Impact of Salt Concentration on Freshwater Fish Mass

During an experiment, a team of scientists analyzed the relationship between the concentration of salt in water and the rate at which freshwater fish maintain their body mass. Five different concentrations of salt (0%, 1%, 2%, 3%, and 4%) were tested over a period of 10 days. The results showed the following average mass changes for fish in each concentration: 0% (no change), 1% (decrease by 2 grams), 2% (decrease by 5 grams), 3% (decrease by 10 grams), and 4% (decrease by 15 grams). The researchers plotted the data on a graph.

Based on these results, which of the following conclusions can be drawn regarding the effect of salt concentration on the body mass of freshwater fish?