Fish Nutrition Flashcards
What is the importance of temperature in fish habitats?
The optimal temperature is that when the fish energy efficiency is highest, and more energy can be invested in growth
• Appetite is high
• 25-30 °C for tropical fish
• There is about 2.5 times increase in growth rate for every 10 °C
What environmental stressors affect nutritional efficacy and requirements? What occurs to O2 as temperature rises? What is the effect and preference of light on fish? What about crowding?
- Environmental stressors (flow rate, water quality) affect nutritional efficacy and requirements
- Oxygen: as temperature increases, water oxygen carrying capacity is reduced
- Therefore, there is a narrow optimum for temperature where oxygen carrying is still high
- Light/darkness: warm water fish do well with more light more similar to their natural habitat
- Overcrowding/undercrowding: some species actually do better at high stocking density
What can affect the metabolic rate in fish? What happens if you underfeed a fish? Excessive feeding? What are the energy requirements in regards to mammals or birds?
- The metabolic rate can be affected by physiological changes such as spawning
- For most species, this is in late summer
- During winter, requirements are usually lowered
- Underfeeding does not let the fish reach full potential
- Excess feeding is wasteful and can contribute to water pollution
- Fish energy requirements are lower than terrestrial animals (5-6% of mammals or birds)
- Low expenditure on supporting locomotion, heat production
What is the digestive anatomy and function in fish?
- The length of the digestive system of the fish is highly variable
- Stomach tends to be larger in carnivores
- Species with a more vegetarian diet, have a more complex system and a longer intestine
What determines a fish’s nutritional requirements?
- Species differences
- Carnivore, omnivore and herbivore
- Life stages?
- Fry→juvenile→adult→broodstock
- Feeding preferences
- Floating / sinking / slow sinking / live / size
What is the protein requirements for fish?
- Fish have requirements for protein and essential amino acids
- Carnivore fish are in constant gluconeogenesis (like cats)
- Protein requirements are highest for growth and reproduction
- Requirements for total protein vary by species, but essential amino acid requirements are similar
Excess protein→excess ammonia
Decreased water quality in a closed system
What are protein sources for fish?
Protein sources
- Mixtures of animal and vegetable protein can provide a good balance of essential amino acids
- Fish meal- can also be used as a highly digestible protein source
- Temperature affects protein digestion, therefore protein requirements can change at varying temperatures
What fish are carbohydrates important for? What do they do? What sources contain carbohydrates? What is converted to? What kind of fish may not do well with a high carb diet?
Important in omnivores
No requirement for them, but provide energy
Sources: grain, cereal
Just like other species- excess energy is converted to lipid and stored
Carnivores may not do well with a high carbohydrate diet • Like cats, they have low hepatic glucokinase enzyme
What occurs in carnivore fish if there is high carbohydrate intake?
What is vulnerable to nutrient leaching? How long do vitamins C, B12 Choline and pantothenic acid dissipate in water? How must it be provided?
- Water soluble vitamins vulnerable to nutrient leaching
- Vitamin C, B12, choline and pantothenic acid dissipate in 30 seconds of feed hitting water
- Need to be provided in a protected form
What is important to note about commercial fish diets?
Many available, not always easy to assess their quality and nutritional content, how appropriate they are for the species
Use a manufacturer with adequate expertise, quality control
Cancomeindifferentsizesand textures for different species
Somecomeasgelstobe reconstituted
What are medicated feeds for fish? What are they susceptible? What complications can they have?
Medicated feeds
- Some feeds are mixed with antibiotics, antifungals, antiparasitic medications
- May be used to treat diseases; however, it is an opening for misuse
- Some medicated feeds can also increase the fish weight and increase growth rate
- On the other hand, this can contribute to antimicrobial resistance
What is malnutrition in fish? When is it usually not seen?
- Diet poor in protein, calcium and phosphorus or vitamin D can cause skeletal malformation, poor growth, and ascites
- These are not often seen with commercial formulated diets
What can occur with excess protein in the diet of fish? Extra phosphorus? What is algae plant growth symbolize? What is important to condsider when selecting fish diets?
- Excess protein- excess ammonia in the water
- Excess phosphorus in the diet
- Phosphorus can have negative impact on water
- Algae plant growth→decaying matter→reduced dissolved oxygen→fish deaths
- Diets need to be optimized for ‘healthy’ growth of fish whilst minimizing waste
How does diet effect fish coloring? Why?
- Some fish can utilize diet to change coloring
- There are more than 600 types of carotenoids.
- There are two broad classifications of carotenoids: carotenes and xanthophylls:
- xanthophylls contain oxygen
- carotenes are hydrocarbons and do not contain oxygen.
- Absorb different wavelengths of light during plant’s photosynthesis process
- xanthophylls are more yellow
- carotenes are orange
- Many fish have chromatophore cells that can utilize these compounds to change color
