As part of a comprehensive study concerning the trophic interrelationship of fish assemblage in the Northwest Arabian Gulf the characteristic ratios of predator-prey weights for 12 common species were calculated. This technique was used to assess the prey size selection by predator fish. Three preference modes of prey size were obtained. The first represents specialised predation on large prey, the second includes species showing less specialisation to select large prey. The third has exhibited specialisation for selection of small prey.