Mitigation Strategies for Harvesting-induced Body Size Miniaturization of Coconut Crab in Vanuatu

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The coconut crab <I>Birgus latro</I> (Linnaeus) is a large crab species distributed in the coasts and islands of the Indo-Pacific Ocean. This crab is an important fisheries resource in the Vanuatu islands. On islands with human populations, harvesting is regulated by a minimum size and total catch limit as well as prohibition of harvesting of ovigerous females. In spite of these regulations, miniaturization of body size occurs. The coconut crab shows slow growth / long life span and closed, inland habitat as adults. These ecological features probably also contribute to miniaturization. Here, we quantitatively describe the effects of harvesting and of these ecological features on body size. Theoretical adult age composition under various conditions of carrying capacity limitation and harvesting strategy was translated into body size distribution using a known relationship between age and thoracic length. The numerical results show that the current regulations induce larger male biased harvesting. We also demonstrate additional mitigation strategies including the protection of large males would be effective after several decade years.
日本水産増殖学会の論文