APPLIED-FISH-PHYSIOLOGY is the study of biological system and steps into practice.

Physiology of Fish

1. APPLIED PHYSIOLOGY TOPICS: Generalized stress response Migration as stress in salmon Acute and chronic hypoxia Acute heat or cold as stressors Effects on anesthesia, handling and scale loss Response to air saturation of water Physiological changes associated with diseases Physiological effects of some toxicants Indications of fish health

2. APPLIED PHYSIOLOGY -is the study of biological systems and steps into practice. - It involves the application of the knowledge of physiological properties to restore core stability and joint stability.

3. GENERALIZED STRESS RESPONSE A. DEFINITION OF STRESS -is an habitual, undesirable aspect of production. -results from biotic and/or abiotic challenges that act in changing or modifying the animal’s natural or homeostatic state. -stress in fishes has been defined as a state resulting from environmental conditions which threaten survival.

4. The approximate location of endocrine tissues involved in the stress response in fish

5. GENERALIZED STRESS RESPONSE B. BEHAVIOR One of the immediate signs of a stressed state of fishes is behavioral response. Activities such as food acquisition, predator avoidance, prey capture, migration & habitat preference are critical to the survival of the organisms, and thus the population, and commonly used as indicators of environmental stressors. Appropriate response to stressor maybe” avoidance or behavioral mitigation” to respond the environment. Behavioral and physiological responses to a stressor are intimately related.

6. Common fish stressors involve alterations in the fish’s immediate environment such as: Chemical stressor - contaminants, low oxygen & acidification. Physical stressor - handling, capture , confinement & transport. Perceived stressor - startling or predators. GENERALIZED STRESS RESPONSE

7. 3 CLASSIFICATIONS : 1. PRIMARYRESPONSE This initial response represents the perception of an altered state & initiates a neuroendocrine response that forms part of generalized stress response in fishes. C. PHYSIOLOGICAL STRESS RESPONSE GENERALIZED STRESS RESPONSE

8. 1. PRIMARY RESPONSE includes the rapid release of stress hormones, catecholamines and cortisol into the circulation. Catecholamines are released from the chromaffin tissue situated in the head (anterior) kidney of teleosts and also from the endings of adrenergic nerves. GENERALIZED STRESS RESPONSE

9. Cortisol is released from the interrenal tissue, located in the head kidney, in response to several pituitary hormones, but most potently to adrenocorticotrophic hormone (ACTH). ACTH stimulates adrenaline release, and chronic cortisol treatment has been shown to affect catecholamine storage & release in trout. GENERALIZED STRESS RESPONSE

10. 2. SECONDARY RESPONSE -also called metabolic response. - increase/changes in plasma glucose concentration. The plasma glucose concentration in circulation is dependent on glucose production and its clearance from circulation. The production of glucose with the occurrence of stress assists the animal by providing energy substrates to tissues such as the brain, gills, and muscles to cope with the increased energy demand. GENERALIZED STRESS RESPONSE

11. GENERALIZED STRESS RESPONSE 2. SECONDARY RESPONSE The liver is the main source for glucose production, and this is achieved by glycogenolysis and glyconeogenesis . Adrenaline and cortisol have been shown to increase glucose production in fishes & play an important role in the stress-associated increase in plasma glucose concentration. Adrenaline from circulation after stress (<30 minutes). Cortisol plays a role in a long-term maintenance of glucose levels poststress in fishes.

12. GENERALIZED STRESS RESPONSE 3. TERTIARY RESPONSE This response represents whole animal and population-level changes associated with stress. If the fish is unable to acclimate or adapt to stressor, whole animal changes may occur, including decrease reproductive capacity & decreased growth . Decreased recruitment and productivity may also alter community species abundance and diversity.

13. GENERALIZED STRESS RESPONSE D. CELLULAR STRESS RESPONSE The generalized stress response at the cellular level is characterized by a family of proteins referred to as heat shock proteins (HSPs). HSPs are highly conserved cellular proteins that have been observed in all organisms, including fishes. FUNCTION: development and aging, stress physiology & endocrinology, immunology, environmental physiology, acclimation & stress tolerance.

14. M IGRATION AS STRESS IN SALMON Pacific salmon ( Oncorhynchus spp .) are well known for their large-scale migrations that can take them thousands of kilometers from inland freshwater systems, where they begin their lives, to rich and fertile ocean habitats for feeding and they return to their natal stream to reproduce, before this lifecycle is repeated by their off­spring. The migratory strategy of reproducing in freshwater, yet feeding primarily in marine waters is known as anadromy . Unlike Atlantic salmon ( Salmo salar ), Pacific salmon are semelparous , meaning that they die after spawning. The dead adults provide energy and nutri­ents for stream ecosystems, which benefit their own offspring after they hatch and begin to feed indepen­dently.

15. M IGRATION AS STRESS IN SALMON Pacific salmon (genus Oncorhynchus ) given many natural challenges that encoun­ter during migration including predators, dynamic river flows and ocean currents, diseases, parasites, variable temperatures, and dramatically variable salinities. In addition, migrating salmon face additional anthropogenic challenges, such as fisheries exploitation, habitat altera­tion, and physical barriers (e.g., dams, climate change, and other ecosystem alterations).

16. M IGRATION AS STRESS IN SALMON Mortality of salmon can also occur due to physiological stress, delay, and physical injury. Migrations are inherently stressful periods of life, particularly those involving tran­sitions between freshwater and saltwater. Exacerbating these stresses are the environmental challenges associated with climate change. Warming rivers are now pushing some populations of adult salmon beyond their optimal temperature such that they have reduced or no aerobic scope for migration. In addition, disease and illness have become more apparent in these warmer migratory environments affecting spawning fish. Less productive and warmer oceans are reducing growth rates and energy reserves and changing migration timing.

17. M IGRATION AS STRESS IN SALMON

18. ACUTE AND CHRONIC HYPOXIA - is a phenomenon that occurs in aquatic environments as dissolved oxygen (DO; molecular oxygen dissolved in water) becomes reduced in concentration to a point detrimental to aquatic organisms living in the system. HYPOXIA - deficiency in the amount of oxygen reaching the tissues . - Oxygen deficiency in a biotic environment. Hypoxia may limit the energy budget or scope for growth and activity of an organism, it may cause an organism to alter its behavior, and/or it may limit the tolerance of an organism to other environmental challenges.

19. ACUTE AND CHRONIC HYPOXIA Hypoxia is often accompanied by hypercapnia (an elevation in water C02), which produces an acidification of the body tissues, including the blood, and has physiological implications that can also be profound and separate from the effects of low oxygen. Hypoxia in fish Examples of responses to hypoxia include a depression in feeding as well as a decrease in molting and growth rates. Many organisms respond to hypoxia by switching from aerobic to anaerobic metabolism and some simply reduce their overall metabolism.

20. ACUTE AND CHRONIC HYPOXIA Hypoxia in fish The manifestations of these effects may be seen as changes in the population structure within a species, changes in the range of distribution, or a decrease in the population density of an organism. In this manner individual organismal effects are transferred to the population and ecosystem levels of organization. Finally, there is evidence that hypoxia can inhibit immune responses, causing greater mortality than would otherwise occur when organisms are challenged with a pathogen.

21. Behavioral and physiological responses of different organisms to hypoxia: Organisms Response to Hypoxia Shrimp Penaeus aztecus -detect and avoid Penaeus setiferus -detect and avoid Penaeus monodon -decrease hemocyte phagocytosis Penaeus stylirostris -decrease total hemocyte count -increased mortality induced by Vibrio alginolyticus

22. Behavioral and physiological responses of different organisms to hypoxia: Organisms Response to Hypoxia 2. Crabs Callinectes sapidus -detect and avoid -decrease feeding -reduce growth rate * Acute Hypoxia -increase ventilation rate -increase heart rate -slight increase in cardiac output * Chronic Hypoxia -decrease oxygen consumption -no change in ventilation -no change in heart rate -increase hemocyanin O2 affinity and concentration

23. Behavioral and physiological responses of different organisms to hypoxia: Organisms Response to Hypoxia Callinectes similis -detect and avoid -increase oxygen consumption -decrease feeding 3. Gastropod Molluscs Stramonita haemastoma -reduce growth rate -large reduction in metabolism -decrease oxygen consumption

24. Behavioral and physiological responses of different organisms to hypoxia: Organisms Response to Hypoxia 4. Molluscs Crassostrea virginica -switch to anaerobic metabolism -small reduction in metabolism -decrease production of reactive oxygen species

25. a. Acute hypoxia/ acute fish stressor b. Chronic hypoxia/chronic fish stressor are events which the animal experience for a short period of time such as handling. are defined as a constant or recurring exposure that causes a prolonged physiological response. During acute exposures to hypoxia some organisms can maintain aerobic metabolism by making effective use of a respiratory pigment, or increasing ventilation rates, or increasing the flow of blood past the respiratory surfaces or combinations of all three. Responses to chronic hypoxia are different and include the production of greater quantities of respiratory pigment and changing the structure of the pigment to one with an adaptive higher oxygen affinity. ACUTE AND CHRONIC HYPOXIA

26. ACUTE HEAT OR COLD AS STRESSORS Rapid decreases in water temperature may result in a number of physiological, behavioral and fitness consequences for fishes termed ‘cold shock’. Cold shock can be defined as an acute decrease in ambient temperature that has the potential to cause a rapid reduction in body temperature, resulting in a cascade of physiological and behavioural responses. Rapid temperature decrease may occur from either natural (e.g. thermocline temperature variation, seiches and storm events) or anthropogenic sources (e.g. varied thermal effluents from power generation and production industries).

27. ACUTE HEAT OR COLD AS STRESSORS Cold shock can occur under natural conditions, such as thermocline temperature variation (e.g. when a fish swims up through in the water column), rapid changes in solar heat, abnormal water movements, rapid precipitation events or rapid changes in seasonal temperatures, yet these sources and their consequences on fish populations are poorly understood. Anthropogenic (i.e. human influenced) sources of cold shock include changes in thermal effluents from power generation and production industries, various water control projects and fish handling practices.

28. COLD SHOCK Schematic representation of natural and anthropogenic sources of cold shock as well as the primary, secondary and tertiary stress responses to cold shock

29. ACUTE HEAT OR COLD AS STRESSORS Primary Response Cold shock results in changes in activation states of the hypothalamus and pituitary gland Sympathetic nerve fibres stimulate catecholamine release from chromaffin tissue Hypothalamus-pituitary- interrenal axis stimulates the release of cortisol Release of cortisol is delayed relative to catecholamine release Cortisol is a sensitive indicator of cold shock but is less sensitive to gradual temperature changes Secondary Response Hematocrit, leucocrit and plasma concentrations of lactic acid are highly variable and may not be sensitive indicators of acute temperature stress Heat Shock Proteins (HSPs) are sensitive stress indicators, but are not well understood in relation to cold shock Cold shock reduces the active influx of ions while diffusional efflux remains constant, resulting in net loss of ions for freshwater fishes Cold shock may affect immune function, particularly for immune- compromised fishes Tertiary Response Developmental rates and juvenile mortality are increased at low temperatures Fish preferentially select habitat based on temperature (i.e., selection of power plant thermal plumes in winter) Cold shock affects swimming behaviour and predation rates Temperature shock can lead to accelerated cataract development and incidence of cold-water disease Cold shock does not appear to cause physical damage to gill tissue

30. EFFECTS ON ANESTHESIA, HANDLING AND SCALE LOSS ANESTHESIA •Immobilize fish •Reduce pain and stress •Easy to handle and distribute •Low toxicity

31. EFFECTS ON ANESTHESIA, HANDLING AND SCALE LOSS ANESTHETICS: CONSIDERATIONS Most anesthesia by a dip or bath treatment in a static bath or with flowing water Correct dosage and choice of anesthetic depends on: Degree of anesthetization required The species, size, and condition of fish Water temperature and water hardness (pH)

32. EFFECTS ON ANESTHESIA, HANDLING AND SCALE LOSS STAGES OF ANESTHESIA:

33. EFFECTS ON ANESTHESIA, HANDLING AND SCALE LOSS Some Common Fish Anesthetics 1. Tricanemethane sulfonate (MS222) 2. Benzocaine 3. Carbon dioxide 4.Clove oil( eugenol ) 5. 2-phenoxy ethanol) 6. Metomidate

34. EFFECTS ON ANESTHESIA, HANDLING AND SCALE LOSS ANESTHETICS and Other DRUGS Anesthetic (loss of sensation) & hypnotic (sleep-inducing) drugs added to the hauling tank water can be helpful in improving the survival of transported fish. These agents can mitigate physiological stress due to excitement and handling, and slow swimming activity. The main purpose of drug additives is to slow metabolic rates and thus reduce oxygen consumption and ammonia & carbon dioxide production. The anesthesia had significant help in preventing injuries due to excitement, such as broken fins, that would ordinarily occur during hauling, and in reducing scale loss- a serious cause of mortality when smolts are transferred directly into seawater

35. EFFECTS ON ANESTHESIA, HANDLING AND SCALE LOSS HANDLING AND SCALE LOSS Handling is an inevitable precursor to any transportation exercise ands may cause mechanical abrasion, induce some degree of stress and result in exhausted animals. Damage to the delicate epidermal layers and mucous covering will allow invasion by pathogens and disrupt osmoregulation. In fish, visible damage is frequently seen as scale loss, but the epidermis will also have been damaged well before scales are shed.

36. RESPONSE TO AIR SATURATION OF WATER Less oxygen can be held in fully air-saturated warm sea water than fully air-saturated cold freshwater. While the oxygen content of the water sets the absolute availability of oxygen in the water, it is the oxygen partial pressure gradient that determines how rapidly oxygen can move from the water into the fish’s blood to support its metabolic rate. This is because oxygen moves by diffusion across the gills of fish. Air-saturated in water 100% air saturation is the equilibrium point for gases in water.

37. RESPONSE TO AIR SATURATION OF WATER Hyperoxia is the state of water when it holds a very high amount of oxygen. At this state, water is described as having a dissolved oxygen saturation of greater than 100% (140-300%). If fish are exposed (at a lower atmospheric pressure) to such water, their blood equilibrates with the excess pressure in the water. Bubbles form in the blood and these can block the capillaries; in sub-acute cases the dorsal and caudal fin can be affected, and bubbles may be visible between the fin rays. The epidermal tissue distal to the occlusions then becomes necrotic and cases are known where the dorsal fins of trout have become completely eroded.

38. In severe cases, death occurs rapidly as a result of blockage of the major arteries, and large bubbles are clearly seen between the rays of all the fins. The remedy is either to remove the fish to normally equilibrated water or to provide vigorous aeration to strip out the excess gas ( Svobodova et al. 1993). In some species such as salmons and fast swimming fishes, the swim bladder acts like an oxygen store, to be used during the hypoxia. When the gads level in the blood is high gases will diffuse from the blood to the bladder. When the water is supersaturated ( hyperoxia ) the bladder becomes over-inflated and this leads to buoyancy problems especially in small fishes (Groot et al. 1995). RESPONSE TO AIR SATURATION OF WATER

39. Successful fish production depends on good oxygen management. Oxygen is essential to the survival (respiration) of fish, to sustain healthy fish and bacteria which decompose the waste produced by the fish, and to meet the biological oxygen demand (BOD) within culture system. Dissolved oxygen levels can affect fish respiration, as well as ammonia and nitrite toxicity. When the oxygen level is maintained near saturation or even at slightly super saturation at all times it will increase growth rates, reduce the food conversion ratio and increase overall fish production. RESPONSE TO AIR SATURATION OF WATER

40. Overall health and physiological conditions are best if the dissolved oxygen is kept closer to saturation. When the levels are lower than those mentioned above, the growth of the fish can be highly affected by an increase in stress, tissue hypoxia, and a decrease in swimming activities and reduction in immunity to diseases. When the oxygen content drops below 59% fish starts to lose its appetite (Randolph and Clemens ,1976). RESPONSE TO AIR SATURATION OF WATER

41. Cold water fish - 6 mg per litre (70% saturation) Tropical freshwater fish- 5 mg per litre (80% saturation) Tropical marine fish- 5 mg per litre (75% saturation) RESPONSE TO AIR SATURATION OF WATER The recommended minimum dissolved oxygen requirements for fish :

42. PHYSIOLOGICAL CHANGES ASSOCIATED WITH DISEASES The Role of Stress in Fish Disease Physiological stress and physical injury are the primary contributing factors of fish disease and mortality in aquaculture. increased fish density and poor water quality (i.e., low dissolved oxygen, undesirable temperature or pH, increased levels of carbon dioxide, ammonia, nitrite, hydrogen sulfide, organic matter in the water); Many potential fish disease pathogens are continually present in the water, soil, air, or fish. Food fish reared under commercial aquaculture conditions are confined to the production unit and are weakened by stress conditions including: injury during handling (i.e., capture, sorting, shipping); inadequate nutrition; and

43. PHYSIOLOGICAL CHANGES ASSOCIATED WITH DISEASES The Role of Stress in Fish Disease These conditions can result in decreased resistance by the fish, resulting in the spread of disease and parasite infestation. poor sanitation Fish are able to adapt to stress for a period of time; they may look and act normal. However, energy reserves are eventually depleted and hormone imbalance occurs, suppressing their immune system and increasing their susceptibility to infectious diseases.

44. PHYSIOLOGICAL CHANGES ASSOCIATED WITH DISEASES Defense against infection -(slime layer) is the first physical barrier that inhibits entry of disease organisms from the environment into the fish. Mucus -It is also a chemical barrier, containing enzymes and antibodies which can kill invading disease organisms. - lubricates the fish, aiding their movement through water, and is important for osmoregulation.

45. PHYSIOLOGICAL CHANGES ASSOCIATED WITH DISEASES Defense against infection Scales and skin function as a physical barrier which protects the fish. These are injured most commonly by handling, rough surfaces of tanks or cages, and by fighting caused by overcrowding or reproductive behavior. Parasite infestations can also result in damage to gills, skin, fins, and loss of scales. Scales and Skin Damage to scales and skin of the fish can increase the susceptibility to infection. It also causes excessive uptake of water by freshwater fish or loss of water from marine species (osmotic stress). Fish which are heavily parasitized may die from bacterial infections which gained initial entrance to the fish’s body through damaged areas in the skin.

46. PHYSIOLOGICAL CHANGES ASSOCIATED WITH DISEASES Defense against infection Inflammation is a natural immune response by the cells to a foreign protein, such as bacterium, virus, parasite, fungus, or toxin. Inflammation is characterized by swelling, redness, and loss of function. It is a protective response, an attempt by the body to wall off and destroy the invader. Inflammation Any stress causes hormonal changes which decrease the effectiveness of the inflammatory response. (Temperature stress: cold temperatures-completely halt the activity of the immune system high temperatures- extremely detrimental to the fish’s ability to withstand infections. - may favor rapid population growth of some pathogens. - reduces the ability of the water to hold oxygen and increases the metabolic rate and resulting oxygen demand of the fish).

47. PHYSIOLOGICAL CHANGES ASSOCIATED WITH DISEASES Defense against infection Antibodies are compounds formed by the body to fight specific foreign proteins or organisms. Antibodies Stress impairs the production and release of antibodies. Temperature stress, particularly rapid changes in temperature, severely limits the fish’s ability to release antibodies, giving the invader time to reproduce and overwhelm the fish.

48. PHYSIOLOGICAL CHANGES ASSOCIATED WITH DISEASES Disease prevention Water Quality Handling and transporting Nutrition Sanitation

49. PHYSIOLOGICAL EFFECTS OF SOME TOXICANTS Impact of Toxicants on the Olfactory System Many metals have been shown to enter the olfactory system of fish where they can potentially cause cell death or disrupt normal olfactory function. Harmful metals example: Cadmium, nickel, manganese, mercury and copper By accumulating in cells of the olfactory system and subsequently causing cell damage or death, toxicants can disrupt electrical transmission of sensory information from the olfactory epithelium to higher levels of the brain.

50. PHYSIOLOGICAL EFFECTS OF SOME TOXICANTS Impact of Toxicants on the Neurotransmission Brain neurotransmitter levels and enzyme function correlate with behavioural states so it is likely that neurological dysfunction induced by toxicant exposure results in behavioural changes. Organophosphates- inhibit brain cholinesterase( ChE ) activity in fish azinphosmethyl chlorpyrifos 2,2-dichlorvinyl dimethyl phosphate fenitrothion diazinon , malathion methidathion carbamate pesticides -inhibit brain ChE activity, Aldicarb carbofuran , diuron nicosulfuron carbaryl thiobencarb

51. PHYSIOLOGICAL EFFECTS OF SOME TOXICANTS Impact of Toxicants on the Endocrine System Endocrine disruption can be due to toxicants agonizing or antagonizing endogenous hormones, or disrupting the synthesis or metabolism of endogenous hormones and their receptors ( Sonnenschein and Soto, 1998) Chemical pollutants: 17ß-estradiol- reduce milt production and gonadosomal index & decreased fecundity. flutamide , vinclozolin , & p,p ′-DDE – decrease sperm counts and/or gonadosomal index. exposure to exogenous sex steroids and other steroid mimics- disturb levels of endogenous reproductive hormones & can alter the activities of enzymes important for endogenous hormone synthesis.

52. PHYSIOLOGICAL EFFECTS OF SOME TOXICANTS Impact of Toxicants on the Metabolic Function Metabolic disruption has been indicated in a number of different ways, most commonly illustrated by altered resting metabolic rates (i.e. oxygen consumption or ventilation rate) or lowered swim performance (i.e. critical swimming speed, U crit ). The storage or mobilization of metabolic substrates such as glucose, glycogen, lactate, lipid, and protein are disrupted by exposure to several trace metals: cadmium, manganese, nickel and metal mixtures in a polluted habitat Similar effects have been observed in fish exposed to pesticides: endosulfan , carbaryl , carbofuran organophosphates,: azinphosmethyl , fenitrothion , and phorate , pyrethroid , deltamethrin , herbicide.

53. INDICATIONS OF FISH HEALTH SYMPTOMS OF STRESS FISH Gasping at the Surface brought by poor water condition (lack of oxygen) Appetite Disease whitespots on the body(itch) Strange swimming Often develop odd swimming patterns (without direction, crashing at the bottom of tank, rubbing himself on gravel or rocks, locking his fins at his side. Observation: not eating

54. VENT • No discharge •No stringy white or brown trailing material (sign of possible cyanide poisoning) SCALES • Flat, not raised • No white or black spots • No discoloration HEAD • No obvious pitting • No milky patches • Dorsal area behind head not pinched FINS • Flared, not clasped • Not ragged • Absence of white spots • Clear, not cloudy • Not discolored MISC. • No buoyancy problems • Not hiding in corners • Active, not listless • No herky-jerky swimming MOUTH • Good appetite • No ulcers OPERCULA • Not flared • Regular rhythmic movement • No discharge SKIN •No discolored spots or patches • No unusual lesions, lumps, growths or open wounds BELLY • Full, not sunken or pinched • Not thin-looking • Not bloated LATERAL LINE • No pitting Signs of Good Health Fish EYES • Clear • Non protruding • Not sunken

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