Estimating the abundance of marine macro-invertebrates
is complicated by a variety of factors: 1) human
factors, such as diver efficiency and diver error; and 2)
biological factors, such as aggregation of organisms,
crypsis, and nocturnal emergence behavior. Diver efficiency
varied according to the detectability of an organism
causing under-estimation of density by up to 50% in some
species. All common species were aggregated at scales
from 10-50 m. Transects need to be long enough to transcend
the scale of patchiness to improve accuracy. Some
species of sea urchins and sea cucumbers (pepinos) which
are cryptic by day emerged at night so that daytime
censuses underestimated their abundance by up to 10
times. In the sea cucumber fishery, estimates of abundance
need to be made at the scale of the population, i.e. at
hundreds of km. A strategy for this is proposed