Fish Notes Part 2

1. Fish Notes Part 2 Feeding patterns, buoyancy, temperature, circulatory, respiration and excretion

2. Feeding Patterns • Mouth’s design tells how fish gets food! • Predators • Have specialized teeth for grasping/chewing prey • razor sharp teeth to remove bite size chunks • Ex. shark, bluefish, piranha • Needle sharp teeth used for grabbing/holding • Ex. barracuda, moray eel • Some allow prey to come together • Ex. grouper, angelfish • Some go after it

3. Nibblers/grazers • Predatory fish that take small bites of food • Ex. sheepshead, triggerfish, parrotfish • Strainers • Filter small particles of food drifting in water • Open their large funnel like mouths and take in large amounts of water • Food is filtered out by specialized gill rakers as flows past gills • Ex. basking sharks, whale sharks and menhaden

4. Suckers • round mouth, large lips, small rasping teeth- some have no teeth (sturgeons) • create a vacuum with mouth and suck food with considerable amounts of mud • Often equipped w/ barbels (whiskers) to detect food on the bottom • Ex. sturgeon, catfish and some carp

5. Parasitic • Feed on other living creatures • Lamprey/hagfish have rasp like tongues that scrape a hole in side of other fish • Lamprey sucks contents out while clinging to outside • Hagfish burrows in and eats from within

6. Digestive System • One way (much like human’s!) • Pharynx  esophagus  stomach  intestines  anus • Esophagus may expand to accommodate anything the fish can get into its mouth • Stomach shape varies • Stomach variations: • May contain grinders • May take in air/allow the fish to blow up • May be absent all together • Carnivores have a short, straight intestine • Herbivores have a long, coiled intestine

8. Buoyancy Control • Swim bladder enable fish to move up/down in the water column by changing the fish’s overall density • May be filled by: • can gulp air from atmosphere • release gas from the blood through gas glands • Can maintain neutral buoyancy – neither sinks nor floats – just hangs there

9. ***Sharks, skates and rays don’t have a swim bladder so they must keep moving or sink to the bottom – they do have a large liver with oil that helps keep them afloat • Descension – causes gas in swim bladder to become more dense – fish must add gas to stay afloat • Ascension – opposite of descension, fish must reabsorb gas to keep from floating to the surface

10. 2 types of systems • Open system – have a tube that leads to the digestive tract • Closed system – require that the fish reabsorb gas to the bloodstream • The speed of upward movement is determined by how fast gas can be removed from the swim bladder.

12. Temperature • Fish are ectothermic so the temperature affects their metabolic rate • An increase in temp. = an increase in metabolic rate • A decrease in temp. = a decrease in metabolic rate • Many predatory fish have a countercurrent system for conserving heat which allows their muscles to stay warm  ex. great white shark, tuna, dolphinfish (mahi mahi)

13. Circulatory System • Much like human’s w/ gills taking the place of lungs • Heart is 2 chambered (yours is 4) – one ventricle and one atrium • have nucleated RBCs (humans do not) • Do have plasma and WBC like humans • Antarctic icefish lack hemoglobin and RBCs and therefore have clear blood!!!!

15. Respiration • Gills allow most fish to take in O2 directly from seawater • Flow of air: • Countercurrent system = blood flows opposite water Mouth  gill arches  gill rakers  gill filaments  gill slits (filter out trash) (O2 diffusion) (screen-like)

16. Operculum • Covers and protects gill chamber • Bony fish possess this – cartilagenous do not • Some fish may take in air by swimming to the surface and gulping it where it may take several hours to diffuse across gills • Lungfish have air-holding sacs

17. How do fish work all this? • Tuna – needs lots of O2 – have 4 gills each with gill arches (each is a double row of gill filaments) • Most sharks swim continuously forcing water through their mouth and over the gills – water leaves by gill slits  can drown when caught in traps because they can’t force water in

19. Excretion and Salt Water Balance • Excretion = the disposal of wastes created by metabolic processes such as CO2, H2O, mineral salts, ammonia and urea • What are the 2 main organs involved in excretion • Gills and kidneys • The removal of wastes is closely associated with the control of water and salt amounts in body fluids

20. Marine bony fish have a salt content of 1.5% • Surrounding water = 3.5% • Diffusion occurs but fish must maintain salt levels of 1.5% • Chloride cells – located in gills – excrete excess salt

21. Fish must also maintain good osmoregulation – regulating water content – allows fish to maintain salt and water content during extreme sailnity changes • Remember: Salt water fish drink large amounts of water to keep their bodies from dehydrating through osmosis and excess salts are removed by chloride cells

23. Fresh water fish drink very little, release a lot or urine because water is coming in through osmosis – constantly needing to get rid of water