Reef Fish Reproduction Odyssey Expeditions Reef Fish Reproduction Odyssey Expeditions – Fish Reproduction

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 Odyssey Expeditions – Fish Reproduction

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

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 Odyssey Expeditions – Fish Reproduction

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 Odyssey Expeditions – Fish Reproduction

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

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 NOAA Migration and Congregation Odyssey Expeditions – Fish Reproduction

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 Spawning Rush Odyssey Expeditions – Fish Reproduction

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 Larvae with yolk NOAA Odyssey Expeditions – Fish Reproduction

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 Sergeant major tending eggs Breeding Odyssey Expeditions – Fish Reproduction

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 Jawfish with eggs Odyssey Expeditions – Fish Reproduction

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 Odyssey Expeditions – Fish Reproduction

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 Birth of live young Odyssey Expeditions – Fish Reproduction

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

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 Odyssey Expeditions – Fish Reproduction

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 Odyssey Expeditions – Fish Reproduction

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 Female NOAA Male Odyssey Expeditions – Fish Reproduction

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

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

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 http://findarticles.com/p/articles/mi_m1272/is_130/ai_8770633 4 Odyssey Expeditions – Fish Reproduction