Module 10 - Fish

Question 1

What are the three main groups of fish?

Answer 1

1. Jawless fish (Class Agnatha);

2. Cartilaginous fish (Class Chondrichthyes); 3. Bony fish (Class Osteichthyes);

Question 2

What determines how fast a fish can swim?

Answer 2

The speed of a fish is about 10 body lengths per second. Locomotion is made with myomeres (Muscles composed of zigzag band). The barracuda can swim 43km/h.

Question 3

Explain the ecological role of fish.

Answer 3

Fish remove problematic insect nymphs and other organism (mosquito). They provide food for higher predators and live in symbiotic relationships with other animals (e. g. Hippo & Tilapia).

Question 4

What is the largest freshwater fish in SA?

Answer 4

Sharp-tooth catfish, 59 kg.

Question 5

What is a fish?

Answer 5

All fish are vertebrates, aquatic, ectothermic (‘cold blooded’), breath by means of gills, move by means of fins and generally covered in scales.

Question 6

Describe scales

Answer 6

1. Cover skin of body of bony fish (growth rings)
2. Protection from injury, predators and parasites
3. Can slide over one another and distort while swimming
4. Hydrodynamic

Question 7

Explain a fish’s senses

Answer 7

1. Sight:
   - Eyes are round (less distortion)
   - No eye-lids
   - Poor 3D vision (no overlap in FOV from eyes)
   - Most see in color
2. Taste: barbels with specialized cells
3. Hearing: Lateral line detects sound and pressure waves, amplified by swim bladder
4. Pheromones: used in breeding season and as alarm signal
5. Touch: barbels

Question 8

Explain Fish feeding behaviour

Answer 8

1. Carnivores
2. Herbivores
3. Filter-feeders
4. Scavengers
5. Parasitic feeders

Question 9

Breeding types in fish

Answer 9

1. Oviparous: Egg (external fertilisation) - Larva - Juvenile - Adult
2. Ovoviviparous: internal fertilisation: Egg develops internaly

Question 10

Breeding strategy in fish

Answer 10

Varies from no parental care to elaborate nests and defensive behavior

Question 11

What determines a fish’s growth?

Answer 11

1. Temperature
2. Age
3. Size of water body
4. Food availability

Question 12

Explain coloration in fish

Answer 12

1. Bright colors warn of predators
2. Translucent larvae and young
3. Dull or cryptic coloration to blend in
4. Countershading (Camouflage and temperature regulation)