Fish Reproduction

Reproductive Systems Cartilaginous Fishes Bony & Jawless Fishes Ducts lead from testes and ovaries to cloaca (common passage for digestive, excretory and reproductive systems) Cloaca leads to the anus Bony & Jawless Fishes Have a urogential opening (separate opening behind the anus for urine and gametes)

Reproductive System – Cartilaginous Fish

Reproductive System – Bony Fish

Hermaphrodites Some fish are hermaphrodites Deep water fish Able to fertilize themselves but usually don’t Sequential Hermaphroditism (a.k.a. Sex reversal) – individuals begin life as one sex but change into the opposite sex Controlled by sex hormones; triggered by social cues Protandry - starts as male and changes to female Example: Clownfish Protogyny - starts as female and changes to male Example: Wrasses

Sequential Hermaphroditism

Reproductive Behavior Adaptations help individuals get together: Migrations Displaying particular colors as sex signals Courtship behavior Dances Postures Nest building

Mating: Release of Gametes Cartilaginous fishes: Copulation (internal fertilization) Claspers used to deliver sperm into female cloaca Male sharks usually bite and hold female Bony fish: spawn (external fertilization) Spawning can occur in pairs or in large groups Eggs fertilized in the water column drift as plankton Some species deposit eggs on rocks or grass Some are laid in nests and are guarded

Time of spawning is critical Spawning controlled by sex hormones Environmental factors trigger production of sex hormones: Daylight Temperature Food Spawning Time of spawning is critical Spawning controlled by sex hormones Environmental factors trigger production of sex hormones: Daylight Temperature Food

Early Development of Bony Fish After a few days of embryo development the eggs hatch into larva (fry) Larva live as plankton Larva develops into juvenile Juvenile develops into an adult

Early Development of Cartilaginous Fishes

Oviparous – Deepsea Cat Shark

Ovoviviparous – Portuguese Shark

Viviparous - Hammerheads

“Low Oxygen in Coastal Waters Impairs Fish Reproduction” Atlantic Croaker

Assignment: Write a short Essay: Use evidence from this article to support your statements Your essay needs to include: Explain how humans are impacting the Atlantic Croaker. Discuss the long term effects of the human impacts Suggest some ways to help the Croakers

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