1. Biology of Cultured Fish
Developed by the Harbor Branch ACTED staff

2. Less than 1% of the Earth is freshwater
Freshwater Fish
Less than 1% of the Earth is freshwater
40% of fish are freshwater
less than 5000 m deep
species are a result of evolutionary isolation and ecological adaptation
No global species
Two species are circumpolar

3. Marine Fish Earth is 71% saltwater 60% of fish are marine
Less evolutionary variable and ecologically isolated
The oceans provide much bigger space
Many have large ranges
7000 m deep
130 global species
Tuna distribution in southern oceans

4. Where are most fish found?

5. And at what depth?

6. Ichthyology “the study of fishes” 25,000 living species
53,000 scientific names
200 new species each year

7. Some definitions… Fish – singular and plural for a species
Fishes – refers to more than one species
Fish
Fishes

8. Why classify organisms?
Taxonomy – scientific classification
Systematics – the study of the relationship among taxa; studies the history of life

9. How are plants and animals classified?
Who? Carolus Linneaus, 1700’s, Europe
What? Developed binomial nomenclature
Kingdom
Phylum
Class
Order
Family
Genus
Species
Red Snapper
Lutjanus campechanus

10. How would an aquaculturist classify fish?
Temperature
Salinity
Reproduction

11. Temperature Cold (trout, salmon) Temp: below 15 C
Cool (catfish, striped bass)
Temp: 15 – 25 C
Warm (tilapia)
Temp: above 25 C

12. Salinity Freshwater (< 1ppt) Brackish water (1-15 ppt)
Saltwater (15-36 ppt)
Euryhaline – adapts to different salinities
Stenohaline – cannot adapt to different salinities

13. Osmoregulation • saltwater species
Aquatic species may be classified in terms of their salinity tolerance as either:
• saltwater species
• brackish water species
• freshwater species
Salinity 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.

14. Osmoregulation Osmosis
The net movement of a solvent across a permeable membrane from the side with the lower concentration to the side with the higher concentration.
Net Direction of Flow
More Concentrated
Less Concentrated
Solvent
Solute particles
Membrane

15. Osmoregulation
For 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.

16. Osmoregulation: Marine Fish
The 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.

17. Osmoregulation: Marine Fish

18. Osmoregulation: Freshwater Fish
The 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.

19. Osmoregulation: Freshwater Fish

20. What is a fish?
Photograph by HBOI

21. 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