CRAMP Study Sites: Molokini Island, Island of Maui
Geographic Name: Molokini Island
CRAMP Site Code: MaMol
20° 37.889‘ N; 156° 29.795‘ W
20° 37.940‘ N; 156° 29.783‘ W
Chart showing Molokini coastline. Red arrows show location of transect sites. (Click image for larger view.)
Physical Features (Physiography) - General Bathymetry, Topography:
Molokini islet is the emergent portion of a cinder cone that erupted on the submerged extension of Haleakala‘s southwest rift zone. The crescent-shaped islet represents the emergent one-third of the rim of a small tuff cone about 400 m in diameter. The other two-thirds of the rim are highly eroded and do not project above sea level. The total land area of Molokini Islet is 1.5 ha with a maximum elevation of 49 m. The crater area of the cinder cone is commonly referred to as a "lagoon". Maximum lagoon depth is 30 m (90 ft) with the surrounding waters is being approximately150 m (450 ft.) deep.
Reef Structure, Habitat Classification:
Rich coral reefs in the crater support a diverse and abundant fish fauna. Coral coverage in this area can reach over 70% of available hard substratum. Boulder, sand and coral habitats are present. The south face of the crater is a nearly vertical wall that extends down to over 100 m (300 ft.) depth and is subjected to seasonal south swells.
Physical Oceanographic Conditions:
Alalakeiki Channel is exposed to strong trade winds that generally follow a diurnal cycle. Often calm conditions prevail in the pre-dawn hours. As the sun heats the atmosphere and land masses of the islands the winds increase in velocity. Boats moored in the cove formed by the crescent shape of Molokini Islet are sheltered from the wind and heavy waves, but tour boats generally leave the area before noon to avoid the increasingly hostile oceanic conditions that develop as the day progresses. Water quality is essentially oceanic in nature, with high transparency and low nutrients.
Adjacent Land Tenure, Land Use:
Molokini islet is state land and is managed as a state seabird sanctuary. Entry onto the island is prohibited.
Human Use Patterns:
Molokini is a major tourist destination. Tour boats will often bring over a thousand visitors per day Molokini. Tourists are picked up from the hotels by bus or drive to wharves at Lahaina, Maalaea and Kihei early in the day in order to avoid heavy Trade Winds and associated swell that occur later in the day. The typical excursion leaves early in the day, with the vessels reaching Molokini by 0900 to 1000. Most of the activity is snorkeling, with fewer SCUBA divers. Many of the tour boats provide lunch before returning to Maui. Nearly all visitors leave Molokini before mid day because of the high winds and wave conditions that occur in the afternoon.
Tours of Molokini bring an estimated eighteen million dollars in direct sales into the economy of Hawai‘i.
This area is a Marine Life Conservation District being managed to preserve its pristine condition. The major potential impact is the fleet of tour boats operating from Maui that bring over a thousand visitors per day to this tiny MLCD during peak season. Anchor damage to corals was previously a serious problem, but has been alleviated by permanent moorings set by the State of Hawai‘i with a great deal of support from concerned citizens and the tour boat operators. The concern about future growth in the numbers of visitors has raised the question of "carrying capacity" of this area. Fish feeding by visitors has been a concern in the past. The practice is now illegal. Sedimentation and nutrients are not of concern here due to the remoteness of sources of these materials and the rapid flushing of the area by strong waves and currents.
An area of past concern during the mid 1980‘s was the existence of unexploded bombs resulting from the area being used as a target site. Only a few bombs were present, and detonation in place was found to be extremely destructive to marine life in the area. Moving of these bombs into nearby deep water is highly dangerous, but apparently local dive clubs did so in order to prevent the Navy from detonating them in place and damaging the reefs.
Noteworthy Flora and Fauna:
The diversity of fishes, corals and other marine life within the MLCD is among the most impressive in the State of Hawai‘i. Black coral was once found in abundance in the deeper waters around Molokini, but was harvested extensively. Harvesting is now restricted, and small colonies can be found on the islet‘s back wall. In the mid 1990‘s an endangered Hawaiian Monk Seal took up residence at Molokini and frequently hauled out on the shoreline of the islet.
Existence of this pristine area not impacted by land runoff (sedimentation, nutrients, toxic materials) or fishing pressure is of critical importance for establishing reference conditions (control baselines) for coral reef communities in the rest of the state. This undisturbed natural ecosystem is ideal.
Molokini Shoal has been a Marine Life Conservation District (MLCD) since 1977. The Molokini Shoal MLCD covers 77 acres and extends 100 yards seaward of both the submerged and projecting parts of the tuff cone. Trolling is permitted only in a subzone extending seaward of the tuff cone. Other types of fishing, fishing gear, taking or injuring marine life is prohibited. Taking of sand, coral or other geological features, or possessing equipment for that purpose is prohibited.
Last Update: 02/24/2011
By: Dan Lager
Hawai‘i Coral Reef Assessment & Monitoring Program
Hawai‘i Institute of Marine Biology
P.O. Box 1346
Kāne‘ohe, HI 96744