I have studied feeding habit of two fish species 1) Amblypharyngodon mola and 2) Mystus tengara; both in lentic environment.  During my study I did not measure any kind of correlation between feeding habit and physico-chemical parameters. But you can go for parameters like temperature, DO, pH which can have the effect on availability on the prey species and thus on the feeding habit. You can also study whether there is any change in feeding habit with change of these parameters and whether these parameters are also affecting the availability of the prey species. Best of luck.

http://link.springer.com/article/10.1134%2FS0032945214060071

Article Food And Feeding Habit Of Amblypharyngodon mola (Hamilton-Bu...

When water temperature lowers down towards the lower border of the thermal range in which the fish species subsists (may change with age and  season), usually its metabolism slows down and, hence, its feeding. The same could be said about the fish' prey and its resulting availability. IMO, studying and learning the species ecology. incl. life history, is a basic requiremant for answering paricular question as yours.

we have been working on commercial shrimp farming. Normally shrimp  feed intake reduces when nitrite levels are high. This is one of the important parameter you can correlate in your study. 

If they are anything like other stream dwelling anadromous salmonids they will be opportunists. Obvious differences based freshwater, brackish, marine feeding will be obvious. In freshwater, many of the stream dwelling salmonids are sit and wait exploiting the hydraulic habitats around instream cover to sit and then feed opportunistically on whatever comes by. We have found drifting invertebrates (mayflies, caddisflies), corixids, small fish, occasional amphibians, and even mice.

To discern the role of anadromy we have using laser ablation on otoliths to examine the cyclical migrations between marine and freshwater. 

Either way The diet using usually pretty accurately estimated by the habitat that is inhabited and the type of feeding strategy.

Buongiorno, 

feeding habits in Salmo macrostigma are very interesting..

I congurgulate to you, you should visit to Turkey for study more and more....I'm tottaly agree with Dr.Gupta, so, Temp., pH, conduktivity,salinity,etc..seston, pleuston, plankton etc..

best

sezginer

Dear Riccardo Lollobrigidi

Many factors affect the habit of feeding fish that are the most important, changes in temperature, salinity and ammonia.

Hi,

I would say salinity would be a good choice. Also, the water transparency because it might influence the prey's detectabillity. In the t ropical freshwater systems it has been found that there is a correlation between water transparency and the feeding strategies of fishes.