Ebooks

Aquaculture and fisheries have emerged as critical pillars of global food security, nutrition, and livelihood. With the world’s population continuing to grow and wild fish stocks depleting, aquaculture offers a promising solution— but only if practiced sustainably. This edited volume brings together frontier research, technological innovations, and ecological insights that collectively aim to revolutionize aquaculture and fisheries science for a resilient future. The book encompasses diverse dimensions of modern aquaculture. It opens with a discussion on cutting-edge technologies that are transforming farming systems, with special emphasis on nanotechnology, next-generation sequencing, nano sensors, and advanced wastewater treatment methodologies. Such innovations herald a new era of precision aquaculture where water quality, disease outbreaks, and productivity can be managed with unprecedented efficiency. Equally crucial are the chapters on fish nutrition and reproductive health, highlighting microbial technologies, phyto-biotics, reproductive hormones, and the impact of environmental contaminants such as heavy metals and pesticides. Together, these contributions reinforce the need for holistic approaches that enhance growth, resilience, and reproductive success in cultured species. As aquaculture faces the pressing challenge of climate change, this work gives special attention to climate-smart solutions: reducing carbon footprints, remediating pollutants through phytoremediation, managing aquaculture sludge through sustainable pathways, and expanding production into offshore environments. These insights chart a course toward low-emission, eco-friendly, and adaptive farming systems.

Introduction Aquaculture, the controlled cultivation of aquatic organisms, has grown into a critical industry for global food security, economic development, and environmental sustainability. As the demand for seafood continues to rise, innovative technologies are revolutionizing aquaculture, making it more efficient, sustainable, and resilient to environmental challenges (Bostock et al., 2010). This chapter explores cutting-edge advancements in aquaculture technology, focusing on automation, precision farming, biotechnology, and digital monitoring systems. Automation and Robotics in Aquaculture Automation is transforming aquaculture operations by improving efficiency and reducing labour costs. Automated feeding systems, underwater drones, and robotic net cleaners are among the latest innovations enhancing fish farming productivity. Automated Feeding Systems Automated feeding systems have significantly improved the efficiency and sustainability of aquaculture operations by ensuring precise feed distribution, reducing waste, and enhancing fish growth rates (Fig. 1). These systems integrate advanced technologies such as artificial intelligence (AI), machine learning, and smart sensors to optimize feeding schedules and feed amounts based on fish behaviour, water quality, and environmental conditions.

Introduction The aquaculture sector is vital in ensuring global food security by providing a substantial share of the world’s protein supply. With the rising demand for aquaculture products, enhancing fish growth and development has become increasingly important. However, traditional approaches, such as dietary supplements and environmental management, often fall short in terms of efficiency and sustainability. In this regard, nanotechnology presents a groundbreaking solution, with nanomaterials offering innovative methods to overcome these limitations. Nanomaterials possess exceptional physicochemical properties, including a high surface area, enhanced reactivity, and nanoscale dimensions, making them highly effective in various fields like medicine, agriculture, and environmental management.Their application in aquaculture has demonstrated the potential to enhance nutrient delivery, boost immune system responses, and improve feed utilization, ultimately promoting better fish growth and health. Additionally, nanotechnology facilitates the targeted delivery of bioactive substances, reducing waste and mitigating environmental impact.This discussion delves into the significant role of nanomaterials in improving fish growth and development, focusing on their mechanisms, advantages, and practical applications. By exploring the interactions between nanomaterials and aquatic biological systems, we can uncover sustainable and innovative solutions to fulfill the increasing requirements of aquaculture sector. In recent decades, aquaculture is the fastest growing sector and has become a vital food source to meet the global growing demand for protein requirements. This sector provides protein source, healthy fat, and essential micronutrients for the people around the world. It offers local employment, livelihood, high export earnings, supporting national GDP. Improved aquaculture practices have increased fin and shellfish production, decreasing dependance on wild seed and fish stocks. Global fish consumption increased by 3% between 1961 and 2019 (FAO, 2023). Nanotechnology is a promising solution, offering unique properties at smaller dimensions (1-100 nm) with novel applications (Matteucci et al., 2018; Shaalan et al., 2015). Recent efforts focus on health management, fish and shellfish development, seafood processing, and water treatment.

Introduction The growing population has a direct impact on fisheries. The demand for food derived from aquatic origin is increasing rapidly. The fish production trend and world population over the years are shown in Figures 1 and 2, respectively.The production from culture-based fisheries has surpassed the capture-based fisheries (FAO, 2024). Global aquaculture production is one of the fastestgrowing sectors among global food systems. With the increasing demand for fish and seafood, there is increasing pressure to find sustainable solutions for feeding farmed fish (Tacon et al., 2011). Traditional fish feed, primarily derived from wild-caught fish (Fishmeal) and land-based crops, presents several environmental and economic challenges. These include overfishing, deforestation, and rising feed costs, which threaten the sustainability of the aquaculture industry. Hence, there is an urgent need for alternate feed ingredients (Olsen and Hasan, 2012). The feed has largest environmental impact in the intensive culture system. Hence, more prominence has to be given to a selection of fish feed ingredients, which can contribute to reduce the environmental impact and target on growth of the animal. Intensification should go in hand with sustainability of the system and feed ingredients play a significant role in it. In response to these concerns, microorganisms have emerged as a promising solution to enhance fish nutrition in a more sustainable manner. Microorganisms, such as bacteria, yeast, algae, and fungi, can be a source of feed ingredients with various advantages, including improving nutrient digestibility, and reducing the environmental footprint of fish farming.

Introduction Climate change has emerged as a vital worldwide concern in contemporary times. It is an incontrovertible fact that the climate has changed in the past, is currently experiencing changes, and will persist in changing irrespective of the extent of mitigation efforts invested. Defined as a substantial shift in weather patterns over a period ranging from a few decades to millions of years, climate change is a phenomenon of critical importance that commands our attention and action. Fisheries and aquaculture are becoming a global industry in terms of food production and employment- enerating sectors. Millions of people in India rely on fisheries for a living, either directly or indirectly, as subsistence fisheries, typically located at the bottom of the economic pyramid, with lower earnings, disorganised jobs, and greater socioeconomic risk (Dutta et al., 2007). The fisheries sector contributes 1.03 per cent of the Indian GDP. Climate change badly hampered the food production sector, the fisheries sector is also not untouched due to its dependency on local weather and climate parameters (Temperature, Precipitation, humidity etc.). In its third assessment report, which was released in 2001, the Inter-Governmental Panel on Climate Change (IPCC) came to the conclusion that new or altered insect pest incidence and decreased crop yields in most tropical and sub-tropical regions would disproportionately affect the poorest nations (IPCC, 2001). To meet the food needs of a growing population in the face of climate change, climate-smart aquaculture (CSA) is an integrated approach to improving technological, policy, and investment conditions to promote sustainable agricultural development for food security (FAO, 2015).

Introduction Biotechnology is a rapidly evolving field that harnesses biological systems, organisms, and cellular components to develop products and processes beneficial to humanity. In fisheries and aquaculture, biotechnology has revolutionized species identification, genetic enhancement, disease management, and sustainable production practices. By integrating molecular biology, microbiology, and genetic engineering, this multidisciplinary science has enhanced aquaculture productivity and contributed to food security. The advent of recombinant DNA (rDNA) technology, along with genomics, transcriptomics, proteomics, and genome editing, has transformed fish biotechnology by enabling precise genetic modifications, improving growth rates, and enhancing disease resistance. A significant milestone in aquaculture biotechnology was the FDA approval of AquaAdvantage salmon, a genetically modified salmon designed to grow faster than its conventional counterparts. This approval marked the beginning of transgenic animal food production, demonstrating the potential of genetic engineering to enhance food production efficiency. In addition, genome-edited fish, such as the CRISPR-Cas9 modified tiger puffer and red sea bream, have been approved in Japan, further showcasing the advancements in gene-editing technologies for improving aquaculture species. These developments highlight the increasing acceptance of biotechnological innovations in fisheries, paving the way for more sustainable and productive aquaculture practices.This chapter focuses on the fundamental principles and methodologies of rDNA technology, molecular techniques, and recent advancements in biotechnology, emphasizing their implications in fisheries and aquaculture.

Introduction Next-generation sequencing (NGS), a High Throughput Sequencing (HTS) methodology, sometimes referred to as deep sequencing or massively parallel sequencing, has completely changed genomic research and DNA sequencing. Compared to the traditional Sanger sequencing approach, which took more than ten years to finish the human genome project, this state-of-the-arttechnology allows scientists to sequence a full human genome in a single day (Behjati and Tarpey, 2013). Although Sanger sequencing has mostly been replaced by NGS in research areas, it is still not widely used in clinical areas (Slatko et al., 2018). High-throughput DNA sequencing techniques have developed quickly over the past 20 years, and new approaches are constantly being developed. A greater range of applications in the basic and applied sciences become available as these technologies advance (Reis-Filho, 2009). Overfishing, pollution, and climate change are putting the world’s aquatic ecosystems, which are home to a wide variety of fish species under previously unheard-of strain (Prakash, 2021). For effective conservation and management, accurate and efficient monitoring of fish diversity is therefore essential (Meinam et al., 2023). Techniques like physical capture and morphological identification have been used historically, but they can be intrusive, time-consuming, and labor-intensive. A new age of fish diversity monitoring has been brought about by the development of NGS technologies, which provide a potent and noninvasive substitute (Kumar and Kocour, 2017). Rapid and thorough genetic material analysis is made possible by NGS, which offers previously unheardof insights into the distribution, composition, and population dynamics of species.

Introduction Water is an essential and irreplaceable environmental resource, fundamental to the survival of diverse living organisms on Earth. Covering approximately 70% of the planet’s surface, water is categorized into freshwater, marine and saline water. The freshwater system is further divided into lentic (e.g., lakes and ponds) and lotic (e.g., streams, rivers and springs), which serve as crucial sources for meeting daily human water needs (Mishra et al., 2015, 2016). Presently, water quality is influenced by both natural and human-induced factors, including climate conditions, irrigation practices, topography and geological features (Harman et al., 2012). Key physicochemical properties— such as temperature, dissolved oxygen, pH, transparency, conductivity and water current—along with chemical parameters like nitrates, phosphates, heavy metals and organic matter, play a vital role in evaluating the effects ofpollution on water quality (Awasthi and Tiwari, 2004). Upto pollution has become a major global challenge, driven by rapid industrialization, population growth and urban expansion (Bijekar et al.,2022). The release of untreated or insufficiently treated wastewater into natural water bodies raises serious environmental and public health concerns (Akpor and Muchie, 2011). Wastewater contains diverse pollutants, including heavy metals, organic compounds, pathogens, pharmaceuticals and microplastics, all of which pose significant threats to aquatic ecosystems and human well-being. Conventional treatment methods such as sedimentation, filtration and chemical treatments often fail to effectively remove emerging contaminants and achieve complete purification. Additionally, these traditional techniques can be costly, energy-intensive and may generate secondary pollutants requiring further treatment. In response, the demand for more efficient, sustainable and costeffective wastewater treatment solutions has fuelled research into advanced technologies like nanotechnology (Palit et al., 2023).

Introduction Aquaculture is one of the food-producing industries with the fastest rate of growth in the world and is widely recognized for its substantial contributions to food security, revenue production, and poverty alleviation (Subhasinghe, 2003). The production of aquaculture has increased dramatically during the last 30 years, from less than 20 million tonnes in the early 1990s to 178.9 million tonnes in 2022. The aquaculture industry reported an average growth rate of 6.7% per year globally from 1990 to 2020 (FAO, 2022). In 2020-22, the global annual per capita fish consumption was 20.4 kg (FAO, 2022). In addition, 58.5 million people were engaged in this sector worldwide for their livelihood. Many new approaches and technologies have been developed to increase the production. However, aquaculture faces significant challenges, including environmental quality, quality seed availability, and disease management (Sitcha et al., 2020; Oglend, 2020). To address these issues, the aquaculture industry adopts new scientific and technological advancements. Among the recent advancements in science, nanotechnology is fast emerging as a novel tool for the next generation of aquaculture and fisheries development. Nanotechnology is rapidly becoming a new tool for the growth of aquaculture and fisheries in the next generation, among other recent scientific breakthroughs (Shah et al., 2020).

Introduction Wastewater management has emerged as a critical environmental concern, posing severe threats to ecosystems, human health, and animal life due to  inadequate treatment and disposal systems. Various technologies have been employed to manage wastewater effectively, among which biological treatment techniques have gained widespread acceptance. These methods are  favoured for their affordability, operational simplicity, minimal reliance on chemicals, lower energy consumption, and eco-friendly characteristics (Smith and Brown, 2020). Among biological treatment processes, both aerobic and anaerobic methods are extensively utilized, with specific focus on Upflow Anaerobic Sludge Blanket (UASB), Expanded Granular Sludge Blanket (EGSB), and UASB-aerobic digester reactors. Comparative analyses of these approaches highlight their treatment efficiencies, advantages, drawbacks, and operational constraints. Additionally, the integration of aerobic and anaerobic treatment systems, particularly the UASB-aerobic digester combination, has shown promising results in optimizing wastewater treatment (Jones et al., 2021). In many underdeveloped and developing regions, inadequate wastewater management has led to severe sanitation challenges, exacerbating health risks and facilitating the spread of waterborne diseases. The lack of proper wastewater treatment, combined with deficient healthcare infrastructure and inadequate housing, further aggravates the situation. Wastewater typically contains high concentrations of biodegradable pollutants such as Total Suspended Solids (TSS), Biochemical Oxygen Demand (BOD), and Chemical Oxygen Demand (COD), which, if discharged untreated, contribute significantly to environmental degradation (Lee and Wang, 2019). Both organic and inorganic contaminants originating from domestic, industrial, and agricultural sources play a major role in water pollution. In regions suffering from water scarcity, the reuse of treated wastewater is an essential strategy for water conservation and sustainability (WHO, 2022).

Introduction Aquaculture has grown into a significant business and is the fastest-growing agricultural production sector in the world, taking new, intense, and diverse directions (Villa-cruz et al., 2009). Aquaculture has experienced intensification in recent years attributable to escalating stocking densities and excessive feed utilization, which have imposed stress on aquatic organisms and ultimately inhibited their growth and immune functionality. Chemotherapy remains a principal approach for the treatment and prevention of aquatic diseases. Nevertheless, a plethora of scholarly articles have indicated that chemical therapeutics exert adverse effects on both human health and ecological systems. The aquatic environment is adversely affected by antibiotics and their residuals, as a significant proportion of bacterial strains are developing resistance to these pharmaceuticals within the ecosystem. Consequently, there has been a concerted emphasis on the exploration of environmentallysustainable alternatives (Kumar et al., 2020). The public increasingly recommend natural compounds, while the utilization of synthetic chemicals, hormones, and antibiotics is increasingly becoming impractical owing to consumer apprehensions and stringent regulatory frameworks in numerous nations (Chakarborty et al., 2014). Phytobiotics can be conceptualized as products originating from plants that are incorporated into animal feed to optimize performance in aquatic species. Predominantly, leaves, roots, tubers, or fruits of various herbs, spices, and other botanical sources may be utilized as phytobiotics (Arts and Hollman, 2005). These substances are typically employed to promote enhanced growth performance in the cultivation of shrimp and fish. Based on their processing characteristics, phytobiotics are divided into categories:

Introduction Freshwater pearl farming is an emerging and promising sector within India’s aquaculture industry, offering significant potential for economic growth and sustainability. As the country modernizes its agricultural and aquacultural practices, the cultivation of freshwater pearls presents a lucrative opportunity for farmers, particularly in regions where traditional agriculture faces challenges. Recognizing its importance, the Indian government has integrated pearl farming into its broader Blue Revolution initiative, which seeks to enhance the fishing sector and improve livelihoods through sustainable practices. China and Japan are the main producers of freshwater and marine pearls, respectively, whereas China is the world’s biggest producer of pearls, including both marine and freshwater pearls, with 3540 tonnes produced, accounting for 98% of global pearl production. Bangladesh, Korea, Thailand, and Vietnam, have recently begun both research and industrial-scale programs in response to the worldwide commerce potential of farmed freshwater pearls (Fassler, 1994). The history of pearl farming in India dates back to 1969 with the stablishment of the Central Institute of Freshwater Aquaculture (CIFA), which initiated the cultivation of freshwater mussels for pearl production. This effort has gained momentum over the years, with states like Gujarat, Maharashtra, and Rajasthan becoming key players in the industry. Farmers in these regions are increasingly adopting pearl farming as a viable and profitable alternative to conventional agriculture. India is home to over 50 species of mussels found in various freshwater ecosystems.When a foreign body becomes lodged within the mantle (the skin) of pearl mussels or oysters, the mantle secretes a nacreous substance in response to the irritation. This process results in the formation of layer-by-layer nacre coating over the intruding object. Nacre consists of 80-90% calcium carbonate (CaCO3) and a protein called Conchiolin. As this sector develops, freshwater pearl farming not only promises to contribute to the economic growth of local communities but also positions India as a competitive player in the global pearl market. By addressing existing challenges and continuing to support innovation and education, the future of freshwater pearl farming in India looks increasingly bright.

Introduction Aquaculture has significantly contributed to the increase in global fish production. However, the domestication of only a limited number of species for intensive aquaculture has been achieved in recent decades. A primary challenge in the domestication and sustainable culture of candidate species lies in the standardization of induced breeding techniques. Controlled reproduction in captivity remains suboptimal for many commercially important aquaculture species. In captivity, females of several species often fail to complete oocyte maturation (Corriero et al., 2021), while males exhibit inadequate milt production (Zohar et al., 1989; Peter et al., 1993). Hormonal manipulation and environmental stimulation are considered effective approaches to overcome these challenges and facilitate captive maturation for induced breeding. Several hormone analogues, such as gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone-releasing hormone (LHRH), have been developed into commercial formulations like Ovaprim™, Ovatide™, and Wova-FH™, which target the brain-pituitarygonad (BPG) axis. However, these hormones have shown limited efficacy in the induced breeding of some commercially important species, including catfish. Recent studies suggest that neurohypophysial nonapeptide hormones also play a crucial role in modulating the GnRH– onadotropin (GTH)–steroid hormone pathway (Joy and Chaube, 2015). In mammals, nonapeptides include oxytocin (OT) and vasopressin (VP), which are homologous to isotocin (IT) and vasotocin (VT) in teleost fish. These nonapeptides, consisting of nine amino acids, are classified as basic (VT and VP) or neutral (OT and IT), depending on the amino acid at the eighth position. For example, VP has arginine, whereas OT has leucine at this position (Stoop, 2012). In Heteropneustes fossilis, a novel neuropeptide gene, savetocin, has been identified, distinguished from IT by the substitution of valine for isoleucine at the eighth position. Nonapeptides also have homologues in other organisms, such as annetocin in worms and insects, inotocin in mollusks, and conopressin in leeches and Lymnaea stagnalis. Among vertebrates, lungfish, amphibians, reptiles, and birds produce mesotocin and vasotocin, whereas marsupials secrete oxytocin and phenypressin (Darlison and Richter, 1999). These findings highlight the diversity and evolutionary significance of nonapeptides, as well as their potential as novel targets for improving induced breeding in aquaculture species.

Introduction Global aquaculture plays a significant role in ensuring food security both directly (by making food more accessible and available) and indirectly (by promoting economic growth). Since the 1980s, aquaculture production has increased, and it has been suggested that there is theoretically enormous potential for further growth. FAO came to the conclusion that the industry should acknowledge the pertinent environmental and social issues as it continues to grow, intensify, and diversify. Climate change, and more especially the greenhouse gas (GHG) emissions that occur along food supply chains, is one of the major environmental (and social) problems. We must comprehend how aquaculture contributes to global GHG emissions and how to reduce them in order to support its sustainable growth (FAO, 2019). What are Green House Gases? Heat-trapping gases in the earth’s atmosphere are referred to as greenhouse gases, or GHGs. Maintaining a temperature on Earth that is conducive to life depends on greenhouse gases. The average temperature on Earth would be around -20°C if the greenhouse effect didn’t exist. Since the beginning of the Industrial Revolution, human activity has raised the atmospheric quantities of greenhouse gases. The major GHG’s emitted into the earth’s atmosphere is given in Fig. 1.

Definition and Scope Offshore aquaculture, also known as open-ocean aquaculture, is an emerging approach to farming aquatic organisms in exposed, deeper waters further from the coastline than traditional nearshore aquaculture. While a precise definition remains elusive due to variations in regulatory frameworks and geographical contexts, offshore aquaculture is generally characterized by its location in deeper, more energetic waters with stronger currents and increased distance from shore (Holmer, 2010). This distinction from nearshore operations, typically situated in sheltered bays or estuaries, has significant implications for environmental impact, species suitability, and technological requirements. Key characteristics of offshore aquaculture • Increased depth and distance from shore: Offshore aquaculture operations are typically situated in waters deeper than 30 meters and at a significant distance from the coast, often beyond the territorial waters of a country (Buck et al., 2018). This exposes the cultured organisms to stronger currents, greater wave action, and a more dynamic environment compared to nearshore farms

Introduction Toxic inorganic and organic compounds are continuously contaminating our environment, endangering both human health and the planet’s ecosystems. This is a major worldwide problem. Because they persist in the environment, these pollutants which are caused by industrial processes, agricultural practices, urbanization, and over use of natural resources are very hard to control. While inorganic contaminants, including heavy metals, are difficult to break down naturally and need more complex remediation techniques, organic molecules may frequently be broken down into less dangerous components. Among these methods, bioremediation has become a viable, environmentally beneficial option that uses the inherent powers of fungus, bacteria, and plants to purify and repair polluted soils and streams. Phytoremediation, a specific form of bioremediation, harnesses the power of green plants to absorb, accumulate, degrade, or stabilize these harmful substances (Wang et al., 2021). This process not only mitigates pollution but also revitalizes ecosystems by improving soil structure, increasing biodiversity, and supporting sustainable land use. Phytoremediation provides a low-cost and less intrusive substitute for conventional cleanup techniques, which frequently entail high-energy procedures, chemical treatments, or considerable excavation, as the globe struggles with the growing danger of environmental deterioration. Rapid industrialisation, urban waste, and natural activities can introduce large quantities of highly toxic organic pollutants, including petroleum hydrocarbons, nitro and halogenated aromatic compounds, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dibenzofurans and dibenzop-dioxins (PCDD/Fs), solvents, explosives, and pesticides, into both aquatic and soil ecosystems (Tanwir et al., 2021). One of the major challenges to reducing water pollution is the presence of heavy metals including cadmium (Cd), lead (Pb), and chromium (Cr) in industrial and agricultural runoff. Associated with other pollutants, these metals disrupt aquatic ecosystems at the species and community levels, which has an array of negative impacts on animal and human health. The World Health Organization (WHO) has emphasized how important it is to keep an eye on these chemicals in drinking water because of their link to serious health concerns including cancer, respiratory disorders, and cardiovascular illnesses.

Introduction The aquatic ecosystem is full with harmful contaminants like heavy metals. Due to farming, mining, geochemical composition, and anthropogenic wastes, their concentration has dramatically increased. Heavy metals contaminate aquatic ecosystems through multiple pathways, such as industrial effluents, agricultural runoff, and atmospheric deposition. Once released heavy metals into water bodies, these metals undergo bioaccumulation, wherein they accumulate in aquatic organism’s tissue, including fish, gradually over time over time. Toxicity of heavy metals due to their long persistence in the environment and non-biodegradable nature. Additionally, heavy metals undergo biomagnification, leading to increasing concentrations as they ascend the food chain, posing greater risks to higher trophic level organisms, including fish. Fish serve as crucial bioindicators for evaluating the potential risks of pollution (Lakra & Nagpure, 2009). Exposure to pollutants, particularly heavy metals like cadmium (Cd), iron (Fe), lead (Pb), and copper (Cu), can lead to both acute and chronic toxicity, disrupting various physiological functions, including reproduction. A  ealthy reproductive system in fish signifies their ability to maintain population sustainability. Fish are widely consumed due to their desirable taste and affordability, making them a vital and cost- effective source of animal protein. Fish are more susceptible to heavy metal pollution than other aquatic species, despite being one of the most widely distributed species. Some heavy metals like cadmium, mercury, arsenic, and lead have no biological significance, while some like iron, copper, and zinc are vital to the metabolism of fish. Heavy metals concentration in the water bodies has increased significantly as a result of farming, mining, geochemical composition, anthropogenic wastes, and other factors. Heavy metals are among the most hazardous and widely distributed contaminants, naturally occurring as trace elements in the hydrosphere (Sankhla & Kumar, 2019). Fish, however, breed in environments that are naturally contaminated with heavy metals. Fish reproduction is essential to the natural ecosystem and is required for the development of aquaculture. Several studies show that heavy metals interfere with fish reproduction by preventing the induction of vitellogenin, postponing oogenesis, increasing the secretion of luteinizing hormone, and lowering the parameters of the gonadal somatic index and ovulation.

Introduction Pesticides play a crucial role in agriculture. During the period of the Green Revolution, the use of pesticides increased dramatically (Matson et al., 1997). According to the Environmental Protection Agency (EPA), pesticides can be defined as compounds that are used for the destruction, repulsion, or prevention of organisms that can be harmful to cultured crops (pests) as well as affect the regulation of plant growth. They are categorized based on several factors, such as their chemical composition (organophosphates, pyrethroids, neonicotinoids, etc.), based on the types of pests they eradicate (herbicides, insecticides, fungicides, etc.), and application methods. Although each pesticide has a distinct purpose, they all have comparable advantages. Some of the primary benefits of pesticide usage are the prevention of disease andan increase in yield, whereas secondary benefits include economic efficiency, an increase in food quality, facilitation of sustainable agriculture, improving public health, etc. However, the extensive use of pesticides has its consequences. These pesticides are meant to control or eliminate pests, but their toxicity could end up in unexpected areas. Its utilization poses significant harm to the environment, particularly to aquatic ecosystems. While they are essential in agriculture, their unregulated application leads to environmental degradation. The level of toxicity is influenced by factors such as pesticide concentration, mode of action, chemical composition, and persistence in the environment. Pesticides can cause both acute as well as chronic health effects. Through runoff or leaching, they indirectly enter water bodies, harming aquatic flora and fauna. A 2001 study revealed that over 90 percent of fish and water samples collected from various streams contained traces of one or more pesticides (Kole et al., 2001).

Introduction The conceptual foundation of environmental DNA (eDNA) can be traced back to French criminologist Edmond Locard’s principle that “every contact leaves a trace.” eDNA, often referred to as the “blueprint of life,” represents the genetic material shed by organisms into their environment. This innovative approach allows scientists to obtain biological information without directly interacting with or disturbing the organisms. eDNA technology is particularly advantageous in studying megadiverse ecosystems, as it enables the isolation and analysis of genetic material from various environmental samples, such as soil, water, and air. The approach of environmental DNA (eDNA) has its roots in metagenomics, which has long been used to study microbial communities in soil, water, and sediment. The concept of eDNA was first applied in microbiological research on marine environments (Orgam et al., 1987; Handelsman, 2004). Early breakthroughs in biodiversity monitoring included the detection of invasive species, such as Rana catesbeiana (American bullfrog), in French swamps, demonstrating the potential of eDNA in ecological studies (Díaz-Ferguson and Moyer, 2014). The persistence of eDNA also depends on the species and habitat: in freshwater, it may last between 15 and 30 days for fish and amphibians, while in marine environments, it typically persists for shorter durations, ranging from 0.9 to 7 days for marine mammals. These variations underscore the importance of understanding environmental and biological factors when applying eDNA methods for monitoring biodiversity and ecosystem health. The transport of eDNA in rivers is particularly rapid, with genetic material potentially traveling tens of kilometers from its source. This dynamic propagation must be accounted for when designing experiments and interpreting results.

Introduction India has a well-established fisheries and aquaculture industry that significantly impacts Gross Domestic Product (GDP), foreign exchange, and nutrition. The fisheries sector plays a crucial role in India’s economy, contributing approximately 1.07% to the national GDP and 6.72% to agricultural GDP in 2021-22 (Economic Survey, 2022). India is second-largest producer of fish in the world (after China), with an annual production of around 16.24 million metric tonnes (MMT) in 2022–23, comprising 12.2 MMT from Inland fisheries and 4.04 MMT from marine fisheries. The fisheries sector has experienced remarkable growth over the decades. Fish production surged from 0.75 MMT in 1950-51 to 12.59 MMT in 2018-19, marking a seventeen-fold increase. This growth has been accompanied by a rise in the sector’s contribution to agricultural GDP, which impressively increased from 0.84% in 1950 to 5.7% in 2017. India is one of the largest seafood exporters, with exports reaching INR 63,969 crores ($8.09 billion) in 2022-23 (Marine Products Export Development Authority - MPEDA). Frozen shrimp is the leading export commodity, followed by frozen fish and cephalopods. The USA, China, the EU, and Southeast Asian nations are key export markets. This robust performance underscores the sector’s role in bolstering India’s foreign exchange reserves. The sector supports direct employment to over 28 million people, mainly in coastal and rural communities (National Fisheries Development Board, 2023) and indirect employment, including processing, transportation, and allied workers. Fish is an important source of protein, essential fatty acids, vitamins and minerals. The harvest, handling, processing and distribution of fish provide livelihood for millions of people and also provide valuable foreign exchange earnings. In both the industrialized and developing countries, fish is an important and cheaper source of animal protein to local communities (Adewolu and Adeoti, 2010). Fish is also used as source of other nutrients such as micro nutrients, minerals, and essential fatty acids mainly in the Low Income Food Deficit Countries. However, the disadvantage with the fish is that it is highly perishable though it is an inexpensive protein source. Due to these characteristics, the fish suffers 50-60% higher post harvest losses compared to agricultural commodities.