The scallops, arugula and spinach are low in calories.....if you stopped the salad right there, you would be under 300 calories. The real culprit is probably the Parmesan crisps, very similar in calorie/fat content to potato chips. Prosciutto and walnuts are gonna bump it up too.
"Light Citrus" dressing could mean light on oil (which would make it high in calories and fat) OR it could mean light in calories.

After that, you have to take into consideration how it is prepared.

Prepared in a restaurant, this salad could easily come in at about 900-1200 calories. At home, if you dumped the crisps, used the prosciutto sparingly, make a true "Light Citrus" dressing and grilled the scallop, you could get this in under 500 calories.

This dish is a real good example of just how much of a diet wrecker a salad could be, if you are not careful.

My guess--------1175 calories. OK, now I am hungry.