1. REPRODUCTION IN FISHES

2. Introduction Great diversity in reproduction patterns of fishes
Many change gender
Some mate for life while others are promiscuous
Different strategies have developed in order to reach a common goal - to have the greatest number of young survive to reproduce
The larger the individual the more gametes produced
Odyssey Expeditions

3. Reproduction Modes Oviparity - external development
Lay undeveloped eggs
External fertilization (most all bony fishes)
Internal fertilization (some cartilaginous fishes)
Ovoviviparity – internal development
No direct nourishment from mother (fert. eggs carried)
Advanced at birth (some cartilaginous fishes)
Larval birth (few bony fishes)
Viviparity – internal development
Direct maternal nourishment (placental)
Fully advanced at birth (adv. sharks and few bony fish)

4. Oviparity Most common Lower energy cost to produce eggs
Survival is low, millions produced in hopes that at least one will survive to reproduce
Larval fishes typically spend 14 – 30 days feeding among the plankton clouds.
Juveniles typically settle in areas far from where they were spawned due to dispersal from the currents
Odyssey Expeditions

5. Ovoviviparous/Viviparous
Eggs have lower rate of predation when carried in mother
Much higher energy cost per egg
Therefore fewer eggs produced
Young born as miniature adults
Young generally stay in the same area as mother
Odyssey Expeditions

6. Live-Bearers Very few bony fishes Typically cartilaginous fishes
Viviparous and Ovoviviparous
Fertilization internal
Sperm transferred into cloaca (opening used for excretion and reproduction) by the males claspers (modified pelvic fin)
Internal fertilization

7. Breeding Chances Semelparous – spawn once then die
Ex. Lamprey, salmon
Iteroparous – spawn more than once
most fishes
Semelparous salmon

8. Mating Systems
Promiscuous – both sexes have multiple partners (mass spawning events, nassau grouper)
Polygamous – one sex has multiple partners
Polygyny – males have multiple partners (most common)
Harem formation – male has breeding right to group of females (wrasses)
Polyandry – females have multiple partners (uncommon)
Monogamous – sexes have one partner (butterflyfishes, anglefishes)
Polygyny Harem
Odyssey Expeditions
Monogamous

9. Genders Gonochroistic – sex is fixed, one sex (most fishes)
Hermaphroditic – contain both sex organs at some point
Simultaneous – both sexes at once (deep water fishes, hamlets)
Sequential – changes sex
Protandrous – male into female (moray eels)
Protogynous – female into male (most common)
wrasses, parrotfishes
Jon Buchheim