South Africa on Monday voiced "great concern" over downward trends in the population of African penguins in the country.

The number of African penguins has declined by over 60 percent in the last 30 years and by over 50 percent in its three most recent generations, the Department of Environment, Forestry and Fisheries (DEFF) said, citing the department's research findings into the species.

The African penguin, Africa's only extant penguin, is endemic to South Africa and Namibia. The South African population of African penguins is found in three areas along the Western Cape coast.

Formerly the most abundant seabird of the Benguela upwelling ecosystem but, following large declines of the species in the 20th century and a collapse of the population in recent years, the African penguin is now classified as endangered by the International Union for Conservation for Nature (IUCN) in 2010.

Since the 1920s, more than a million breeding pairs of African penguins inhabiting along the Western Cape coast have shrunk to a population of fewer than 18,000 pairs, official statistics show.

Despite the Draft Biodiversity Management Plan (BMP) adopted by South Africa in 2013 with the aim of conserving the African penguin and halt the decline of the species in the country, it has not been successful to reverse the decline, according to the DEFF.

One of the reasons for the decrease of African penguins is a scarcity of penguins' prey due to excessive fishing and oil spills through the zoning of shipping and bunkering near penguin colonies, the department said.