Lecture 15 Fish Behavior

1. Reproduction

2. Migration

3. Symbiosis

4. Predation

Behavioral ecologySelection keeps a watchful eye… …organisms behave in ways that maximize their fitness

Parental care

Some form of defense or manipulation of eggs or young

•  90 families include species that provide care

•  31% Biparental care, 69% uniparental care•  most common caregiver male

•  External fertilizers 89%, Internal fertilizers 11%•  External: 90% male care•  Internal: 86% female care

•  Male care likely evolved to insure no other males fertilize eggs…

HermaphroditesWhy change sex?

Increased fitness•  change sex when, at a given size, the reproductive

success of the other gender becomes higher

•  females limited by number of gametes produced, males limited by number of matings•  sex change theory predicts it best to be male when

small and female when large

However, sex change also depends on ecologies of individual species…

Protogynous Hermaphrodites

Juvenile

Female

Male

- almost universal in wrasses (Labridae)

Embiotoca jacksoni, E. lateralisBlack surfperch, Striped surfperch

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Embiotoca jacksoni

Embiotoca lateralis

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Fixed Action PatternsFixed Action Patterns: stereotypical innate

behavior. The organism will carry it out almost no matter what, even if it doesn’t seem appropriate.

Three-spined stickleback Gasterosteus aculeatus

Fixed Action Patterns Male three spined stickleback: attacks other

males with red bellies – attacks anything red

Learning & Cognition

•  Change in behavior based on experience–  e.g., Habituation, Imprinting, Conditioning:

Pavlov

•  Cognition – The connection between nervous system

function and behavior– Consciousness and awareness

Halichoeres garnotiYellowhead wrasse

Use of a rock as an anvil Coyer, 1995

Tool Use in Fishes

Orange-dotted tuskfishChoerodon anchorago

Learning in Archerfish

Migration

•  Spatial orientation and mapping– Migration: Piloting, orientation

(directional headings), navigation (relative location)

– The role of learning in migration– (magnetite, light, etc..)

Daily MigrationThe deep scattering layer

Migration

complex migration patterns

Migration

Spawning migration

Tagging Great White Sharks

http://topp.org/features/fab_flight_white_shark

A white shark tagged with both acoustic (front) and pop-up satellite (rear) tags. The acoustic tag is detected when the shark swims within 250 m of a listening station, while the pop-up satellite tag records information about location, temperature and depth – and relays it to the laboratory when the tag releases itself from the shark.

Weng et al. 2007

Weng et al. 2007

White Sharks by the Season

Symbiosis

•  Fish - Fish

•  Fish - Invertebrates

•  Fish - Other vertebrates

Trumpetfish / herbivores

Symbiosis Fish-Fish

Symbiosis Fish-Fish

Alternative Strategies

Clownfishes / Anemones

Symbiosis Fish- Inverts

Pearlfishes and their hosts…

Goby and Ghost Shrimp

Symbiosis Fish-other verts

Predation

Two different categories of predators have evolved

•  Speed to overtake prey

•  Minimal aerobic effort – deceptive tactics

The Need for Speed

Over take prey with speed

Predationlie and wait – sometimes involves deception