India, a megadiverse tropical country is grappling with the rising trend of aquatic invasions. Out of 532 introduced non-native fish, 16 species of freshwater aquaculture and aquarium were assessed invasive by using a risk assessment protocol, ‘Fish Invasiveness Screening Test’. Six major identified invasion pathways of the aquatic invasive species were inadvertent or deliberate releases, escapes, contaminants from hatcheries, river corridors, stowaways and unaided introductions. Invasion mechanism further elucidated the factors promoting successful invasion in freshwater ecosystems. For predictive future performance of invasive fish, the concrete and predictive values based on mean abundance by weight was calculated. Over 28.67% and 29.02 % persistent increased yield of the invasive Tilapia and Common Carp respectively was predicted in the Ganga river in the coming decades. Single species Tilapia invasion facilitated multiple species fish invasion, manifesting in invasion meltdown. The trophic changes due to fish invasion exhibited biotic homogenization with trophic downgrading. Aquatic invasive species were found highly competitive interacting with native species causing serious biodiversity loss, health hazards, and economic damage consequently affecting the ecosystem services. In spite of available regulatory approaches and guidelines to manage aquatic invasive species, fish invasion has been on the rise. This paper suggests modifications and stringent implementation of the existing regulatory mechanisms besides adopting linkages, cutting-edge research on invasion science and modern molecular containment tools for effective management.

Biological invasions are a worldwide threat to the aquatic systems and have the potential to homogenize entire foodwebs and shift species abundance distributions to more skewed ones. Invasion impacts include effects on the foodweb structure and ecosystem functioning leading to a loss in native fish biodiversity and commercially important fisheries in many open water systems. The impacts of invasives are generally devastating as they spread in the foodweb with each species potentially interacting with multiple species. The foodweb modeling studies conducted in different inland aquatic ecosystems show that not all exotics cause a detrimental effect on the resilience of an ecosystem. Information on the foodweb structure and ecosystem properties is a prerequisite for formulating management protocols for conserving biodiversity, enhancement programmes and sustaining fisheries. The present paper reviews the impacts of invasive fishes in Indian aquatic ecosystems in the context of a changing foodweb scenario due to exotic fish species invasions. The information generated here could be applied for future research on similar ecosystems for deducing management actions.

Often regarded as a potential threat to the native fish fauna worldwide, the Brown Trout (Salmo trutta), has successfully established its population in the majority of the Himalayan rivers post its introduction dating back to the eighteenth century. Over the years, the species has gained infamy as a sport fish and is considered a profitable source of income to the locals ensuing a heightened propagule pressure due to lack of appropriate management actions. No comprehensive study has been conducted to date in order to understand the mechanism by which the Brown Trout poses threat to the native fish populations. Through the present study, we could assess its competition with the native Snow Trout (Schizothorax richardsonii) to understand the spatial assemblage of both the species across space in Tirthan, a pristine high-altitude river of the western Himalaya. River Tirthan is one of the major tributaries of River Beas traversing for most of its stretch within the protected boundaries of the Great Himalayan National Park Conservation Area. A total of 108 sampling points were chosen from confluence to origin of rivers/streams, ranging from 989 to 3677msl. A total of 28 explanatory variables were recorded at each point. Overall, the Brown Trout adults were found to be greater in relative abundance (66.1%) than the Snow Trout adults (33.9%). The fingerlings of Snow Trout on the other hand, were distinctively high in relative abundance (61.9%) than those of the invasive Brown Trout (38.1%). Non-native trout showed higher abundance in the higher stream orders i.e. in the main streams while natives mostly restricted themselves to the lower order streams. Redundancy analysis (RDA) for species and environmental covariates resulted in 40.75% of constrained variance with higher eigen values for Redundancy analysis1 and Redundancy analysis2. Ward's minimum variance clustering of Hellinger transformed data revealed sites agglomerating into six reasonable distinct subgroups with respect to species abundances. Immature individuals of non-native and native trout used similar habitat conditions, but they differed in using habitats at adult stage. Our results show a competitive dominance of Brown Trout in terms of higher abundance and maximum space utilization that highlight an urgent action for preventing its introductions to new areas. We recommend a national policy of ‘The Indian Invasive Species Act’ and management level interventions to control overstocking in the areas of established population.

In order to assess the distribution pattern and understand the prevailing factors for predicting further expansion of an exotic fish Oreochromis niloticus, this study was undertaken in the Ganga river flowing through the state of Uttar Pradesh using MaxEnt model. The authors report the distribution pattern of O. niloticus and prevailing causative factors mounting the expansion of O. niloticus in the Ganges based on MaxEnt modeling technique. The presence only occurrence data-set for this invasive species was prepared from the field data and also from data collated from the authenticated publications of different fisheries researchers. The data-set was analyzed with environmental and topographical variables typically incorporating seasonal and temporal variability using MaxEnt, a maximum entropy algorithm which showed that the area under curve was much closer to 1 (0.999). The model predicted elevation as the most influential predictor variable with permutation importance of 69.2% followed by slope_steepness (10.1%), Tmax_1 (7.3%) and Srad_5 (6.8%). The findings from the results suggest that invasive O. niloticus tend to spread in rivers where elevation is lower as well as slope_steepness of the river is higher and thus indicated that invasion might be higher in the downstream of the river. The model suggests that topography and its derived variable are the most significant predictors for distribution of invasive O. niloticus. The results of this study also confirm that the water qualities of the Ganga river are suitable for O. niloticus and if the model is supplemented with water quality variables data, the influential predictor variable in water quality can be well investigated with permutation importance.

The catch pattern of the exotic Common Carp (Cyprinus carpio) and their relationship with water quality along with maturity status of fishes were assessed during 2017-2019 to understand overall establishment and impact of the species in Buxar stretch of River Ganga in West Bihar, India. A total of 64 fish species were recorded including two exotic fishes (C. carpio and Oreochromis niloticus) from the river stretch during the study period. The annual production data depicted Cyprinus carpio to be the most dominating fish species encountered from the study area sharing 57.07% (by weight) during the period 2017-19. Calculated average ‘Invasion coefficient index (I_x)’of 0.25 in entire three-year study period revealed that the invasion has moderately impacted the indigenous fish diversity. Landing of Indian Major Carp (IMC) indicated severe decline (76.4 - 95.6%) in comparison to the catch data recorded earlier from Buxar. Data generated on sex structure of Common Carp indicated that the overall sex ratio showed positive recruitment within the smaller size range of 282-307 mm and thus avails a competitive breeding advantage over other carp fishes. Gut content of Common Carp from the stretch observed major share of phytoplankton (81.04%) and zooplankton (17.18%) and thus there are significant dietary overlap of Common Carp with other valuable species. The stretch has been impacted with anthropogenic loading as identified through significantly higher water specific conductivity (580 µScm^-1), Biochemical Oxygen Demand (3 mgl^-1), etc. in drastically reduced water discharge regime. Among different water parameters, river flow, Biochemical Oxygen Demand and Total Phosphate showed positive whereas specific conductivity showed negative correlation with Common Carp seasonal abundance. Future conservation management measures may be formulated keeping in view of the identified factors through the present study for reducing the impending risks of the invasive fish species in Buxar stretch of River Ganga.

We present results of the first major attempt to record the distribution of aquatic alien species in the Western Ghats Biodiversity Hotspot using Geographical Information System. A total of 32 alien species, including four macrophytes (Salvinia molesta, Pistia stratiotes, Eichhornia crassipes and Cabomba furcata) and 28 fish were recorded from the southern part of the Western Ghats. Seven of these have established natural populations and are invasive, which includes Oreochromis mossambicus, O. niloticus (Cichlidae), Poecilia reticulata, Gambusia affinis (Poeciliidae), Pterygoplichthys pardalis (Loricariidae), Cyprinus carpio (Cyprinidae) and Clarias gariepinus (Clariidae). Oreochromis mossambicus is the most extensively distributed invasive fish in the region. Major reservoirs serve as a spawning hub for species such as C. gariepinus and C. carpio. Significant pathways for the establishment of most alien species in Western Ghats were aquarium trade and aquaculture. Given the increasing records of alien species and proliferation of invasive species in the southern region of the Western Ghats, urgent research and policy interventions are suggested, including the development of a comprehensive database on distribution, trade, invasion biology, as well as determining both short-term and longterm impacts on endemic fauna.

India is endowed with a wide range of ecosystems, of which oceanic island ecosystems viz. Andaman and Nicobar and Lakshadweep are unique and ecologically fragile because of the high degree of endemism in species composition. Altogether 25 species under different faunal groups such as cnidarians, polychaetes, cirripedes, mollusks, and ascidians are reported as invasive species in Indian islands, of which 24 species are found in Andaman and Nicobar Islands, while 4 species are available in Lakshadweep. Ship-mediated invasions, especially ballast water discharge and ship-hull fouling, are the major source of invasions as these islands are located in the vicinity of the international sea route. In the present paper, we have represented these non-native species of fauna and flora to discriminate and identify them as non-native or invasive. This study deals with the diversity and distribution of aquatic invasive species in islands and their detrimental impact on the island ecosystem.

The present article is aimed at understanding current policies and implementation strategies for the management of aquatic invasive species in India and identifying opportunities for improvement. Existing management approaches and policies have briefly been put into place concerning fish introductions and aquatic invasive species, but looking at their effectiveness, it is argued that mitigating the negative impacts caused by invasive species should be at the core for their successful management. International institutions have explicitly recognized the need to contain and eradicate biological invasions and have set of relevant guidelines and enforcements. In India, risk assessment, risk management, quarantine, biosecurity and regulatory mechanisms have been developed and implemented to filter fish introductions and consequently check aquatic invasions. Nevertheless, invasive species introduced into the inland waters are emerging as ‘chronic risks’to the aquatic biodiversity and ecosystem services. It is imperative that these emerging issues are put on the National Agenda and Action Plan to regulate fish invasions and minimise their adverse impacts. A National Policy on prevention and control of aquatic invasive species is urgently needed to deal with nuisance and harmful impacts. Some future needs have also been suggested to tackle this issue.

This article examines the non-native fishes in the freshwater bodies of Andaman and Nicobar Islands with a focus on understanding the perception of stakeholders towards providing management solutions. A total of 56 freshwater fish species were reported from Andaman and Nicobar Islands of which 23 species were non-native to the Islands introduced either accidentally or deliberately. Among the 23 fishes introduced, 13 species were found to be transplanted from Indian waters into the Islands and 10 species were non-native to Indian waters. Mosquito Fish (Gambusia affinis), Mozambique Tilapia (Oreochromis mossambicus), Silver Barb (Barbonymus gonionotus), Red Bellied Pacu (Piaractus brachypomus), and Common Carp (Cyprinus carpio) are some of the important invasive species found here. Stakeholder perception studies were undertaken through semi-structured questionnaire and five point likert scale questions. The respondents (N=133) were classified into two groups as a) Fish farmers and b) Research/development personnel. Multinomial logistic regression analysis revealed that the profession of the respondents significantly influenced the awareness about the non-native fishes (p<0.001). Fish farmers (4.04±0.04) and Research/development (4.47±0.21) respondents mutually agreed on the need for awareness and education on the issue of non-native fishes (p<0.01). A management framework is suggested to address the issue of non-native fishes towards effective planning, conservation and management of the fragile Island ecosystems.

Ornamental fish culture and aquarium keeping have become a booming sector worldwide. It has been observed that a number of stakeholders are involved in introducing exotic ornamentals in India as well, as the takers are interested on variants and new species. Most of the exotic ornamental fishes are also being domesticated in India, since the demand is readily fulfilled through adequate supply to the hobbyists. This sector provides livelihood option to many people and helps to earn millions of dollars to our country every year, however, the invasion of exotic ornamentals in our natural water bodies needs to be assessed, monitored and controlled with due attention as it is a staid menace to our biodiversity. Around 400 species / variants of exotic freshwater ornamentals and around 100 exotic marine ornamental species including invertebrates are found to have introduced in the trade. It is significant to note that an apparent violation in the trade is taking place by concealing the Government of India approval, which is given only for 92 species / variants of fishes for import. Further, as some of the freshwater ornamental fishes currently available in the aquarium trade have invaded through natural water bodies, their impacts need to be studied in detail. To deal with the situation, the proper precautionary approach should be implemented by adopting measures after having proper quarantine, meticulous risk analysis and strategic prevention methods as well. Combined efforts of industry stakeholders with different government agencies, academic and research institutions is required and a suitable protocol has to be formulated for permissible import, sustainable production, supply and management.

Waterbirds are used as a bioindicator for analyzing wetland health because they are very sensitive to changes in ecosystems at the nutrient level and through exposure to pollutants. In the present study, bioaccumulation of trace elements (Cu, Zn, Ni, Pb, Co, Cd, and Mn) was investigated in Common Coot Fulica atra, Gadwall Anas strepera, and Eurasian Teal Anas crecca at Taunsa barrage and Chashma barrage located on Indus River, Punjab, Pakistan. Samples of water, sediments, and waterbirds tissues were collected during autumn 2018 and the spring of 2019. Metal concentrations were assessed by using a flame atomic absorption spectrophotometer (Thermo Scientific iCE 3000 Series). We found that the maximum bioaccumulation in birds was of cadmium. Order of metal accumulation was Cd > Pb > Zn > Co > Mn > Cu > Ni (Common Coot) and Cd > Pb > Zn > Co > Cu > Ni > Mn (Gadwall and Eurasian Teal) at Taunsa barrage. At Chashma barrage metal accumulation order was Cd > Zn > Pb > Co > Cu > Mn > Ni (Common Coot), Cd > Zn > Pb > Cu > Co > Ni > Mn (Gadwall) and Cd > Zn > Pb > Co > Cu > Ni > Mn (Eurasian Teal). A. crecca was the species in which the most of the trace elements (Cu, Ni, Pb, Co, and Mn) were accumulated at Taunsa barrage, while at Chashma barrage Zn, Pb, Cd, and Co accumulated in F. atra. Zn, Pb and Cd (avg. > 10) had a high bioaccumulation ratio and Co, Cu, Ni, and Mn (avg. < 10) had low bioaccumulation ratio. When tissues were compared for accumulation, the highest concentrations were observed in the intestine followed by gizzard, probably because of the feeding habits of these waterbirds.

Contamination by dangerous heavy metal in the estuarine environment has risen with concern to the safety of coastal fish as seafood. Anthropogenic emission in the coastal areas becomes the primary source of heavy metal pollution in the aquatic environment, which then accumulates in fish species. Therefore, marine fish has a potency to be used as a bioindicator for heavy metals contamination in the coastal environment, since it may vary, as the results of marine hydrodynamics. This research presents seasonal variations (west monsoon, east monsoon, and intermediate monsoon) of heavy metals accumulation in fish from the coastal region of Cirebon, Indonesia. Three types of economic fish (Scatopagus argus, Siganus canaliculatus, and Nibea albifor) were taken, and the heavy metals (Cr, Co, Cu, As, Cd, Hg, and Pb) content were examined by inductively coupled plasma - mass spectrometry (ICP-MS). The results showed a significant difference (p<0.05) of seasonal variation of heavy metals concentration in seawater and sediment. The contamination in seawater was higher during the east monsoon season, while the contamination in sediment was higher during the west monsoon season. The observation was also revealed variation on heavy metals accumulation in fish species. However, this study found no significant correlation (p>0.05) between the concentration of heavy metals in the environment and fish. Consequently, precaution is needed when using fish as a bioindicator for heavy metals contamination in coastal environments.

Carbamazepine is a pharmaceutical used in patients with seizures and bipolar disorder, which has been found in wastewater and many water resources. This is due to the inadequate disposal of pharmaceutical waste and the lack of treatment of municipal wastewater, as is the case in Colombia. The two main hydrographic basins of Colombia are the Cauca and Magdalena rivers, which are inhabited by the endemic species Striped Catfish (Pseudoplatystoma magdaleniatum). This has become an endangered species for various reasons, including the high contamination level of these rivers. In 2019, mature adult P. magdaleniatum of both sexes were caught in the Cauca river in Colombia. This was in order to assess the concentration of vitellogenin, as a biomarker of endocrine disruption, resulting from exposure to different levels of concentration of the emerging contaminant carbamazepine for 4 months. These tests were carried out in a fish farm. A significant decrease in the vitellogenin concentration was verified in females at concentrations of 25 µg l^-1 and 50 µg l^-1, and in males at 50 µg l^-1 of carbamazepine, with a significance level of p<0.05. Carbamazepine could cause a negative feedback in gonadotropin secretion, acting as an estrogen mimicker that causes a decrease in the level of vitellogenin.

Shoreline wetlands along Lake Ontario are valuable, multi-functional resources that have historically provided large numbers of important ecosystem goods and services. However, alterations to the lake's natural hydrologic regime have impacted traditional meadow marsh in the wetlands, resulting in competition and colonization by dense and aggressive Typha angustifolia and Typha x glauca (Cattails). The shift to a Typha-dominated landscape resulted in an array of negative impacts, including increased Typha density, substantial decreases in plant species richness and diversity, and altered habitat and changes in associated ecosystem services. Successful long-term adaptive management of these wetland resources requires timely and accurate monitoring. Historically, wetland landscapes have been surveyed and mapped using field-based surveys and/or photointerpretation. However, given their resource- and cost-intensive nature, these methods are often prohibitively time- and labor-consuming or geographically limited. Other remote sensing applications can provide more rapid and efficient assessments when evaluating wetland change trajectories or analyzing direct and indirect impacts across larger spatial and temporal scales. The primary goal of this study was to develop and describe methodology using U.S. Army Corps of Engineers National Coastal Mapping Program hyperspectral imagery, light detection and ranging data, and high-spatial resolution true-color imagery to provide updated wetland classifications for Lake Ontario coastal wetlands. This study used existing field-collected vegetation survey data (Great Lakes Coastal Wetland Monitoring Program), ancillary imagery, and existing classification information as training data for a supervised classification approach. These data were used along with a generalized wetland schema (classes based on physical and biological gradients: elevation, Typha, meadow marsh, mixed emergent, upland vegetation) to generate wetland classification data with Kappa values near 0.85. Ultimately, these data and methods provide helpful knowledge elements that will allow for more efficient inventorying and monitoring of Great Lake resources, forecasting of resource condition and stability, and adaptive management strategies.