eChapters

Introduction

In aquaculture practises carried out in open environments (e.g. ponds, cages and pens), natural interaction between the culture and non-culture species, where the culture species are been fed by the non-culture species (predation) can occur, causing significant economic loses (Ross, 1988). As many as thirteen different predators are considered to cause loss or damage on salmon farms in Scotland alone among which cetaceans are notable. Seals, sea lions, aquatic birds, dolphins, whales, otters, crabs, starfish, snail, snakes, rats etc are generally considered as predators (SSGA, 1990; Miron et al., 2005), but cetacean species are not notable predators within salmon farms. It is necessary to develop an environment friendly and economically feasible methods or technologies to limit the useless natural interaction. Manual chasing away or removal of predators, usage of scarecrows, anti-predatory nets, covering nets and increasing the tension of nets are some methods used to prevent predations in different aquaculture scenarios.

Acoustic Deterrent Devices (ADDs) otherwise called as Acoustic Harassment Devices (AHDs) help to prevent predation as they produce strong underwater noises (sound waves) that disturb and scare off the predators (Gordon & Northridge, 2002). AHDs are comparatively higher energy output devices than ADDs that operate at a power level of above 185 dB re 1µPa @1m. However, as the hearing threshold of different predators differ, the term “ADDs” are generally used for those that are efficient to deter the predators irrespective of their operating power levels (Götz & Janik 2010). One of the first usage of different unspecified sounds (eg: killer whale’s recorded voice) to deter predators (seals) were during the 1970s and no sounds were then found efficient in a long-term run (Anderson and Hawkins, 1988). Later through the 1980s, the precursor of modern ADDs (175-210 dB re 1uPa @1m) that emit out sound waves of frequency range (8-17 kHz), which is similar to the predator’s (seals) most sensitive hearing range were developed (Mate et al.,1987).

Introduction

In the face of a burgeoning global population, the imperative for robust advancements in food production, especially within the aquaculture industry, is more pressing than ever. The expansion of this industry necessitates a nuanced consideration of environmental, economic, and social factors underpinned by a commitment to sustainable development. However, the intensification of aquaculture, particularly in coastal regions, poses long-term environmental risks due to increased organic matter in water, demanding innovative solutions.

In recent decades, recirculating systems have emerged as a step toward sustainable aquaculture, offering an effective approach to control wastewater. High operating costs have hindered widespread adoption despite their potential, particularly in developing countries. Enter the need for a game-changing, cost effective, and environmentally friendly technology that resonates with farmers on a large scale. This is where the Biofloc system, or Biofloc technology (BFT), takes center stage. A beacon of cost-effectiveness, sustainability, and environmental friendliness, the BFT reduces water exchange to almost zero and slashes artificial feeding ratios. This revolutionary system enhances water quality and generates microbial protein for aquatic species, addressing critical challenges faced by the aquaculture industry.

Sustainability Issues Regarding Major Marine Raw Materials Used in Aquaculture Diets

In 2018, more than 70% of the fish production is from fed aquaculture where f ish meals (FMs) and fish oils (FOs) are the main marine raw materials used in aquaculture diets or fish feed (Hua et al. 2019). They are derived or reduced products from the catch of small, pelagic, low-priced marine fish (forage fish) like Peruvian anchoveta that are rich in protein, micronutrient and lipid and are commonly termed as the ‘feed grade marine fishery’ (Bell and Waagbø, 2008; Bendiksen et al. 2011). The whole fish or any other f ish processing by-products are either cooked and then pressed to produce a liquid which on centrifuging produce the fish oil or are dried and crushed into powder-like material which is called as the fish meal (FAO, 2020). FM has the enough balance and concentration of essential amino acids and FO are rich in n-3 essential fatty acids especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). FM and FO are the main ingredients in aquaculture diets as they are relatively cheap, readily available, accepted and digested by the fish. The highest amount of these ingredients are often used in feeds for the high value aquatic organisms like carnivorous finfish (eg: Dicentrarchus labrax, Rachycendron canadum) (mostly marine), eels, salmonids, trouts, marine shrimps and freshwater crustaceans (see figure 1) etc. (Houlihan et al. 2001; Halver and Hardy, 2002; Miller et al. 2008) which are mainly imported by prosperous countries adding to good seafood trade value. All the intensive aquaculture production systems like recirculatory aquaculture systems, raceway aquaculture systems, aquaponics, cage culture, shrimp ponds etc are the major end users of the marine raw materials.

With constantly increasing population and need for food security in the present era, an alternate option to safeguard the nutritional well-being of human civilisation is the utmost necessity of the hour. Aquaponics is a system which combines two food-producing systems such as a recirculatory aquaculture system and hydroponics in such a way, that, the waste of one system is utilised in the other system making it a perfect example of the eco friendly model. This system is a soil-less system which can be set up in small vicinity, providing higher outputs. The designs can be changed according to one’s needs, but the main components of the unit should be kept in mind. The main components consist of a fish tank, mechanical filter, biological filter, hydroponics unit along with sump. Although the hydroponics unit are of various kinds but broadly it can be classified into three main types-1. media bed, 2. Nutrient film technique and 3. Deep water culture. If there is a scarcity of land and water or if the quality of soil is poor, usage of aquaponics will be sustainable.

Introduction

Aquaponics is a combination of hydroponics with recirculatory aquaculture system(RAS) as a single production system. Water with fish wastes coming from the fish tank circulates and passes through the filters, the plant grows on beds and water recycles back to the fish tank in an aquaponic system. At f irst solid waste are removed by mechanic filtration followed by biofiltration for removal of dissolved wastes. Ammonia, which is poisonous to fish, is converted to nitrate, a more readily available fertiliser for plants, by bacteria in the biofilter. The plants absorb nitrate and other nutrients when the water passes through plant growing beds, filtering it prior to its arrival in the fish tank.

Introduction

In the 21st century aquaculture has become one of the most important booming industries in the world. With just a mere contribution to the worlds fish production in 1960’s, and able to contribute to about nearly 50% in 2021, production from aquaculture has increased manifolds. Successful aquaculture relies on creating a suitable environment for growth of aquatic animals. Water quality has to be the most important component for successful aquaculture production. Throughout the farming period, it is necessary to maintain good water quality to ensure high survival and fast growth of cultured species. There are numerous water quality parameters that can impact the well-being of fish and crustaceans, most of which are discussed in this chapter.

Factors like salinity and water temperature play a critical role in assessing the suitability of a location for the cultivation of specific species. Additionally, factors such as alkalinity, turbidity, phosphorus, and nitrogen hold significance due to their impact on plant productivity, which, in turn, affects aquaculture production. As the cultivation progresses, factors like dissolved oxygen, carbon dioxide, ammonia, and others gain importance, as they have the potential to create stress for the cultured animals. This chapter offers an overview of the presence and behavior of each of these variables in both natural water environments and aquaculture ponds.

Crabs are one of the fast-growing animals from phylum arthropod. Freshwater crabs is now becoming as an important shellfish in freshwater aquaculture production due to its delicacy and nutritional richness. Freshwater crabs are considered good for human consumption and economically important crustacean in many developing countries such as India, China, Nigeria, Japan etc. Freshwater crabs are distributed in the tropical region of the world and they spend their entire lives in freshwater. In Indian territory Western ghats of Maharashtra and north east part of India are considerably more diverse in freshwater crab biodiversity. While only freshwater crab species Barytelphusa cunicularis is commonly observed all over India. In Maharashtra Kolhapur and Konkan region stands out for well-established crab market, driven by high freshwater crab consumption. Freshwater crab serve as good protein food, lipid and cheap carbohydrate source as well as valuable mineral source for human consumption particularly tribal and poor people. Freshwater crab aquaculture, like other types of aquaculture practices, offers a wide range of culture systems, extensive monoculture to intensive monoculture. In freshwater crab aquaculture crab farmers mainly prefers Barytelphusa cunicularis as a culture species.

Introduction

The global population is expected to reach 10 billion by 2050, with seafood making up about 15% of the animal protein consumed, averaging 20.2 kg per person in 2020 (Boyd et al., 2022). Due to the overfishing of fish stocks, estimated at 93.8%, aquaculture is seen as crucial to meet future seafood demand (FAO, 2022). Aquaculture offers a promising solution to food security challenges by leveraging our oceans, seas, and freshwater bodies to produce healthy and nutritious food. However, it's worth noting that aquaculture has been linked to the loss of mangroves, with shrimp farming accounting for 38% of historical global mangrove depletion (Friess et al., 2019).

Mangrove forests play a crucial role in supporting diverse ecosystems and providing essential services, primarily in tropical and subtropical coastal areas where they thrive in intertidal zones. However, these same areas are often utilized for aquaculture activities, leading to significant mangrove forest conversion. For instance, aquaculture has been responsible for converting approximately 5,44,000 hectares of mangrove forests in eight tropical countries (Hamilton, 2013). To address the challenge of balancing mangrove conservation with aquaculture production, integrated mangrove aquaculture (IMA) has been proposed. IMA involves planting mangroves within or alongside shrimp or f ish ponds. However, it's important to note that mangroves within IMA shrimp systems typically do not provide the same level of biodiversity and ecosystem functions and services as intact mangrove forests.

According to the facts, groundwater salinization and the scarcity of freshwater are indeed expanding. In the coming decades, saline water will replace freshwater as the principal resource for agriculture and aquaculture. Over 8.62 million hectares of land in India and over 397 million hectares of land worldwide have been rendered unusable for traditional agriculture as a result of secondary salinization. Use of salinized land and the water resources for aquaculture is a flexible solution to reduce environmental problem with multiple potential benefits on the economic, social, and environmental fronts. As aquaculture demand has increased, new production methods have been developed. Inland saline aquaculture, here defined as a land-based aquaculture system using saline groundwater and surface water, is practised by a number of countries, including Israel, USA, India, and Australia. The possibility that saline groundwater may differ chemically from coastal seawater is one of the key barriers to the growth of inland saline aquaculture. One must either change the chemistry or choose species that can tolerate the fluctuations to get around this. Several species are farmed or evaluated for their potential including finfish like tilapia, Indian Major Carps, catfishes, climbing perch, Asian sea bass, cobia, milkfish, mullet, and sturgeons. By combining the usage of resources, cultural systems play a significant part in attaining the disruptive technology of inland saline aquaculture. This review revealed the finfish species raised in inland saline resources as well as culture methods such as pond-based, tank-based, biofloc, and aquaponic systems for inland saline aquaculture. One of the cutting-edge food production methods required to boost aquaculture productivity and meet the expanding seafood demand is inland saline aquaculture. In spite of this, inland saline aquaculture has yet to become an industrial-scale and rural business to produce sustainably from unutilized lands.

Introduction Shrimp aquaculture is a rapidly growing sector worldwide due to transform the intensive cultural practices. The demand for shrimp in the global trade market has increased significantly. The commercially farmed shrimp species, Pacific white leg shrimp, P. vannamei, dominate the market compared to tiger shrimp, P. monodon. Achieving higher shrimp aquaculture production often involves employing high stocking densities and large volumes of feed. This intensification can lead to increased waste and the accumulation of toxic substances, resulting in water pollution, requiring costly management measures to address these issues (Liu et al., 2019; Abakari et al., 2021). Therefore, addressing waste management and water quality concerns is crucial for sustaining the productivity and profitability of shrimp aquaculture operations. In addition to these, several other associated problems – decline in available land resources, escalated environmental pollution, the spread of recurring diseases, the emergence of drug-resistant microorganisms, and the impacts of climate change – with the development of shrimp aquaculture were reported (Santos and Ramos, 2018). To avoid these issues, it is essential to regulate and implement sustainable shrimp aquaculture practices that can be achieved through species and system diversification and environmentally sustainable technologies. Adopting these BFT systems allows for a more sustainable and resilient aquaculture operation (Zhao et al., 2016; 2021).

Fisheries management has evolved, acknowledging the intricate connections between individual fisheries, ecosystems, and human activities. Discards, the portion of the catch discarded at sea, have garnered attention due to their significant global impact. Analysing the global research landscape on discards, the USA, Spain, and Australia lead in publications, highlighting the global interest in addressing this issue. This review article explores the reasons for discarding, its consequences, and the subsequent fate of discarded catch. Discards result from factors like economic considerations, fishing regulations, and storage constraints. The aftermath of discarding involves various outcomes; the survivability of discarded fish varies, with high mortality observed in small fishes and those with gas bladders, death, or being used as bait. The timeline of discards, spanning from the 1970s to the present, reflects the increasing awareness and international efforts to address this issue. In 2019, the estimated annual global discards were 10.5 million tonnes, recorded significantly in the northwest Pacific and southwest Atlantic regions. This review article delves into gear-wise and species-wise discards, revealing variations in discarding practices across fisheries. The Indian scenario highlights the decline in discards, especially in shrimp freezer trawlers. The decline in discards is attributed to changes in fishing technologies such as bycatch reduction devices, management actions like discard bans, quantifying the economic disincentives due to discards, and societal attitudes that aim to mitigate discards. Regulations and initiatives worldwide, assessing discards in fisheries is crucial for sustainable resource utilization, as depicted in a flowchart illustrating the necessity of such assessments. In conclusion, reducing discards contributes to healthier ecosystems, sustainable fisheries, and long-term global food security, calling for continued efforts to minimize wasteful practices in fisheries, this article emphasizes the need for responsible fishing practices.

Introduction

Tumaria wetland (29° 18' N & 78° 57'E) is a manmade wetland near Corbett Tiger Reserve, Nainital district, Uttarakhand (Figure 1). It was constructed in the year 1961 and has an average depth of 3.1 m. It was mainly used for irrigation, fish production and has been a favorite place for several migratory birds during winter season (Bhattacharjee and Bargali, 2013; Bhattacharjee,2014). Tumaria bears a humid subtropical climate; emprises hot and dry summer which commences from early October to the mid of June. The area experience wet season from the mid of June to early October and then feels the cold winter. The reservoir catchment area is 284.16 sq. km and its north area is covered with thick, reserved forest of Jim Corbett National Park (Figure 2). The infestation of Salvinia weed is one of the major problems being faced by this wetland.

The exotic free-floating weed, Giant Salvinia (Salvinia molesta Mitchell), belongs to Salviniaceae family and is a native of south-eastern Brazil (Forno, 1983). It is commonly known as water fern, water weed, Kariba weed or water spangle and African payal in India (Jones, 1987). During the past 50 years, it has widely extended throughout the world and has infester the areas of Australia, New Zealand, Africa, southern USA, the Indian subcontinent, south-east Asia and some Pacific islands (Thomas and Room, 1986) (Figure 3). In India, it was f irst established in the state of Kerala since early 1970s (Cook, 1976; Thomas, 1976 and 1979). This aquatic weed has invaded in various aquatic habitats, such as lakes, wetland, rivers, reservoirs and paddy fields.