Abstract: Apparatus for determining the position of a bivalve shellfish (10), particularly a scallop, which is to be processed to recover an edible portion. A shell shape complement (30) has at least a partially complementary shape such as a concavity or recess to fit with at least a part of the shape or profile of the shellfish (10) such as the projecting part (18) at the hinge region (11). Moving means (40) rotates the shellfish relative to the shell shape complement (30) while the shellfish is maintained in contact with the shell shape complement (30) by biasing means operative to bias the shell shape complement (30) against the circumference (15) of the shellfish as the shellfish is rotated by the moving means (40) until a fit of the shellfish (10) with the complement is achieved. A sensor (45) is located within the concavity to sense and signal the achievement of the fit.