Species composition was analyzed for fish communities in two Brazilian rivers.The higher (headwaters), middle, and lower (floodplain) sections of both the Iguatemi River and the Jogui River were sampled.The Iguatemi had 34 species and the Jogui had 31.In both rivers, some species occurred only in the headwaters, others only in the floodplains.Water velocity decreased and turbidity increased from the headwaters to the floodplains.Neither river had rooted vegetation, and the communities did not differ significantly from season to season.The factor most important in determining species composition in the two rivers was most likely
A) temperature.
B) prevalence of non-rooted vegetation.
C) changing characteristics from headwaters to floodplains.
D) richness of fish species.
E) presence of endangered species.

Question

Quizplus · Accepted Answer

The fact that some species occurred only in the headwaters and others only in the floodplains suggests that changing characteristics from headwaters to floodplains is an important factor in determining species composition in the two rivers. Water velocity and turbidity were noted as changing, and the lack of rooted vegetation suggests that this factor was not significant. Temperature and the presence of endangered species were not mentioned as relevant factors, and while richness of fish species was noted, it is not clear from the information given whether this was a determining factor in species composition.

Species Composition Was Analyzed for Fish Communities in Two Brazilian