Conservation and community benefits from traditional coral reef management at Ahus Island, Papua New Guinea

Published source details Cinner J.E., Marnane M.J. & MCClanahan T.R. (2005) Conservation and community benefits from traditional coral reef management at Ahus Island, Papua New Guinea. Conservation Biology, 19, 1714-1723.
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Summary

Traditional coral reef management practices were investigated at Ahus Island, Papua New Guinea. For generations Ahus Islanders have prohibited spear and net fishing within six (tambu) areas of their reef lagoon. One to three times a year, fish are briefly harvested from the restricted areas to provide food for ceremonial occasions. The main study objectives were to quantify the effects of the traditional reef closures on the condition of reef resources, and to examine the social role of the traditional reef closure and compliance with the restrictions.

Study Site: Research was conducted between May and June 2002 at Ahus Island (01'56.48 S, 147'05.60 E) Manus Province. Ahus is a 28 ha coral island with approximately 600 inhabitants. Coral reefs and lagoons surrounding Ahus and Onneta islands encompass approximately 550 ha. Fishing is restricted within six reef areas encompassing 33.2 ha.

Social and cultural aspects of traditional reef closure: The main socioeconomic indicators examined were dependence on and use of coastal resources, perceptions of what can affect and improve fishery resources, coastal resource governance practices and compliance with these. Surveys were conducted at 51 of the 105 households, with additional, interviews with key informants.

Reef resource assessment: Assessments of reef resources were carried out on shallow reefs within three tambu areas and three nearby control sites (no management regulations) chosen randomly from a number of suitable sites (i.e. as similar as possible in reef profile, current and wave exposure). Abundance of relatively non-cryptic reef fish species was recorded along three 50 m transects within two depth contours per site: 2 to 4 m and 6 to 8 m. To calculate fish biomass (kg fish/ha of reef), fish length and fish frequency were recorded.

Effects of a periodic harvest on fish stocks: During the study, one of the tambu areas was harvested for a ceremonial feast. Fishing restrictions were lifted for around 3 hours and the area was fished intensively. A monofilament gill net was laid across a reef channel and 65 canoes and a number of swimmers drove fish into the net where speared. Fish biomass assessments were conducted before and after the harvest.

Effects of management: Tambu areas contained 62% greater fish biomas (205 kg/ha) than unrestricted areas (127 kg/ha). The overall average fish sizes from families commonly targeted were larger in the tambu areas (10.2 cm long) than in control areas (8.5 cm). No significant differences were detected in overall fish abundance, fish species richness, live coral cover, or coral diversity within or oustside tambu areas.

Effect of harvest on fish stocks: No changes in fish biomass were detected within the tambu area before compared with after the harvest event. These results were supported by biomass data of fish removed during the harvest (estimated at 190 kg) and between approximately 5 and 10% of the standing stock of fishes available within the tambu area, based on underwater surveys.

Discussion: Compliance with the tambu fishing restriction system is attributed to its perceived legitimacy, its ability to provide community benefits, and local socioeconomic circumstances. The authors conclude that limited-take closure systems, such as on Ahus, that can serve community needs may provide a viable conservation alternative in situations where compliance with fully closed protected-area regulations is low and resources for proper enforcement are lacking.

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://www.blackwell-synergy.com/doi/full/10.1111/j.1523-1739.2005.00269.x