Environmental Factors on Aquatic Animal Health, Welfare, and Productivity PDF

Environmental Factors on Aquatic Animal Health, Welfare and Productivity Fishes are adapted to different extreme situations as their evolutional success depends on their ability to thrive in a variable medium: water WATER QUALITY Includes all physical, chemical and biological factors that influen...

Environmental Factors on Aquatic Animal Health, Welfare and Productivity Fishes are adapted to different extreme situations as their evolutional success depends on their ability to thrive in a variable medium: water WATER QUALITY Includes all physical, chemical and biological factors that influence the beneficial use of water  Environmental factors affecting health, welfare and productivity of fish Chemical Physical Factors Factors Biological Factors Social Factors  Physical Factors These factors influence not only the biological processes of fish but also their habitat, behavior, and overall survival. 1. Water temperature It is a measure of intensity of heat energy stored in a volume of water; warmness and coldness of water It affects metabolic rates, growth, and immune system function in fish. Too high or too low temperature can lead to stress, reduced immune response, and increased susceptibility to disease  Physical Factors 2. Turbidity Caused by suspended particles in the water High turbidity can reduce the penetration of sunlight. Excessive turbidity can also clog gills, reduce feeding efficiency, and cause stress. In clear water, feeding and monitoring of fish behavior is easier, leading to better management practices.  Physical Factors 3. Water Flow Proper water flow in aquaculture ensures steady supply of oxygen and the removal of wastes products, improving growth rates. Prevents algal blooms, which can release toxins or deplete exygen.  Physical Factors 4. Light Controlled photoperiods are used to manage spawning of fish. Improper light levels can lead to stress or disorientation in species sensitive to changes in light intensity.  Physical Factors 5. Sediment load Fine Sediment: High levels of suspended sediments can clog fish gills, reduce light penetration, and smother eggs or larvae on the substrate. This can decrease reproductive success and reduce the survival of juvenile fish. Habitat Degradation: Sediment accumulation in breeding and feeding habitats can lead to habitat degradation, reducing available food sources and shelter.  Physical Factors 5. Noise and Vibration Acoustic Pollution: High levels of underwater noise from ships, drilling, or industrial activities can disrupt communication, feeding, and reproduction in fish. Noise pollution may also cause stress and disorientation. Behavioral Changes: Fish exposed to consistent noise may alter migration routes, avoid areas, or change their behavior in ways that reduce their overall fitness and welfare.  Chemical Factors These factors influence water quality, which directly affects the physiology, behavior, and immune fuction of aquatic species. 1. Water Quality Parameter - pH High pH - Alkalosis Measure the hydrogen ion concentration. Low pH - Acidosis Indicates wheter the water is basic or acidic. Excessive mucous production, skin becomes corroded, milky and turbid Skin erosion, gill erosion, damage to lens and cornea and fraying fins Darting movement and jump in an attempt to leave the water  Chemical Factors 2. Water Quality Parameter - Dissolved Oxygen Low dissolved oxygen can exacerbate the toxic effects of ammonia and other harmful chemicals. Can cause Asphyxiation/Hypoxia. Fish, invertebrates, and other aquatic organisms depend on adequate oxygen levels for cellular respiration. Declining Oxygen levels - high stocking rates and decomposition of organic matter Hypoxia  Chemical Factors 2. Water Quality Parameter - Dissolved Oxygen In a balanced ecosystem (left) some nutrients fuel the growth of microscopic algae, which are the base of the aquatic food chain. In an unbalanced ecosystem (right), excess nutrients cause too many algae to grow. The excess algae die, sink to the bottom, and are decomposed by bacteria, which use up oxygen in the water.  Chemical Factors 4. Water Quality Parameter - Ammonia In water, the Total Ammonia Nitrogen (TAN) occurs in two forms, unionized Ammonia (NH3) (toxic) and Ammonium (NH4+) (less harmful) Effects of Ammonia in fish includes presence of bloody gills, spongy appearance of gil filaments, excessive production of slime, Distended operculum and poor growth.  Chemical Factors 5. Water Quality Parameter - Nitrites and Nitrates Nitrites result from oxidation of ammonia and highly toxic. Nitrates are less harmful end product of nitrogen metabolism. Excessive exposure of fish can reduce growth rates and reproductive success, leads to lower productivity.  Chemical Factors FEEDS 1. Fish Excretion, Uneaten feeds, Bottom sediment etc. 6. NO3 NITROGEN 2. NH3/NH4+ (AMMONIA and (Nitrate) Ammonium Ion) CYCLE 5. Nitrobacter Bacteria 3. Nitrosomonas Bacteria 4. NO2 (Nitrite)  Chemical Factors 6. Water Quality Parameter - Phosphates Source: Fertilizers and detergents Increase in phosphate concentration = increase in turbidity, decrease in pH, and decrease in Disolloved Oxygen  Chemical Factors 7. Water Quality Parameter - Salinity Salinity Requirement of fish – marine or freshwater in origin Total concentration of dissolved ions in water Freshwater: 0.5ppt Seawater: 30-40 ppt Changes in salinity occurs during high precipitation or evaporation; increasing salinity decreases the solubility of dissolved oxygen Osmoregulatory stress, impaired growth rates and reduced disease resistance Progressive emaciation, scale loss and opaque eye lenses  Chemical Factors 8. Pollutants and Contaminants Heavy Metals – Mercury, Lead, Cadmium, Arsenic Accumulate in tissues, causing physiological damage. Pesticides and Herbicides - Runoff from agriculture can harm fish health. Oil and Hydrocarbons: Pollution from spills or runoff can disrupt fish metabolism and development.  Chemical Factors 9. Chemicals used in Aquaculture Medications – Antibiotics Used to treat diseases, but improper use can harm fish and affect food safety. Disinfectants and Cleaners – Residues can be toxic to fish if not properly managed. Chemicals used in water treatment – Chlorine, chloramines. Excess levels can harm fish if not properly neutralized  Biological Factors Encompass the livng organisms and interactions within the aquatic environment 1. Pathogens Microorganisms (bacteria, virus, fungi, and parasites) that proliferate within their hosts and are capable of producing disease. Presence of pathogens can weaken the immune system, disrupt normal biological functions, cause lesions, tissue damage, systemic infections, stress and mortality.  Biological Factors 1. Pathogens Bacteria Flavobacterium columnare Edwardsiella tarda Pseudomonas spp. Streptococcus spp. Aeromonas spp. Vibrio spp. Nocardia sp. septicaemia characterized by skin, gills, and internal organ hemorrhages, pop eyes, and skin ulcerations  Biological Factors 1. Pathogens Fungi Saprolegnia sp. Aphanomyces invadans Brachiomyces sanguinis Ichthyophonus sp. Exophiala sp. Aspergillus flavus  Biological Factors 1. Pathogens Virus Viral Nervous Necrosis Iridovirus Spring Viremia of Carp Virus Koi Herpesvirus Tilapia lake virus  Biological Factors 1. Pathogens Parasites Protozoa (Ciliates and Flagellates) Myxozoan and Microsporidia Helminths (Monogenean, Digenean, Cestodes, Nematodes, Acantocephala, marine leeches) Crustacean (Branchiuria, Copepods, Isopods)  Biological Factors 2. Predation Predators such as birds and larger fish can cause behavioral changes, hiding or reduced feeding, which negatively impacts growth and production.  Social Factors interactions between individuals within the same species (conspecifics), such as competition, aggression, hierarchy formation, schooling, and cooperative behaviors. 1. Stocking Density number of animals per unit of space in aquaculture systems or natural habitats. Overcrowding can lead to increased aggression, competition for food and space, and elevated stress levels, which weakens the immune system and makes animals more vulnerable to disease. Inadequate space may also limit movement, causing physical injuries or deformities.  Social Factors 2. Feeding Competition When multiple individuals compete for limited food resources, dominant animals may monopolize feeding opportunities, leaving weaker or smaller individuals with insufficient nutrition. This can lead to malnutrition, stunted growth, and increased stress levels among those who are unable to compete effectively. Unequal access to food leads to growth variability within a stock, which complicates management and reduces overall productivity.  Social Factors 3. Parenteral Care and Brood Care Disrupting the natural behaviors of caring for or protecting young can cause stress for both parents and offspring. Inadequate care may lead to higher mortality among juveniles.  Social Factors 4. Social Hierarchy and Dominance Territoriality: Many fish species are territorial, establishing dominance hierarchies to access resources such as food, space, and mates. In crowded or poorly managed environments, dominant individuals may bully or exclude subordinates, leading to: Stress and Injury: Subordinate fish often face aggression, resulting in injuries or chronic stress, which lowers immune function and increases susceptibility to diseases. Unequal Resource Access: Dominant fish may monopolize food, leaving subordinates undernourished and affecting overall productivity. Space and Shelter Competition: In both natural and farm environments, competition for hiding spaces or breeding grounds can lead to aggressive behaviors, impacting social harmony and welfare.  Social Factors 5. Aggression and Cannibalism Aggressive Interactions: Aggression in fish can be triggered by competition for resources, territory, or mates. In aquaculture, poorly managed environments, especially with high densities, can exacerbate aggression, resulting in: Injuries and Mortality: Aggressive encounters can cause wounds, fin damage, and stress, increasing susceptibility to infections and lowering survival rates. Cannibalism: In some species, particularly under stressful or resource-scarce conditions, larger or more dominant fish may prey on smaller or weaker individuals. Cannibalism can reduce overall productivity in farmed environments. Resource Competition: Aggression often arises from competition for food, space, or shelter. Ensuring that these resources are adequate and evenly distributed can reduce the likelihood of harmful social interactions.  Social Factors 6. Species Mixing Interspecies Aggression: In some aquaculture systems, different species may be kept together (polyculture), which can lead to aggression if their behaviors, resource needs, or social structures are incompatible. Territorial Disputes: Species with different territorial behaviors may conflict, leading to stress and injuries. Disease Transmission: Different species may have varying levels of resistance to diseases. Mixing species can increase the risk of cross- species disease transmission, affecting overall health and welfare.  Social Factors 7. Human handling and Social Stress Handling and Transport: In aquaculture, frequent handling or poor transport conditions can cause stress, which is further amplified by social disruption. Fish may experience crowding, changes in social structure, and altered behavior during these processes.Stress Responses: Stress from handling and transport can reduce immune function, making fish more vulnerable to diseases. Social Reorganization: Handling may force fish into unfamiliar social settings, leading to increased aggression or stress as they attempt to re-establish hierarchies or group cohesion.  Social Factors 8. Feeding Behavior and Social Dynamics Competition for Food: In environments where food distribution is uneven or scarce, competition for feeding can lead to aggression and social stress, especially for lower-ranking individuals. Uneven Growth: Dominant individuals often outcompete subordinates for food, leading to uneven growth rates. This can impact overall productivity, as smaller or undernourished fish do not grow as efficiently. Feeding Hierarchies: Some species develop feeding hierarchies, where only certain individuals have access to food at a given time. In aquaculture, ensuring equal access to food can minimize stress and aggression.