Diversity of Fishes - Key Concepts Notes

Definition of Fish:

Fishes are a group of vertebrate species sharing a common ancestor over 500 million years ago.

Characteristics include: vertebrate skeletons, aquatic living (fresh, marine, brackish), fins, scales, ectothermy.

Migration & Osmotic Changes:

Fish may migrate for reproduction and to adapt to environmental changes.

Understanding osmoregulation is essential as it relates to fish survival in varying salinities.

Biological Structure:

Fish gills are crucial for oxygen extraction; changes in water temperature can affect oxygen availability.

Taxonomy of Fish:

"Fish" are not a biological clade; they are nested within all vertebrate species, including humans.

Taxonomical classifications have evolved from outward similarities to genetic relatedness.

Different Types of Fish:

Categories include jawless (lampreys, hagfishes), cartilaginous (sharks, rays), and bony fish (teleosts).

Examples of unique processes include viviparity in certain marine species (e.g., spiny dogfish), and filter feeding in menhaden.

Physiology and Behavior:

Fish have adaptations for buoyancy (swim bladders in bony fish, oily livers in sharks).

Many fish are active predators; there is a physiological link between swimming habits and energy usage.

Gill Functionality:

Fish utilize a two-chambered heart and a closed circulatory system for effective oxygen transport.

Daniel Pauly’s gill oxygen limitation theory suggests that body growth is limited by available gill surface area.

Impact of Temperature on Fish:

Increased water temperatures can limit fish growth due to reduced dissolved oxygen and increased metabolic rates.

Examples of Migration:

Salmon (anadromous) spawn in freshwater, while eels (catadromous) migrate to saltwater to reproduce.