I. Jawless Fish: -there are 2 types -both are parasites Unit 8 The Fishes

I. Jawless Fish: -there are 2 types -both are parasites

A. The Lamprey 1. Have no fins, jaws, scales or bones

2. Are anadromous: born in fresh water, migrate to ocean, and return to fresh water to spawn

3. Life cycle: Hatch and live as juveniles (4-6 years) in fresh water a. Undergo “metamorphosis” (about 2 months) and become mature

b. Swim to ocean and live as parasites about 2-3 years

c. return to streams and spawn (reproduce) d. die within 4 days

The mouth of a Lamprey

What Damage do Sea lampreys Inflict on the Fishery? Lampreys have been enormously destructive since they invaded the Great Lakes. Sea lampreys feed on body fluids, often scarring and killing host fish.

During its life as a parasite, each sea lamprey can kill 40 or more pounds of fish. Sea lampreys are so destructive that under some conditions, only one of seven fish attacked by a sea lamprey will survive.

Sea lampreys prey on all species of large Great Lakes fish such as lake trout, salmon, rainbow trout and others. Sea lampreys have had an serious negative impact on the Great Lakes fishery.

Because sea lampreys did not evolve with naturally occurring Great Lakes fish species, their aggressive, predaceous behavior gave them a strong advantage over their native fish prey. Their aggressive feeding behavior contributed significantly to the collapse of fish species that were the economic mainstay of a vibrant Great Lakes fishery.

For example, before sea lampreys entered the Great Lakes, Canada and the United States harvested about 15 million lbs. of lake trout in lakes Huron and Superior annually. By the early 1960s, the catch was only about 300,000 lbs. The fishery was devastated.

B. Hagfish 1. Has long eel-like body (16-32 inches)

2. Produces slime around its body to protect against predators

3. Attaches to fish and sucks out blood and tissue

The mouth of a hagfish

II. Cartilaginous fish

A. Are about 600 species including sharks, skates and rays B. Have no bones, only cartilage Sting Ray

C. Have placoid scales - tiny teeth deeply embedded in skin.

placoid scales

Electron micrograph image of shark skin

D. Have visible gill slits for breathing

E. Have more rigid fins than bony fish

1. Rays a. have flat bodies with large pectoral fins

b. Many are bottom dwellers (move along the bottom where they get food)

c. Mouth and gills on underside - have spiracles behind eyes which bring clean water to gills

spiracles

d. Most have tails which sting as defense

Skates

What’s the difference between a Ray and a Skate? The major difference between skates and rays is the way in which they reproduce: Rays are viviparous (live bearing) while skates are oviparous (egg laying), releasing their eggs in rectangular cases sometimes called "mermaid's purses". Also, Skates normally have prominent dorsal fins while those of rays are absent or reduced in rays.

III. Bony Fishes -make up 95% of fish on Earth -have a skeleton made of bone (including a backbone)

-have mucus covered scales

A. Breathing 1. Have gills 2. Gills are covered by operculum - flap of tissue which opens and closes with each breath

B. Movement Use fins: pectoral A. pectoral - paired on the sides of the body (similar to front or upper limbs in animals) B. pelvic or ventral - paired on the lower side of the body near the head (similar to back or lower limbs in animals)

C. dorsal - fin on the upper side of the body D. anal - fin on the lower side of body, near tail E. caudal - tail fin

B. Speed 1. depends on body shape

2. uses caudal (back) fin for greater speed 3. fastest fish: swordfish, tuna, dolphin, barracuda

Which fish are fast swimmers?

C. Buoyancy (ability to float) 1. Fish need to be able to float or rise in water to rest 2. Have a swim bladder - a gas filled organ to help with buoyancy  Muscles contract (tighten) - bladder shrinks and fish sinks  Muscles relax - bladder gets bigger and fish floats

D. Anatomy of fish 1. Have a 1 way digestive tract (in mouth and out anus) 2. Have closed circulatory system (have blood vessels and arteries) 3. Have 2 chambered heart

4. Have no external ears, but good hearing 5.Have well developed nervous system: Have a lateral line - small openings (pores) on sides of fish that sense vibration in water.

E. Reproduction 1. Most have external reproduction 2. Sperm and eggs are released during spawning

3. During larval stage, fish live as plankton 4. Stages that follow: post larval, juvenile, and adult