In this paper a comparison is made between the growth and morphology of barred mudskippers (Periophthalmus argentilineatus) from six mangrove forests along the coast of Tanzania. The fish populations from unpolluted sites consisted of different size classes, whereas only small sized fish were present in the polluted Mtoni mangroves. Age estimation based on the examination of otoliths revealed that the mudskippers followed similar growth patterns in all sites with limited pollution. However, the age estimates from the polluted Mtoni site revealed an abnormal growth pattern. The occurrence of unilateral anophthalmia in the Mtoni mudskippers suggested that these fish were affected by pollutants during early development. The study showed that the presence of urban and industrial wastes from Dar es Salaam city, as indicated by isotopic enrichment, correlated with abnormal growth and developmental effects in mudskippers. We hypothesize that pollution might also affect fish species that use the mangroves as a temporary habitat.