Question

A researcher is trying to understand the distribution of a particular species of freshwater fish. The fish, a small tetra, occurs in slowly-moving streams with abundant vegetation, and is absent from streams lacking vegetation.

She is interested in knowing whether biotic or abiotic factors influence the distribution of this fish, or both.

In her first series, she sets up the following.

She creates sixteen wire enclosures, and places them in two different river environments. Eight are placed in slow moving areas with heavy vegetation. The other 8 are placed in rapidly-moving areas with few plants. She stocks all the cages with 24 fish, each of which was weighed. She returns 24 days later.

In all 8 of her center-stream enclosures, all 24 fish survived. In her vegetation-heavy enclosures, 2 cages lost one fish each.

The mean weight gained by the fish was actually much HIGHER all of the center-stream enclosures, compared to the others.

Anecdotally, she notices predatory killifish circling the center-stream enclosures, but not the othes.

What is going on here? What do these results show? What might you suggest next?

Answer 1

Ans 1(a) Here the how much a population can grow is determined by biotic condition that termed as limiting factor for that are placed in slow moving areas with heavy vegetation. due to availability of high nutreint the mean weight gained by the fishes.

(b) the result showed that the fishes that placed in rapidly-moving areas with few plants are still smaller in size due to less food, while the Killifish are larger in size than these center -stream fishes circling them for food. Prey size also influences food selection, in this case fishes that are placed in slow moving areas with heavy vegetation are much bigger the the centerally placed fishes.

(c) in this case both biotic and abiotic factors influence the distribution of the fishes acts as limiting factor. As rapidly-moving areas have less vegetation as the fishes remain small.