Biology of Cultured Fish
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Biology of Cultured FishDeveloped by the Harbor Branch ACTED staff
Freshwater FishLess than 1% of the Earth is freshwater40% of fish are freshwater less than 5000 m deepspecies are a result of evolutionary isolation and ecological adaptation No global species Two species are circumpolar
Marine FishEarth is 71% saltwater60% of fish are marine Less evolutionary variable and ecologically isolatedThe oceans provide much bigger spaceMany have large ranges 7000 m deep130 global speciesTuna distribution in southern oceans
Where are most fish found?
And at what depth?
Ichthyologythe study of fishes 25,000 living species 53,000 scientific names 200 new species each year
Some definitionsFish singular and plural for a species
Fishes refers to more than one speciesFishFishes
Taxonomy scientific classification
Systematics the study of the relationship among taxa; studies the history of lifeWhy classify organisms?
How are plants and animals classified?
How would an aquaculturist classify fish? Temperature Salinity Reproduction
TemperatureCold (trout, salmon)Temp: below 15 CCool (catfish, striped bass)Temp: 15 25 CWarm (tilapia)Temp: above 25 C
SalinityFreshwater (< 1ppt)Brackish water (1-15 ppt)Saltwater (15-36 ppt)Euryhaline adapts to different salinities
Stenohaline cannot adapt to different salinities
OsmoregulationAquatic species may be classified in terms of their salinity tolerance as either:saltwater speciesbrackish water speciesfreshwater speciesSalinity requirements may differ for a given species at different stages in its life cycle.Species adapted to a narrow range of salinities are described as stenohaline . Species which are able to tolerate a wide range of salinities are described as euryhaline.
OsmoregulationOsmosis The net movement of a solvent across a permeable membrane from the side with the lower concentration to the side with the higher concentration.
OsmoregulationFor fish we can think of the body fluids as one solution, the surrounding water as the other solution, and the parts of the body separating the two solutions as the membrane.In most organisms the gills are the primary membranes where osmosis occurs.
Osmoregulation: Marine FishThe body fluids of saltwater species are hypotonic (dilute) relative to the surrounding water, so these species tend to lose water to the environment.Osmoregulation in saltwater species requires intake of water and excretion of excess salts.
Osmoregulation: Marine Fish
Osmoregulation: Freshwater FishThe ionic composition of the body fluids of freshwater species is hypertonic (more concentrated) to the surrounding water, so these species tend to accumulate water from the environment.Osmoregulation in freshwater species involves excretion of water and active uptake and retention of salts.
Osmoregulation: Freshwater Fish
What is a fish?Photograph by HBOI
Anatomy & Physiology Lives in water? Carnivore, Omnivore, Herbivore Vertebrate Poikilotherm cold blooded Fins Gills Senses Lateral line Scales Slime (mucus) Swim bladder buoyancy compensator External or Internal Reproduction