1. “They’re in schools but they’re just not learning.”
FISH
“They’re in schools but they’re just not learning.”

2. 3 Major Groups of Fish Superclass Agnatha – jawless cartilaginous fish
Class Chondrichthyes – jawed cartilaginous fish
“Osteichthyes” – jawed boney fish

3. Agnatha (Superclass) 2 Classes: Hagfish & Lamprey
About 500 Million Years Old
Lack jaws, scales, and paired fins
Cartilaginous skeleton
Porelike gill openings
Eel-like body form
External fertilization

4. Agnatha (Superclass) Hagfish – marine only
Mostly scavengers; also predators of molluscs and crustaceans
Almost blind, rely on keen sense of smell and touch
Exudes a milky slime as defense
Five to 16 pairs of gills
No larval stage
No stomach!

5. Agnatha (Superclass) Lamprey – live in marine or freshwater
Anadromous (“running upward” - marine go back to freshwater to spawn)
Parasitic
Seven pairs of gills
Well developed senses (including eyes)
No stomach
Long larval stage (3 to 7 years)
Extensive damage to fish of the Great Lakes

6. Chondrichthyes (Class)
5 to 7 pairs of gills
Internal Fertilization
Mostly marine
about 850 species
Cartilaginous skeleton
Skin with placoid scales
Teeth not fused to jaw, regularly lost and replaced
Stomach; intestine with spiral valve
No swim bladder
2 Chambered Heart; cold blooded (except Great White Shark family)
About 400 Million Years Old

7. Chondrichthyes (Class)
Elasmobranch (Subclass)
Sharks, skates, rays (nine Orders)
Well developed senses, especially smell, touch (vibration), vision, and electroreception
Lateral Line System – pores along the head and the side of the body - pick up low frequency vibrations
Ampullae of Lorenzini – little dots along head that pick up bioelectric field that surround all animals

8. Chondrichthyes (Class)

9. Osteichthyes (old term meaning “boney fish”)
Two Classes:
Actinopterygii - Ray-finned fish (“ray wing”)
Sarcopterygii – Lobe-finned fish (“flesh wing”)

10. Actinopterygii (Class)
Boney skeleton
3 Types of Scales – ganoid (ancestral) cycloid, or ctenoid – light, thin and flexible
Paired and median fins present, supported by long dermal rays, muscles control fin movement
Gills covered by OPERCULUM
Swim bladder which provides buoyancy
Two chambered heart, cold blooded (except tuna)
Sexes usually separate
Fertilization usually external
Over 24,000 species
Marine and fresh water

11. Sarcopterygii (Class)
Boney skeleton
Strong, fleshy paired lobed fins – used more like legs to scuttle along bottom
Thick, heavy scales
Only 7 species (6 lungfish and 1 coelacanth)
Have gills and lung like structures; gills are used mostly, except in times of extreme dryness
Estivation – bury themselves in mud to await rain, secrete mucus to help prevent dehydration
Amphibians evolved from this class of fish

12. Caudal Fin (tail) Shapes
Heterocercal -different on top than bottom (most sharks)
Homocercal – same on top and bottom (most ray fins)
Diphycercal – dorsal fin and tail fin joined (most lobe fins)

13. Problems Facing Fish
Destruction, degradation, and pollution of wetlands and reefs greatly reduces fish populations
Global warming – 3 major effects
- destroys coral reefs (less O2 – endosymbiotic algae)
- enhances harmful effects of pollution
- more UV – hurts surface dwelling species
Overfishing – leads to commercial extinction; fleets have grown twice as fast as the rise in catches (takes decades to recover IF the fishing stops). Recent years spent $125b to catch $70b in fish – led to government subsidies = more overfishing

14. Overfishing Four Types of Fishing
TRAWLING – drag a funnel shaped net along bottom; huge nets (could fit 12+ jumbo jets); small fish escape, everything else is caught; scrapes up sea floor – destroys bottom habitats; Bycatch is thrown back dead or dying
Kills turtles and seals
T.E.D.

15. Overfishing
PURSE-SEINE – used for surface dwelling fish (pelagic) such as tuna; once a school is found, surround with net and tighten; kills dolphins who swim above the tuna

16. Overfishing
LONGLINING – put out fishing lines over 80 miles long, with thousands of baited hooks; catch anything that grabs the bait

17. Overfishing
DRIFT-NETTING – nets which hang as much as 50 ft below surface, over 30 miles long; leads to overfishing of the desired species and huge quantities of unwanted fish & marine mammals
A 1992 UN ban on nets longer than 1.6 miles was put in effect in international waters; has helped, BUT: 1) hard to monitor
2) compliance is voluntary
3) led to more longlining,
which leads to similar
results as drift-netting

18. THE END