Biology of Cultured Fish

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

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

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 • 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 asstenohaline . • Species which are able to tolerate a wide range of salinities are described aseuryhaline.

14. More Concentrated Membrane Less Concentrated Solute particles Solvent Net Direction of Flow 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.

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 ishypertonic(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