The objective of this study was to investigate the spatial patterns in green sea urchin (Strongylocentrotus
droebachiensis) density off the coast of Maine, using data from a fishery-independent survey program, to estimate the exploitable biomass of this species. The dependence of sea
urchin variables on the environment, the lack of stationarity, and the presence of discontinuities in the study area made intrinsic geostatistics inappropriate for the study; therefore, we used triangulated irregular
networks (TINs) to characterize the large-scale patterns in sea urchin density. The resulting density surfaces were modified to include only areas of the appropriate substrate
type and depth zone, and were used to calculate total biomass. Exploitable biomass was estimated by using two
different sea urchin density threshold values, which made different assumptions about the fishing industry. We
observed considerable spatial variability on both small and large scales, including large-scale patterns in sea urchin density related to depth and fishing pressure. We conclude that the TIN method provides a reasonable spatial approach for generating biomass estimates for a fishery unsuited
to geostatistics, but we suggest further studies into uncertainty estimation and the selection of threshold
density values