~ 26 ~ International Journal of Fisheries and Aquatic Studies 2013; 1 (1): 26-28 ISSN: 2347-5129 IJFBS 2013; 1 (1): 26-28 Received: 12-10-2013 Accepted: 30-10-2013 Paul J.Udo Fisheries and Aquaculture Unit Institute of Oceanography University of Calabar Calabar, Nigeria. Correspondence: Paul J.Udo Fisheries and Aquaculture Unit Institute of Oceanography University of Calabar Calabar, Nigeria. Length -Weight / Girth Relationship and Condition Factor of the Periwinkle Tympanotonus fuscatus, (Cerithidae: Gastropoda) of the Cross River, Nigeria Paul J. Udo ABSTRACT Morphometric parameters as well as the condition factor of the periwinkle; Tympanotonus fuscatus were investigated in 1,500 specimens obtained at Esuk Nsidung, Calabar from fishermen who fished the Cross River estuary, Nigeria. The length-weight, girth-length and weight-girth relationships were positively correlated. The calculated “b” for length-weight relationship was 2.05 which was significant < 3(t=1.05, df = 2, 55, P<0.02) while those calculated for weight-girth and length–girth relationships were 0.30 and 0.67 respectively. This species is not overexploited in the South East of Nigeria. Condition factor estimated for the specimen was 0.28. The implications of these results in relation to the fisheries of the species in the Cross River estuary are discussed. Keywords: Morphology, condition factor, Tympanotonus fuscatus, Cross River 1. Introduction The length-weight relationship (LWR) and its accompanying parameters are inevitable tools in the practical assessment of stocks of aquatic species (fin and shell fishes). Quantitative comparison of shell fishes necessary for managerial purposes necessitates different morphometric measurements for population estimates. Estimation of the length-weight relationships of organisms are essential among other reasons; for assessing the relative well- being of fish and other species/population [5] and for inter and intra-species morphological comparisons [19] . This also allow for the estimation of the average weight of the fish of a given length group by establishing a mathematical relationship between the two [4] . Pauly [19] and Nwosu et al [20] listed several stock assessment situations when LWR may be needed to include; the conversion of length of individual fish to weight, estimating the mean weight of the fish of a given length class, conversion of growth equation for length into a growth equation for weight and morphological comparisons between populations of the same species or between species. Available literature on LWR’s concentrates more on fin-fishes than shell-fishes especially in West Africa and on the bivalve mollusk than the gastropods in other parts of the world. Nair and Nair [17] revealed a larger deviation in height with greater depth in the brackish water oyster (Crassostrea madrasensis) of the Cochin Harbor (India); variation in height did not also result in corresponding variations in depth with increased height. The formula; y = bx k, where `y´ is a linear measurement of weight of a part and `x´ that of the whole while `b´ and “k” are constants, has been used to describe differential growth in a number of forms including mollusks, crustaceans, insects and mammals. When `K´ equals unity, the part bears a constant relation to the whole, and its proportion is unchanged with increasing size; this is “isogonic growth”. Positive and negative heterogony is when `K´ is greater or less than unity and the part increases or decreases relatively with increased size of the whole. The magnitudes of the constants are influenced by the parts and the organism investigated while `b´ in addition is dependent on the unit of measure.