The goals of this thesis were to address the environmental and anthropogenic factors which may be influencing sea cucumber decline in the nearshore environment around Tongatapu. Physiology, regeneration biology, ecology, biochemistry and environmental chemistry techniques were used to contribute biologically-meaningful data to the Tonga Fisheries Division, to assist in informing management decisions of this important resource. The regeneration study was undertaken to determine the energetic costs of a traditional fishing method on the fishery species Stichopus horrens, and the sustainability of traditional fishing practices. The findings of this research component indicate that S. horrens can survive and regenerate organs following their harvest, but that this process comes at an energetic cost. The second component of this research involved the quantification of sea cucumber species and their length-distribution in the nearshore environment of Tongatapu. The results of the ecological surveys indicate that sea cucumber stocks are low in some areas, and that this is relatively unrelated to habitat variables. Finally, trace metal concentrations of sediment and holothuroid tissue samples from Tongatapu Island group were determined and used to conduct ecological and human health risk assessments. Sediments were low in all trace metals except Hg, which exceeded the ‘low’ trigger values but were lower than the ‘high’ trigger values. The human health risk assessment identified that consumption of holothuroids from this region may result in exposure to Ni, As, and Zn above regulatory limits.