Prosanta Chakrabarty

Marine habitats and ecosystems are increasingly being impacted by global climate change and the global spread of captive breeding. In this study, we focused on five typical Trachinotus species (Trachinotus anak, Trachinotus blochii, Trachinotus mookalee, Trachinotus goreenisi, Trachinotus ovatus) as research subjects. We utilized species distribution models and ecological niche models to predict the present and future potential distribution of these species, as well as to assess ecological niche overlap and evaluate the early warning of invasion by Trachinotus species. T. ovatus stands out with its broad distribution range and high adaptability to different environments. It occupies 1.114% of medium-high suitable areas, spanning 100,147 km2. Our predictions also suggest that T. ovatus would undergo a significant expansion (approximately 55% of the total area) under both past and future environmental scenarios, demonstrating a higher tolerance and adaptability to changes in ambient temperatures. It can be discerned that T. ovatus exhibits strong environmental adaptability, which may potentially lead to biological invasion along the southeastern coast of China. The T. anak, on the other hand, showed a higher expansion trend under high carbon dioxide concentrations (RCP8.5), indicating a certain convergence with carbon dioxide concentration. Our models showed that under future climatic conditions, T. ovatus would become the dominant species, with increased competition with T. mookalee and decreased competition with T. goreenisi, T. mookalee, and T. anak. Based on our findings and the net-pen culture mode of T. ovatus, we identified the hotspot habitat of T. ovatus to be located in the Indo-Pacific convergence zone. However, there is a possibility of an expansion trend towards the southeast coast of China in the future. Therefore, it is crucial to provide an early warning for the potential biological invasion of T. ovatus.

Global warming has significantly altered fish distribution patterns in the ocean, shifting towards higher latitudes and deeper waters. This is particularly relevant in high-latitude marine ecosystems, where climate-driven environmental changes are occurring at higher rates than the global average. Species Distribution Models (SDMs) are increasingly being used for predicting distributional shifts in habitat suitability for marine species as a response to climate change. Here, we used SDMs to project habitat suitability changes for a range of high-latitude, pelagic and benthopelagic commercial fish species and crustaceans (10 species); from 1850 to two future climate change scenarios (SSP1–2.6: low climate forcing; and SSP5–8.5: high climate forcing). The study includes 11 Large Marine Ecosystems (LME) spanning South America, Southern Africa, Australia, and New Zealand. We identified declining and southward-shifting patterns in suitable habitat areas for most species, particularly under the SSP5–8.5 scenario and for some species such as Argentine hake (Merluccius hubbsi) in South America, or snoek (Thyrsites atun) off Southern Africa. Geographical constraints will likely result in species from Southern Africa, Australia, and New Zealand facing the most pronounced habitat losses due to rising sea surface temperatures (SST). In contrast, South American species might encounter greater opportunities for migrating southward. Additionally, the SSP5–8.5 scenario predicts that South America will be more environmentally stable compared to other regions. Overall, our findings suggest that the Patagonian shelf could serve as a climate refuge, due to higher environmental stability highlighting the importance of proactive management strategies in this area for species conservation. This study significantly contributes to fisheries and conservation management, providing valuable insights for future protection efforts in the Southern Hemisphere.

Urbanisation and water developments in South Africa have created numerous challenges in managing water resources. Consequently, the native fish species Oreochromis mossambicus, prominent to freshwater ecosystems in South Africa now faces the threat of extinction amidst introductions of alien Oreochromis species. The species has recently been classified as Vulnerable on the IUCN Red List. Despite the economic importance of O. mossambicus within the South African region, little is known about the genetic and population dynamics of the species. In this study, we aimed to establish baseline genetic and population data, and determine the impact of water management practices on population structure. This data is crucial for the conservation and monitoring of this species across South Africa. The study revealed relatively low genetic diversity within sample localities but significant differentiation among populations. The analyses identified 16 geographically correlated genetic clusters, indicating substantial differentiation across catchments. Anthropogenic activities, changes in catchment use, and water management strategies significantly influenced the genetic population structure in the studied regions. Given the distinct genetic patterns, conservation-oriented management should prioritise maintaining existing genetic diversity to ensure the long-term survival of this vulnerable species.

AbstractAbstract. neighboring countries. Recently, an increase in biological surveys and access to natural preserves has led to a better understanding of species distributions in Nicaragua and across Central America. Here, we provide new departmental records for three species of didelphid, 18 chiropterans (Phyllostomidae, Molossidae, Vespertilionidae), one geomyid, and one mustelid from 21 sites across the country. This work underscores the need for additional sampling across Nicaragua to fill gaps in the known distribution of many species. This information can facilitate or inform conservation actions in established and proposed preserves in Nicaragua.

The Amazon basin, spanning approximately 540,000 km 2 , exhibits distinct fluviometric surfaces that differentiate between the dry and rainy seasons. This seasonality, along with hydrological connectivity and the creation of new habitats during the rainy season, significantly promotes the migration, reproduction, and feeding of potamodromous fishes. To estimate the realized niches of species, species distribution models (SDMs) employ the extrapolation of environmental predictors and species occurrence data. Our objective was to compare the spatial distribution of migratory fish species in the Amazon basin using SDMs based on variables characterizing the dry season, rainy season, and a combination of both. All evaluated treatments demonstrated high performance and exhibited different distribution ranges in the applied SDMs, particularly when combining environmental variables with occurrence data during the rainy season. These findings support the hypothesis that spatial distribution is influenced by seasonality. The increased fluviometric surface and enhanced connectivity of the rainy season favor both longitudinal and lateral migrations of Amazonian migratory catfishes. Moreover, the spatial distribution reveals four critical spatial overlap (CSO) regions with higher population densities regardless of the season. These CSOs primarily coincide with the Amazon alluvial plain, which exhibits the highest rates of endemism, species richness, and abundance of organisms. Considering the discontinuous and heterogeneous nature of fluviometry when performing niche modeling processes is pivotal, although SDMs applied in the Amazon generally ignore such regional seasonality.

Desert spring systems of the American southwest hold high local fish endemism and are ranked among the most threatened ecosystems in the world. The prioritization of conservation resources to protect species living within these arid landscapes requires knowledge of species abundance and distribution. The plight of Conchos pupfish (Cyprinodon eximius) is representative of freshwater fishes the world over, including population extirpations caused by human poisoning of streams and reservoir construction, to the extent that the species was once considered extinct in the USA. We developed a distance‐sampling framework to monitor Conchos pupfish abundance and coupled this approach with species distribution modeling to guide conservation actions. Our multiscale approach included surveying abundances within 5‐m transects at three reaches of the Devils River, where the last known USA populations persist. We combined this fine‐scale analysis with species distribution modeling for stream segments across the range of the species in Mexico and USA. Modeling revealed Conchos pupfish abundance among transects was negatively correlated with current velocity and detection was negatively correlated with water depth. Estimated abundance at a reach where the species was previously reintroduced was greater than other reaches combined in November 2019, lowest in March 2021 when reach water levels were very low, then equivalent with other reaches by October 2021 after water returned to the reach. Modeled Conchos pupfish distribution illustrated a high probability of occurrence on the periphery of the species' overall range within Texas, USA and broadly across Chihuahua, Mexico, where proposed protected areas might benefit the species. Our study provides conservation guidance by establishing (1) baseline and trajectory values for abundance, (2) transect locations where abundances might be managed within existing protected areas, (3) reaches where high abundances could be used for future repatriation, and (4) stream segments where future surveys might be conducted to assess conservation opportunities.

Amphibia is the most threatened animal group among all land vertebrates in the context of anthropogenic global change. Filling the conservation gaps for this taxonomic group could help achieve the ambitious target of covering 30 % of the land by 2030 (‘3030’ target) set by the 15-th meeting of the Conference of the Parties (COP15). In this study, we compiled the most up-to-date occurrence records and corresponding species-specific traits and phylogenies of amphibians in China (particularly those newly described in the past decade) to explore the spatial distribution patterns of multidimensional diversity (including taxonomic, functional, and phylogenetic) for different species groups (including all, endemic and threatened). Additionally, a new conservation gap index (CGI) was proposed and applied to the analysis of multi-objective conservation strategies. The results showed that the spatial distribution of taxonomic, functional and phylogenetic diversity of amphibians in China is markedly geographically diverse, with common hotspots for all three concentrated in the humid mountainous regions of southern China. The CGI, which is independent of arbitrary threshold selection and grid cell size, showed that the conservation gap for amphibians in China is largest in biomes such as tropical and subtropical moist broadleaf forests and temperate broadleaf and mixed forests. The multi-objective conservation analysis revealed that the Yangtze River basin, Pearl River basin and Southeast Basin in China have pivotal roles in achieving the ‘3030’ target due to their high taxonomic, phylogenetic and functional diversity, relatively high proportion of threatened and endemic species, and low coverage of existing nature reserves. Notably, sustainable management of less-protected habitats, including farmlands and grasslands, can reduce the area requirement of strict protection for reaching the ‘3030’ conservation goal. This study provides practical strategies for guiding amphibian conservation by systematically integrating multidimensional biodiversity information, habitat features and the spatial distributions of the existing natural reserves.

Largemouth Bass (Micropterus salmoides, LMB) and Smallmouth Bass (Micropterus dolomieu, SMB) are among the most highly invasive species across the globe, but are simultaneously among the most highly sought-after game fish. To explain these disparate views, data on invasive status and angling participation of these two species were compiled at the country level. Largemouth Bass were found established in 62 countries on five continents, whereas SMB were found established in only nine countries on the same five continents. Invasive risk assessments were disparate between the species, with more for SMB (N = 29) than LMB (N = 27). In every instance save one (Finland), SMB were considered “invasive” compared to LMB, which were “invasive” in only 74% of assessments. Twenty-eight countries with non-native black bass have groups that participate in high-profile fishing tournament such the Black Bass World Championship, BASS (Bass Anglers Sportsmans Society) Nation, and Major League Fishing. Most countries with fishing tournaments occur in countries with established LMB populations than in countries with established SMB populations, suggesting a greater economic importance on LMB fishing. The struggle between conserving biodiversity and relying upon economic benefits from fishing for introduced species is a wicked problem likely to continue into the future.

We examined the phylogeny and biogeography of the glassperch family Ambassidae (Teleostei), which is widely distributed in the freshwater, brackish and marine coastal habitats across the Indo-West Pacific region. We first built a comprehensive time-calibrated phylogeny of Ambassidae using five genes. We then used this tree to reconstruct the evolution of the salinity preference and ancestral areas. Our results indicate that the two largest genera of Ambassidae, Ambassis and Parambassis, are each not monophyletic. The most recent common ancestor of Ambassidae was freshwater adapted and lived in Australia about 56 million years ago. Three independent freshwater-to-marine transitions are inferred, but no marine-to-freshwater ones. To explain the distribution of ambassids, we hypothesise two long-distance marine dispersal events from Australia. A first event was towards Southeast Asia during the early Cenozoic, followed by a second one towards Africa during mid-Cenozoic. The phylogenetic signal associated with the salinity adaptation of these events was not detected, possibly because of the selective extinction of intermediate marine lineages. The Ambassidae shares two characteristics with other freshwater fish groups distributed in continental regions surrounding the Indian Ocean: They are too young to support the hypothesis that their distribution is the result of the fragmentation of Gondwana, but they did not retain the phylogenetic signal of their marine dispersal.

Freshwater ecosystems are highly vulnerable to the detrimental impacts of both biological invasions and climate change. Piscivorous alien fishes drive populations of small-bodied native fishes to extinction and warming is already driving extreme temperature events in lakes and rivers globally. Here, we use Ecological Niche Modelling (ENM) to predict how climate change will alter the geographical space of six alien fishes and five native fish genera (which include multiple endemic species) in Turkey, a hotspot of freshwater fish diversity. The models predicted that the geographical space of the alien fishes already present in Turkey would generally increase (including pikeperch Sander lucioperca and perch Perca fluviatilis ), but with the most substantial increases in largemouth bass Micropterus salmoides , a species not yet present in Turkey but that is invasive in countries nearby and is highly popular for sport angling. For the native fish genera, general predictions were for reduced geographical space, especially in the south and east of the country, suggesting the endemic species will become increasingly imperilled in future. Their populations will also be at increasing risk of deleterious impacts from the alien piscivores, as the predictions were also for increasing overlaps in the geographical space of both the alien fishes and native fish genera. These predictions suggest that the conservation of these endemic species need to consider measures on preventing both the introduction of alien species (e.g. largemouth bass) and the further dispersal of extant alien species (e.g. pikeperch), as well as habitat interventions that will limit the effects of climate change on their populations. These results also indicate that the combination of climate change and alien invasions could have substantial impacts on—and similar—hotspots of freshwater diversity.