Help with test

I've got a data set where I want to look at prawns reaction times to touch food (algae or fish), with and without predator cues, whilst also incorporating how their body size influences this. I've been looking at ANCOVA's, but I'm not sure if that's the correct test to use, it doesn't feel like it is. The only other way I an think of is doing 4 linear regressions for each treatment (algae, algaepred, meat & meatpred). I've been trying to figure this out for days now, can someone please give me some advice?