Behavioral Ecology
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
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Reach maturity in 15 to 25 years
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Only a subset of adult population mates each year
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In spring, lake sturgeon migrate up their natal river to spawn
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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
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.
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
