Population Characteristics of the Mangrove Crab Scylla serrata (Decapoda: Portunidae) in Kosrae, Federated States of Micronesia: Effects of Harvest and Implications for Management¹

Abstract

Apparent declines in abundance of mangrove crabs Scylla serrata (Forsskål, 1755) in Kosrae, Federated States of Micronesia, have prompted concern regarding long-term persistence of this important cultural and economic resource. To support development of effective management strategies, we gathered basic biological information about mangrove crabs on this island, where S. serrata is the only mangrove crab species present. In particular, we were interested in understanding movement patterns and evaluating spatial variation in population structure. Many population characteristics, including estimated life span, ontogenetic shifts in habitat use, sex-specific allometric relationships, male-biased sex ratios, and evidence for limited (<2 km) alongshore movement, are similar to those reported elsewhere in the range of the species. Therefore, insights from S. serrata populations elsewhere might usefully inform management of the species on Kosrae. Moreover, information reported in this study, for which there is no ambiguity about species identification, has broader relevance. Spatial variation in size structure of the population appears to be driven by variable harvest pressure that reflects distribution of the human population and location of emerging commercial harvest operations. Effective management of mangrove crabs is therefore likely to benefit from application of size-based or sex-based restrictions on harvest and might usefully incorporate spatially explicit strategies, such as partial or complete reserves. Development and implementation of effective management will necessarily depend on cultural as well as scientific information.

Life-history, movement, and habitat use of Scylla serrata (Decapoda, Portunidae): current knowledge and future challenges

“…In unfished populations, female mud crabs can be three-fold outnumbered by males, for example in Kosrae, Micronesia the male: female ratio can be as high as 3:1 (Bonine et al, 2008). Similar ratios have been reported from other studies (Heasman, 1980).…”

“…In general, crabs ([100 mm CW) that live in enclosed habitats such as narrow mangrove-fringed creeks, normally do not move more than 1 km (Hill, 1975;Perrine, 1978;Hyland et al, 1984;Bonine et al, 2008), whereas in southern Moreton Bay, Queensland, crabs that are found in open environments like intertidal flats in open bays show larger movement (average 3.7 km) (Hyland et al, 1984). It is suggested that these different distances of routine movement (daily movements, e.g., foraging activity) are dependent on the availability of alternative feeding grounds at high tide.…”

Body Weight, Carapace Length and Width Relationship and Condition Factor of the Mud Crab Scylla serrata (Forskal) in Mangrove Ecosystem

“…Ewel (2007) has investigated mean carapace width of S. serrata at different locations in Kosrae. Allometric relationship between carapace width and weight in mangrove crabs (S. serrata) on Kosrae of Macronesia has been reported by Bonine et al (2008). Studies on carapace width and weight relationships, relative condition factor of mud crabs S. serrata and S. tranquebarica have been made by Mohapatra et al (2010) in Chilka lagoon.…”

Kajian Struktur Ukuran Dan Parametr Populasi Kepiting Bakau (Scylla serrata) di Ekosistem Mangrove Teluk Bintan, Kepulauan Riau

“…Menurut La Sara (2010) Scylla serrata pada fase juvenil memiliki lebar karapas <70 mm, fase muda (lebar karapas dari 70 -<120 mm) dan fase dewasa (lebar karapas >120 mm). Menurut Bonine et al (2008) kepitng bakau (Scylla serrata) jantan dewasa kelamin rata-rata ketika lebar karapas mulai ukuran 90-110, sedangkan kepitng betina mulai matang gonad pada rata-rata ukuran lebar karapas 80-120 mm. Ilustrasi distribusi frekuensi lebar karapas kepiting bakau di Teluk Bintan disajikan pada Gambar 3.…”