Blue swimming crab (Portunus pelagicus) supports a valuable export fishery in Indonesia, currently estimated at over $400 million per year and employing over 250 thousand workers. High demand has led to the overexploitation of P. pelagicus in recent decades. However, accurately assessing stocks and harvest rates can be difficult. Variation in estimates of harvest sustainability among government, industry, and independent institutions highlights the need for comprehensive assessments. In this study, we examine the crab population in an artisanal nearshore fishery in Parepare Bay, South Sulawesi. We conducted a monthly analysis of the fishery for one year using two methods: (1) surveys of harvested crabs at a landing site and (2) collections of unharvested crabs from four sites in the bay using crab traps. From both methods, the average carapace width for male and female P. pelagicus was approximately 10 cm, and around half of the harvested crabs had not reached maturity. Estimates of spawning potential ratio for P. pelagicus in this fishery were 4%–9%, indicating overexploitation of the stock and impaired recruitment. As an additional aim, we examined the relative abundance of species in the crab community. We found that the bay is dominated by other species of swimming crab, namely Charybdis anisodon and Thalamita crenata. These other species may be predators of P. pelagicus, and high predation rates may further contribute to juvenile mortality in this stock. Achieving a sustainable harvest of P. pelagicus will likely require multiple actions such as enforcement of regulations, restocking of juveniles, and the restoration and protection of nearshore habitats.
The overfished and endangered reticulate whipray genus ( Himantura spp.) comprises up to eight genetically separate lineages that are considered distinct species: H. uarnak , H. undulata , H. leoparda , H. tutul , H. australis , and three possibly undescribed species ( Himantura spp. 1-3). Their geographic distributions so far have not been clearly determined, possibly because of persistent misidentification when using morphological criteria. To circumvent this problem, we provide diagnoses based on an updated nucleotide-sequence dataset at the CO1 locus for all seven species that have been sequenced at this locus. Species distribution maps based on genetically-validated records are presented. Notably, H. uarnak was confirmed as endemic to the Red Sea and the western part of the Indian Ocean while its sister species H. leoparda was endemic to the Indo-Malay archipelago. Two other sister-species, from the Indo-Malay-Australia region, Himantura sp. 1 and H. australis , were geographically distributed in a parapatric fashion. Himantura tutul was distributed from the Western Indian Ocean to the Sunda Shelf while H. undulata ’s range extended from the Arabian Sea to the Sunda Shelf. The present molecular taxonomic revision of the threatened genus Himantura thus clarifies the identity of the sequences in public repositories and provides new information on their distribution that will be highly relevant to their conservation. Himantura sp. 1, which is endemic to the Indo-Malay archipelago, is described as a new species.
Aquaculture production and restoration often require the sampling of oyster gonad tissues to monitor gametogenesis and reproductive traits, and for biosecurity practices. This is particularly relevant to Ostrea species, the sexes of which cannot be determined based on gametes release during the spawning phase. However, sampling of oyster tissue relies predominantly on destructive methods, which involve the removal of oyster shells and the dissection of tissues for histology. This approach prevents the monitoring of the same individuals over time, leading to approximation of sex ratios and overestimation of oyster reproductive parameters. It also involves the sacrifice of oysters, which is undesirable and prohibitive, particularly for restoration practices and endangered species with limited broodstock availability. The development of efficient and reliable non-invasive techniques is crucial, particularly within commercial and research aquaculture, to enable the selection of breeding and biosecurity screening protocols. The present study compared two non-sacrificial methods, in isolation and in combination with biopsy of oyster gonadal tissue. The effect of shell drilling, a novel non-sacrificial sampling method, and weekly exposure to anaesthesia (MgCl2), was assessed on the European flat oyster Ostrea edulis health and survival, using mortality rates and physiological parameters (growth and clearance rate). Although the combination of anaesthesia and biopsy is currently used in aquaculture and research, the weekly exposure to this method resulted in substantial oyster mortality (25%) and significant reduction in clearance rate (p ≤ 0.012) after 4 weeks of experiment, which indicates a clear physiological stress response to frequent use of this technique. The combination of shell drilling and biopsy, however, resulted in no oyster mortality (0%) and fast shell regeneration (100% in 3 weeks). Therefore, it represents a promising alternative to destructive approaches, which could facilitate future monitoring and manipulation of sex ratios, and genetic and disease screening, without sacrificing remnant depleted stocks.
The grooved carpet-shell clam ( Ruditapes decussatus ) is a native clam species that inhabits estuaries, lagoons, and coastal flats along the Mediterranean Sea and the northeast Atlantic. This highly prized bivalve is an ecosystem engineer that provides major ecological functions, including water filtration and sediment bioturbation. A decline in production has recently been observed in several areas of southwestern European and the Mediterranean region; however, data documenting this phenomenon remain scarce and are largely unpublished. To address this knowledge gap, we conducted a study based on official statistics, the expertise of 24 marine ecosystem experts from eight countries covering 17 coastal sites, and a preliminary literature map. This approach enabled the development of an expert-informed regional perspective on the reported declines of R. decussatus , as well as a synthesis of the regulatory measures and restoration actions implemented across the study area. The findings indicate a sharp decline in both production (−32 to −100%) and stocks (≈ −80%) over the past two decades. The onset of the decline varied among sites, occurring between 2003 and 2024. According to the participating experts, the main suspected drivers of the decline were disease, overfishing, competition with alien species, and climate change. The most common regulatory measures were minimum conservation reference sizes, closed fishing seasons, and licenses. Only a few restoration projects were identified, focusing on restocking through seeding, the collection of natural broodstock, harvesting natural spat or substrate modification. This study provides a preliminary overview of the seemingly widespread decline of R. decussatus across the southwestern European and Mediterranean region and highlights the need for coordinated research to elucidate the causes of this reported decline, as well as for restoration actions to support the recovery of this native species.
Clams are coastal resources widely exploited by both fishing and aquaculture. Most inhabit shallow waters, especially lagoons, that are transitional zones between the sea and land. In the Mediterranean French lagoons, two clam species are usually exploited: the native European clam, Ruditapes decussatus , and the introduced Manila clam, Ruditapes philippinarum , whereas several others are not of fishing interest, such as the golden carpet shell, Polititapes aureus . Those animals are relatively small, spend most of their lives buried, and can be difficult to identify based on shell morphology. Therefore, we tested a metabarcoding approach to detect clam species from environmental DNA (eDNA) samples. After an in silico comparison between a universal and a group-specific metabarcode, we conducted an in vivo experiment to characterise this metabarcode on clams and tested it in situ in two French lagoons. Specifically, we aimed to answer the following questions: (1) Is the group-specific metabarcode developed for freshwater Venerida also usable for marine Venerida and, more specifically, for clam species? (2) What clam species are detected in two French Mediterranean lagoons? (3) Is the intraspecific information of interest in characterising the populations and improving the surveys? The metabarcode proved to be very powerful to detect the targeted clam species and allowed support for a very significant depletion of the European clam in one lagoon and the predominance of the Manila clam in another lagoon. This eDNA metabarcoding protocol allows species identification with an easy deployment on the field and no clam sampling.
Consumer-driven aquaculture development is becoming increasingly critical in order to satisfy the growing global demand for seafood. This is particularly relevant for high-value species like prawn, where understanding market preferences is essential for aligning production in accordance with consumer demands. This study examined the factors that influence consumer preference and willingness to pay for prawn, taking into account intrinsic, sensory, extrinsic, and demographic attributes. A survey of 300 consumers from Bangladesh, analyzed using logistic regression, revealed that product quality attributes are the primary driver of prawn choice. Among the attributes, freshness and size of prawn significantly enhanced preference: consumers were nearly six times more likely to select fresh prawn while over three times more likely to choose larger ones, and commanded willingness to pay premiums of US$2.41/kg and US$1.78/kg, respectively. Further analysis confirmed that taste and availability have a positive impact on preference, while odor and increasing prices were detrimental. Demographic segments, including younger, higher-income consumers, exhibited a greater preference for premium qualities. The results suggested that producers should prioritize quality, promote larger prawn, and avoid low-margin early harvests. In parallel, a market segmentation strategy based on prawn size and consumer income will be crucial to differentiate products and align with market demand.
This study examines the dietary composition and variation in the feeding of the invasive blue crab Callinectes sapidus in Mellah Lagoon, a safeguarded coastal habitat in northern Algeria. During a one-year period (February 2021–March 2022), 287 stomachs from adult crabs were examined quantitatively and qualitatively, considering sex, reproductive condition, and season. Yearly average stomach vacuity rate was 37.6%, with substantial seasonal variations and significant differences between ovigerous and non-ovigerous females. Prey items were classified into nine taxonomic groups, with the majority being Arthropods (37.42%), followed by unidentified organic matter (27.46%), mollusks (15.47%), teleost fish (11.49%), and plant material (7.8%). A significant level of trophic similarity was observed between males and females. In contrast, the correlation between ovigerous and non-ovigerous females was positive but not statistically significant. Seasonal comparisons also showed non-significant correlations between winter and autumn and between winter and spring. The estimated trophic level (3.3) supports the classification of C. sapidus as an opportunistic omnivore.
Taxonomic uncertainties, often arising from cryptic species or lineages, present a significant impediment to wildlife conservation. This problem has been partially alleviated by the advent of DNA barcoding. Uncovering unrecognized sympatric species/lineages, in turn, provides an opportunity to examine their respective responses to potentially shared historical environmental oscillations within a comparative phylogeographic and demographic framework. Based on four mitochondrial genes, we detailed the phylogenetic diversity of a species complex within the genus Saccostrea Dollfus and Dautzenberg, 1920—a group of tropical and subtropical oysters—along the coasts of Ishigaki and Iriomote Islands in the Ryukyu Island Arc, Japan. We further assessed mitochondrial diversity and historical demography for each identified lineage to evaluate the impacts of the Last Glacial Maximum (LGM) on their population trajectories. Our survey revealed nine distinct lineages, including one previously unrecorded. This finding, combined with known lineages, brings the total to at least 12 lineages within the Ryukyu Island Arc. These lineages were generally characterized by elevated mitochondrial diversity and non-star-like haplotype networks, indicative of long-term population stability. Our demographic reconstructions based on Bayesian skyline plot analyses further suggested that population sizes remained stable throughout the LGM. By integrating these findings with regional paleoceanographic context, we discuss the mechanisms underlying this apparent population stability.
The rearing of hatchery-produced European clams, Ruditapes decussatus (Linnaeus, 1758), was tested for the first time in suspended lantern nets deployed on a pre-existing offshore longline structure originally installed for mussel Mytilus galloprovincialis rearing within an innovative offshore Integrated Multi-trophic Aquaculture (IMTA) system. This approach was designed to evaluate the growth performance of clam seed reared offshore in suspended culture as a strategic storage and grow-out solution to address several major challenges facing shellfish aquaculture during critical warm periods, including summer heat waves, declining water quality, and pathological risks associated with climate change. Two lantern nets were deployed, and clam seed were assigned to two experimental groups according to shell length. The pre-fattening group included individuals with shell lengths below 13.28 ± 1.52 mm, whereas the fattening group consisted of individuals with shell lengths exceeding 15.90 ±1.53 mm. Each lantern contained two size classes per experimental group, and each size class was represented in duplicate. Both groups were reared simultaneously in suspended lantern nets over a 316-day experimental period extending from June 2023 to May 2024. Our results revealed a significant mean length gain reached 2.6 ± 0.86 mm in the pre fattening and 1.18 ± 0.36 mm in the fattening, respectively with a relatively low mortality (<36.13% for pre-fattening;<4% for the fattening). These findings highlight the feasibility of European clam rearing into a pre-existing offshore IMTA longline and support this approach as a sustainable storage strategy, particularly during the summer period.
Different types of tags and markers are commonly used for various fish monitoring and tracking purposes. Effects of tags and markers on fish and the retention rates can affect the interpretation of mark-recapture data on both the individual (e.g. growth and body condition) and population level (e.g. survival and production estimates), making studies of this issue important. In this study, we examined tag retention of Carlin tags and potential effects on growth and body condition of Passive Integrated Transponder (PIT)-tags on the European eel (Anguilla anguilla). We used data from several long-term tagging projects conducted in a natural Swedish lake, combining outlet trap monitoring with catch data from a commercial fisher. The longest of these studies spanned over 27 years, covering the majority of the eel's resident life stage. We found that the retention rate of Carlin tags was 92%, with 64% of the Carlin-tagged silver eels being recaptured. The recapture rate of PIT-tagged eels released as juveniles in the lake was 12%. This recapture rate indicates little or no effect on survival when compared to other studies of both tagged and untagged eels. No major impact of PIT-tags on growth and condition in eels was found. We conclude that both Carlin and PIT-tags are suitable methods for tagging European eel, each with strengths in its respective area of use.
Restocking and mariculture of hatchery-bred sandfish Holothuria scabra are practiced in some countries to restore depleting wild populations and increase the global dried trepang or beche-de-mer supply. However, releasing cultured juveniles into the wild often results in slow growth and high predation mortalities, which may be related to their ontogenetic level of chemosensory ability to detect food and avoid predators. In a series of experiments using two-chambered aquaria, this study examined the preference responses (e.g., attraction, avoidance, or stationary) of hatchery-bred sandfish juveniles when presented with odors from predators (crab and fish), food (periphyton and formulated feed), combinations of odors, or the absence of odors (i.e., seawater only). Two groups were tested: small-sized sandfish (3–5 g, 4 months old) and medium-sized sandfish (15–20 g, 7 months old). Results showed that sandfish, overall, exhibited the lowest preference for predator odors, tending to remain stationary or select chambers either with seawater only or with food odors. When presented with conflicting predator and food odors, sandfish (particularly the small-sized group) showed a pronounced preference to be stationary, instead of being attracted to or avoiding any chemical odors. These results indicate that sandfish juveniles can detect and discriminate among chemical odors, with responsiveness and behavioral patterns varying across ontogenetic stages, sizes, and rearing histories. These findings provide essential insights that may improve husbandry protocols and optimize sandfish productivity in aquaculture or restocking operations.
Sardinellas ( Sardinella aurita and Sardinella maderensis ) are small pelagic fish that play a critical ecological and socio-economic role in West African coasts. These species primarily feed on plankton, a rich source of long chain polyunsaturated fatty acids (LC-PUFAs), including docosahexaenoic acid (DHA), arachidonic acid (ARA), and eicosapentaenoic acid (EPA). This study investigated the relationship between the muscle and gonad LC-PUFA profiles and the physiological status in both males and females at two periods of the upwelling season (January and March, 2022). Fatty acid profiles were measured in storage and membrane lipids to capture environmental and physiological variations, respectively. The ARA and DHA contents were largely enriched in membrane lipids as compared to reserve lipids. Within membrane lipids, gonads contained higher levels of LC-PUFA compared to muscle, suggesting preferential allocation to gonad structures. From January to March, Le Cren body condition index increased, associated to increasing reserve lipid storage. Additionally, gonad membrane showed an increasing DHA and a decreasing ARA contents. Altogether, these results suggest increasing lipid storage and investment for reproduction for both species and sexes. However, the gonado-somatic index of females remained stable between the two sampling periods, highlighting the importance to distinguish between the dynamics of gonadal biochemical composition and their morphological growth, two processes that may be decoupled depending on the maturation stage. Inter-specific differences were, however, observed: S. maderensis exhibited higher DHA and EPA concentrations in muscle reserves, and a higher ARA content in both reserves and membranes lipids compared to S. aurita , suggesting differential dietary LC-PUFA trophic regimes between species. Overall, our findings highlight the strong coupling between environmental conditions, dietary LC-PUFA availability and reproductive physiology in sardinellas. This emphasizes the critical role of LC-PUFA in supporting their reproductive success, and thus, to sustain the management and conservation of their populations in upwelling ecosystems.
In the short term, climate change is forecasted to affect fish quality by decreasing omega-3 reserves, thereby impacting human health. Together with scientific uncertainties, climate change imaginaries are diffused among the public, who struggle to make sense of them and imagine the consequences for their own diets. Our study scrutinizes the sociogenesis of representations associated with changes in fish food that are not visible for nonexperts, using an extensive, qualitative study based on semi-structured interviews with consumers. After a thematic analysis related to the imagined impacts of climate change on fish, we analyzed the anchoring process of representations in scrutinizing the role of food antinomies through three categories of fish eaters (traditional, nutrient-oriented, and ecology-oriented) that emerged from the interviews. The results indicate that preexisting food antinomies allow sorting out significant/nonsignificant climate change imaginaries and guide the anchoring process in reducing the psychological distance of climate events while making more concrete their impacts on fish food for consumers. This study contributes to bridging theories on food antinomies, imaginaries – as cognitive resources for envisioning wider changes – and social representations – as cognitive processes for anchoring the “unknown” and turning it into more significant correspondence with food materiality. Our study provides key insights for shaping more integrated health policies that address the combined challenges of marine climate change and nutrition, while water-centric communication can help the public grasp the links between ocean and human health.
This study assessed the status of the Cunene horse mackerel (Trachurus trecae) stock in Guinea-Bissau (2018–2023) using fishery-dependent and independent data. Catches ranged from 29.1 kt (kilotones) in 2020 to 10.2 kt in 2023, dominated by Chinese (57.2%) and Guinean (22.6%) fleets. Fishing was concentrated between January and May, mainly in the 10–12°N and 16–18°W area, with demersal trawl accounting for 52.1% of catches. Biological parameters revealed negative allometry with b = 2.80 [2.75–2.84], L50 = 20.0 [19.6–20.3] cm for grouped sexes, L∞ of 48.8 [46.4–52.2] cm, K of 0.55 [0.34–0.74] yr−1, and M of 0.67 [0.47–0.87] yr−1, indicating a “fast” life history. Length-based indicators show reduced yields and loss of large spawners, suggesting current exploitation patterns might be unsustainable, but results were considerably sensitive to life history parameter values, particularly L∞ and L50, which warrants continued data collection. These findings call for immediate science-based management, which might include seasonal closures, reduced fishing effort, improved gear selectivity, and enhanced monitoring. Enhanced institutional capacity and regional cooperation are critical to strengthening monitoring efforts.
Since the end of the 20th century, the maximum sustainable yield (MSY) has been at the core of debates in the fisheries sector from a biological, economic, and geopolitical perspective. In theory, MSY aims to maximize fishery yields while preventing harmful declines in stock biomasses. However, MSY is primarily derived from monospecific population dynamics and does not necessarily achieve a suitable balance between exploitation, socioeconomic objectives, and foodweb and ecosystem functioning. Since the reform of the European Common Fisheries Policy (CFP) in 2013, FMSY has been the management target for European fisheries. Given the high prevalence of overexploited stocks at the time, fisheries theory suggests that, for those stocks, a reduction in fishing mortality should lead to an increase in biomass, which in turn should result in an increase in fishing opportunities. While some of the indicators calculated to monitor the effectiveness of the CFP show encouraging signs regarding stock status, the fishing industry, which in the meantime has also been affected by a series of crises, does not seem to perceive the expected benefits. Using a meta-analysis of 92 stocks assessed by ICES in the Northeast Atlantic, we examined how scientists' advice on fishing opportunities has evolved and whether it has responded to changes in F and SSB since the last CFP reform. While the analyses show that fishing opportunities have increased mainly in cases where fishing mortality and spawning stock biomass have changed the most, they also appear to be evolving more slowly, and the picture remains rather mixed. This may also reflect adverse signals of global change and the impact this may have on future fishing opportunities.
Fish quantity has long been the most needed information for stock management as the main source of uncertainty for the fishing sector. However, as the rate of global environmental change accelerates, degradation of fish quality has become a new source of concern. Indeed, evidence is accumulating on a general decrease in fish size and fat content and on the increase of the occurrence of various contaminants. Small pelagic fishes (SPFs) are valuable food rich in fatty acids but, for this reason, are also prone to the accumulation of organic pollutants. While environmental impacts on fish quality are increasingly documented, knowledge on how these propagate to the fishing industry is still very limited. In our study we explored how the various components of the SPF French social-ecological system, from plankton to fish to fishers to the canning industry and the market, interact in their response to global change. First, by analysing the national catches of sardine and anchovy from 2000 to 2024 across the three French maritime regions, we highlighted the strong seasonal dynamics of both fisheries and the strong interannual trends over the period. Second, focusing on Bay of Biscay sardines, we revealed that on both seasonal and interannual scales, the fishing sector was caught between a bottom-up environmental control through its effects on fish quality, namely fat content and size, and a top-down control resulting from canning industry strategies in provisioning and marketing, ultimately mediated by the preferences of consumers. The fishing fleets appeared as the most vulnerable component in the system, while the processing industry appeared more flexible. Our results indicate that a decrease in fish quality can threaten an entire fishing industry. We recommend collaborative efforts between scientists and stakeholders to co-construct adaptation strategies aiming at strengthening the resilience of fisheries social-ecological systems in the face of global change.
Despite major advantages associated with rapid growth, the variation in body size among individuals within a population remains remarkably large. Indeed, fast growth in itself might come at a cost in terms of oxidative stress. In the Bay of Biscay, sardines (Sardina pilchardus) face growth-related issues: body size at age 1 has declined substantially during the last decades, and sardines with higher growth during their first year have lower survival rates. We therefore tested the hypothesis that 1-yr-old sardines with larger body size exhibit higher levels of oxidative damage than their smaller conspecifics. To this end, we measured protein (protein carbonyl) and lipid (malondialdehyde) oxidative damage in dorsal muscle samples of sardines caught during five surveys conducted in the Bay of Biscay in spring and in autumn. We categorized “large” and “small” 1-yr-old sardines within each survey based on their length distribution, balancing their spatial coverage. As larger 1-yr-old sardines are more likely to be mature, which might influence the relationship between growth and oxidative damage, we included sardines’ maturity stage in our analyses. While there was no relationship between sardine body size and malondialdehyde levels, we found that larger sardines had greater protein carbonyl content compared with smaller ones. Furthermore, we found no evidence for the effect of maturity stage on either protein carbonyl or malondialdehyde levels. Overall, the greater accumulation of protein oxidative damage in larger sardines, regardless of their maturity stage, supports the hypothesis that faster growth might indeed lead to an oxidative cost in this wild fish species.
Regional fisheries management organizations are mandated to reduce impacts of commercial fishing activities on non-target species. This is particularly important because fishing associated with natural drifting objects and artificial fish-aggregating devices across the oceans poses adverse impacts on non-target species, including juveniles of tuna species. In the Indian Ocean off Sri Lanka, deep-sea fishing boats are engaged in fishing with gillnets, longlines, and encircling nets associated with natural floating objects. The present study aimed at investigating whether target species and bycatch species in the catches of fishing methods can be differentiated to introduce effective management to the fisheries and to perceive driving forces in terms of the nature of fishing strategies with a view to recognizing appropriate management measures. From the boats operated from four fishery harbors of southern Sri Lanka from February 2018 to December 2020, species compositions of landings of 1915 fishing operations consisting of gillnetting, longlining, flotsam-associated ring netting, and a combination of ring netting with gillnetting and longlining were analyzed separately for each fishing method. Also, cost components of individual fishing operations and corresponding net revenues, gleaned from logbook records of boats, were scrutinized. This analysis underscored that there was a noticeable difference in species caught in the five types of fishing boats, consisting of large tuna and tuna-like species in the landings of longlines and drift gillnets. Landings of flotsam-associated ring netting were dominated by shade-loving species and juvenile tunas. As fuel cost is considerably lower in ring net fisheries than in gillnet and longline fisheries due to shorter trip duration and as there is higher net revenue from the fishing operations, there is an increasing trend of ring netting associated with floating objects. Under the existing legal framework, this fishery can be restricted by introducing high seas licenses.
The tall sea pen Funiculina quadrangularis (Pallas, 1766), a widespread octocoral species found in Mediterranean soft-bottom habitats, is recognized by the Food and Agriculture Organization of the United Nations as a vulnerable marine ecosystem indicator due to its sensitivity to bottom trawling. Adapted to stable environments, its distribution could be affected by the combined impacts of climate change, particularly warming bottom waters, and trawling activities. Records from the Mediterranean International Trawl Survey program and other sources were used in an ensemble species distribution modelling approach to predict current habitat suitability and project potential habitat shifts under the intermediate IPCC climate scenario SSP2–4.5 for 2050 and 2100. Results indicated a widespread distribution across the Mediterranean continental shelf and slope, with the species typically found between 100 and 750 m depth (occasionally as shallow as 20 m) and tolerating temperatures between 12°C and 16°C. By 2050, over 80% of the current habitat was projected to remain suitable. However, only 50% were expected to serve as climate refugia by 2100, likely due to warming bottom waters and increased salinity. Some habitat gains were projected (e.g., Ligurian Sea, Corsican waters, deep Eastern Mediterranean), but uncertainties persist regarding the species’ ability to colonize these new areas. Despite its presence in trawled areas, suggesting a relatively lower fishing pressure sensitivity than other VME taxa, significant habitat shifts were projected under future climate conditions. Therefore, it is essential to prioritize conservation efforts in areas projected to remain suitable over time. The climate refugia identified through this study offer critical guidance for future climate-smart VME management plans, helping to ensure the long-term survival of F. quadrangularis in the Mediterranean Sea.
This study examines the early invasion of Nile tilapia (Oreochromis niloticus) in Panam Reservoir, Gujarat, marking the first record of an exotic fish species establishing itself in this large reservoir system. Using Rapid Rural Appraisal and participatory approaches, the introduction pathway was traced to an accidental escape from cage culture initiated in 2018, with a major loss event in 2019. Initially seen sporadically until 2022, tilapia quickly expanded its presence, accounting for over 20% of the total catch by 2023 and ranking third among landed species. Ecological evaluations showed significant dietary overlap with native fishes, an association with eutrophic conditions, and traits such as trophic plasticity and high reproductive rates, indicating strong invasive potential. Although tilapia has increased overall fish biomass and contributed to local protein supply through higher landings, it presents ecological and economic threats by displacing native species and reducing the value of indigenous fisheries. The study highlights the need for strict biosecurity measures, regulated enclosure culture, and integrated management strategies to balance productivity with biodiversity conservation.
