Fish Flashcards
(35 cards)
3 types of fish
jawless
Cartilagenous
Ray-finned (largest group 90% fish)
Jawless Fish
Agnatha: Lampreys and hagfishes
Cartilaginous Fish
Chondrichthyes: Chimaeras, Sharks, Rays & Skates
Ray-finned Fish
Actinopterygii
Teleosts and allies
% of species marine and freshwater
58% Marine
42% Freshwater
Largest Fish
heaviest Fish
Largest- Whale Shark 12m+
Heaviest- Ocean Sunfish- 2000Kg
Environmental Requirements
Water Salinity - freshwater, brackish, marine
Temperature- polar (-2-2C), temperate (0-20C), tropical (20+*C)
Oxygen- requirements highly variable
Behaviour
Feeding
Water Quality
Territorial through to shoaling
Surface, substrate, predators, herbivores, planktivores
Key togood health e.g. pH, ammonia, nitrite, nitrate
Ornamental Fish Industry
1/10 households inUK have ornamental fish
estimated 20-25 million tanks,20 million ponds
~4000 different species kept as pets or in public aquaria
£3-4billion
Main Considerations for environment
Oxygen, temperature tolerance, salinity, pH requirements (acidic, basic), water hardness, space requirements
Main Behaviour Considerations
Shoaling/solitary
Agression
Main Health Considerations
Maintainance of water quality
Why need filtration
Fish release metabolic waste ammonia from the gills (75%) and their urine (25%)
Faeces and other solid wastes decay in the water
Releases ammonia and other waste
Ammonia is very toxic- less then 1ppm can be fatal
Filtration System
Removes solid and dissolved waste from the water
£ sequential sections of filtration system
Mechanical
Biological
Chemical
Mechanical Filtration
Filter matts
Sand filters
Swirl filters
Brushes
Biological filtration purpose
To encourage the growth of beneficial autotrophic bacteria which will breakdown the toxic nitrogenous waste into a harmless formvia nitrification
Process of biological filtration
Breakdown toxic ammonia to nitrite (used as energy source)
Ammonia oxidising bacteria- AOBs
(Nitrite varies in toxicity- freshwater fish can be highly toxic, less for marine fish)
Nitrite to less toxic nitrate
Nitrite oxidising bacteria- NOBs
A biofilter needs to be looked after but can last indefinitely
Chemical Filtration
Purpose: to remove (adsorb) specific undesirable substances from the water- locked up
Carbon granules to remove colour from water (e.g. phenols give water a yellow colour)
Zeolite can remove ammonia and can be recharges (freshwater only)
Phosphate removing granules prevent algae growth
3 approaches to fish management (from least intensive to most intensive)
Open
Semi-closed
Closed
Open Systems
Caged environments in rivers, lake esturies,open sea
Lack intensive water quality management, rely on natural system to maintain WQ
Sea bass, salmon
Range from systems keeping low densities of fish (often with natural feeding) to very high density with active feeding
controversial due to potential for pollution and health risks to wild and captive fish
Semi-closed Systems
Flow-through or once through systems or raceways Inland aquaculture canals/basins, usually of concrete inlet and outles, fast continous water flow Freshwater: trout, catfish, tilapia Brackish water: sea bass, sea bream Allows higher densities of fish Needs active feeding Needs continuous water source
Closed Systems
Recirculating aquaculture systems (RAS) Water re-conditioned and recirculated Marine and freshwater High fish densities Minimal water and land use Reduced wastewater volume Highly controlled growth conditions Needs very efficient bio-filtration Expensive to set up and maintain Needs highly trained staff Higher greenhouse gas emissions than others
Ornamental Set Up
Tank,cover, filter, food, enrichment, oxygenator, thermostat, timed lights
