Effect of Temperature and salinity change

1. Effect of Temperature and salinity
change in metabolic and Energy
Conversion in Fish
Pranali Prabhakar Marbade
Department of Fish Biotechnology

2. Introduction
Content of topic
• Effect of temperature
• Effect of temperature on tropical and temperate fishes
• Effect of Salinity
Freshwater fish
Seawater Fish
• Effects of salinity and temperature interaction

3. Effect of Temperature
• The physiology of most fish is heavily influenced by temperature because
they are ectotherms in their metabolic rate, their energy balance, and
activity, like locomotor and eating behaviors, which are affected by
temperature.
• The ability/desire of animals is influenced by temperature the fish's ability
to eat and digest food, as well as how they absorb nutrients and store
surplus energy throughout the gastrointestinal tract

4. • The temperature has a variety of consequences exposure timing, intensity, and
length, as well as the rate at which temperature rises and falls are all factors to
consider alterations take place acute short-term temperature swings can have
a big impact, but long-term progressive changes can have negative impacts on
fish physiology.
• Their metabolic heat production and storage processes are insufficient to
keep their bodies warm. As a result, they are rigorous temperature conformers
and obligate poikilotherms, whose body temperatures are determined by the
temperature of the surrounding environment.
• The abiotic ecological master factor, temperature, has such a big impact on
fish

5. Effect of temperature on tropical and
temperate fishes
• Fish are cold-blooded animals also known as ectothermic or
poikilothermic which means they can't regulate their body temperature
• Instead, they control their metabolisms and activity levels based on the
temperature of their surroundings. They are less active, their hunger is
diminished, and their immune systems are weakened.
• Higher latitudes are projected to see larger temperature variations, fish
residing in temperate and polar regions may be more useful (as
compared to tropical areas where a small temperature increase is
predicted) in temperate climates, an increase in water temperature would
extend the fish growing season
• The increased temperature may lessen the stress of overwintering in
temperate fishes. As a result, a longer growing season and less winter
stress may boost temperate fisheries’ productivity.

6. • Temperate ectothermic species, which occur in the midlatitudes where
seasonal temperature changes are highest, have greater thermal performance
ranges, lower optimum temperatures, and are colder- and heat-tolerant than
tropical species.
• Size (small animals have a faster metabolic rate per unit weight than large
animals), age, and developmental and reproductive stages are some of the
other fundamental features that influence temperature preference
• Two types of lethal thermal limits can be developed: incipient (or chronic)
and ultimate (acute) lethal temperatures. When fish are exposed to this
temperature for an extended period of time, significant mortality (typically
50% of the group, TL50) occurs. If the exposure period is reduced, fish can
withstand higher/lower temperature exposure. The acute lethal temperature is
reached when the temperature of the water is rapidly increased.

7. Effect of Salinity
Freshwater Fish
• In both freshwater and seawater, the ability to control body fluids independently
of the external environment is crucial for fish survival.
• In freshwater fish, the major challenge to maintaining osmoregulatory
homeostasis is the need to maintain extracellular fluid composition and volume in
the face of continuous osmotic gain of water from a very dilute medium, coupled
with a steady diffusive loss of major fluid ions including Na+ and Cl-

8. • Freshwater stenohaline fishes live in hypotonic habitats
and must deal with diffusive ion losses from salt
transport and osmotic water gain via dilute urine
excretion.
• Ion absorption is an energy-intensive mechanism in
freshwater fish that contributes significantly to the fish's
resting metabolic rate rise in salinity below the isotonic
level may lessen the osmotic gradient between the water
and the fish body, lowering the energy cost of freshwater
fish osmoregulation.
• As the salinity level drops below the isotonic level, it's
reasonable to suppose that the resting metabolic rate of
freshwater fish decreases
• Fish species' resting metabolic rates were lower at near-
isosmotic salinity than at hypo-osmotic salinity, other
fish species' resting metabolic rates showed no changes,
linear increases, and bell-shaped variations as salinity
increased

9. Seawater Fish
• Seawater fish are considerably hypotonic to the surrounding
• To restore lost water, marine fish have to drink more; this leads to a very
large salt load for the body
• The branchial mitochondria-rich cells (MRCs) in the skin and gill epithelia
that are responsible for the active secretion of excess Na+ and Cl- ions by
fish in seawater.

10. • Balancing osmotic pressure is a high energy cost activity for marine fish
and research has shown that 20-50% of their total energy budget is
dedicated to osmoregulation, although some studies show that the energy
budget is only 10% approximately.
• That fish under osmotic stress were able to survive and grow at salinities
ranging from freshwater to 48‰, but individuals reared at 24‰ showed
better growth and the highest food intake and best FCR.
• High energy demand for osmoregulation leading to effects on growth rate
and metabolism, osmoregulatory requirements can also affect
reproduction and larval development in artificial culture

11. • The bioenergetics of osmoregulation in tilapia has discovered that routine
metabolic rates (RMR) are higher in fish raised in or acclimated to, it has
been claimed that this difference in energy expenditure may account for faster
growth rates in SW-acclimated fish relative to FW-reared fish.
• Salinity exposure is known to affect growth performance reproductive
capacity, digestive capacity, blood parameters, immune function parameters,
antioxidant status, plasma osmolality, respirometry response, metabolic rate,
histopathology, and behavior.
• The metabolic rate is an indirect measure of the entire energy-demanding
aerobic metabolism of ingested food and routine metabolic processes that
sustain biological processes aerobic metabolism, oxygen turns ingested food
into energy (ATPs), which is then used for a variety of functions, including
growth, locomotion, digestion, reproduction, and maintenance

12. • During aerobic metabolism in fish, protein is more efficiently catabolized into
energy sources than lipids and carbohydrates, resulting in an increase in
nitrogenous waste in the form of ammonia and urea.
• To compensate for the high energy requirement, fish are thought to increase
their ventilation rate and oxygen intake and excrete higher ammonia
concentrations in response to protein metabolism.
• The metabolic cost of osmoregulation at increased salinity varies by species
and can provide contradictory results
• Drought, evaporation, and seawater intrusion produced by climate change are
causing low-level salinity increases in freshwater fish in estuaries and
aquaculture farms along coasts.
• Increases in salinity influence fish structural, biochemical, physiological, and
life cycle processes through changing the osmotic flow of water and the
diffusion of ions between the water and the fish body.

13. • It has been claimed that fish tolerance capacity to environmental stress is
linked to metabolic performance indicators such as resting metabolic rate (the
minimum energy required to sustain basal demands) and maximal metabolic
rate (the greatest energy required to maintain basal demands) (the highest rate
of aerobic metabolism)
• A higher resting metabolic rate may correspond to fast ventilation flow
through the gills, while a higher maximum metabolic rate may represent a
larger gill surface area.
• It can be hypothesized that both of these conditions may positively affect ion
exchange between the water and fish bodies and then result in a high
vulnerability to salinity higher than isotonic conditions

14. • These metabolic variables may play negative roles in the salinity tolerance
capacity of fish, resulting in individuals with both higher resting and
maximum metabolic rates having lower salinity tolerance capacities.
• The maximum metabolic rate is limited by the respiratory gas exchange
capacity of fish, an increase in salinity would affect the maximum metabolic
rate of fish.
• The available information on the salinity tolerance capacity of each individual
was characterized by the upper salinity tolerance limit of fish.

15. • The lowest salinity level that starts to change each characteristic variable of
this species, in terms of population, was established as the salinity tolerance
threshold of that characteristic variable.
• We predicted that
(1) individuals with lower metabolic rates have a higher upper salinity tolerance
limit,
(2) increasing salinity would reduce the resting metabolic rate. We also aimed to
see how the structure and physiology of the gills change due to changes in the
demands of gaseous and ionic exchange as salinity increases

16. Effects of salinity and temperature
interaction
• Effects of the interaction between salinity and temperature on fish growth
performance, survival rates, and associated physiological parameters are
complex and are in general, poorly known reported that growth and food
conversion rate.
• The influence of environmental salinity and temperature on osmoregulatory
ability, organic osmolytes, and plasma hormone profiles in the tilapia
• Plasma osmolality increased significantly as environmental salinity and
temperature increased. Marked increases in gill Na+, K+ - ATPase activity
were observed at all temperatures in the fish acclimated to 200% SW. By
contrast, Na+, K+ -ATPase activity was not affected by the temperature at any
salinity.

17. • Plasma glucose levels increased significantly with the increase in salinity and
temperature. Significant correlations were observed between plasma glucose
and osmolality.
• In the brain and kidney, the content of myo-inositol increased in parallel with
plasma osmolality. In muscle and liver, there were similar increases in glycine
and taurine, respectively.
• Glucose content in the liver decreased significantly in the fish in 200% SW.
Plasma prolactin levels decreased significantly after acclimation to SW or
200% SW. Plasma levels of cortisol and growth hormone were highly variable,
and no consistent effect of salinity or temperature was observed.
• These results indicate that alterations in gill Na+, K+ -ATPase activity and
glucose metabolism, the accumulation of organic osmolytes in some organs as
well as plasma profiles of osmoregulatory hormones are sensitive to salinity
and temperature acclimation in tilapia

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