while Dericorys annulata was the pickiest, feeding on only five. Plant families such as Poaceae, Fabaceae, Asteraceae, and Amaranthaceae appeared in the diets of nearly all the grasshoppers, whereas Nitrariaceae, Caprifoliaceae, and Tamaricaceae were consumed by only one or two species. Among the three grasshoppers that fed primarily on grasses, each showed a distinct favorite: Oedaleus decorus showed high-preference feeding on Poa annua, Bryodema gebleri on Stipa capillata, and Calliptamus barbarus on Setaria viridis. Dericorys annulata fed almost exclusively on Amaranthaceae, Oedipoda caerulescens favored Asteraceae, and Notostaurus albicornis combined Poaceae and Amaranthaceae in its diet.

The most striking discovery concerned sex differences. For three species, Oedaleus decorus, Bryodema gebleri, and Calliptamus coelesyriensis, whether a grasshopper was polyphagous or oligophagous depended entirely on its sex: females behaved as generalists, feeding broadly across many plant species, while males behaved as specialists. Bryodema gebleri females consumed plants from 11 species across five families, whereas males took only seven species from three families. Calliptamus coelesyriensis females ate plants from eight species in five families, while males restricted themselves to just two species in two families. Even their primary food sources diverged: Bryodema gebleri females fed mainly on Amaranthaceae at 46.50 percent of their diet, while males consumed Poaceae at 93.12 percent. Multivariate analysis of variance confirmed that these sex-based differences were statistically significant for multiple plant species across all seven grasshoppers.

The researchers propose that these dietary splits reflect fundamental physiological needs. Female grasshoppers, which are heavier and must produce eggs, require protein-rich food to support ovarian development, and their larger bodies demand greater overall food intake. Males, by contrast, need high-fat foods to fuel flight. Females also tend to move along the lower parts of plants or along the ground surface more frequently than males, partly because they lay their eggs in the soil, which changes the plants they encounter. Similar sex-based dietary differences have been documented elsewhere: female Romalea microptera prefer Spartina alterniflora while males favor Sesbania macrocarpa, and female Oedaleus decorus in earlier studies preferred Leymus chinensis over Artemisia frigida, the reverse of male preference.

Individual grasshoppers within the same species also differed in their diets, and the pattern followed a clear rule: the narrower a species’ feeding range, the more consistent its individuals. The oligophagous grasshoppers, including male Oedaleus decorus, male Bryodema gebleri, and Dericorys annulata, showed small individual dietary variance, with Kendall’s coefficient of concordance values between 0.116 and 0.175. The polyphagous species, particularly Calliptamus coelesyriensis and Notostaurus albicornis, showed the greatest individual variation, with Kendall values as low as 0.037 and 0.047. Intriguingly, the results challenge a long-standing hypothesis in insect ecology, that population-level polyphagy arises from each individual specializing on a different resource. Instead, most individuals within the polyphagous species were themselves polyphagous, with only a minority of specialists: Oedaleus decorus had the highest proportion of oligophagous individuals at 50 percent, while other polyphagous species ranged from 0 to 30 percent.

The niche analysis added another layer of insight. Notostaurus albicornis and Oedaleus decorus had the widest ecological niches, measured at 5.22 and 4.02 respectively, while Oedipoda caerulescens and Dericorys annulata had the narrowest, at 2.49 and 1.22. Overall, food niche overlap among the seven species was low, ranging from 0 to 0.31, suggesting limited potential for competition at the population level. However, when the analysis was broken down by sex, a different picture emerged: male Bryodema gebleri and male Oedaleus decorus showed an overlap of 0.76, well above the 0.6 threshold generally considered biologically significant, indicating a potential competitive relationship between these two groups. Calliptamus barbarus showed the strongest overall potential for competition with the other six species, while Dericorys annulata had almost none, with overlaps of just 0.00 to 0.09.

The study’s authors emphasize that grasshoppers did not simply eat whatever was most abundant in their habitats, which is indirect evidence that these insects actively select their food. Plant characteristics such as leaf toughness, epidermal hairs, nutrient content, and secondary compounds all influence feeding decisions, and grasshoppers are known to balance their intake of carbohydrates, proteins, and water with remarkable precision. The researchers suggest that some choices, such as Calliptamus coelesyriensis feeding on the water-rich Peganum harmala, may even reflect the need to stay hydrated during dry periods. Because the study covered only one habitat and season, the team calls for future work across different altitudes, latitudes, and habitats, with careful attention to sex differences. The practical implications are considerable: knowing which plants each species and sex prefers could enable ecological management strategies, such as planting less-preferred species in areas prone to grasshound plagues, offering a more targeted alternative to broad-spectrum chemical control in a region where grasshoppers remain one of the greatest threats to grassland productivity.

Subject of Research: Food-plant choice, sex-specific feeding, and interspecific competition among seven dominant grasshopper species in the Xinjiang grasslands of China

Article Title: Food-plant choice of seven dominant grasshopper species in the Xinjiang grasslands

Article References: Ren, J.-L., Kang, W.-J., Li, J.-X., Jin, X., Li, K.-X., & Zhao, L. (2024). Food-plant choice of seven dominant grasshopper species in the Xinjiang grasslands. Journal of Orthoptera Research, 33(1), 157-168. https://doi.org/10.3897/jor.33.110690

Image Credits: AI Generated

DOI: 10.3897/jor.33.110690

Keywords: grasshoppers, Xinjiang grasslands, feeding ecology, sex differences, diet analysis, ecological niche, interspecific competition, polyphagy, oligophagy, Orthoptera, crop content analysis, host-plant preference

The investigation focused on Chiroptera and Aves, two clades of vertebrates that possess the capacity for powered flight. While these animals are often perceived as having unlimited dispersal ability, the study demonstrates that their genetic variation is constrained by a complex interplay of landscape features and organismal traits. The researchers processed data from the phylogatR database, which aggregates geographic information from specimen repositories and sequence data from GenBank and BOLD. After rigorous quality control, which involved removing sequences with high divergence or missing data, the analysis retained 126 bat species and 214 bird species. This filtering process was essential to ensure that the estimated breaks reflected true biological structure rather than artifacts of sampling gaps or taxonomic misidentification.

Monmonier’s algorithm was employed to estimate these phylogeographic breaks by converting genetic data into a network and identifying the edges associated with the highest degree of genetic differentiation. Unlike methods that rely on a priori division of samples, this approach allows for the detection of spatial genetic structure without external geospatial inputs. The results showed that 54% of the bat species and 44.4% of the bird species exhibited conspicuous phylogeographic breaks. In bats, these breaks were concentrated in biodiversity hotspots such as southern Central America, northern South America, and Southeast Asia. In contrast, bird breaks were more widespread, extending across temperate zones and tropical regions, likely due to the larger average geographic ranges of the bird species included in the dataset.

To identify the factors predicting these breaks, the researchers utilized a random forests classifier, a machine learning technique that evaluates the importance of various predictor variables. For bats, the most significant predictors included occurrence area, latitudinal range, maximum latitude, and the presence of mountains within the species’ range. Notably, bat species with phylogeographic breaks tended to have larger occurrence areas at higher latitudes. Additionally, morphological traits such as brain mass and body-size-corrected wingspan were significant, with species exhibiting breaks having smaller brains and shorter wingspans. These findings indicate that physical barriers like mountain ranges still play a crucial role in structuring genetic diversity in bats, despite their ability to fly.

In birds, the predictors differed slightly but remained focused on morphology and ecology. The top variables included invertivory, migratory status, granivory, and the use of semi-open habitats. Bird species with phylogeographic breaks were found to have maximum latitudes closer to the Equator, smaller adult mass, and a smaller hand-wing index. The hand-wing index is a measure of wing aspect ratio, with higher values indicating longer, thinner wings that are more aerodynamically efficient. The study suggests that birds with wing morphologies adapted for efficient long-distance flight exhibit fewer genetic breaks, likely because they can maintain genetic connectivity across their ranges more effectively.

The role of wing morphology in dispersal ability is a central theme of the study. Wing loading, defined as the ratio of mass to wing surface area, and wingspan are critical factors influencing flight efficiency. In bats, higher wing loading is correlated with flight speed and distance, which can enhance genetic connectivity. However, the study found that body-size-corrected wingspan was a top predictor of breaks in bats, with species having shorter wingspans more likely to exhibit genetic structure. This implies that bats with less efficient flight capabilities are more susceptible to barriers that restrict gene flow. Similarly, in birds, the hand-wing index was a key predictor, reinforcing the link between aerodynamic efficiency and the ability to overcome geographic obstacles.

Feeding ecology also emerged as a significant factor in the formation of phylogeographic breaks. In birds, trophic niche categories such as invertivory and granivory were among the most important predictors. Wing shape in passerines is closely associated with diet and foraging behavior, suggesting that ecological specialization can limit dispersal. For example, species that specialize in specific habitats or food sources may be less likely to move across different environmental gradients, leading to genetic differentiation. This interaction between feeding ecology and genetic diversity highlights the intricate relationship between an organism’s lifestyle and its evolutionary trajectory.

The study also considered the potential influence of phylogeny on these patterns. By using taxonomic classification as a proxy for phylogeny, the researchers found that only specific avian orders, such as Procellariiformes and Caprimulgiformes, were among the top predictors. Procellariiformes, which are adapted for foraging over the open ocean, did not exhibit phylogeographic breaks, possibly due to their specialized ecological niche facilitating connectivity. In contrast, Caprimulgiformes species were predicted to contain breaks, which may correspond to the presence of multiple named subspecies. These results suggest that phylogenetic effects are not the primary explanation for the observed patterns, but rather that specific traits and ecological factors are more influential.

This research contributes to the field of macrogenetics, which involves the re-analysis of genetic data to infer large-scale evolutionary processes. By leveraging existing databases and machine learning techniques, the study provides a comprehensive view of how intraspecific genetic variation is structured in volant vertebrates. The findings underscore the importance of considering both geographic and organismal traits when studying biodiversity. The study also highlights the potential for using repurposed data to identify global trends in genetic structure, offering a starting point for more detailed investigations into the processes of diversification and speciation.

Ultimately, the study demonstrates that volant vertebrates are not equal in their dispersal capabilities. Species capable of flying long distances with efficient wing morphologies are less likely to contain intraspecific genetic structure. The interplay between wing shape, feeding ecology, and geographic range characteristics provides a nuanced understanding of how genetic breaks form. These insights have implications for conservation biology, as they help identify areas and species that may be particularly vulnerable to genetic isolation. By recognizing the factors that contribute to phylogeographic structure, researchers can better predict and manage the genetic diversity of flying vertebrates in a changing world.

Subject of Research: Phylogeographic breaks in volant vertebrates

Article Title: Bats of a feather: Range characteristics and wing morphology predict phylogeographic breaks in volant vertebrates

Article References: Decker, S. K., Provost, K. L., & Carstens, B. C. (2025). Bats of a feather: Range characteristics and wing morphology predict phylogeographic breaks in volant vertebrates. Frontiers of Biogeography, 18, Article e139911. https://doi.org/10.21425/fob.18.139911

Image Credits: AI Generated

DOI: 10.21425/fob.18.139911

Keywords: phylogeography, bats, birds, wing morphology, genetic structure, dispersal ability, monmonier algorithm, random forests, feeding ecology, biodiversity, feather, Range

The rainbow trout, Oncorhynchus mykiss, is one of the most widely introduced fish species on the planet. Native to the rivers of the Pacific coast of North America, it has been translocated to waters on every inhabited continent, and established feral populations are documented across much of Europe and beyond. In the Ammer River itself, the species does not maintain a fully self-sustaining wild population; rainbow trout in this section originate from regular stocking for recreational angling, with individuals typically 30 to 40 centimeters in length released annually from Bavarian aquaculture facilities. The 39-centimeter specimen that carried the snakes therefore represents exactly the size class that anglers encounter in this reach each season.

The capture itself followed standard practice. The fish was taken on fly fishing gear with a dry fly, humanely stunned by a single percussive blow to the head, and dispatched by bleeding in accordance with German fisheries and animal welfare regulations. Dissection was performed shortly after capture using a standard surgical hemostat of 15 centimeters length, and the entire procedure was documented on video. That footage proved scientifically valuable: by comparing the snakes visible in the stomach against the hemostat in the recording, the observers could estimate that each of the three grass snakes measured approximately 20 centimeters in total length, a level of quantification that most historical predation records lack.

Reptiles as prey of salmonids are exceptionally rare in the scientific literature. Keiz reported in 1963 a predation attempt by a rainbow trout on an adult grass snake at a fish farm. Eder and colleagues in 1988 described an unsuccessful attempt by a rainbow trout of about 30 centimeters on a grass snake of around 50 centimeters, and additionally reported a dead lake trout whose digestive tract contained a grass snake measuring 50 to 60 centimeters. Bernini and colleagues in 2006 found remains of a wall lizard, a slow worm, and an unidentified snake of the genus Natrix in rainbow trout from northern Italy. Smith in 1973 noted snake remains in the stomachs of pike and eel, and more recent records include a hatchling Natrix helvetica in France and several juvenile reptiles, including a Natrix species, in northern Italy. Until now, however, no record had documented multiple snakes of the same species inside a single salmonid.

The new observation is remarkable precisely because it shows repetition rather than a single opportunistic mistake. Three juvenile grass snakes in one stomach indicates that the predator did not merely blunder into one unlucky hatchling; it encountered several suitable prey items in quick succession and consumed them all. The authors interpret this as evidence that predation events on small reptiles are not necessarily restricted to isolated cases but may occur repeatedly when the prey is locally abundant. This is consistent with the observations of Bernini and colleagues, who reported reptiles in the diet of salmonids mainly during the summer months, when these animals are especially active near the water.

The size and season of the snakes carry their own biological clues. Grass snakes in Central Europe usually hatch between July and September, so a hatching event in May can be excluded. The juveniles found in the trout were therefore most likely overwintered individuals from the previous year. During spring, such young snakes frequently occur near the shoreline or swim on the water surface, behavior that makes them particularly conspicuous and vulnerable to visually hunting predators such as trout. A rainbow trout holding position in a river section where juvenile grass snakes were crossing or swimming would have had every sensory cue it needed to strike, and the dry fly capture suggests the fish was feeding near the surface at the time.

The feeding ecology of rainbow trout has been examined in numerous studies across its introduced range. Most of these works focus on aquatic macroinvertebrates, fish, and occasionally terrestrial insects as the main prey. Amphibians can play a locally important role in salmonid diets during certain seasons or in specific regions, whereas reptiles have so far only been reported from single events. The new record considerably expands this fragmentary evidence and documents a specific interaction between salmonids and semi-aquatic snakes that has so far received little systematic attention. It also complements earlier single observations of fish acting as predators of snakes and demonstrates that such interactions may occur in wild populations, not only in the confined and artificial conditions of fish farms.

Opportunistic feeding is widely considered a key factor in the global establishment success of rainbow trout. Studies from Patagonia to the Alps have shown that the species can exploit terrestrial food resources when these are available, switching flexibly between aquatic and terrestrial prey according to season and availability. The authors emphasize that such observations do not necessarily imply negative ecological impacts on grass snake populations but rather reflect the pronounced trophic plasticity of this introduced salmonid. Under certain environmental conditions, the species is capable of consuming unusual prey such as small reptiles without this necessarily having ecological relevance for the prey populations.

There is, however, a risk side to this flexibility, and it falls on the predator itself. Previous observations have documented salmonids that ingested comparatively large or unsuitable snakes, and these cases show that the consumption of oversized prey can in rare instances be physiologically stressful or even harmful to the fish. Keiz’s 1963 record and the 1988 account of a 30-centimeter trout attempting a 50-centimeter snake both illustrate the mismatch that can arise when a visually guided predator misjudges prey size. The three 20-centimeter juveniles in the Ammer River trout, by contrast, were small enough to be swallowed without apparent difficulty, representing a more successful execution of the same opportunistic strategy.

The presently reported finding represents one of the few confirmed records of reptiles as prey of salmonids in Central Europe and highlights the value of incidental dietary records in expanding our understanding of trophic plasticity in an introduced fish species. The video documenting the dissection is publicly available on Figshare, allowing independent verification of an observation that might otherwise be dismissed as anecdote. For a species whose adaptive potential has made it a global invader, the ability to add juvenile snakes to an already broad menu is one more illustration of why rainbow trout thrive almost anywhere they are released, and why even a routine angling catch on a Bavarian river can still yield a genuinely novel scientific record.

Subject of Research: Predation of juvenile grass snakes by rainbow trout in a Bavarian stream

Article Title: Three juvenile Natrix natrix ( Reptilia ) as prey of Oncorhynchus mykiss ( Actinopterygii , Salmoniformes , Salmonidae ) in a Bavarian stream

Article References: Vogelmann, C., Wendt, P., & Martens, A. (2026). Three juvenile Natrix natrix (Reptilia) as prey of Oncorhynchus mykiss (Actinopterygii, Salmoniformes, Salmonidae) in a Bavarian stream. Acta Ichthyologica et Piscatoria, 56, 23-25. https://doi.org/10.3897/aiep.56.176058

Image Credits: AI Generated

DOI: 10.3897/aiep.56.176058

Keywords: rainbow trout, grass snake, predation, Bavaria, invasive species, feeding ecology, trophic plasticity, salmonids, Three, juvenile, Natrix, Reptilia

The sharpsnout seabream is a commercially valuable demersal member of the seabream family, the Sparidae, distributed from the Bay of Biscay and the Canary Islands through the Mediterranean and into the Black Sea. Historically more abundant in the Mediterranean, the species has been expanding northward in the Atlantic, a shift that researchers have linked to rising water temperatures. Its physiological toolkit helps explain this success: the fish tolerates water temperatures from 15 to 29 degrees Celsius and shows relative resistance to variation in oxygen availability, traits that would favor persistence under the notoriously variable conditions of the Black Sea. Reports from both the Sea of Marmara and the Black Sea in recent decades confirm that local populations are not just transient visitors but appear able to survive and reproduce in the basin, which represents the northernmost margin of the species’ known distribution.

Ecologically, D. puntazzo is typically found over rocky substrates and seagrass beds at depths from the surface down to 150 meters, though it is most common in the shallow infralittoral zone above 60 meters. Unlike some of its relatives, such as the white seabream D. sargus, which feed predominantly on benthic invertebrates, the sharpsnout seabream is omnivorous with a digestive system well adapted to herbivory. That dietary flexibility has already been on display in the southeastern Black Sea, where the species was previously observed opportunistically feeding on the egg capsules of the invasive veined rapa whelk, Rapana venosa, during the summer months. The new specimen adds a seasonal twist to that story.

Maximum body size matters in fisheries science because it underpins growth modeling, life-history assessment, and stock evaluation. Although the species can reportedly reach 60 centimeters in total length and live 10 to 18 years elsewhere, individuals exceeding 40 centimeters appear uncommon in the Black Sea. Prior regional records include a 41.6-centimeter, 1,007.2-gram specimen from Hopa, a 45.4-centimeter fish from Ordu, and a 44.5-centimeter individual from a broader morphometric study spanning Samsun to Hopa. Given the species’ growing presence in Turkish national fishery statistics, documenting rare large adults has real value for understanding regional growth potential, particularly because maximum length is closely tied to population dynamics assessments.

The methods behind the new record were deliberately rigorous. After capture, the specimen was transported to the laboratory on ice and weighed on a precision electronic balance accurate to 0.01 grams. High-resolution lateral photographs were taken with a scale reference using a Canon EOS R50 camera, and morphometric measurements were extracted digitally with ImageJ software following an established protocol. To guard against measurement error, total, fork, and standard lengths were recorded both manually and digitally, with the two approaches agreeing within 0.1 centimeters. Taxonomic identification followed standard references, sex was determined by macroscopic gonad examination, and the stomach was removed for dietary analysis. The meristic formula was recorded as D X, 14; A III, 12; P 14; V I, 6; C 20.

The numbers tell a nuanced story. The fish measured 47.6 centimeters in total length, 42.5 centimeters at the fork, and 39.5 centimeters in standard length. While the gain in length over the previous record is modest, the weight increase is substantial, and the explanation appears to be shape rather than reproduction. The specimen’s maximum body depth was 16.0 centimeters, compared with 13.6 centimeters in the earlier record fish from Ordu. Because the gonads were not prominent at the time of capture, even though November overlaps with spawning periods reported for some populations elsewhere, the researchers attribute the extra weight partly to this deeper body form and improved somatic condition rather than to ripening gonads. Regionally, the specimen surpasses maximum lengths reported from most Aegean studies and even exceeds the Adriatic maximum of 46.7 centimeters, though it remains below the Adriatic weight record of 1,545 grams.

The stomach contents delivered perhaps the most intriguing finding. Macroscopic examination revealed only macroalgae: the green alga Ulva rigida and red algae of the genus Ceramium, with no invertebrate prey at all. This late-autumn vegetarian meal contrasts sharply with the summer observations of rapa whelk egg capsule predation in the same region, suggesting that D. puntazzo exhibits genuine seasonal dietary flexibility in the Black Sea. For a recently established population, such flexibility could be a decisive advantage, allowing individuals to exploit whatever food resources are locally available as the seasons change. The authors also raise, cautiously, the possibility that coastal land reclamation and rock-fill structures along the southeastern Black Sea create artificial hard-bottom habitats offering shelter and feeding opportunities for reef-associated fishes, though they stress this interpretation remains hypothetical until dedicated habitat-use studies are done.

Equally significant is how the fish was caught. It was not taken by a trawler or a commercial net but by a recreational spearfisher, a selective method that targets individual fish. The researchers argue this hints that large specimens encountered in recreational fisheries may be underrepresented in conventional fishery records, potentially skewing our picture of the species’ true size structure in the basin. They are careful to flag the inference as preliminary, since a single opportunistic capture cannot establish how much recreational fishing contributes to total removals. Still, they call for dedicated monitoring of recreational catches, particularly spearfishing, alongside continued biological monitoring focused on size structure, habitat use, and fishery interactions rather than isolated maximum-size records alone.

The study’s limitations are clearly acknowledged. Everything rests on one specimen, so no population-level conclusions about size structure, growth rate, or abundance can be drawn. The fish’s age was not determined through otolith or scale reading, leaving its growth history and longevity unknown, and a single stomach sample reflects only recent late-autumn feeding rather than the species’ overall diet. The authors propose a research agenda to fill these gaps: systematic seasonal sampling, otolith-based age determination, quantitative diet analysis, habitat-use assessment, and monitoring of recreational catches.

Even with those caveats, the record matters. It confirms that large adult sharpsnout seabream do occur in the southeastern Black Sea, updates the regional maximum to 47.6 centimeters and 1,452 grams, and provides a biological reference point for future studies of growth potential, trophic ecology, habitat use, and fishery interactions in a species whose regional relevance is only growing. As warming waters continue to reshuffle marine communities across the Mediterranean basin and beyond, quietly tracking the giants of the fringe populations may prove one of the most informative windows into how species adapt, and thrive, at the edge of their range.

Subject of Research: New maximum size record and autumn feeding ecology of sharpsnout seabream in the Black Sea

Article Title: Unveiling the hidden stock: a new maximum size record for sharpsnout seabream ( Diplodus puntazzo ) from recreational fisheries in the Black Sea

Article References: Dokuzparmak, Ü., & Dürrani, Ö. (2026). Unveiling the hidden stock: a new maximum size record for sharpsnout seabream (Diplodus puntazzo) from recreational fisheries in the Black Sea. Scientific Annals of the Danube Delta Institute, 31, 15-23. https://doi.org/10.3897/saddi.31.196822

Image Credits: AI Generated

DOI: 10.3897/saddi.31.196822

Keywords: sharpsnout seabream, Diplodus puntazzo, Black Sea, size record, spearfishing, Sparidae, feeding ecology, macroalgae, Ulva rigida, invasive species, recreational fisheries, Trabzon

An international team led by Xaver Neitemeier-Duventester and Harry Wilhelm Palm of the University of Rostock, together with colleagues from Udayana University in Bali, examined twenty-three rays purchased at the Pasar Ikan Tradisional Kedonganan fish market on Bali’s southern coast between November 2018 and September 2021. Twelve of the specimens belonged to Rhinobatos jimbaranensis, a species recorded so far only from the eastern Indian Ocean off southern Bali and listed as threatened on the IUCN Red List. The remaining eleven were R. penggali, an endemic relative known from the southern coasts of Java, Bali, and Lombok. Both rays live on inner island shelves at depths of one to sixty meters and were described to science only in 2006.

The researchers focused on the order Trypanorhyncha, one of the most species-rich groups of marine cestodes and a group whose members are distributed worldwide. These tapeworms are prized by parasitologists as biological indicators because their life cycles weave through the marine food web: larvae develop in invertebrates or fish, and adult worms settle in the intestines of sharks and rays. By cataloguing which tapeworm species infect a host, scientists can infer details about its diet, migration, and zoogeographic distribution without directly observing the animal at sea.

Using standardized dissection and a gut-wash technique to flush every worm from the stomach and spiral valve, the team recovered twelve trypanorhynch species in total, ten from R. jimbaranensis and eight from R. penggali. Six species infected both ray species: Dollfusiella spinosa, Parachristianella indonesiensis, Parachristianella monomegacantha, Prochristianella clarkeae, Pseudochristianella jimbaranensis sp. nov., and Trygonicola macropora. Four species appeared only in R. jimbaranensis, including Dollfusiella hemispinosa, an unidentified Dollfusiella, the new Prochristianella bicki sp. nov., and Proemotobothrium linstowi. Two others, Dollfusiella michiae and Kotorelliella jonesi, were found exclusively in R. penggali. In all, the survey established thirteen new host records and eight new locality records.

The two new species were diagnosed through a combination of classical morphology and cutting-edge imaging. Specimens were stained with Mayer-Schuberg’s acetic carmine, cleared in eugenol, and mounted permanently in Canada balsam for light microscopy. The team then turned to confocal laser scanning microscopy at the University of Rostock, using Leica DMI6000 CS and Stellaris 8 instruments to build three-dimensional reconstructions of the tentacles and their hook armatures, and to scanning electron microscopy at the Rostock University Medical Centre, where critical-point-dried specimens coated with gold revealed surface details at the micrometer scale.

Prochristianella bicki sp. nov., named in honor of Dr. Andreas Bick, former supervisor of the lead author, is a small worm measuring roughly 1.3 to 1.9 millimeters in length, found in the spiral valve of R. jimbaranensis. Its tentacle armature is heteroacanthous and heteromorphous, with solid hooks arranged in ascending half spirals of nine to ten hooks. A distinctive feature is that the first pair of hooks disappears beyond the eleventh or twelfth metabasal row, leaving only a rudimentary hook in row twelve. The species also carries a characteristic basal armature with four rows of enlarged billhook-shaped hooks on the basal swelling, and it lacks the prominent microtriches visible in several of its closest relatives. Its nearest morphological counterpart, Prochristianella mooreae, can be distinguished by its ten to twelve hollow hooks per half spiral, compared with the nine to ten solid hooks of the new species.

Pseudochristianella jimbaranensis sp. nov., named after both the type locality and the type host, proved to be the most common parasite in the study. Seventy-three specimens were recovered from R. jimbaranensis and thirty-five from R. penggali, giving it a prevalence of 83.33 percent in the former and 90.91 percent in the latter, the highest recorded in either host. The worm bears four to six proglottids, roughly forty-eight to fifty-two testes, and a metabasal armature of fifteen solid hooks per half spiral that reduces to thirteen toward the tip. Its defining trait lies in the basal armature: two rows of enlarged slender uncinate hooks, followed by four rows of small spiniform hooks, and approximately thirty-five to thirty-six billhooks arranged on the external surface of the basal swelling, a configuration that clearly separates it from the three previously described species of the genus.

Beyond the taxonomy, the parasite community told a story about feeding ecology. Most of the recorded trypanorhynchs belong to the superfamily Eutetrarhynchoidea, whose larvae typically develop in crustaceans, consistent with the known diet of both rays, which feed primarily on small bottom-dwelling invertebrates. But two of the recovered worms belong to families with fish intermediate hosts. Kotorelliella jonesi, a tentaculariid, was found only in R. penggali, a species already suspected of eating small bony fish based on stomach content analyses. More intriguingly, Proemotobothrium linstowi, an otobothriid whose plerocercus larvae have been documented in teleosts, appeared only in R. jimbaranensis. That finding suggests that this ray, like its congener, also occasionally includes fish in its diet, a behavioral nuance that stomach sampling alone had not confirmed for the species.

The study also revealed patterns of parasite community structure. Species of Parachristianella and Pseudochristianella showed high prevalences and abundances in both ray hosts and appear to function as core species in Balinese Rhinobatos, while the four Dollfusiella species, despite their taxonomic richness, occurred at low intensities and are best regarded as non-core members of the community. The dominance of eutetrarhynchoid tapeworms mirrors patterns seen in other Rhinobatos species worldwide, from R. productus in the Gulf of California to R. planiceps in Chile and R. rhinobatos in Tunisia, all of which host parasite assemblages dominated by the genera Dollfusiella, Prochristianella, Parachristianella, and Pseudochristianella.

The findings carry weight beyond parasitology. Indonesia hosts the richest elasmobranch fauna on Earth, with 221 species of sharks and rays, and once operated the world’s largest chondrichthyan fishery, landing more than 100,000 tonnes annually in the early 2000s. Today, roughly forty percent of shark species face extinction risk from habitat loss, prey depletion, and overfishing. Because parasites like trypanorhynchs encode ecological information about their hosts, documenting them can support conservation planning for species such as R. jimbaranensis, whose range is among the most restricted of any ray. The authors note that knowledge of the trypanorhynch fauna of Bali remains scarce, with only a handful of published surveys, and they call for further studies to explore the full species diversity of these tapeworms in Balinese waters. Holotype and paratype specimens of both new species were deposited in the Zoological Museum Bogor in Indonesia, with additional paratypes held at the Berlin Natural History Museum, ensuring the material remains accessible in the country of origin.

Subject of Research: Trypanorhynch tapeworm diversity and feeding ecology of endemic Rhinobatos rays from Bali, Indonesia

Article Title: Trypanorhyncha (Cestoda) from Endemic Rhinobatos Species (Elasmobranchii: Rhinobatidae) from Bali, Indonesia, with the Description of Two New Species

Article References: Neitemeier-Duventester, X., Suryaningtyas, E. W., Riegert, J. W., Damriyasa, I. M., Arthana, W., & Palm, H. W. (2026). Trypanorhyncha (Cestoda) from Endemic Rhinobatos Species (Elasmobranchii: Rhinobatidae) from Bali, Indonesia, with the Description of Two New Species. Acta Parasitologica, 71(5), Article 227. https://doi.org/10.1007/s11686-026-01365-3

Image Credits: AI Generated

DOI: 10.1007/s11686-026-01365-3

Keywords: Trypanorhyncha, Cestoda, Rhinobatos jimbaranensis, Rhinobatos penggali, Bali, Indonesia, new species, parasitology, feeding ecology, elasmobranchs, confocal laser scanning microscopy, marine biodiversity