Fisheries science

Definition :

Fisheries science is an interdisciplinary field focused on the study, management, and conservation of aquatic resources, including fish and other marine life, both wild and farmed

Ichthyology

It is the branch of science dealing with the study of fishes, with the study of commercial aspects of fishes.

Aquaculture

Aquaculture is the farming of organism such as fish,shellfish and aquatic plants in controlled environments.

Methods of Aquaculture

Extensive Systems:

These systems are low-input and typically rely on natural resources like plankton and nutrients in the water.

Intensive Systems:

These are high-input systems where fish are raised at high densities, often in tanks or net pens.

Recirculating Aquaculture Systems (RAS):

A form of intensive aquaculture where water is filtered and reused, reducing water usage.

Sustainability concerns :

• Overfishing of Wild Fish for Feed

• Diseases Management

• Pollution

Benefits of Aquaculture:

• Food Security

• Economic Growth

Pressure on Wild Fisheries

Innovations in Aquaculture

• Genetically Improved Organisms (GIOs)

• Aquaponics

• Offshore Aquaculture

Composite Fish Culture

Stocking of fishes of different habits,in same pond is called Composite fish culture.

1.Pre-stocking Management

Construction of a Fish Farm

• Site Selection

• Water quality

• Drainage

• Soil quality

For good production from cultured fish soil pH should be in between 7.5-8.5.

• Fish seed

• Fish feed

They need to be fed with grass like- para, napier, maize leaves, banana leaves, chopped green cattle fodder,, etc.

• Climatic factors

• Industrial and agricultural pollution

• Availability of labour

Skilled, unskilled, casual and construction labours

Pond Construction

1. Nursery pond:

• Area of nursery pond ranges from 100- 500 m’ and the depth of water should be in between 1-1.5 m.

• The pond covers 5 per cent area of total productive area of the fish farm.

2.Rearing pond:

. • Area of rearing pond varies between 500- 1000 m² and the depth of water ranges from 1.5- 2.0 m.

• This type of pond covers 15 per cent area of the total productive area of the fish farm.

3.Stocking pond:

• Area of stocking pond varies between 1000- 20000 m²and the depth of water ranges from 2-2.5 m.

• This type of pond covers 60-70 per cent area of the total productive area of the fish farm.

Fish farm is constructed in 2 ways

· Dug out pond

· Embankment pond

Pond Preparation for Stocking with Fish

Liming and Fertilization

· Lime is generally spread on the pond bottom for 10-15 days before stocking the pond with fish.

· Cow dung 670 Kg/ ha/year is applied as organic fertilizer.

· Inorganic feetilizer

· Urea @ 13 kg/ha/ year,

· SSP @3 kg/ha/year and

· Muriate of potash @ 12 kg/ha/year is applied after 15 days of application organic fertilizer.

2.On-Stocking Management

Selection of Species

• Fast growth rate.

• Good food conversion efficiency.

• Acceptability of supplementary and natural food.

Cultivated species

· Rohu (Labeo rohita),

· Catla (Catla catla),

· Mrigal (Cirrhinus mrigala),

· Silver carp (Hypophthalmichthys molitrix),

· Common carp (Cyprinius carpio),

· Grass carp (Ctenopharyngodon idella),

· Tilapia (Oreochromis mossambicus),

· Magur (Clarias batrachus),

· Java puthi (Puntius javanicus)

· Kurhi (Labeo gonius), Fresh water prawn, etc.

Size, Quality, Number and Composition of Fish Species to be Stocked

· Size of Fish Seed to be Stocked - Fish fingerling i.e. 10- 15 cm size

· Number of Fish - The rate of 7000- 8000 nos./ha. (900-1000 nos./ha).

· Water quality

(a)Water Temperature:

A water temperature between 20-30°C is generally good for fish farming.

(b) Oxygen

Over- stocking of fish in the pond could be another possible cause of oxygen shortage problems.

This should preferably range between 6.7 and 8.6

(d) Turbidity

High turbidity of water can decrease fish productivity, as it will reduce light penetration into the water and thus oxygen production by the water plants.

Fish Nutrition

· Natural fish food

It consists of phytoplankton, zooplankton, periphyton, water plants, etc. produced in the pond itself.

· Supplementary fish feed

It is produced outside the pond and supplied to the fish regularly to further increase the amount of nutrients in the pond.

Fish Reproduction

· Controlled reproduction will provide you with seed when you require it, and not just during the few months of the year when natural spawning occurs in the wild.

Harvesting the Fish

· Harvesting can start (usually after 5 to 6 months).

· In the latter method, usually the larger fish are taken out and the smaller fish are left in the pond to keep growing.

Postharvest Management

· To prevent spoilage of the harvested fish, either the bacteria present in them must be killed, or their growth must be suppressed.

Different methods exist to suppress bacterial growth.

· Salting

· Drying

· Smoking

· Fermentation

Canning

· Cooling and freezing

Physico-Chemical Characteristics of Pond Water for Fish Culture

· Light

Light also provides Oxygen and food to the fish and the organisms of water,

· Temperature

Water temperature in range of 20-37Cis favours all major carps growth.

· Turbidity

Indian major carps can tolerate turbidity upto 2000 ppm.

· Dissolved Oxygen Content

Carps need 6-7 mg/litre dissolved oxygen for aquatic breathing.

· pH Level

Generally, neutral or slightly alkaline (pH-7.8)

· Carbondioxide

Carbondioxide comes into the pond-water through decomposition organic materials,

· Nitrogen and Phosphorus

• The optimum limit of nitrogen can be in the range of 0.3 to 0.3 ppm.

• 60-120 ppm of phosphorus is supposed to be ideal for high productivity.

HATCHERY MANAGEMENT

A hatchery is a facility where eggs are hatched under controlled conditions, especially those of fish, poultry, or other animals.

Fish Hatchery:

Breeds and raises young fish (like salmon or trout) to restock natural water bodies or for aquaculture.

Management:

1.Breeder Stock Management

• Select healthy and genetically strong parent stock.

2. Egg Collection & Handling

• Collect eggs frequently and carefully to prevent contamination or damage.

3. Incubation

• Monitor and adjust settings to optimize embryo development.

4. Hatching Process

• Transfer eggs to hatching trays a few days before hatch

5. Post-Hatch Care

• In fish hatcheries:

Feed and care for fry until they are ready for stocking or sale.

6. Biosecurity & Disease Control

• Strict sanitation protocols.

• Use vaccinations and regular health checks.

7. Record Keeping

• Analyze data to improve efficiency and troubleshoot problem.

Objectives of Good Hatchery Management:

• Maximize hatchability and survival rates.

• Minimize disease outbreaks.

• Ensure uniform and healthy offspring.

Advantages of Hatchery Systems

· Controlled Environment

· Year-Round Production

· Genetic Improvement

· Higher Survival Rate

· Efficient Scaling

· Disease Monitoring & Control

· Employment & Economic Opportunities

Disadvantages of Hatchery System

· High Initial Investment

· Technical Skill Required

· Biosecurity Risks

· Dependency on Technology

· Limited Genetic Diversity

· Environmental Impact

· Ethical Concerns

FISHERY BIOLOGY

Fisheries Biology is the branch of science that studies fish populations, their habitats, reproductive cycles, growth, and interaction with ecosystems—mainly to manage and conserve fishery resources sustainably.

Fish Classification & Anatomy

· Scientific naming (taxonomy)

· Body structures: fins, gills, scales, swim bladder, etc.

· Identification of species in different habitats

Fish Ecology

• Habitat types:

Freshwater – Murrels

Marine - Sardines,Tuna

Estuarine - Tachysurus sp

• Feeding behavior:

Herbivores – Plants and algae

Carnivores - Insects

Omnivores – Both plants and insects

Fish Population Dynamics

• Growth: How fish increase in size and weight

• Mortality: Natural vs. fishing mortality

• Recruitment: Number of young fish entering a fishery

• Models used: von Bertalanffy, logistic growth models

Reproductive Biology

• Spawning behavior and seasons

• Egg development and hatching

• Sex ratio and maturity stages

Age and Growth Studies

• Aging fish using otoliths (ear bones), scales, or spines

• Growth rings (like tree rings) show yearly growth

• Growth curves help in population management

Fisheries Management

• Setting catch limits, fishing seasons, and gear regulations

• Protecting endangered species

• Marine Protected Areas (MPAs) and closed seasons

Tools & Techniques in Fishery Biology

• Tagging and tracking fish migration

• Sonar and remote sensing for population surveys

• DNA barcoding for species identification

• GIS mapping of habitat

Importance of Fishery Biology

• Supports sustainable fishing

• Protects marine ecosystems

• Ensures food security and economic stability for communities

FISHERY ECOLOGY

Fishery Ecology is the study of how fish and other aquatic organisms interact with each other and with their physical environment in water ecosystems (like oceans, rivers, lakes).

Aquatic Ecosystems

Types:

• Marine (saltwater),

• Freshwater (lakes, rivers),

• Brackish (estuaries)

Ecosystem components:

• Fish, plankton, aquatic plants, invertebrates, predators (e.g. birds, seals)

Habitat and Niche

• Fish live in specific zones: surface, midwater, bottom (benthic)

• Each species has a niche – role in the ecosystem (e.g., predator, grazer)

Examples:

Coral reefs, mangroves, open ocean, deep sea

· Producers:

Algae, phytoplankton

· Primary consumers:

Zooplankton, small herbivorous fish

· Secondary/tertiary consumers:

Larger carnivorous fish (e.g., tuna, cod)

· Migration:

Fish move to spawn (e.g., salmon), feed (e.g., tuna), or avoid predators

· Schooling:

Fish swim in groups for protection and efficiency

· Predation:

Big fish eat small fish

· Competition:

Different species compete for food or habitat

· Symbiosis:

Mutualism, parasitism in aquatic life

· Environmental factor

Temperature , salinity, oxygen, light, and currents all affect fish behavior and distribution

· Fishery Ecology Matters

• Helps predict fish population changes

• Supports sustainable fishing policies

• Aids in restoring damaged habitats

• Guides marine protected area (MPA) design and management

FISH GENETICS

Fish genetics is the study of heredity and variation in fish species, focusing on how traits (like size, color, growth rate, disease resistance) are passed from parents to offspring.

Basic Genetic Concepts

• Genes

• Chromosomes

• DNA

• Alleles

Mendelian Inheritance

• Dominant and recessive traits

• Genotypes and phenotypes

• Traits in fish (e.g., scale pattern, body color) follow these rules

Genetic Variation

• Comes from mutations, gene flow, recombination

• Variation helps populations adapt to environmental changes

• Measured using molecular markers (e.g., microsatellites, SNPs)

Selective Breeding in Aquaculture

• Choosing parent fish with desirable traits (fast growth, disease resistance)

• Improves fish farming yields

• Example: Selective breeding in Tilapia or Atlantic salmon

Genetic Engineering

• Inserting genes from one species into another

• Example: Transgenic fish like faster-growing GM salmon

• Raises ethical and environmental concerns

Population Genetics

• Studies gene frequency and distribution in wild fish populations

• Important for conservation of endangered species

• Helps track inbreeding, genetic drift, and adaptation

DNA Barcoding and Species Identification

• Uses a short DNA sequence (usually from the mitochondrial COI gene)

• Identifies fish species accurately—useful in illegal fishing, biodiversity studies

Cytogenetics

• Study of fish chromosomes under a microscope

• Used to identify hybrids or chromosomal abnormalities

Applications of Fish Genetics

Area

Role of genetics

Aquaculture

Faster growth, disease resistance

Conservation

Protect genetic diversity, manage wild stocks

Breeding Programs

Develop superior fish strains

Fisheries Management

Detect population structure, prevent overfishing

Forensics

Identify species in seafood and fish markets

FISH BIOTECHNOLOGY

Fish biotechnology is the application of biological techniques and tools (like genetic engineering, molecular biology, and tissue culture) to improve fish health, breeding, growth, and sustainability—especially in aquaculture and conservation.

Genetic Engineering

· Inserting specific genes into fish to improve traits like:

• Faster growth (e.g. transgenic salmon)

• Disease resistance

• Cold or salinity tolerance

• Uses techniques like CRISPR, gene cloning, and transgenesis

Molecular Markers

· Used to study genetic variation, population structure, and parentage

· Common markers: Microsatellites, SNPs, RAPD, AFLP

· Important for selective breeding and conservation

DNA Barcoding

· Identifies fish species using short DNA sequences

· Helps in:

• Detecting mislabeled seafood

• Monitoring biodiversity

• Combating illegal fishing

Chromosome Manipulation

· Triploidy and gynogenesis used to produce sterile or all-female fish

· Controls breeding and improves meat quality

· Common in trout and carp farming

Cryopreservation

· Freezing and storing sperm, eggs, or embryos

· Preserves genetic material for future use

· Helps in conservation of endangered species

Fish Cell Culture

· Growing fish cells in labs for:

· Vaccine development

· Toxicology studies

· Disease research

Recombinant DNA Technology

· Producing fish hormones, vaccines, or proteins in lab-grown cells

· Example: recombinant fish growth hormone (FGH) to increase yield

Bioremediation

· Using genetically modified fish or microbes to clean polluted water

· Still experimental, but promising for aquatic ecosystem health

Applications of Fish Biotechnology

Field

Application

Fish Health

DNA vaccines, disease diagnostics

Food Industry

Identifying fish products, improving quality

Environment

Water quality monitoring, pollution control

FISH NUTRITION

Fish nutrition is the study of dietary requirements and feeding practices of fish to ensure healthy growth, reproduction, immunity, and overall well-being—especially important in aquaculture.

Nutrient type

Functions

Proteins

Growth, tissue repair, enzymes, hormones

Lipids (Fats)

Energy source, cell structure, vitamin

Carbohydrates

Secondary energy source

Vitamins

Immunity, metabolism, reproduction

Minerals

Bone formation, osmoregulation, enzyme activity

Water

Digestion, circulation, temperature control

Protein Requirement

· Carnivorous fish need more protein than herbivorous/omnivorous fish

· Example: Salmonids (like trout) need 40–55% protein in diet

Energy Balance

· Protein:lipid:carbohydrate ratio is carefully balanced in formulated feeds

Essential Amino Acids

· Fish can’t synthesize all amino acids

· Must be supplied through diet (e.g., lysine, methionine)

Essential Fatty Acids (EFAs)

· Omega-3 and omega-6 fatty acids are vital for fish health

· Required for immune function, reproduction, and membrane integrity

Feed Conversion Ratio (FCR)

· FCR = Feed given (kg) / Weight gain (kg)

· Lower FCR means more efficient feed (e.g., FCR of 1.2 is good)

Feeding Methods

· Manual, automatic, or demand feeders

Types of Fish Feed

Feed types

Characteristics

Dry Feed

Pellets, flakes

Semi-moist Feed

Higher moisture, faster digestion

Wet Feed

Raw fish or meat

Extruded Feed

Floating or sinking

Applications of Fish Nutrition

· Efficient aquaculture production

· Lower feed costs and waste

· Healthier fish and improved water quality

· Enhanced product quality (meat texture, omega-3 content)al

FEED FORMULATION

Fish feed formulation is the process of designing and preparing nutritionally balanced diets for fish using different feed ingredients to meet their growth, health, and production needs.

Goals of Feed Formulation

· Meet the nutritional needs of the fish (protein, fat, vitamins, minerals)

· Maximize growth and feed efficiency

· Minimize cost and waste

· Improve meat quality and disease resistance

Nutritional Requirements (Typical Ranges)

Nutrient - Protein

Carnivorous - 40–55%

Omnivorous - 30-40%

Herbivores - 25-35%

Nutrient - Lipid (Fat)

Carnivorous - 8-15%

Omnivorous - 5-10%

Herbivores -4-8%

Nutrient - Carbohydrates

Carnivorous - 10-20%

Omnivorous - 20-30%

Herbivores - 25-35%

Nutrient - Fiber

Carnivorous - <8%

Omnivorous - <10%

Herbivores - <10%

Nutrient - Ash (minerals)

Carnivorous - 10-15%

Omnivorous - 8-12%

Herbivores - 8-12%

Common Ingredients in Fish Feed

🔹 Protein Sources:

• Animal-based:

Fish meal, meat and bone meal, blood meal

• Plant-based:

Soybean meal, groundnut cake, cottonseed meal

🔹 Energy Sources:

• Carbohydrates:

Wheat bran, rice bran, corn, cassava

• Lipids (Fats):

Fish oil, vegetable oil

🔹 Vitamin & Mineral Premix:

• Commercially available mixes or natural additives (e.g., kelp, spirulina)

• Basic Feed Formulation Example (Tilapia Feed – 100 kg Batch)

Steps in Feed Formulation

· Determine nutritional needs (based on species, size, age)

· Select ingredients based on cost, availability, and digestibility

· Balance the formula to meet protein, energy, and nutrient needs

· Mix and pelletize the ingredients

· Dry and store feed in a cool, dry place

Tools for Feed Formulation

· Pearson’s Square Method (for 2-ingredient protein balancing)

· Linear Programming software (e.g., WinFeed, FeedSoft, Excel-based tools)

Considerations

· Avoid anti-nutritional factors (e.g., trypsin inhibitors in raw soybean)

· Monitor feed conversion ratio (FCR)

· Prevent spoilage (due to molds, pests, or poor storage)

FISH PROCESSING TECHNOLOGY

Fish processing technology refers to the methods and techniques used to handle, preserve, and convert fish into safe, high-quality, and marketable products. It ensures longer shelf life, reduces post-harvest losses, and adds value to fish and fishery products.

Objectives of Fish Processing

· Extend shelf life

· Improve product safety and quality

· Reduce waste

· Produce value-added products

· Ensure consumer safety and regulatory compliance

Main Steps in Fish Processing

· Pre-processing / Handling

• Sorting by size and species

• Washing to remove slime, blood, or contaminants

• Deheading, gutting, and descaling

• Icing or chilling immediately after catch

· Preservation Methods

Chilling and Freezing

• Chilling (0–4°C) slows down spoilage for short-term storage

• Freezing (-18°C or lower) for long-term storage

Drying and Smoking

Canning

Chemical Preservation

• Use of preservatives like sodium benzoate, sorbates

Irradiation

• Uses ionizing radiation to kill bacteria and parasites

Value-Added Fish Products

Product type

Examples

Cured Products

Dried fish, salted fish, smoked fish

Ready-to-eat

Fish fingers, fish balls, burgers

Surimi

Fish paste for imitation seafood

Canned Products

Canned tuna, sardines

Fermented Products

Fish sauce, pickled fish (e.g., bagoong,

Fish Processing Equipment

· Gutting and filleting machines

· Freezers and ice machines

· Vacuum packers and sealing machines

· Smokehouses and dryers

· Canning equipment (retorts, fillers, seamers)

Quality Control in Fish Processing

Aspects

Techniques/Tools

Microbial safety

Total plate count, pathogens check

Chemical safety

Histamine test, heavy metals

Sensory quality

Smell, appearance, texture

Nutritional analysis

Protein, fat, moisture tests

Importance of Fish Processing Technology

· Reduces post-harvest losses (up to 40% in some areas)

· Enhances export and trade opportunities

· Promotes hygiene, food safety, and economic growth

INLAND FISHERIES

Inland fisheries refer to the capture and culture of fish and other aquatic organisms from freshwater bodies such as rivers, lakes, reservoirs, ponds, canals, and floodplains. Unlike marine fisheries, inland fisheries occur in landlocked or freshwater environments.

Types of Inland Fisheries

1. Capture Fisheries (Wild Fisheries)

• Fish are caught directly from natural freshwater sources

Examples:

river fishing, lake fishing

2.Culture Fisheries (Aquaculture)

• Fish are bred and raised under controlled conditions

Examples:

Carp farming, catfish farming, tilapia culture

Common Fish Species in Inland Fisheries

· Indian Major Carps: Rohu (Labeo rohita), Catla (Catla catla), Mrigal (Cirrhinus mrigala)

· Exotic Carps: Common carp, Grass carp, Silver carp

· Tilapia: Oreochromis niloticus

· Catfishes: Clarias batrachus, Pangasius

· Trout (in cold water regions): Oncorhynchus mykis

Importance of Inland Fisheries

• Provides protein-rich food to rural areas

• Supports millions of fishers and farmers

· Boosts rural economy, supports small-scale industries

• Supports sport fishing and ecotourism

· Conserves native and endemic freshwater species

Management & Development Practices

· Stock enhancement (restocking natural water bodies with fingerlings)

· Water quality management (control of pollution and eutrophication)

· Fishing regulations (closed seasons, mesh size limits)

· Integrated Fish Farming (fish + poultry/duck/vegetables)

· Artificial breeding and hatchery production

Challenges in Inland Fisheries

· Overfishing and habitat degradation

· Water pollution (industrial/agricultural runoff)

· Invasive species (e.g., tilapia in native carp habitats)

· Climate change impacts (temperature and rainfall patterns)

· Conflicts over water use (agriculture, industry vs. fisheries)

MARINE FISHERIES

Marine fisheries involve the capture and culture of fish and other aquatic organisms from saltwater environments, including oceans, seas, estuaries, and coastal areas.

Types of Marine Fisheries

1.Capture Fisheries (Wild Fisheries)

Fish are harvested directly from the sea.

2.Mariculture (Marine Aquaculture)

Farming of marine organisms (fish, shellfish, seaweeds) in controlled ocean environments

Common Marine Species Fished