General Concepts in Fish Reproduction

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 fryMaximize survival of eggs and fry – natural habitat vs. man-made Ultimate FactorsUltimate Factors – food supply – absence of predators – water quality

Reproductive Strategies Ultimate FactorsUltimate Factors Proximate FactorsProximate Factors – environmental cues – anticipate future spawning

Day Length and Temperature

Reproductive Strategies SynchronousSynchronous –All eggs are spawned and the fish dies (What fish have we seen that fits this?)

Reproductive Strategies SynchronousSynchronous –All eggs are spawned and the fish dies Group SynchronousGroup Synchronous –Multiple spawning and seasonal spawners (Any examples?)

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

Stages of Reproduction Stage 1Oocyte developmentStage 1Oocyte development – Gonadotropin independent – Body size dependent

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

Stages of Reproduction Stage 1Oocyte developmentStage 1Oocyte development Stage 2VitellogenesisStage 2Vitellogenesis Stage 3Oocyte maturationStage 3Oocyte maturation – Germinal vesicle migration – Resumption of meiosis – Water uptake

Stages of Reproduction Stage 1Oocyte developmentStage 1Oocyte development Stage 2VitellogenesisStage 2Vitellogenesis Stage 3Oocyte maturationStage 3Oocyte maturation Stage 4SpawningStage 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 5RecoveryStage 5Recovery – Restore body condition – 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 miltRelease of eggs and milt – Fertilization Simulate natural environmentSimulate natural environment Dry strippingDry stripping Hormone inductionHormone induction

Spawning Simulate natural environmentSimulate natural environment – Milk cans – Ammo boxes – Floating nests – Fiber mats

Spawning Dry StrippingDry Stripping – Express eggs and milt – Mix together – Add water Activate eggs and miltActivate eggs and milt closure of micropyle closure of micropyle – Silting MS222 is toxic to eggs and milt!

Spawning Induced SpawningInduced Spawning – Stage 3 Oocyte maturation – Egg Sampling Egg sizeEgg size Yolk clarityYolk clarity Oil globulesOil globules

Spawning Hormone InjectionHormone Injection –Carp Pituitary Extract –Human Chorionic Gonadotropin Single or multiple injectionSingle 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