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Population Characteristics of the Mangrove Crab Scylla serrata (Decapoda: Portunidae) in Kosrae, Federated States of Micronesia: Effects of Harvest and Implications for Management
Kimberly M. Bonine, Eric P. Bjorkstedt, Katherine C. Ewel, and Moses Palik, 1
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.
Hawaiian Limpet Harvesting in Historical Perspective: A Review of Modern and Archaeological Data on Cellana spp. from the Kalaupapa Peninsula, Moloka‘i Island
Mark D. McCoy, 21
The isolated Kalaupapa region, Moloka‘i Island, Hawai‘i, offers archaeologists and ecologists a unique opportunity to study traditional Hawaiian limpet (‘opihi) (Cellana spp.) harvesting from the Proto-Historic Period (1650–1795), Early Historic Period (1795–1866), and the present day. In this study, archaeological collections, modern harvests, and field observations are used to describe a regular pattern of slightly larger mean limpet size in western shoreline harvests and an increase in average limpet size from the Proto-Historic Period to the present. Although further investigations are necessary to test alternative explanations, these results suggest (1) that shelter from ocean currents and trade winds may provide a microenvironment favorable to local limpet growth, and (2) a lessening of harvesting pressure concurrent with the massive depopulation of the study area after European contact. Future studies should focus on identifying possible ecological factors impacting average size, documenting changes in limpet size using specimens from archaeological deposits, and accounting for the impact of population change on marine resources in historic and prehistoric Hawai‘i.
Growth and Mortality of Coral Transplants (Pocillopora damicornis) along a Range of Sediment Influence in Maui, Hawai‘i
Gregory A. Piniak and Eric K. Brown, 39
Fragments of the lace coral Pocillopora damicornis (Linnaeus, 1758) were transplanted to four sites on the south-central coast of Maui, Hawai‘i, to examine coral growth over a range of expected sediment influence. Corals remained in situ for 11 months and were recovered seasonally for growth measurements using the buoyant weight technique. Average sediment trap accumulation rates ranged from 11 to 490 mg cm-2 day-1 and were greater at the wave-exposed reef site than at the protected harbor sites. Coral growth was highest at the donor site and was higher in the summer than in the winter. A stepwise linear regression found significant effects of sediment trap accumulation and light on growth rates, but the partial correlation coefficients suggest that these factors may be only secondary controls on growth. This study did not show a clear link between coral growth and sediment load. This result may be due, in part, to covariation of sediment load with wave exposure and the inability of trap accumulation rates to integrate all sediment effects (e.g., turbidity) that can affect coral growth.
Environmental versus Genetic Influences on Growth Rates of the Corals Pocillopora eydouxi and Porites lobata (Anthozoa: Scleractinia)
L. W. Smith, H. Wirshing, A. C. Baker, and C. Birkeland, 57
Reciprocal transplant experiments of the corals Pocillopora eydouxi Milne Edwards & Haime and Porites lobata Dana were carried out for an 18-month period from September 2004 to March 2006 between two back reef pools on Ofu Island, American Samoa, to test environmental versus genetic effects on skeletal growth rates. Skeletal growth of P. eydouxi showed environmental but not genetic effects, resulting in doubling of growth in Pool 300 compared with Pool 400. There were no environmental or genetic effects on skeletal growth of P. lobata. Pool 300 had more frequent and longer durations of elevated seawater temperatures than Pool 400, characteristics likely to decrease rather than increase skeletal growth. Pool 300 also had higher nutrient levels and flow velocities than Pool 400, characteristics that may increase skeletal growth. However, higher nutrient levels would be expected to increase skeletal growth in both species, but there was no difference between the pools in P. lobata growth. P. eydouxi is much more common in high-energy environments than P. lobata; thus the higher flow velocities in Pool 300 than in Pool 400 may have positively affected skeletal growth of P. eydouxi while not having a detectable effect on P. lobata. The greater skeletal growth of P. eydouxi in Pool 300 occurred despite the presence of clade D zooxanthellae in several source colonies in Pool 300, a genotype known to result in greater heat resistance but slower skeletal growth. Increased skeletal growth rates in higher water motion may provide P. eydouxi a competitive advantage in shallow, high-energy environments where competition for space is intense.
Life Cycle of Chrysaora fuscescens (Cnidaria: Scyphozoa) and a Key to Sympatric Ephyrae
Chad L. Widmer, 71
The life cycle of the Northeast Pacific sea nettle, Chrysaora fuscescens Brandt, 1835, is described from gametes to the juvenile medusa stage. In vitro techniques were used to fertilize eggs from field-collected medusae. Ciliated planula larvae swam, settled, and metamorphosed into scyphistomae. Scyphistomae reproduced asexually through podocysts and produced ephyrae by undergoing strobilation. The benthic life history stages of C. fuscescens are compared with benthic life stages of two sympatric species, and a key to sympatric scyphomedusa ephyrae is included. All observations were based on specimens maintained at the Monterey Bay Aquarium jelly laboratory, Monterey, California.
A Review of the Octocorallia (Cnidaria: Anthozoa) from Hawai‘i and Adjacent Seamounts: The Genus Narella Gray, 1870
Stephen D. Cairns and Frederick M. Bayer, 83
The nine Hawaiian species of Narella are revised, including the description of six new species. All species but one (N. ornata) are described and illustrated using SEM; all species are keyed and included in a detailed table of comparison. A brief history of octocoral taxonomic research in the Hawaiian Islands is presented, resulting in a total of 90 named species for this region, only five of which occur in shallow water. Specimens were collected from throughout the archipelago and adjacent seamounts, including Cross, Pensacola, Bishop, and Bushnell, from depths of 326 to 1,977 m.
Patterns of Nestedness in Remote Polynesian Ant Faunas (Hymenoptera: Formicidae)
Lloyd W. Morrison, 117
The entire ant faunas of remote Polynesian islands consist of introduced species. An important question concerning the assembly of Pacific island ant faunas is whether these species are a random assortment of the available species pool, or whether they exhibit highly ordered occurrence patterns (i.e., nested subsets of species). I evaluated nestedness for the ant faunas of two island groups in remote Polynesia: (1) the Hawaiian Islands, and (2) French Polynesia and the Cook Islands. Wilcoxon two-sample tests were used to analyze nestedness patterns for individual species and islands; the degree of nestedness for species assemblages and archipelagos was determined by combining tail probabilities of individual species and islands. Both island groups revealed highly significant nestedness at the level of the assemblage (a per-species approach) as well as the archipelago (a per-island approach). Considered individually, most species (73–95%) and most islands (89–100%) demonstrated significant nestedness. Instances of nonsignificant nestedness were frequently associated with low statistical power. These results reveal a strong deterministic element in the assemblage of remote Polynesian ant faunas. Dispersal opportunities along with presence of appropriate habitat type are likely the most important mechanisms underlying the observed patterns.
Characteristics of the Psidium cattleianum (Myrtaceae) Seed Bank in Hawaiian Lowland Wet Forests
Amanda L. Uowolo and Julie S. Denslow, 129
Psidium cattleianum Sabine (strawberry guava) is one of Hawai‘i’s most disruptive alien plants. Dense stands can suppress growth and establishment of native species, support high populations of crop-damaging fruit flies, and preclude restoration or management of native forests. Our research investigated factors affecting persistence of P. cattleianum seeds in lowland wet forest soils. We collected soil cores from four forested sites immediately after fruit fall and 6.5 months later. We found abundant germination of P. cattleianum seeds immediately after fruit drop. Soil collected under mature P. cattleianum clumps yielded 761 viable seeds/m2. We found no viable seeds 6.5 months after fruit drop. We evaluated seed longevity using seed bags buried below the litter layer that we retrieved after 28, 56, 196, and 365 days. Seeds either germinated or deteriorated rapidly after fruit drop; after 28 days, 22.3% of the buried seeds were viable and there were no viable seeds at 196 days. Predator effects were assessed using trays with a known number of seeds with and without predator exclosures. After 28 days, 37% of the seeds in the open trays were damaged by predators. The lack of a persistent seed bank likely is due to a combination of rapid, high germination rates, postdispersal seed predation, and seed mortality. We suggest that chemical or mechanical control efforts would be most efficient and effective if conducted at least 3 months after the fruiting season, when the vast majority of seeds have either germinated or died.
Subfossil Land Snail Fauna (Mollusca) of Central Chichijima, Ogasawara Islands, with Description of a New Species
Satoshi Chiba, Tetsuro Sasaki, Hajime Suzuki, and Kazuo Horikoshi, 137
The fossil record provides useful information to estimate what island communities were like before human colonization. We examined the species composition of the subfossil land snail fauna of dune deposits at the Yatsuse River, central Chichijima, Ogasawara Islands, and compared it with the species recorded in Chichijima since the nineteenth century. The 22 species in the dune deposits included 13 species that are now extinct in Chichijima. Live specimens of 11 of these extinct species were recorded in the early twentieth century, but no living Mandarna pallasiana and Ogasawarana obtusa Chiba et al., n. sp., have ever been recorded. Age of the sediment, estimated by radiocarbon (14C) dating, was 720 years B.P., and it is possible that these two land snail species became extinct as a result of the impact of human colonization of the island, which started in 1830. Specifically, Ogasawarana obtusa, n. sp., became extinct before the start of taxonomic studies of the land snails of Ogasawara. The sample included Hawaiia minuscula, which is generally now considered a cosmopolitan species introduced from North America. This finding suggests that Hawaiia minuscula is not alien in Ogasawara but indigenous.
First Record of Fossorial Behavior in Hawaiian Leafroller Moth Larvae, Omiodes continuatalis (Lepidoptera: Crambidae)
Cynthia King and Daniel Rubinoff, 147
Larvae of the endemic Hawaiian leafroller moth, Omiodes continuatalis (Wallengren), were used in controlled exposure trials on the island of Maui, Hawai‘i, in May–August 2006, to examine effects of introduced parasitoids on native Hawaiian Lepidoptera. During the trials we observed O. continuatalis larvae burrowing up to 14 cm into the soil beneath plants on which they were deployed. This discovery reflects the first record of fossorial behavior not associated with pupation in larvae of Hawaiian Omiodes and suggests how O. continuatalis, a species once listed as extinct by the U.S. Fish and Wildlife Service, may persist despite intense pressure from introduced biological control agents.
