1. Reproduction in fishes

2. Reproduction
what defines ‘male’ vs. ‘female’?

3. Reproduction
what defines ‘male’ vs. ‘female’? – reproductive investment
sexual strategies:
females must be ‘careful’ in mate selection due to cost

4. Reproduction what defines ‘male’ vs. ‘female’? sexual strategies:
females must be ‘careful’ in mate selection due to cost
male investments in reproduction :
advertisement, colors, tubercules, kypes, displays
nest building, territorial defense
parental care, brood guarding

5. Reproduction bioenergetics: C = E + M + G + S + R C – consumption
E – excretion
M – metabolism
G – growth
S – storage
R – reproduction

6. Reproduction sexual strategies:
females must be ‘careful’ in mate selection due to cost
- energy investment in eggs
- migration, brooding
male investments in reproduction :
- advertisement, colors, tubercules, kypes, displays
- mate competition
- nest building, territorial defense, migration
- parental care, brood guarding

7. Anatomy hagfish, lamprey: single gonads
no ducts; release gametes into body cavity

8. Anatomy hagfish, lamprey: single gonads
no ducts; release gametes into body cavity
sharks: paired gonads
internal fertilization
sperm emitted through cloaca, along grooves in claspers

9. Anatomy hagfish, lamprey: single gonads
no ducts; release gametes into body cavity
sharks: paired gonads
internal fertilization
sperm emitted through cloaca, along grooves in claspers
chimaeras, bony fishes: paired gonads
external and internal fertilization
sperm released through separate opening

10. Anatomy hagfish, lamprey: single gonads
no ducts; release gametes into body cavity
sharks: paired gonads
internal fertilization
sperm emitted through cloaca, along grooves in claspers
chimaeras, bony fishes: paired gonads
external and internal fertilization
sperm released through separate opening
most teleosts:
ova maintained in continuous sac from ovary to oviduct
exceptions: Salmonidae, Anguillidae, Galaxidae, non-teleosts
- these release eggs into body cavity when ripe

11. Anatomy in general: gametes produced only during spawning season
gonads reduced during non-reproductive season

12. Timing and location of spawning
strategy:
avoid competition for spawning habitat
maximize access to food for offspring
minimize access to offspring by predators

13. Timing and location of spawning
strategy:
avoid competition for spawning habitat
maximize access to food for offspring
minimize access to offspring by predators
example: Lake Champlain
anadromous – salmon
catadromous – eels
fall spawners – lake trout, whitefish
spring spawners – smelt
littoral spawners – sculpins, sunfishes, basses
stream spawners – suckers, darters, minnows, sturgeon
pelagic eggs – burbot

14. Reproduction fecundity egg size and number inversely related
egg number directly related to female size (within species)
related to food supply, competition
= population-regulating mechanism

15. Reproduction fecundity
fractional spawners – produce eggs continuously,
spawn frequently
batch spawners – single reproductive season
release all eggs in a short period

16. Reproduction onset of reproduction
males typically mature earlier and smaller than females
mature earlier if survival and growth are low
stable environment – delayed reproduction

17. Reproduction onset of reproduction
males typically mature earlier and smaller than females
mature earlier if survival and growth are low
stable environment – delayed reproduction
survivorship
high if egg production is low, and vice versa
high fecundity fish respond more rapidly to change

18. Reproduction frequency of reproduction
semelparity - spawn and then die
- huge investment in egg production
iteroparity - repeated reproduction
allows compensation for a “bad” year
more common in more unstable environments
may not spawn every year (sturgeon)

19. Reproductive strategies
fertilization
external except livebearers (elasmobranches, Poecilidae, etc)
mass spawning events (Clupeiformes, smelt, etc.)
several males to each female (Salmoniformes, lampreys)
several females to each male (Gobiidae)
single-pair matings (guppies)

20. Reproductive strategies
non-guarders
- pelagic (broadcast) spawners
semi-buoyant eggs
high fecundity
egg and larval ‘migrations’

21. Reproductive strategies
non-guarders
- pelagic (broadcast) spawners
- benthic spawners
on coarse substrates (lake trout)
on vegetation (carp, perch)
on fine substrates (smelt)

22. Reproductive strategies
non-guarders
- pelagic (broadcast) spawners
- benthic spawners
- brood hiders
build redd on coarse substrates (salmon, lamprey)
Hiding from what? Predators, or currents
credit: Thomas B. Dunklin

23. Reproductive strategies
non-guarders
- pelagic (broadcast) spawners
- benthic spawners
- brood hiders
build redd on coarse substrates (salmon, lamprey)
beach spawners (grunion)
use another species (bitterling)

24. Reproductive strategies
guarders
- nest builders (largemouth bass)

25. Reproductive strategies
guarders
- nest builders (largemouth bass)
rock and gravel (like a lentic redd - sunfishes)
plant material (sticklebacks)
holes, crevices, cavities (gobies, sculpin, blennies)
froth (bettas)
anemones (clown fish)

26. Reproductive strategies
Bearers - carry eggs and/or fry with them

27. Reproductive strategies
Bearers
- external bearers
transfer: Gasterosteidae, Sygnathidae (pipefishes, seahorses)
grade from attachment to skin, to open pouch,
to closed pouch
gill chambers, forehead
obstetrical catfish carry eggs on ventral surface
Seahorse reproduction still limited by energy/time of female to produce eggs – she is choosy about mate, not vice versa

28. Reproductive strategies
Bearers
- external bearers
mouth: males or females
some cichlids and bonytongues

29. Reproductive strategies
Bearers
- external bearers
- internal bearers (viviparity)
facultative - killifishes
obligate - Lake Baikal sculpins,
marine rockfishes (Scorpaenidae)
livebearers - Poeciliids, many sharks
gradient of nutrient supply from mother
superfetation
placental viviparity - sharks
- some egg laying killifishes may ‘accidentally’ have internal eggs fertilized and retained

30. Reproductive strategies
the other extreme: minimal male investment
Lophiiformes: deepsea anglerfishes

31. Alternative reproductive strategies
sexual vs asexual – pros and cons

32. Alternative reproductive strategies
Hermaphroditism
synchronous (or simultaneous) hermaphrodites
Myctophiformes: (laternfishes) - several families
Atheriniformes: Aplocheilidae, Poeciliidae
Perciformes: Serranidae (sea basses, hamlets),
Labridae (wrasses), and others
"Egg-trading" in black hamlets Hypoplectrus nigricans (serranid)
generally alternate as male or female
a few species may self-fertilize prior to oviposition

33. Alternative reproductive strategies
Hermaphroditism
consecutive (sequential) hermaphrodites
first male (protandrous) – less common
Stomiiformes (lightfish, dragonfish)
Scorpaeniformes: Platycephalidae
Perciformes: Serranidae, Labridae, and others
blue-headed wrasse

34. Alternative reproductive strategies
Hermaphroditism
consecutive (sequential) hermaphrodites
first male (protandrous) – less common
first female (protogynous)
Synbranchiformes (swamp eels – only freshwater example)
Perciformes: Serranidae, Maenidae, Labridae
from 100% female -> 100% male
from 100% female -> 50% male / 50% female
some do not pass thru a female stage ("primary males")

35. Alternative reproductive strategies
Unisexual species
processes of DNA re-assortment in sexual species:
1. crossing-over during first meiotic division
2. random segregation of chromosomes in second meiotic division
3. addition of male and female chromosomes after fertilization

37. Alternative reproductive strategies
parthenogenesis:
females produce diploid eggs, no sperm used
premeiotic endomitosis - mitotic division without cytokinesis

38. Alternative reproductive strategies
parthenogenesis:
females produce diploid eggs, no sperm used
premeiotic endomitosis - mitotic division without cytokinesis
gynogenesis:
females produce diploid eggs, use sperm to stimulate development
male genome not used
congeneric species are used for sperm
example: Poecilia formosa (Amazon molly)

39. Alternative reproductive strategies
parthenogenesis:
females produce diploid eggs, no sperm used
premeiotic endomitosis - mitotic division without cytokinesis
gynogenesis:
females produce diploid eggs, use sperm to stimulate development
male genome not used
congeneric species are used for sperm
androgenesis – does not exist (why?)

40. Alternative reproductive strategies
parthenogenesis:
females produce diploid eggs, no sperm used
premeiotic endomitosis - mitotic division without cytokinesis
gynogenesis:
females produce diploid eggs, use sperm to stimulate development
male genome not used
congeneric species are used for sperm
hybridogenesis: one genome from female in egg,
male genome discarded - then uses sperm to restore ploidy
- no crossing over
example: Poeciliopsis monacha-lucida

41. Alternative reproductive strategies
Alternative male strategies
- jacks (salmon and trout)

42. Alternative reproductive strategies
Alternative male strategies
- jacks (salmon and trout)
- sneakers (“SF”s) in bluegills, wrasses, sunfishes
evolutionarily stable strategy - if small, become SF,
avoid stress of being parental male

43. Alternative reproductive strategies
Alternative male strategies
- jacks (salmon and trout)
- sneakers (“SF”s) in bluegills, wrasses, sunfishes
evolutionarily stable strategy - if small, become SF,
avoid stress of being parental male
- satellite males (mimic females) in bluegills, hover near nest

45. DEVELOPMENT

46. variable shape, attachments variable buoyancy water hardening
Developmental stages
egg <0.5 mm - 10 cm
variable shape, attachments
variable buoyancy
water hardening
skate
(5 cm)
lake trout
(5 mm)
yellow perch egg mass
round goby
(0.5 mm)

47. embryo - dependent on mother or yolk sac for food (free embryo)
Developmental stages
egg
embryo - dependent on mother or yolk sac for food (free embryo)
Credit: Fly Anglers online
Susan Middleton & David Liittschwager

48. Developmental stages
egg
embryo - dependent on mother or yolk sac for food (free embryo)
larvae - not fully functional, may look totally unlike adult
ends when axial skeleton is formed

49. Developmental stages
egg
embryo - dependent on mother or yolk sac for food (free embryo)
larvae - not fully functional, may look totally unlike adult
ends when axial skeleton is formed
juvenile - small functional individual, immature
adult reproductively mature

50. embryo - dependent on mother or yolk sac for food (free embryo)
Developmental stages
egg
embryo - dependent on mother or yolk sac for food (free embryo)
larvae - not fully functional, may look totally unlike adult
ends when axial skeleton is formed
juvenile - small functional individual, immature
adult reproductively mature
Credit: USFWS, GLFC

51. indirect development (perch)
- larval stages go through trophic phases different from
adults
intermediate (salmonids)
- embryonic stage with yolk; virtually no larval stage
direct development (gobies)
- juvenile is fully functional miniature of adults
(no larval stage)

52. Genetics

53. Genetics
Sex determination
heterogametic sex can be male or female

54. Genetics Sex determination heterogametic sex can be male or female
Polyploidy - more than two sets of chromosomes
critical difference between odd and even sets

55. Genetics Sex determination heterogametic sex can be male or female
Polyploidy - more than two sets of chromosomes
critical difference between odd and even sets
- use of triploid grass carp

56. Genetics Natural polyploids
triploids - Cyprinidontiformes: Poeciliid triploids
- different solutions to the problem of triploid gametes….

57. Genetics Natural polyploids
triploids - Cyprinidontiformes: Poeciliid triploids
tetraploids (autotetraploids vs. allotetraploids)
Acipenseriformes (sturgeons and paddlefish)
Salmonidae (all trouts - autotetraploid)
ancestral chromosome doubling event
Cypriniformes
some cyprinids
all catostomids are allotetraploid
Siluriformes
Corydoras catfishes
Perciformes
Only Lucioperca sandra: 2n = 24 in Sweden
but 2n = 48 in Finland

58. Genetics Natural polyploids
triploids - Cyprinidontiformes: Poeciliid triploids
tetraploids (autotetraploids vs. allotetraploids)
hexaploids and octaploids (rare in carp)

59. Genetics
Natural hybrids
salmonids
centrarchids