P : Sexually mature female weed shiners in stream A (fast flow) will be larger than those in stream B (slow flow).

Hypothesis:
Female weed shiners that mature at larger body sizes are better able to resist strong currents and successfully maintain nests, so faster streamflow selects for larger females.

Prediction:
If the flow/strength hypothesis is supported, sexually mature females in faster streams will be larger than females in slower streams.

Scenario 2 (resource allocation)

Hypothesis:
Slower streamflow supports higher insect availability, providing females with more resources for growth and leading to larger body size at maturity.

Prediction:
If the resource allocation hypothesis is supported, sexually mature females in slower streams will be larger than females in faster streams.

Female weed shiners in slow flowing streams have a larger food abundance which leads to a larger body size at sexual maturity due to their being more aquatic insect larva for them to eat.

Prediction:

Sexually mature female weed shiners in stream B will be larger than those in stream A

P: Weed shiner size will be greater at maturity in slower streams than faster streams.

Variation in body size of sexually mature female weed shiners is mostly due to the availability of food in their stream. Food is more abundant in slower streams, so the fish eat more and grow bigger.

Prediction:

Sexually mature females in a stream with slower flow (stream B) will be larger than those in a stream with faster flow (stream A).

Flow speed influences growth rate indirectly through temperature, with females growing smaller in the colder water in faster streams.

Prediction:

If faster flow reduces water temperature thereby reducing size, females in Stream A (fast) will be smaller.

Prediction: If food availability drives body size, then sexually mature female weed shiners in Stream B, which has a slower flow, will be larger on average than those in Stream A, which has a faster flow.