Exploring Marine Fish: An Ichthyology Guide

2. Marine Fish • Kingdom Animalia • Phylum Chordata • Subphylum Vertebrata • All fish possess a notochord  later modified into a backbone w/ moveable vertebrae – it allows animals to bend and wiggle and serves to protect the spinal cord • Ichthyology = study of fish

3. Typical Fish Characteristics • Adapted to live in water • Have gills for breathing • Fins for locomotion and stabilization • Internal skeleton • Often covered in scales • Cold-blooded (ectothermic)  colder temps. slow the metabolism

4. Classes of Fish • Agnatha • Chondrichthyes • Ostiechthyes

5. Agnatha • Jawless • Most primitive • Fewer in # due to inability to compete w/ jawed fish • Feed by suction – have round mouths w/ rows of teeth • No fins or scales • Ex. hagfish and lamprey

6. Chondrichthyes • Cartilaginous – cartilage skeleton • Ventral mouth • Many have replaceable razor-sharp teeth • Some have small teeth but gigantic mouths • Ex. rays, skates and sharks

7. Osteichthyes • Bony fish • Skeleton made of true bone • Most successful class • Terminal mouth • 20,000+ species in almost every aquatic habitat • Greater speed and maneuverability • Specialized mouths w/ protrusible jaws • Swim bladder to control buoyancy Don’t need a skeleton to provide support because the water does.

9. Body Forms • Body shape is directly related to lifestyle. They have all types of body forms, for example: • Fusiform • Streamlined, torpedo shaped – “swimming machines” • Designed to rapidly move through the water in pursuit of prey • Efficiency is higher due to: • Ability to fold fins into depressions along body • Smooth eyes flush w/ head • Gills covered w/ flap = operculum • Slime coating • Ex. salmon, bass, tuna, swordfish

11. Body Forms (con’t) • Compressed • Squished side to side • Allows for easy movement among plants and narrow spaces – like coral reef • Ex. flounder, perch, butterfly fish

13. Body Forms (con’t) • Attenuated • Tube like • live in narrow spaces – rocks, coral reefs, etc. • Usually secretes a large amount of slime • Ex. eel • Depressed • Flattened top to bottom (dorsoventrally) • Usually bottom dwellers • Shape of a Hershey’s kiss • Ex. sea robin, rays, skates

14. Depressed

15. Attenuated

16. Fins • principle function is locomotion • Shape is related to method of controlling position or altitude in water • Shapes, sizes, and function differ from fish to fish – there are 6 • Pelvic - soft dorsal • Anal - spiny dorsal • Caudal - pectoral

17. Locations of fins depends on function too: • dorsal - used as rudder to prevent rolling • Anal – used as a rudder • Pelvic/pectoral – used in turning, braking, balancing • caudal – pushes against water and used in forward mvmt.

18. One of the major differences b/n bony and cartilaginous fish is the shape and function of the fins: • Sharks rely on fins for lift (to keep from sinking) • Fin function – reason why bony fish are more maneuverable than cartilagenous fish

19. Three major typs of caudal fins • Heterocercal – sturgeon or shark – use fins to regulate depth (no swim bladder) – also aid in swimming • Pushes head downward and lifts tail as it beats side to side • Pectoral fins act as airplane wings • Shark fin soup – a delicacy in the orient – dump the rest of the organism back to die • Ex. shark

21. Diphycercal • No real lobes • ex. lungfish

22. Homocercal – modern bony fish • Use fins as swimming aids and for turning and stopping – or just moving forward • Lobe same size • Ex. perch