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

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

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

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!

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

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

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

Chondrichthyes (Class)

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

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

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

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)

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

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 http://www.youtube.com/watch?v=ulucJnxT7B4 T.E.D. http://www.youtube.com/watch?v=6okkvwh8sFc&feature=related http://www.youtube.com/watch?v=sTuB88KaIpQ

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 http://www.youtube.com/watch?v=gBxgdskXTy8&feature=related

Overfishing LONGLINING – put out fishing lines over 80 miles long, with thousands of baited hooks; catch anything that grabs the bait http://www.youtube.com/watch?v=7XYBebUOq4c

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

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