The International Union for Conservation of Animals (IUCN) Red List categorises the hectori sub-species (South Island) as endangered and the maui sub-species (North Island) as critically endangered.
A 2004 study (Dawson et al., 2004) showed that the south island sup-population has around 7,270 individuals, while the north island population numbers around 111 (Slooten et al., 2006) see here. Approximately 50% of the Hector’s dolphins are mature individuals (Slooten et al., 200o).
Analyses of population viability based on current abundance, known entanglement rates and past/current fishing effort indicates a high risk of population decline, most specifically attributed gillnet entanglement (Martien et al., 1999; Slooten, 2007). Abundance of the Maui sub-species in the late 1990′s was only ~25% of the 1970 estimate of 437 individuals (Martien et al., 1999) and more recently the estimated abundance is only at 7% of the 1970 population (Slotte, 2007).