Fish Flashcards
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
Traditional Goldish Bowl
No filtartion
relies on water changes tomaintain WQ
Welfare issues
Widely banned on welfare grounds
External features in cartilaginous Fish
Unpaired, median fins
2 sets of paired, lateral fins, pectoral fins and hydrofoils
Pelvic fins with claspers in males cartilaginous fish as intromittent organ for internal fertilisation
5 gill slits, separating 4 internal gill arches, no cover in cartilaginous fish
spiracle in some remnant of of ancestral anterior gill slit in some cartilaginous fish
lateral line organ as mechanoreceptors detecting minute water pressure changes on body surface
Many of the anatomical and physiological differences between fish and tetrapods can be explained by their use of….
Water as respiratory medium
Fish Gill
unidirectional flow
pressure pump
4 gill arches on each site
Arch with 2 rows of filaments
Filamentwith hundreds of lamellae on both sides
Large surface area
Highly efficient counter-current flow of water and blood
Thin lamellae with short diffusion distance for respiratory gases
High gill ventilation rates allow….
Excretion of nitrogenous waste as NH3
Urea less toxic but metabolically …… ………….. to produce
More Expensive
Uric acid even more ……. and almost water …….
Expensive
Insoluble
Major role of ….. in nitrogenous waste excretion
Gills
Fish are generally ecotherms/endotherms
Ectotherms
What is body temperature determined by?
Environmental Temperature
Partial endothermy evolved several times independently - they use….
Counter current vascular heat exchangers
Venous blood leaving working muscles pre-warms incoming cold arterial blood from gills
