Behavioral Ecology

Behavioral Ecology

Fish Mating



Fish Mating Systems

  • Use of genetic data offers the ability to assess many aspects of mating systems that cannot be determined observationally
  • Most studies have focused on species where one parent is known (i.e. nest tending males)



Lake Sturgeon Mating System

  • Reach maturity in 15 to 25 years
  • Only a subset of adult population mates each year
  • In spring, lake sturgeon migrate up their natal river to spawn
  • Congregate in large groups on spawning grounds
  • Broadcast spawners – no parental care for offspring
  • Prior to egg release females will swim upstream presumably to attract mates
  • Females spawn with multiple males simultaneously
  • Males compete vigorously to obtain closest possible position to females
  • Females can carry 100,000s of eggs
  • Adults will spawn multiple times in a life time
  • Eggs incubate rapidly depending on water temperature before juveniles hatch and drift downstream



Fish Mating

Spawning Behavior Video

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Observational Constraints

  • Difficult to determine who is actually spawning with who in large groups
  • Not possible to determine if all individuals are successfully spawning
  • Difficult to keep track of how many mates each male and female has
  • Not possible to determine which males and females have the highest reproductive success


Reproductive Isolation In Space and Time

Groups of individuals within a population can become reproductively isolated and genetically differentiated as a result of two major mechanisms including isolation by distance (IBD where individuals or populations differ genetically as a function of the distance between them) and isolation by time (IBT where reproductive isolation occurs because breeding occurs at different times). Compared to IBD, which has been well-studied in species exhibiting homing behavior to natal areas, IBT was less commonly reported. If spawning time has a genetic basis (i.e., is a heritable trait) IBT can limit opportunities for mating between individuals that spawn at different times, especially early and late in the spawning season, leading to genetic differentiation within a population. Depending on the degree and duration that reproductive isolation is maintained, increases in genetic relatedness among individuals within groups can develop.


Reproductive Isolation Time Chart



Reproductive Success Charts


Mating System Summary

  • Similar positive relationship between reproductive success and mate number for males and females.
  • Larger males have more offspring and higher mate number than smaller males. These positive relationship were weak for females.
  • No evidence of nonrandom mating by size
  • No consistent trends of differences in RS among females spawning at different times and location


Reproductive Success And Mate Number

Reproductive Success Graph