White-tailed eagle more vulnerable than many. Besides vulnerability, habitat and prey behaviour, fish body size may be a driver in the piscivorian dietary preferences. Studies have indicated that fish less than are taken infrequently, since they have a lower yield, fish of up to are taken secondarily and fish between are preferred since they have the highest nutritional benefit. Fish taken can exceed but since they can start to considerably exceed the weight of the eagle itself, they may be prove too difficult to overpower. One large Atlantic halibut ("Hippoglossus hippoglossus") was found with the disembodied feet of a white-tailed eagle still
Demersal fish benthic fish are denser, with negative buoyancy so they can lie on the bottom without any effort. Most demersal fish are benthopelagic. As with other bottom feeders, a mechanism to deal with substrate is often necessary. With demersal fish the sand is usually pumped out of the mouth through the gill slit. Most demersal fish exhibit a flat ventral region so as to more easily rest their body on the substrate. The exception may be the flatfish, which are laterally depressed but lie on their sides. Also, many exhibit what is termed an "inferior" mouth, which means that the mouth