Early Life and Spawning. GOALS Background on an important part of fish ecology that is often...
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Transcript of Early Life and Spawning. GOALS Background on an important part of fish ecology that is often...
Early Life and Spawning
GOALS
Background on an important part of fish ecology that is often overlooked
Generalizations of early life history of fish
Spawning strategies
Basic Background
Life History
Embryo/Egg
Larvae
Adult
Early Life History Stages
• Embryonic period
• Larval Period
• Juvenile Period
What do Fish Larvae Look Like?
Diversity of Larvae
Lake Sturgeon
Yellow Perch
Lake Trout
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?
Key Reason
1. Survivorship of young influence future generation’s abundance (year class strength)
a. Majority of mortality occurs early in life
b. Boatloads of things affect early survivorship
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 survivalSpawning 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?
Predation
Lake trout eat alewives…right?
What about larval lake trout?
Great lakes LT spawning reefs
Must fill swim bladder at surface (physoclistous )
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
Yellow perch hatch
Yellow perch hatch
Eat small copepods, then switch to Daphnia
Eat small copepods but Daphnia show up too late
Conditions match what is needed
Conditions don’t match what is needed
Timing is everything…Figure from Cargnelli and Gross 1996
Evolution at work!
Egg Size (r vs K strategist)
• Larger eggs more developed at hatching
Herring: eggs, newly hatched, and 7-10 months
Newly Hatched Steelhead
Altricial: Mouths just formed at yolk depletion (Long Larvae)
Precocial: Good predators at yolk depletion (Short Larvae)
Yolk Size of Various Fishes
Fish evolve to spawn in different locations
Temiscamie – strain
Tributary spawner
Assinica- strain
Outlet spawner
Little Tupper strain
Shoal spawner
Why...think about the emerged fry!
Lentic vs. Lotic Patterns
• Lentic Fish often have pelagic larvae
• Lotic Fish often have benthic larvae
How often: Semelparous = once, Iteroparous = more then once
Common Spawning Strategies
Life history strategies
Multiple strategies: Bluegill – parental care or Cuckolder
http://publish.uwo.ca/~bneff/research_beea.htm
Female mimic
Common Spawning Strategies
Non-guarding vs. guarding
Pelagic vs. Benthic
Fine vs. Coarse substrate
Vegetation
Livebearers
Non-gaurding , Pelagic
Alewife - inshore waters, eggs settle
Gizzard shad - Often move up rivers, eggs drift down
High fecundity
High early stage mortality
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
Sticklebacks make nests of algae and macrophytes and then lay eggs inside the nests
Guarding , Nests – nests of plants
Guarding means higher survival
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
Smallmouth bass
American brook lamprey
Gaurding , Nest – fine sedimentBluegill 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