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Reef Fish Reproduction

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  1. Odyssey Expeditions Reef Fish Reproduction Odyssey Expeditions – Fish Reproduction

  2. Odyssey Expeditions 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 – Fish Reproduction

  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) Odyssey Expeditions – Fish Reproduction

  4. Odyssey Expeditions 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 – Fish Reproduction

  5. Odyssey Expeditions 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 – Fish Reproduction

  6. Reproductive Strategies • Broadcast spawning • Majority of bony fishes • Release thousands to millions of tiny eggs into water column • Benthic egg laying • Some bony fishes • Tens to thousands of eggs laid in nest • Live-bearing • Few bony fishes • Most cartilaginous fishes • Young emerge from parent free swimming • Few young produced • More parental care = less eggs • Goal is to have maximum number of young reproduce Odyssey Expeditions – Fish Reproduction

  7. NOAA Migration and Congregation Broadcast Spawners • Generally occurs at dusk (fewer predators around) • Typically done on an out-flowing tide to get eggs away from predators on the reef • Typically performed at a specific site • May migrate to areas of large congregations (snappers, groupers) or stay on resident reef • Gamete production lowest in energy cost per gamete Odyssey Expeditions – Fish Reproduction

  8. Spawning Rush Broadcast Spawners • Males and females make an upward dash and release gametes, called spawning rush • Egg and sperm meet in water column • Hundreds to thousands of eggs released in each dash • Higher level of polygamy, but pair spawning common Odyssey Expeditions – Fish Reproduction

  9. Larvae with yolk NOAA Broadcast Spawners • Fertilized eggs at mercy of currents • Hatch after ~24 hours • Larvae live off yolk after hatching for a short time • Larvae may be spined to reduce predation. • Survival is very low • Theorized that they are able to locate settling habitat by sound and smell • Settle onto reef at night Odyssey Expeditions – Fish Reproduction

  10. Sergeant major tending eggs Breeding Benthic Egg Layers • Oviparous • Typically spawned at daybreak • Fishes generally small in size • High energy cost to males who prepare nests and tends the eggs (remove debris, defend eggs) • Way to ensure he is the only one to fertilize eggs (he hopes) • Female deposits eggs in nest built by male • Males come along periodically and fertilizes them • Nests may have more than one females clutch Odyssey Expeditions – Fish Reproduction

  11. Jawfish with eggs Benthic Egg Layers • No migration or surface dash risks • Larvae developed after ~7 days and generally begin a planktonic existence for dispersal and feeding. • Male jawfishes and some cardinalfishes keep eggs in mouths. • Male sygnathids (seahorses and pipefishes) brood eggs in a pouch Odyssey Expeditions – Fish Reproduction

  12. Internal fertilization 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) Odyssey Expeditions – Fish Reproduction

  13. Birth of live young Live-Bearers • Sperm fertilizes few eggs • In hammerhead and requiem families (viviparous) young may be cannibalistic, eating other young and eggs in the womb. • Gestation period of 6 to 22 months. • Birth to live young Odyssey Expeditions – Fish Reproduction

  14. Semelparous salmon Breeding Chances • Semelparous – spawn once then die • Ex. Lamprey, salmon • Iteroparous – spawn more than once • most fishes Odyssey Expeditions – Fish Reproduction

  15. Polygyny Harem Odyssey Expeditions Monogamous 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) Odyssey Expeditions – Fish Reproduction

  16. JonBuchheim 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 Odyssey Expeditions – Fish Reproduction

  17. Male Female NOAA Secondary Characteristics • Monomorphic – no visible external differences between sexes (most fishes) • Dimorphic – Visible external differences • Male typically more colorful and ornate • May be permanent or only during spawning • Wrasses, blennies, parrotfishes Odyssey Expeditions – Fish Reproduction

  18. Courting • Aids in species recognition • Pair bonding • Spawning site orientation • Synchronous gamete release • Overcome territorial aggression • May be simple or complex • Change color, make sounds, “dance” Odyssey Expeditions – Fish Reproduction

  19. Alternative Mating Strategies • Satellite males – Mimic female behavior and coloration • Move into nest of male and releases sperm without the immediate attention of the male • Sneaker males – Generally smaller and immature in appearance (may look like females) • remain hidden and then dart through nests or spawning rush and deposit sperm on the fly. • Able to release sperm without guarding male stopping them Odyssey Expeditions – Fish Reproduction

  20. References • Buchheim, Jason. Tropical Marine Biology. 1995 • Deloach, Ned and Paul Humann. Reef Fish Behavior: Florida Caribbean Bahamas. Florida: New World Publications, Inc., 1999 • Helfman, Gene, Bruce Collette, and Douglas Facey. The Diversity of Fishes. Massachusetts: Blackwell Publishers, 1997 • Spying on the sex lives of wild fish – Reproduction – Brief Article. June 2002. USA Today (Society for the Advancement of Education). 11 Jan. 2007 4 Odyssey Expeditions – Fish Reproduction