Sicydium sp., commonly known as gobies, are migratory freshwater fish that spend most of their life cycle in rivers, but when the larvae emerge they drift downstream to the sea where further development of juveniles occurs. Although Sicydium sp. are abundant in Jamaican rivers, little is known about the ecology of these species on the island and throughout the Caribbean. This study examines aspects of the ecology and biology of Sicydium populations in Jamaica. Fish sampling was carried out using dip nets and bottom kick nets at sites along the south coast in the Yallahs River, and along the north coast in the Swift River. A total of 850 gobies were captured, measured, and weighed. The values of the allometry coefficient or growth pattern (b) in the length weight relationships (LWR) were significantly different among males, females, and juveniles (p < 0.05). The growth pattern derived from LWR's was positive for females, males, and juveniles in the Yallahs River, and positive for females and juveniles but negative for males in the Swift River. The mean Fulton's condition factor (K) indicates that fish populations in both rivers are healthy and in good condition. These results augment the body of knowledge on Sicydium gobies in Jamaica.