Journal of Fish Biology

This study investigates the impact temperature-induced vertebral anomalies have on the C-start escape response of Astyanax mexicanus, a model species in evolutionary developmental biology. Employing three temperature treatments to induce varying degrees of skeletal anomalies, we assessed their effects on key swimming performance metrics including, C-start time, curvature coefficient, head displacement distance, and displacement velocity. Through the use of linear mixed models and generalized linear mixed models, our results reveal that specific anomalies such as vertebral fusions and anomalous haemal and neural spines affected the curving ability of C-start escape responses. However, these did not negatively impact other performance parameters, with velocity, distance, and response time showing no significant impacts from any anomaly types, when assessed individually. This suggests a complex interplay between structural deformities and compensatory physiological mechanisms that maintain functional performance. Other variables measured had a stronger and significant impact on swimming performance, including standard length, vertebral number, and temperature treatment, which influenced escape speed, curving ability, and overall locomotor performance. Our findings challenge conventional perceptions about the debilitating impact of vertebral anomalies, indicating that many affected fish can still effectively perform escape maneuvers critical for survival.

The white shark Carcharodon carcharias (Linnaeus, 1758) is one of the most iconic and threatened marine predators globally and is listed as critically endangered by the IUCN in the Mediterranean Sea, where populations are primarily affected by fishing pressure and the degradation of critical habitats. Available information on Mediterranean white sharks mostly relies on fishing interactions and opportunistic surface records, thereby limiting evaluations on the species ecology. Here, we report an exceptionally rare underwater encounter with this species, documented by divers involved in an expedition aimed at removing ghost fishing gear from a World War II shipwreck in the Strait of Sicily (SoS), central Mediterranean. Given the exceptional nature of this observation, we analysed the video footage in detail with the aim of providing morphological information and novel insights into the species ecology. The footage analysis also allowed close observations on behavioural aspects and on interspecific and parasitic associations, thus providing information that is rarely achievable through surface sightings or from captured individuals, which historically represent the majority of records for this species in the region. To contextualize this observation within the SoS--an area suggested to function as a nursery and reproductive ground for the species--we also provide an updated compilation of records reported in the scientific literature over the last decade, adding 18 new records to existing datasets. This study highlights the value of shipwrecks as observation sites for rare and elusive species, and underscores the importance of non-invasive, video-based approaches in advancing knowledge of a species whose ecology in the Mediterranean remains poorly understood.

Cruising speed is a key factor affecting prey-search efficiency and migration range in continuously swimming animals. Tunas and lamnid sharks (e.g., white sharks) have convergently evolved traits for high-speed cruising, including the ability to maintain slow-twitch, aerobic red muscle (RM) warmer than ambient water, known as RM endothermy. Despite their well-known high cruising speeds, kinematic features underlying their elevated speeds remain unclear. Swim speed is the product of tailbeat frequency (TBF; Hz) and stride length (SL, the absolute distance traveled per tailbeat; m). RM endothermy is expected to elevate TBF by enhancing muscle contraction performance. Furthermore, within RM-endothermic fishes, tunas and lamnid sharks may exhibit distinct kinematic features because of differences in caudal fin morphology and tailbeat amplitude. Here, we compiled kinematic parameters from 20 fish species, including five RM-endothermic species, measured in the wild using animal-borne sensors. Comparative analyses showed that, for a given body mass and water temperature, RM-endothermic fishes exhibited 1.9 times higher cruising speed and TBF than ectothermic fishes, while SL remained similar. Within RM-endothermic fishes, tunas exhibited 2.3 times higher TBF than similar-sized lamnid sharks, whereas lamnid sharks showed 1.7 times longer SL than similar-sized tunas. These results indicate that RM endothermy is generally associated with higher TBF, while significant kinematic differences remain between tunas and lamnid sharks. This divergence may be partly explained by the greater caudal fin area and tailbeat amplitude in lamnid sharks. It may also reflect contrasting skeletal types of teleosts and elasmobranchs, which potentially influence body stiffness and swimming kinematics.

Chinese Bahaba (Bahaba taipingensis, Sciaenidae) is a Critically Endangered, Grade I state-protected marine fish in China. Reliable, non-invasive monitoring tools are urgently needed to inform conservation and restocking efforts. We developed and validated three TaqMan probe-based qPCR assays targeting mitochondrial 12S rRNA, ND5, and control region (D-loop) loci for species-specific detection of B. taipingensis. Primer-probe sets were designed from complete mitochondrial genomes and evaluated in silico against GenBank and in vitro against tissue DNA from B. taipingensis and closely related sciaenids, plus positive eDNA samples; sensitivity was quantified using serial dilutions of synthetic target DNA. All three assays showed high specificity and consistent amplification; 12S rRNA assay (Bhb_12S) was selected for field screening based on superior low-copy sensitivity and minimal by-products. We applied the Bhb_12S assay to 414 seawater samples collected from 23 sites in western Hong Kong during 2025 surveys, detecting B. taipingensis eDNA in the September samples (0.71-2.85 copies per L; mean 2.05), with positive detections confirmed by Sanger sequencing. Overall, these validated qPCR assays provide a robust molecular toolkit for non-invasive monitoring of B. taipingensis and will aid conservation planning, restocking evaluation, and long-term biodiversity assessments in the Pearl River Estuary and adjacent coastal waters.

Here, we report the first genetic confirmation of golden mussels (Limnoperna fortunei) in North America, and the subsequent development, optimization, and deployment of golden mussel eDNA monitoring procedures. Aquatic species invasions are economically costly, disrupt ecosystem functionality, and impact native aquatic communities. Early detection of new invasive species enables rapid response via implementation of effective eradication or control measures and is key for reducing harmful outcomes. Initial species detection and taxonomic identification can be aided by genetic methods that have high detection sensitivity and accuracy. Genetic methods such as environmental DNA (eDNA) sampling can be used to detect invasive species before they become established in new systems, providing an early alert system to inform resource managers. Golden mussels were first detected in North America in October 2024 near the Port of Stockton in the San Francisco Estuary (SFE). The SFE is particularly vulnerable to invasion due to the access and connectivity provided by the presence of engineering infrastructure and shipping lanes. Collaborative efforts between public agencies and academic institutions are underway to develop a coordinated detection and response plan. Early detection followed by a rapid response is the best defense against prolific invasive species, such as the golden mussel.

Downstream migration and sea entry are periods of high mortality for sea trout smolts and migration timing is a critical aspect of survival. We aimed to investigate migration timing of PIT-tagged sea trout smolts across a latitudinal gradient in five freshwater systems across Europe: Norway, Sweden, Denmark, France and Portugal. In two systems, smolt migration was further examined to assess a) differences in sex, body size and condition between autumn and spring migrants; b) the influence of spatial origin within the stream; and c) relationships between individual body size and migration date. Tagged smolts were not detected migrating in the Portuguese watershed. Spring migration timing differed significantly between watersheds in Norway, Sweden, Denmark and France. Generally, there was a trend of earlier migration at lower latitudes. Autumn vs spring migration was examined in Gudso-Denmark. Autumn migrants were larger in both length and mass, with no differences in sex ratios or body condition. Fish originating from an upstream site were more likely to migrate in the autumn compared to the spring and vice versa. Size dependent migration was found in the Swedish system, Haga [a]-Sweden, with larger individuals migrating earlier in the spring than smaller individuals. Outward-migrating smolts were also more likely to originate from a downstream site than an upstream site. Overall, these results show both large-scale geographic and fine-scale individual influences on migration timing. Given that climate change may have large impacts on migration patterns in sea trout, understanding variability in migratory patterns across a latitudinal gradient is an important tool for predicting responses to environmental changes.

1. Detecting environmental DNA (eDNA) from rare or low-abundance aquatic species remains a major challenge, particularly when it is highly degraded, present at low concentrations, and dominated by DNA from non-target taxa. These challenges are further amplified in sedimentary ancient DNA (sedaDNA) studies, where thousands of years can degrade eDNA further, making the detection and quantitative interpretation of weak biological signals difficult. 2. Metabarcoding is commonly used to produce high-throughput community-level data from eDNA but is inherently compositional and influenced by amplification biases. Nonetheless, metabarcoding read abundance or PCR replicate detection frequency are increasingly used as proxies for relative DNA concentration, but their quantitative interpretation has rarely been evaluated against independent measures of absolute DNA abundance. 3. We used droplet digital PCR (ddPCR) to quantify mitochondrial DNA from Atlantic cod (Gadus morhua) and Atlantic herring (Clupea harengus) in 136 ancient eDNA extracts from Icelandic marine sediment cores spanning the last three millennia. We compared ddPCR copy number estimates with metabarcoding (18S) derived relative abundance and detection frequency, and evaluated whether temporal DNA trends corresponded with proxy reconstructed sea surface temperature (SST) variability. 4. We found that ddPCR-measured fish sedaDNA abundance was positively correlated with the proportion of metabarcoding PCR replicates for both Atlantic cod and Atlantic herring. Moreover, temporal trends in Atlantic herring DNA abundance were consistent with proxy reconstructed SST variability, supporting the ecological relevance of the molecular signal. 5. Overall, our results show that ddPCR-derived DNA concentrations and metabarcoding PCR replicate detection frequency capture consistent patterns in low-abundance fish sedaDNA from marine sediments. The observed agreement between approaches supports the use of PCR replicate detection frequency as a semi-quantitative proxy for low-abundance sedaDNA.

Sustainable management of commercial and recreational fisheries depends on accurately resolving population connectivity, across both ecological and evolutionary timescales. However, dispersal can vary markedly among life stages, making stock connectivity difficult to resolve using single-method approaches that often differ in spatio-temporal resolution. Here, we integrated population genomics, otolith stable isotope chemistry, and mark-recapture analyses to provide a multi-faceted assessment of stock connectivity in mulloway (Argyrosomus japonicus). Mulloway are a commercially, culturally, and recreationally important estuary associated fish distributed throughout the Indo-Pacific region, including south-eastern Australia where this study was conducted. Genome-wide single nucleotide polymorphism (SNP) analyses revealed significant genetic differentiation between regions influenced by different current systems, but limited structure within regions across distances exceeding 900 km. In contrast, otolith {delta}13C and {delta}18O signatures revealed fine-scale spatial structuring among estuaries, consistent with prolonged occupancy of local habitats. Mark-recapture analyses supported this interpretation, with most fish exhibiting strong estuarine fidelity over extended periods despite occasional long-distance coastal movements. Reconstructed age structures from fish otoliths revealed remarkably similar cohort composition among estuaries, with populations dominated by cohorts originating from a major recruitment pulse centred on 2011-2012, likely associated with a broad-scale flood-driven spawning and recruitment event. Together, our findings indicate that mulloway fisheries function as regionally connected networks of partially independent estuarine assemblages, where strong local residency is periodically offset by dispersive individuals and episodic recruitment events that maintain long-term demographic and genetic connectivity. Consequently, local estuarine populations may be vulnerable to localised depletion despite broader regional connectivity, particularly where sustained fishing pressure coincides with reductions in freshwater flows that constrain spawning and recruitment. More broadly, our study demonstrates the value of integrating complementary approaches to identify biological connections and define meaningful management units in species with complex life histories.

Animal personality is the expression of consistent among-individual variation in a behavioural trait across time and context. The application of this theory to behavioural research provides a valuable framework to investigate the among- and within-individual variation in behaviour. The animal personality theory is particularly relevant to understand and diagnostic fish welfare. It can be integrated within the nature-based welfare framework, which emphasizes the expression of species-specific behaviours and the maintenance of consistent behavioural patterns over time. Because behavioural trait such as boldness may be closely linked to other functional phenotypes, such associations reflect the broader concept of animal personality, whereby a behavioural trait can covary with another phenotypic trait to support an adaptive responses to environmental conditions. Although these relationships are both species and context dependent, they are consistently shaped by environmental conditions and environmental complexity tend to promote species specific behaviours and reduce maladaptive traits. Here we examined how structural environmental complexity shapes personality in Arctic charr and their covarying functional phenotypes, specifically growth rate and brain size. We propose that environmental complexity promotes alternative behavioural and functional phenotypes through multivariate phenotypic plasticity. We found that environmental complexity did not influence mean boldness between both treatments, but repeatability of boldness in the complex environment was remarkably consistent over a longer-term period, while estimates collapse after seven days in the plain treatment. Our findings are a clear evidence that environmental complexity foster stable behavioural trait expression and that a plain environment may suppress personality. Our results provide compelling evidence that behavioural structure and dynamics are embedded within patterns of behavioural variance. Although we found no support for behavioural covariation or associations with growth rate and brain size, we suggest that the animal personality framework may offer a valuable approach for diagnosing fish welfare issues through the partitioning of behavioural variance.

Brydes whales (Balaenoptera edeni edeni) are nationally protected in China, and the waters around Weizhou Island in the Beibu Gulf support one of the countrys few regularly observed coastal groups. However, acoustic data for this population remain limited, and the potential effects of local vessel noise are poorly described. We conducted 16 vessel-based surveys around Weizhou Island and adjacent waters in January 2024 using a low-disturbance sailboat platform and passive acoustic recorders, with concurrent visual observations where possible. We identified 734 low-frequency signals classified as putative Brydes whale vocalizations and quantified their temporal and spectral parameters. Call duration was significantly negatively correlated with maximum frequency and center frequency, but not with minimum frequency or bandwidth. Comparisons with published records indicate that the recorded signals are most similar to vocalizations previously reported from juvenile Brydes whales or mother-calf pairs, although individual source attribution could not be confirmed. Speedboat passage significantly increased root-mean-square sound pressure levels, and the dominant noise band overlapped the frequency range of the recorded Brydes whale signals, indicating potential for acoustic masking. These results expand the bioacoustic baseline for Brydes whales in Chinese coastal waters and provide evidence relevant to the management of vessel activity and whale-watching tourism around Weizhou Island.

Knowledge regarding variation in habitat use among individuals is crucial for understanding population dynamics and for management and conservation measures. This is especially important for diadromous fishes that shift between habitats, being affected by external pressures and environmental change in different habitats over ontogeny. Herer, we assessed individual variation in habitat use of European eel along a salinity gradient, ranging from fully marine to freshwater in northern Europe, using otolith microchemistry data from >3600 eel together with established time-series segmentation and clustering methods. We show that eel display high degree of individual variation in habitat use. Assigned life-histories included coastal resident, freshwater resident, and coastal and freshwater habitat shifting individuals. Coastal resident eels were observed in a large range of salinities. Given the widespread occurrence of migration barriers in freshwater, it is unknown whether the coastal resident eel preferred that habitat, or if it was the only available habitat for them. Our findings nonetheless highlight the need to include coastal habitats when assessing population development and silver eel production of the critically endangered European eel.

Ranges of small benthic fauna are notoriously difficult to assess. In some of these cases, modern eDNA methods can shed light on species occurrence. Here we conduct an exploratory study on the fish eDNA recoverable from the gastrovascular cavities of the easy-to-sample pore water siphoning benthic invertebrate, Cassiopea, across six sites within the Florida Keys. Twenty-seven fish 12S identities were recovered from water samples, two from sediment samples, and seventeen from Cassiopea gut swabs. In total, thirty-two different species were identified from nineteen families, including one shark species (Ginglymostoma cirratum), and five species of cryptobenthic reef fishes (f: Gobiidae, Labrisomidae). Additionally, five species were identified from medusae samples that were not recovered in water or sediment samples. The species identities recovered may provide insight into the fish in direct proximity to Cassiopea assemblages, as well as indicate that Cassiopea may accrue disproportionate eDNA from cryptobenthic reef fish compared to surrounding environmental samples. The unorthodox sampling technique of using eDNA recovered from jellyfish stomachs yields another avenue for epibenthic community data acquisition.

Congenital disorders of glycosylation and deglycosylation are rare, serious, and lethal disorders afflicting humans. CDGs and CDDGs result in loss of function enzymes which fail to build or break down oligosaccharides on proteins. This can produce protein aggregates and, in turn, reactive oxygen species that harm the cell eventually leading to autophagy and apoptosis. Because sperm contain high concentrations of polyunsaturated fatty acids, they are especially sensitive to these effects, which is understood as one of the leading factors in human male infertility. Sperm are developed in zebrafish similarly to humans and are useful models to examine human reproductive health, as well as genetic disorders. The combination of these advantages makes the analysis of sperm from zebrafish with heterozygous ALG1 or DPAGT1 CDGs or the NGLY1 CDDG suitable. Analysis of sperm concentration, motility, status, viability, and hypoosmotic swelling demonstrated the effects of these disorders on sperm quality. Results showed a significant decrease in sperm concentration, motility, and hypoosmotic swelling for all mutant zebrafish compared to the wild type. This suggests that CDGs and CDDGs influence the amount of sperm produced, the percentage of sperm cells that are mobile, and the integrity of the plasma membrane.

Wildlife biobanking depends on consistent, reproducible cell culture outcomes, yet no standardised framework exists for assessing culture quality across taxa or for integrating quality metrics into institutional collections management systems. Here, we present the Cell Viability and Utility Index (CVUI), a scored pipeline framework validated in a pilot study of 154 culture rounds from 46 species held in the Ian Potter Australian Wildlife Biobank at Museums Victoria Research Institute. The CVUI was adapted from the Wildlife Sperm Index (Jacobs et al., 2026) and assigns weighted scores encompassing four sequential culture stages -- establishment, first passage, expansion, and cryobanking -- with a continuous viability modifier applied at the cryobanking stage. Survival analysis identified individual animal identity as the primary source of variance in culture establishment, whereas taxon was the primary predictor of first-passage success. Beyond first passage, failure rates were too low to reliably assess either effect, with critical attrition concentrated at the earliest pipeline stages. These findings informed the differential weighting of CVUI components and have direct implications for workflow prioritisation and banking strategy. Monitoring can now be targeted at establishment and first passage, the stages where intervention has the greatest impact, with taxon-specific attention warranted at first passage and individual-level attention at establishment, while the robustness of the late-stage protocol means that banking yield is largely determined before a culture reaches P1. Integration of CVUI scores into collections management platforms such as Axiell EMu (Electronic Museum) would transform passive record-keeping into active decision support, enabling real-time quality tracking, early flagging of at-risk cultures, and longitudinal benchmarking of biobank performance across species, collectors, and tissue types. This framework provides a foundation for optimising wildlife fibroblast biobanking protocols, developing taxon-specific culture standards, and expanding standardised quality assessment across wildlife biobanks nationally and internationally.

Context Pumping stations pose a threat to fish globally through land use change, habitat fragmentation and entrainment risk, with the catadromous and critically endangered European eel particularly impacted. Objectives/methods Establish, model, assess and understand the present-day distribution of European eel and resident fishes in 152 pumping station catchments in a once extensive wetland (The Fens) using eDNA metabarcoding (855 samples over two and half years), with specific focus on anthropogenic influences on hydrological connectivity and habitat quality. A removal survey design maximised confidence in negative results while minimising time and consumable costs. Results Eel occurrence upstream of pumping stations was low (occupancy = 28.3%) and positively associated with catchment area, fish species richness and natural hydrological connectivity (gravity drainage or flooding) and negatively associated with distance from the tidal limit. Fish species richness replaced catchment area and improved model performance, potentially acting as a biotic indicator of habitat quality and connectivity. Pumped catchments with manually operated upstream water transfers had reduced eel presence, potentially linked to the direction of water flow or the timing of operation. By contrast, fish species richness increased in these catchments during summer, suggesting displacement into unsuitable long-term habitats. Physical habitat maintenance had no detectable effect on eel occurrence or fish species richness. Conclusions This study provides the first landscape-scale assessment of European eel distribution and drivers of occurrence in pumped river catchments. The highly novel and comprehensive insights have implications for European eel conservation as well as infrastructure and catchment management, including compliance with legislation (EC Regulation No. 1100/2007).

Mesozooplankton is a vital component of pelagic food webs, serving as a key trophic link between primary producers and higher marine organisms, and driving coastal and oceanic biogeochemical cycles. This study investigated the abundance, biovolume, community structure, and spatial distribution of mesozooplankton in relation to hydrographic variables in the Northeastern Arabian Sea (NEAS 15{whitebullet}N - 21{whitebullet}N) during the Spring Intermonsoon (March 2019) on board FORV Sagar Sampada. Sampling across 14 stations comparing coastal (> 50 m) and oceanic (< 1000 m) waters revealed distinct environmental gradients. Both Sea Surface Temperature (SST: 24.33{whitebullet}C - 28.68{whitebullet}C) and Sea Surface Salinity (SSS: 35.25 - 36.65) exhibited a declining trend toward northern latitudes, whereas Dissolved Oxygen (DO: 4.55 - 5.24 ml * L-1) increased northward. Chlorophyll concentrations were significantly higher in coastal regions (mean 1.45 mg * m-3) than in oceanic waters (mean 0.36 mg * m-3). Correspondingly, mesozooplankton biovolume (excluding large gelatinous taxa) was threefold higher in coastal waters (mean 1.39 mL * m-3) compared to oceanic waters (mean 0.38 mL * m-3). Mean numerical abundance was also higher coastally (605 ind. * m-3) than oceanically (524 ind. * m-3). A total of 21 mesozooplankton taxa were identified. Copepods dominated the community structure across both regimes (coastal: 61.07%; oceanic: 56.69%). In coastal waters, Chaetognatha (14.76%), Cladocera (9.39%), and Decapod larvae (5.69%) were the secondary drivers, with localised salp and siphonophore swarms observed at 17{whitebullet} - 19{whitebullet}N. In oceanic waters, Ostracoda (22.93%) and Salpidae (12.51%) were major secondary contributors. These results indicate that during the Spring Intermonsoon, the NEAS exhibits moderate productivity representative of a receding winter cooling regime.

In this study, we investigate alliance formation and complexity in male Indo-Pacific bottlenose dolphins around Mikura Island using five years of data collected through underwater observations. Focusing on 18 mature males, we examined affiliative behaviors (proximity and rubbing), consortships, and associations. To determine male relationships, we evaluated a simple model (small units) and a complex model (large units). In both models, units were identified by association, and models were evaluated by the extent to which affiliative behaviors and consortship were concentrated within units. All types of behaviors were more concentrated within units determined by the complex model than the simple model, and thus the former was further investigated. The unit sizes determined by the complex model were three, seven, and eight, and variation in association frequency was observed within units. Within units, two to four males engaged in a single consortship irrespective of association frequency. Given that units are mediated by affiliative and cooperative relationships, it is reasonable to interpret units as alliances. Considering the variation in both alliance size and within-alliance relationships, as well as the fact that only a few males cooperate in a single consortship, we suggest that a multi-level structure is plausible in the Mikura community.

The rariphotic zone, typically spanning depths of approximately 130 to 300 meters, represents a key transition between light-dependent coral reef ecosystems and the aphotic deep sea. Despite its potential ecological importance, including its proposed role as a refuge for species exposed to climate-driven stress, rariphotic ecosystems remain poorly understood. In this study, we conducted a systematic review and synthesis of the scientific literature on these habitats from 1970 to 2025. Following the PRISMA 2020 protocol, we analyzed 185 studies to characterize the historical development of research, identify geographic and methodological biases, and assess shifts in research priorities over five decades.Our results show a marked increase in research effort over the last decade, driven in part by advances in underwater technologies such as Remotely Operated Vehicles (ROVs), Human Occupied Vehicles (HOVs), and Baited Remote Underwater Video Station (BRUVS). However, this growth remains uneven, with persistent biases toward benthic rather than pelagic studies and a strong concentration of research in geographically accessible regions. Multivariate analyses of research novelty indicate that technological innovation and the formal recognition of the rariphotic zone in 2018 corresponded with major structural shifts in literature. Although the rariphotic zone is now increasingly recognized as an ecologically distinct component of the reef continuum, it remains underrepresented in ecological theory and conservation frameworks. Future research should move beyond descriptive taxonomic mapping toward integrative, data-driven functional ecology, with particular emphasis on long-term monitoring and depth-stratified connectivity.

The sea star Patiria miniata is a widely used and powerful model organism for cell, developmental, and reproductive biology, but it has lacked genetic tools for expressing transgenes or endogenously tagging proteins. We developed a protocol to endogenously tag a broadly expressed actin gene and to express additional fluorescent markers from the same locus, using CRISPR/Cas9 genome editing. We also identified and isolated a promoter sequence of this actin gene which drives expression of transgenes. This promoter and transgene cassette can be introduced via a plasmid into the genome and persist through metamorphosis into the juvenile stage. Robust methods to induce metamorphosis that result in healthy juveniles are essential for developing stable transgenic lines and have been lacking in the field. Here we report a fast and efficient approach to induce the metamorphosis of larvae into healthy juveniles by introducing surf clam shells. Thus, we present a reliable method to generate both CRISPR/Cas9 knock-in and plasmid-integrated transgenic juvenile P. miniata, enabling future research on their fascinating biology, including regeneration, oogonial stem cells, metamorphosis, and more.

DNA metabarcoding of faeces is a powerful, non-invasive method for assessing predator diets. However, when studying the diet of generalist predators, broad PCR primers are used to amplify the wide range of potential prey species and metabarcoding outputs are often dominated by sequences from the predator. While blocking primers can be used to reduce PCR amplification of predator DNA, they frequently cause partial predator suppression and unintended prey blocking. Peptide nucleic acid (PNA) clamps, offer a promising, underutilised alternative by binding strongly and selectively to predator DNA to block its PCR amplification. In this study we designed and validated a novel PNA clamp targeting the 18S rRNA gene to suppress bird and mammal predator DNA in dietary samples. We tested this clamp on tissue mixtures and faecal samples from three seabird and two seal species across temperate, subantarctic, and Antarctic regions. The PNA clamp substantially increased the proportion of prey reads recovered while maintaining consistent prey community composition across all predator species. Our results demonstrate not only the general effectiveness of PNA clamps over standard blocking primers, but also provide a powerful, broadly applicable new tool to improve the accuracy in DNA diet metabarcoding studies.