Fish Basics

Fish Basics

Diversity of Fish

  • Fish make up > ½ the 55,000 species of vertebrates

    • 515 families, 62 orders

    • 27,977 living species

      • 108 = jawless

      • 970 = cartilaginous — sharks, rays, skates

      • 26,000+ = bony fishes

        • Fish = one species, fishes = more than one species

  • Wide diversity of physiological characteristics and habitats

    • Sizes range from 7mm minnow to 12 meter whale sharks

    • Can live in everywhere from alkaline springs—hypersaline lakes

    • Habitat: everywhere from sunless caves, temporary ponds, anoxic swamps

    • Lifespan = 10 weeks to 150 years

What makes a fish a fish?

  • Aquatic vertebrates

  • Poikilothermic (temperature varies), ectothermic (derives body temp from environment)

  • finned appendages

  • gills for respiration

  • body covering is made of scales

  • Exceptions exist to all of these.

Unusual Adaptations of Fish

  • Lungfishes can remain dormant for up to 4 years in drought (using a swim bladder)

  • Antarctic fishes can survive water that is colder than the freezing point of their blood

  • Deep sea fish can swallow prey larger than them (not very many prey items swimming by, so they must be able to eat whatever comes along)

  • Gender change is common (like clownfish, if the male dies then the female becomes the male, and young breeding clownfish become the breeding female)

  • Wide variety of parental care

  • Bioelectricity

  • Ability to produce light

  • Predatory tactics

Fish Evolution and Classification

  • Most jawless fish are parasitic, and they suck on other fish