Different species of fish are specialized for different levels of salinity. Fish found in high salinity areas migrate into tidal creeks with high tide following the increasing salinity level. Fish that are regularly in the lower salinity areas of the tidal creek migrate farther up tidal creeks away from the approaching high salinity water and with the lower salinity water. Some species of fish seem to tolerate low, mid, and high salinity areas. Some factors beyond salinity that may influence the distribution of fish in tidal creeks are the availability of food and presence of predators.
Any good science considers the limitations of their study.
What may have affected our results were that we changed nets in the middle of our experimentation. The nets were different in that one had a larger mesh than the other. This could have had an affect on the size fish we caught. We also may have gotten more accurate results if we sampled more and collected more data. A clearer plan would also have been useful.