The timing and intensity of reproduction by reef fish may influence subsequent patterns of recruitment into populations.

Remember, the majority of marine organisms have a bipartite life history, with a dispersive early life history stage and a relatively sedentary adult phase.

Thinking about "Juvenile" (larval or zygotic) biology vs "adult" biology

Current emphasis.... "Juvenile Biology" rules: oceanic processes are of primary importance in structuring marine populations:

Most studies of fish and marine invertebrates generally emphasize how pulses of juvenile recruitment may determine patterns of adult distribution and abundance.

These typically downplay or ignore how aspects of the adult environment may initially drive patterns of larval supply by influencing the timing and intensity of reproduction.

The potential importance of "Adult Biology":

Recent work with herbivorous coral reef fish demonstrates that food availability can constrain the reproductive ecology of adults on a variety of spatial and temporal scales.

What factors constrain the timing of reproduction?

Consider seasonal patterns of reproduction by coral reef fishes

Conventional wisdom: reproductive seasonality of coral reef fishes is linked to aspects of their larval biology (adults try to target temporal windows of opportunity for their pelagically dispersed young).

This idea comes from studies in temperate water

Several recent studies of coral reef fish demonstrate that shifting conditions on the reef itself can influence seasonal patterns of growth and reproduction.

Detecting "adult" constraints upon reproduction

1) Look for life history tradeoffs

2) Examine reefs in the same geographic area that appear to differ in their reef environments

Look for consistent localized variance in growth, reproduction and mortality between such reefs.

3) Experimentally alter the reef environment and then look for shifts in life history tactics in response to the manipulations

Consider these in light of Clifton's research on the reproduction of the beugregory damselfish, Stegastes leucostictus.

Why is S. leucostictus a good subject?

Common and localized (easy to map and census)

Easy to catch (tag, measure, etc..... can quantify growth)

Females lay eggs in nests guarded by males (can quantify reproduction)

They are herbivores (food can be quantified)

They show seasonality in reproduction

 

The study:

These fish were monitored almost continuously (virtually every day) for over two years.

Feeding experiments

Evidence for a trade off in life history characteristics?

 

Evidence for differences in reproduction between nearby reefs?

 

Results of experimental feeding studies

Conclusion: Adult biology plays a critical role in the seasonal timing of reproduction by these herbivorous coral reef fish.