THE river crab is the largest invertebrate to occur in Rhodesian trout streams, but standard quantitative sampling methods reveal insignificant numbers of this animal. As has been suggested by Van Someren in Kenya1, it is doubtful if anglers have been correct in assuming that the crab is an important trout-food item. Nevertheless, preliminary Rhodesian studies2 indicate that it occurs in trout stomachs with a median percentage frequency occurrence of 13.1 ; furthermore, there is a 100.0 per cent frequency and 97.5 per cent volumetric occurrence in droppings of the clawless otter, Aonyx capensis Schinz. These figures are based upon slightly more than 1,000 stomach contents, and exactly 1,000 otter samples. In such circumstances the river crab takes on a certain economic standing, even if ignored as a competitor or scavenger.