Transcript reproduction and early life 2008

Announcements and Such
Limnology Hiring Fair Wednesday April 2nd at 5pm in the Red
Gym (check “today in the union” postins for exact location)
Comments on the Midterm
Assignment: Peer Review Draft
Outline for the Day
How to Write a Scientific Paper Lecture (Reminders of
Expectations)
Reproduction and Early Life History
2nd Half of Wisconsin Fishes
GOALS
Background on an important part of fish ecology that is often
overlooked
Generalizations of early life history of fish
Spawning strategies
Basic Background
What do you mean “larval fish”?
Embryo/Egg
Adult
Larvae
Early Life History Stages
• Embryonic period
• Larval Period
• Juvenile Period
What do Fish Larvae Look Like?
Diversity of Larvae
American Eel
Diversity of Larvae
Lake Sturgeon
Lake Trout
Yellow Perch
Diversity of Larvae
Brown Bullhead
Northern Pike
Largemouth Bass
How we sample larvae
Bongo Nets
Opening Discussion
Why are early life histories important to fish ecology?
Answers Kornis Came Up With
1. Survivorship of young influence future generation’s
abundance (year class strength)
a. Majority of mortality occurs early in life
2. Survivorship is affected by spawning strategies
a. Time of hatch
b. Habitat selection
c. Size of larvae at hatch
Factors that influence early life survival
Temperature
-How quickly adult fish mature and spawn
-How quickly eggs hatch
-Growth rate of larvae and YOY
Factors that influence early life survival
Food availability
-Is the right food
available once yolk sac
is used up?
-As they grow does the
food out grow them?
Do they outgrow the
food?
Factors that influence early life survival
Spawning Site
-Water Level:
Eggs can be left
high and dry or
smothered?
-Refugia: Egg
survival can
depend on size of
substrate or
degree to which
they are hidden
-Flow: Too fast
and eggs are
swept away. Too
slow and not
enough oxygen
Factors that influence early life survival
Predation
-Do larvae face a predator gauntlet?
Brandt et al. 1987
Predation
Lake trout eat alewives…right?
What about larval lake trout?
Must fill swim bladder at surface
(physoclistous )
Great lakes LT spawning reefs
Strength of Year Class
• Match/Mismatch Hypothesis
– Food and other conditions are good for
survival = strong year class
• Food is abundant
• Predators are not abundant
• Temperature is appropriate
– Cues for Spawning
– Several factors can disrupt matching and
result in weak year classes
Match/Mismatch Hypothesis
Conditions match
what is needed
Yellow perch hatch
Eat small copepods, then switch to Daphnia
Conditions don’t
match what is needed
Yellow perch hatch
Eat small copepods but Daphnia show up too late
Timing is everything…
Figure from Cargnelli and Gross 1996
Evolution at
work!
Yolk Size and Larvae Survival
Temperature and Development of Fish at
Hatch
Lake Trout (Coldwater)
Pygmy Sunfish (Warm water)
Temperature also effects how long egg stage lasts
Egg Size (r vs K strategist)
• Larger eggs
hatching
more developed at
Herring: eggs, newly hatched,
and 7-10 months
Altricial: Mouths
just formed at yolk
depletion (Long
Larvae)
Newly
Hatched
Steelhead
Precocial:
Good
predators
at yolk
depletion
(Short
Larvae)
Yolk Size of Various Fishes
Fish evolve to spawn in different locations
Temiscamie – strain
Little Tupper strain
Tributary spawner
Shoal spawner
Assinica- strain
Outlet spawner
Why...think about the emerged fry!
Lentic vs. Lotic Patterns
• Lentic Fish often have pelagic larvae
– Major period of dispersal
– Major period of mortality
• Lotic Fish often have benthic larvae
– Avoid being swept away
– Exist for short periods, under heavy cover
Common Spawning Strategies
How often: Semelparous = once, Iteroparous = more then once
Life history strategies
Multiple strategies: Bluegill – parental care or Cuckolder
Female mimic
http://publish.uwo.ca/~bneff/research_beea.htm
Common Spawning Strategies
Non-guarding vs. guarding
Pelagic vs. Benthic
Fine vs. Coarse substrate
Vegetation
Livebearers
Non-gaurding , Pelagic
Alewife - inshore waters, eggs settle
High fecundity
High early stage
mortality
Gizzard shad - Often move up rivers, eggs drift down
Non-gaurding , Pelagic
Freshwater drum eggs float on surface until hatch
Paddlefish eggs are sticky when fertilized, adhere
to the first thing they touch
Non-gaurding , Benthic – fine substrate
Spottail shiners spawn on gravel and silt substrates
Non-gaurding , Benthic - Crevice
Spotfin shiners use rock crevices to hold eggs
Non-gaurding , Benthic – stream
Pacific salmon and brown trout dig redds – clean gravel
where stream water upwells
Non-gaurding , Benthic –vegetation
Northern pike
prefer flooded
vegetation in
backwaters
Guarding , Nests – nests of plants
Guarding means
higher survival
Sticklebacks make nests of algae and macrophytes and
then lay eggs inside the nests
Gaurding , Benthic – Underside of rocks
Both round gobies and Johnny darters spawn under rocks,
attaching the eggs to the underside of the rocks
Aggressive defense
can incur high costs
to parents or death
Gaurding , Nests – gravel
Common in centrachids
also lamprey, nests are
often fanned to increase
water flow and remove
sediments
American brook
lamprey
Smallmouth bass
Gaurding , Nest – fine sediment
Bluegill nests
associated with fine
sediments
Gaurding , Nests – Holes and burrows
Catfish and
bullheads make
burrows or use
existing holes
Livebearers , (none native) Mosquitofish
60 -100 progeny per brood, born live, male has modified
anal fin to impregnate female