1 odyssey expeditions – fish reproduction odyssey expeditions reef fish reproduction

1 Odyssey Expeditions – Fish Reproduction

Reef 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


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)


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


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 motherOdyssey Expeditions


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


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


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


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

http://www.intervet.com/aah/bin/fisheggs.jpg


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


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


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


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


Breeding Chances

• Semelparous – spawn once then die– Ex. Lamprey, salmon

• Iteroparous – spawn more than once– most fishes Semelparous salmon


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

Monogamous

Polygyny Harem


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


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

http://www.unep-wcmc.org/marine/coraldis/cd/I/pred_lrg.jpg


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”


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


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

1 odyssey expeditions – fish reproduction odyssey expeditions reef fish reproduction

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