General Concepts in Fish Reproduction Christopher A. Bidwell Department of Animal Sciences Purdue University

General Considerations Natural habitat of speciesNatural habitat of species Body size and first parityBody size and first parity Annual vs. multiple spawningAnnual vs. multiple spawning Eggs are hardest to produceEggs are hardest to produce Hormone treatmentsHormone treatments

Reproductive Strategies Maximize survival of eggs and fry - natural habitatMaximize survival of eggs and fry - natural habitat Ultimate Factors - food supply - absence of predators - water qualityUltimate Factors - food supply - absence of predators - water quality

Reproductive Strategies Ultimate FactorsUltimate Factors Proximate Factors - environmental cues - anticipate future spawningProximate Factors - environmental cues - anticipate future spawning

Day Length and Temperature

Reproductive Strategies Synchronous –All eggs are spawned and the fish dies

Reproductive Strategies Synchronous –All eggs are spawned and the fish dies Group Synchronous –Multiple spawning and seasonal spawners

Reproductive Strategies Synchronous –All eggs are spawned and the fish dies Group Synchronous –Multiple spawning and seasonal spawners Asynchronous –Multiple and daily spawning –All oocyte development stages present

Stages of Reproduction Stage 1Oocyte (immature egg) development - Gonadotropin independent - Body size dependentStage 1Oocyte (immature egg) development - Gonadotropin independent - Body size dependent

Stages of Reproduction Stage 1Oocyte developmentStage 1Oocyte development Stage 2Vitellogenesis - Egg yolk production - High nutritional demand - Longest phaseStage 2Vitellogenesis - Egg yolk production - High nutritional demand - Longest phase

Stages of Reproduction Stage 1Oocyte developmentStage 1Oocyte development Stage 2VitellogenesisStage 2Vitellogenesis Stage 3Oocyte maturation - Germinal vesicle (nucleus) migration - Resumption of meiosis (cell division) - Water uptakeStage 3Oocyte maturation - Germinal vesicle (nucleus) migration - Resumption of meiosis (cell division) - Water uptake

Stages of Reproduction Stage 1Oocyte developmentStage 1Oocyte development Stage 2VitellogenesisStage 2Vitellogenesis Stage 3Oocyte maturationStage 3Oocyte maturation Stage 4Spawning - Optimum environment - Mating behaviorsStage 4Spawning - Optimum environment - Mating behaviors

Stages of Reproduction Stage 1Oocyte developmentStage 1Oocyte development Stage 2VitellogenesisStage 2Vitellogenesis Stage 3Oocyte maturationStage 3Oocyte maturation Stage 4SpawningStage 4Spawning Stage 5Recovery - Restore body conditionStage 5Recovery - Restore body condition - New oocyte development - New oocyte development

Stages of Reproduction Stage 1Oocyte developmentStage 1Oocyte development Stage 2VitellogenesisStage 2Vitellogenesis Stage 3Oocyte maturationStage 3Oocyte maturation Stage 4SpawningStage 4Spawning Stage 5RecoveryStage 5Recovery

Spawning Release of eggs and milt - FertilizationRelease of eggs and milt - Fertilization Simulate natural environmentSimulate natural environment Dry strippingDry stripping Hormone inductionHormone induction

Spawning Simulate natural environment - Milk cansSimulate natural environment - Milk cans - Ammo boxes - Ammo boxes - Floating nests - Floating nests - Fiber mats - Fiber mats

Spawning Dry Stripping - Express eggs and milt - Mix together - Add water activate eggs and milt closure of micropyle - SiltingDry Stripping - Express eggs and milt - Mix together - Add water activate eggs and milt closure of micropyle - Silting MS222 is toxic to eggs and milt!MS222 is toxic to eggs and milt!

Induced Spawning? Produce hybrids that are different from the parent species;Produce hybrids that are different from the parent species; Produce sterile polyploid fish(for example, sterile triploid grass carp for aquatic weed control);Produce sterile polyploid fish(for example, sterile triploid grass carp for aquatic weed control); Synchronize reproduction of large numbers of fish for simultaneous spawningSynchronize reproduction of large numbers of fish for simultaneous spawning Produce fry outside the normal spawning seasonProduce fry outside the normal spawning season

Spawning Induced Spawning - Stage 3 Oocyte maturation - Egg Sampling Egg size Yolk clarity Oil globulesInduced Spawning - Stage 3 Oocyte maturation - Egg Sampling Egg size Yolk clarity Oil globules

Spawning Hormone Injection - Carp Pituitary Extract - Human Chorionic GonadotropinHormone Injection - Carp Pituitary Extract - Human Chorionic Gonadotropin Single or multiple injection - Stage 3 complete in hSingle or multiple injection - Stage 3 complete in h Natural Environment or Dry StrippingNatural Environment or Dry Stripping

Conclusions Reproductive strategies are variableReproductive strategies are variable Aquaculturist provides proximate and ultimate factorsAquaculturist provides proximate and ultimate factors Early stages critical for egg viabilityEarly stages critical for egg viability Hormone treatments induce egg maturationHormone treatments induce egg maturation