Mollusk Habitats and Fisheries in Kiribati: An Assessment from the Gilbert Islands

Abstract

Biological and ecological attributes of 24 species of edible bivalves and gastropods from the Gilbert Islands Group, Kiribati, Micronesia, were assessed for their resilience by examining size at maturity, intertidal burying, adjacent subtidal populations, benthic mobility, and larval type. Foraging for mollusks is largely confined to the intertidal and shallow subtidal regions, although modern diving gear and outboard motors now provide human foragers access to offshore resources. Changes brought about by human demographic pressures have resulted in overexploitation of a number of molluscan resources. It is suggested that the sustainable use of invertebrates and other marine species for food and nonfood purposes in Kiribati rests on a remodeled form of marine tenure.

Atolls present a variety of marine environments and molluscan resources that have provided subsistence living to generations of Pacific islanders (Tebano et al. 1993, Taniera 1994). Kiribati (Figure 1) is but one of more than 20 nations in the Pacific, each of which possessed a rich inshore fisheries tradition and lore. In recent years, however, traditional ecological knowledge (TEK) has suffered the inevitable decline that characterizes similar bodies of knowledge throughout most of Oceania. High human population density, urban drift, more efficient extractive technologies, and expanding market opportunities all have inevitably affected the ocean resources of these islands. In this study, I examined the prey biology and ecology of mollusk fisheries in Kiribati, Gilbert Islands, looking at factors distinguishing vulnerable from resilient resources, and their effect on subsistence.

Can traditional ecological knowledge be wedded with modern technology to revive the fisheries? Because the thrust of this paper is limited to prey biology and ecology in the context of mollusk fisheries, details of analytic methodology related to foraging efficiency are not discussed here, but can be found in Thomas (1999).

Data on molluscan resources of the Gilbert Islands date back to the 1950s when Banner and Randall (1952) described the invertebrates of Onotoa Atoll, but identifications were poor and there were few detailed descriptions of exploitive strategies. A major interdisciplinary environmental survey on the main atoll of Tarawa, Republic of Kiribati (Abbott and Garcia 1995), expanded species identification and habitat description, and provided an assessment of the impact of human activities (Figure 2). The Tarawa Lagoon Project of 1992-1994 (Paulay 1995) is a major study of the lagoon, and data from that project are included in this study.

Materials and Methods

Several communities engaged in subsistence and commercial exploitation of mollusks were investigated intermittently between 1993 and 1998. Research focused on four atolls in the central Gilberts: Abaiang, Tarawa (both urbanized and rural sectors), Maiana, and Abemama, and one atoll in the Southern Group, Tabiteuea North (Thomas 1999). Data on various aspects of mollusk gathering were obtained by participant observation, interviews, and from the Shellfish Gatherer Survey (SGS) of the Tarawa Lagoon Project (TLP), in cooperation with BioSystems, Inc., of Santa Cruz, California.

Figure 1.

The Republic of Kiribati (modified from Motteler 1986:16; reprinted with permission from Bishop Museum Press, Honolulu, Hawai'i).

I accompanied foragers, both individuals and groups, on 73 foraging trips covering 69 days, for a total of 139.63 hr of direct observation (286.92 forager-hours). Mean group size was 2.6 foragers (SD = 0.9, n = 146). Fifty-nine different individuals took part in these activities. When it was not possible to record foraging activities directly, the relevant information was elicited via interviews. A total of 65 foraging trips was recorded over a period of 51 days, for an estimated total of 88.5 hr of foraging effort (161 forager-hours). Mean group size was 3.1 foragers (SD = 0.7, n = 148). A total of 19 different individuals was interviewed.

Information was also derived from data sheets made available by personnel of the TLP. These data originated from landings along the southern portion of Tarawa Atoll, with samples taken between December 1992 and February 1994. This information greatly expanded the sample size of foraging events, with 83 foraging trips covering 26 days and approximately 191 hr of foraging time (257 forager-hours). Mean group...