Morphometric and Heavy Metals Accumulation in the Muscles of Five Demersal Seafoods Sampled in Nigerian Coastal Waters

Abstract

This study examined the morphometric and heavy metals accumulated in the muscles of five demersal sea-foods: Parapenaeopsis atlantica, Penaeus monodon, Penaeus notialis, Portunus validus and Cynoglossus browni from Nigerian coastal waters. 506 deep frozen samples (at -200C) each of the five demersal species were taken upon arrival from thirty-one (31) industrial fishing trawler vessels owned by a private fishing company in Lagos, Nigeria. Samples were thawed and morphometric characteristics such as weight, total length, standard length, body depth and carapace length/head length were measured. The heavy metals [Lead (Pb), Iron (Fe), Zinc (Zn), Arsenic (As), Mercury (Hg) and Cadmium (Cd)] were analyzed using 210 Atomic Absorption Spectrophotometer (AAS). The morphometric characteristics revealed that P. atlantica and P. notialis showed no significant difference in mean values only for their carapace lengths while both species showed statistically different observations for other variables. The order of the heavy metals mean concentration was Zn>Fe>Pb. As and Cd had relatively very low values of <0.01mg/kg while Hg was not detected in all samples. The findings of this study revealed high and increasing values of Zinc in all five demersal species under consideration exceeding maximum limits for FAO/WHO and NIS (Nigerian Industrial Standard). The zinc value of the species appears to be contained in this order; P. notialis > C. browni > P. monodon > P. validus >P. atlantica. However, Iron value for P. atlantica is above the limit of FAO/WHO.  Consumption of the species invariably leads to a rise in the Zinc contents in diets and in humans which may cause gastrointestinal disorders, kidney and liver abnormal functioning especially in infants and children while other heavy metals contained in the species do not pose a threat to human health.