Reproduction of Fish 1 Objectives 1. To examine the reproductive anatomy of fish. 2. To analyze the different modes of reproduction among fish. 3. To describe the importance of induced
spawning in fish. 2 The Reproductive System Is the group of organs used in the reproductive process Focuses primarily on gametes and the organs through which they are transported, stored and
matured Gamete reproductive cell, such as a sperm or egg, capable of fusing with a gamete of the other sex in order to obtain fertilization 3 Fish Reproduction Involves three basic steps: maturation: gametes develop so fertilization
may occur ovulation: eggs are released from the ovary spawning: uniting of egg and sperm, causing fertilization 4 Fertilization Occurs when the sperm reaches the egg sperm discharged into the water are chemically attracted to the eggs
eggs attract only sperm from the same species the farther away from the eggs the sperm is emitted, the fewer eggs are fertilized 5 Male Fish Reproductive tracts include the following: testes efferent ducts epididymis
seminiferous tubules 6 The Testes Are two elongated, oval shaped structures found inside the body cavity of fish on either side of the kidneys Produce milt, which is the sperm-containing secretion of male fish Increase in size during sexual maturity
7 The Efferent Ducts Transport mature sperm away from the testicles Connect the testes to the epididymis Emit the sperm from the body 8
The Epididymis Stores mature sperm Allows sperm to further mature and gain the following abilities: become motile (swim forward) fertilize an egg 9 Seminiferous Tubules Are located inside the testicles
Convert the germ cells into spermatozoa Release sperm outside the body to fertilize eggs Germ Cells basic structures from which new organisms develop; gametes prior to being sperm or eggs 10 Female Fish Reproductive tracts include the following: ovary oviduct
ova 11 The Ovaries Are located in the body cavity and connect to the peritoneum House the female gametes known as ova Produce hormones which regulate secondary sexual characteristics
Increase in size during breeding season, accounting for nearly 1/3 1/4 of the fishs total body weight Peritoneum membrane lining the abdominal cavity 12 The Oviduct Is an open, funnel shaped organ located near the ovary Draws mature eggs from the ovary
Delivers eggs from the ovaries to the outside of the body 13 The Ova Are the specialized female sex cells also known as eggs Creates protective layers and travel from the ovaries to the oviduct and outside the body in oviparous animals
Are fertilized outside the body by sperm 14 Oviparous Animals Produce eggs which mature and hatch after being expelled from the body May or may not require internal fertilization Include almost all fish 15
The Pituitary Gland Is a small, oval gland which lies at the base of the brain Is found in both males and females Influences hormones and gonad functions 16 Modes of Reproduction In fish include the following:
heterosexual hermaphroditic parthenogenic 17 Heterosexual Fish Use sexual reproduction Possess only one sexs reproductive organs Require a member of the opposite sex in order to fertilize eggs
18 Hermaphroditic Fish Possess both male and female reproductive organs May be divided into the following two categories: synchronous: both sets of organs are active at the same time sequential: only one organ is active at any given time 19
Parthenogenic Fish Use asexual reproduction Are females which do not need a male in order to fertilize the eggs Offspring lack diversity and may form adverse mutations 20 Reproductive Cycles
Are the times of year fish will reproduce Differ between species of fish Occur during periods which will promote the best chances of survival for the fingerlings Are influenced by environmental factors such as photoperiod, temperature and seasonal rainfall Photoperiod the amount of time during the day which a plant is exposed to light 21
Induced Reproduction Is the injecting of hormones into fish to promote reproduction Occurs in fish which do not breed in captivity due to the differences in captive and natural environments May be used to manipulate the timing of reproduction to suit production needs 22 Induced Reproduction
Most frequently occurs in the following two ways: replicating natural environment injecting hormones 23 Replicating the Natural Environment Inducing spawning involves imitating conditions under which fish would reproduce in nature
Includes the following: changing the amount of light fish receive providing necessary vegetation, enclosed spaces or other factors depending on species of fish altering water temperature 24 Hormones Most commonly injected are:
pituitary extracts purified gonadotropin LHRHa dopamine blockers steroids 25 Pituitary Extracts Increase hormone levels Are removed from the pituitary gland of a
fish in order to obtain hormones which are then injected into another fish Offer an expensive method of obtaining hormones which do not provide a long shelf life 26 Purified Gonadotropin Stimulates the testes and ovaries and induces ovulation Includes the following:
luteinizing hormone: promotes the production of testosterone follicle-stimulating hormone: promotes the production of sperm in males and estradiol in females Estradiol the steroid which influences reproductive and sexual functioning in females 27 Luteinizing Hormones Releasing
Hormone Analogs (LHRHa) Regulate the rate at which luteinizing hormones are released luteinizing hormones aid in the production of testosterone and induction of ovulation Are more pure and are not metabolized as quickly by fish than normal LHRH May be used alone or in synchronicity with dopamine blockers 28
Dopamine Blockers Slow the rate at which dopamine is released Enhance the strength of LHRHa in order to stimulate the pituitary gland Dopamine a chemical found within the brain which acts to regulate movement and emotion; slows down the functions of LHRH 29
Steroids Directly stimulate the gametes Include injecting pure testosterone and estradiol into the fish 30 Determining Maturity of Fish Includes recognizing the following characteristics:
females: rounded and soft abdomen; swollen, reddened, protruding genital area; swollen and reddened anal area; secondary sex characteristics are present males: release milt when abdomen is gently pressed; secondary sex characteristics emerge 31 Determining the Sex of a Fish
May be easy in some fish while extremely difficult in others Includes the following characteristics: males are often larger and more colorful males often have longer fins females often have a plumper abdomen 32 Caring for Eggs and Fingerlings Include the following techniques:
remove parents if they are aggressive fish do not rapidly change water temperature or pH do not move eggs isolate eggs and fingerlings if in a community tank 33 Reproduction of Fish
ASSESSMENT 34 Assessment 1. Which of the following describes milt? A.Reproductive cell, such as a sperm or egg B.Membrane living in the abdominal cavity C.Sperm containing secretion of male fish used for fertilizing D.Uniting of egg and sperm 2. Which of the following is NOT one of the three methods of
reproduction? A.Heterosexual B.Hermaphroditic C.Parthenogenic D.Asexual 35 Assessment 3. What is a gamete? A.Reproductive cell, such as a sperm or egg B.Membrane living in the abdominal cavity
C.Sperm containing secretion of male fish used for fertilizing D.Uniting of egg and sperm 4. Which of the following is NOT a reason producers induce reproduction? A.To manipulate breeding seasons B.Because it discourages the need to use hormones C.To obtain more product D.Because fish may not reproduce under captive conditions 36
Assessment 5. Female fish are usually brighter in color than males. A.True B.False 6. The efferent ducts transport mature sperm away from the testicles. C.True D.False 37
Assessment 7. Estradiol is the steroid which influences reproductive and sexual functioning in female fish. A.True B.False 8. The farther away from the eggs the sperm is discharged, the more eggs will be fertilized. C.True D.False
38 Assessment 9. Which of the following causes fertilization? A.Maturation B.Ovulation C.Spawning D.None of the above 10. Eggs are also known as which of the following? E.Ova F.Germ cells
G.Gametes H.Both A and C 39 Resources Hermaphroditism www.reefscapes.net Fish Biology and Husbandry www.dar.uiuc.edu Reproductive System
au.encarta.msn.com 40 Resources Characteristics of Sexual Maturation of Wild and Hatchery Reared Baltic Salmon www.ekoi.lt Induced Reproduction in Fish www.seagrant.umn.edu Hormonal Control of Reproduction in Fish for
Induced Spawning govdocs.aquake.org Acknowledgements Project Coordinator: Production Manager: Meghan Blanek Dusty Moore
Production Coordinator: Executive Producers: Brandon OQuinn Gordon Davis, Ph.D., Graphic Designer: Jeff Lansdell
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