Losing the Bounty? Investigating Species Richness in Isolated Freshwater Ecosystems of Oceania
Robert Schabetsberger, Gabriele Drozdowski, Eugen Rott, Rupert Lenzenweger, Christian D. Jersabek, Frank Fiers, Walter Traunspurger, Nicola Reiff, Fabio Stoch, Alexey A. Kotov, Koen Martens, Heinrich Schatz, and Roland Kaiser, 153-179
The South Pacific freshwater ecosystems have never been investigated systematically. Although their ecological value has long been recognized and recommended for protection, little action has been taken so far. Here, we present results of 39 lentic water bodies on 18 islands belonging to seven countries. Temperature, conductivity, and pH were measured and samples of aquatic organisms were collected. Freshwater algae, nematodes, rotifers, ostracods, copepods, cladocerans, and aquatic oribatid mites were identified to genus or species level. Sixty-six percent of all taxa recorded have a cosmopolitan distribution, 14% are circumtropical/tropicopolitan species, and for 20% a restricted distribution predominantly in Australasia has previously been reported. Eleven new copepod and three new ostracod taxa were discovered. Out of 39 water bodies we found at least 17 stocked with nonindigenous fish species. Salinization and uncontrolled introduction of alien fish species may lead to reduced species richness in these remote freshwater ecosystems. The highest species richness was recorded in old, shallow, fish-free softwater lakes at high altitude.
Dietary Shifts by Green Turtles (Chelonia mydas) in the Kāne‘ohe Bay Region of the Hawaiian Islands: A 28-Year Study
Dennis J. Russell and George H. Balazs, 181-192
The green turtle, Chelonia mydas, has modified its feeding behavior to include the increasing abundance of nonnative algae growing in the greater Kāne‘ohe Bay area of O‘ahu in the Hawaiian Islands. Changes in diet of the green turtle are correlated with an increase in abundance of seven species of nonnative algae between 1977 and 2005. Turtles were found to be eating 130 species of marine vegetation, and the three most common were the nonnative species Acanthophora spicifera, Hypnea musciformis, and Gracilaria salicornia. These three abundant and nutritious food sources are now an important part of the turtle diet in addition to native species found in and near Kāne‘ohe Bay. Chelonia mydas behavior has shifted to include these new seaweeds within 10 years of their introduction to the region. The turtles have also gradually included an additional four less-prolific slow-growing nonnative algal species (Eucheuma denticulatum, Gracilaria tikvahiae, Kappaphycus striatum, and Kappaphycus alvarezii), but the time it has taken turtles to include these species has been longer, 20–30 years, after the seaweeds were introduced. During this same 28-year time period numbers of C. mydas have increased throughout the Hawaiian Islands.
Ciguatera in the Introduced Fish Cephalopholis argus (Serranidae) in Hawai‘i and Implications for Fishery Management
Jan Dierking and Cara E. Campora, 193-204
The Peacock gouper (Cephalopholis argus) was introduced to Hawai‘i in 1956 to establish a new fishery. It has become abundant, but the fishery failed due to concerns about ciguatera fish poisoning, a neurological disease in humans caused by ingestion of fish containing ciguatoxin. The aim of this study was to provide better understanding of geographic patterns of ciguatoxicity in C. argus and of the correlation of toxicity with morphometric characters of this species, with the goal to assess the possibility of a safe fishery. Overall, 18.2% of C. argus specimens from sites around O‘ahu and Hawai‘i Island contained ciguatoxin in concentrations potentially harmful to humans. This was higher than the rate of occurrence in Hawaiian reef fishes in general, and on the scale of ciguatoxicity in species banned from sale in fish markets. Toxicity was high around both analyzed islands. However, toxic individuals were significantly less common around O‘ahu than around Hawai‘i Island (8% versus 24%). Regular geographic patterns in toxicity within islands (e.g., gradients along coastlines) were not present, and variability in toxicity within each sample site was high. Toxicity was significantly but weakly positively correlated with C. argus length but not with fish condition (measured by length at weight). In conclusion, high prevalence of toxic individuals, variability in toxicity on all analyzed spatial scales, and low explanatory power of morphometric characters make the avoidance of ciguatoxic C. argus individuals difficult. A safe fishery for this species in Hawai‘i therefore does not appear feasible at present.
Distribution, Density, and Biomass of Introduced Small Mammals in the Southern Mariana Islands
Andrew S. Wiewel, Amy A. Yackel Adams, and Gordon H. Rodda, 205-222
Although it is generally accepted that introduced small mammals have detrimental effects on island ecology, our understanding of these effects is frequently limited by incomplete knowledge of small mammal distribution, density, and biomass. Such information is especially critical in the Mariana Islands, where small mammal density is inversely related to effectiveness of Brown Tree Snake (Boiga irregularis) control tools, such as mouse-attractant traps. We used mark-recapture sampling to determine introduced small mammal distribution, density, and biomass in the major habitats of Guam, Rota, Saipan, and Tinian, including grassland, Leucaena forest, and native limestone forest. Of the five species captured, Rattus diardii (sensu Robins et al. 2007) was most common across habitats and islands. In contrast, Mus musculus was rarely captured at forested sites, Suncus murinus was not captured on Rota, and R. exulans and R. norvegicus captures were uncommon. Modeling indicated that neophobia, island, sex, reproductive status, and rain amount influenced R. diardii capture probability, whereas time, island, and capture heterogeneity influenced S. murinus and M. musculus capture probability. Density and biomass were much greater on Rota, Saipan, and Tinian than on Guam, most likely a result of Brown Tree Snake predation pressure on the latter island. Rattus diardii and M. musculus density and biomass were greatest in grassland, whereas S. murinus density and biomass were greatest in Leucaena forest. The high densities documented during this research suggest that introduced small mammals (especially R. diardii) are impacting abundance and diversity of the native fauna and flora of the Mariana Islands. Further, Brown Tree Snake control and management tools that rely on mouse attractants will be less effective on Rota, Saipan, and Tinian than on Guam. If the Brown Tree Snake becomes established on these islands, high-density introduced small mammal populations will likely facilitate and support a high-density Brown Tree Snake population, even as native species are reduced or extirpated.
Critically Endangered Fijian Crested Iguana (Brachylophus vitiensis) Shows Habitat Preference for Globally Threatened Tropical Dry Forest
Clare Morrison, Gunnar Keppel, Nunia Thomas, Isaac Rounds, and Peter S. Harlow, 223-251
Tropical dry forests are a unique and threatened ecosystem in the Pacific and globally. In Fiji, the endangered Fijian crested iguana (Brachylophus vitiensis) is endemic to tropical dry forests. Yadua Taba Island contains one of the best remaining stands of tropical dry forest in the Pacific along with the largest (and only secure) population of B. vitiensis in Fiji and has been proposed as a translocation source for iguana conservation. In this study we determined the major vegetation types on Yadua Taba and identified forest habitat preferences of B. vitiensis to (1) characterize the island’s habitats for tropical dry forest regeneration monitoring and (2) understand which forest types are preferred by iguanas for future translocation projects. Vegetation data were collected using reconnaissance, entitation, line transects, and aerial photos. Iguana abundance data were collected by nocturnal surveys of permanent transects. Six major vegetation types were identified of which tropical dry forest was the largest (46% of the island), followed by a combination of rocky cliff–shrubland/grassland vegetation (26%). Our conservative estimate of B. vitiensis population size on Yadua Taba is 12,000 iguanas, the majority of which occur in tropical dry forest. Superabundance of the dry forest understory tree Vavaea amicorum, the favorite fruit species of iguanas, may help account for the high density of iguanas observed. These results highlight the ecological link between tropical dry forest and B. vitiensis and emphasize the importance of rehabilitation or conservation of tropical dry forest habitat in potential iguana translocation sites as part of the management plan for B. vitiensis throughout the Fiji Islands.
Distribution of the introduced scincid lizard Carlia ailanpalai Zug in the Federated States of Micronesia (FSM) is reviewed. It is common in open grassy areas but seldom occurs in mature forest. Preliminary surveys indicate that it is well established in Yap, though less frequently encountered at increasing distance from Colonia, the main settlement, and it is unrecorded in the extreme northern and southern parts of Yap. It is the most common species of lizard in open, grassy, ruderal habitats throughout Weno Island, Chuuk, being nearly the only species encountered in the commercial district, but it is unknown elsewhere in Chuuk State. The only record for Kosrae is a single specimen collected in 1988 (first record for the FSM), but there is no evidence of an established population. There are no records for Pohnpei State. Guam is likely the primary source for the Yap and Chuuk populations (and Kosrae specimen), but the time of initial introduction is unknown. Carlia ailanpalai appears to have spread rapidly, at least on Weno, Chuuk, where it has become the predominant lizard in open habitats islandwide, possibly since the late 1960s. How C. ailanpalai interacts with other species in the FSM requires further study, but preliminary surveys of distribution and relative abundance suggest that it has a negative impact on populations of Emoia jakati and, to a lesser extent, on other Emoia species as well. Populations of C. ailanpalai in the FSM meet the criteria for invasive species status as it is defined by numerous U.S. government agencies and international conservation groups.
Evidence of a Possible Decline since 1989 in False Killer Whales (Pseudorca crassidens) around the Main Hawaiian Islands
Randall R. Reeves, Stephen Leatherwood, and Robin W. Baird, 253-261
Recent evidence indicates that there is a small, demographically isolated, island-associated population of false killer whales (Pseudorca crassidens) around the main Hawaiian Islands. Although it is known that false killer whales in Hawai‘i are sometimes killed or seriously injured in the Hawai‘i-based long-line fishery, it is not known whether such interactions have resulted in a reduction in population size or whether other factors have been negatively influencing population size. We report the results of an aerial survey in June and July 1989, the purpose of which was to obtain a minimum count of the number of false killer whales around the main Hawaiian Islands. The false killer whale was the third most commonly seen species of odontocete off the island of Hawai‘i during the survey, representing 17% of sightings. Groups of more than 300 individuals were seen on three different days, with minimum counts of 380, 460, and 470 individuals in these groups. The encounter rate, relative species ranking, and average group size from the 1989 survey were all substantially greater than those from more recent aerial and ship-based surveys. The largest group observed in 1989 (470) contained almost four times as many whales as estimated for the entire main Hawaiian Islands from recent aerial surveys (121 individuals, CV = 0.47) or mark-recapture analyses (123 individuals, CV = 0.72). Therefore, the population of false killer whales around the main Hawaiian Islands may have declined substantially since 1989. The cause or causes of such a decline are uncertain.
Andvakia discipulorum, A New Species of Burrowing Sea Anemone from Hawai‘i, with a Revision of Andvakia Danielssen, 1890
Marymegan Daly and Roger H. Goodwill, 263-275
We describe Andvakia discipulorum Daly & Goodwill, n. sp., from an intertidal mudflat of Kāne‘ohe Bay, O‘ahu, Hawai‘i. Members of this species are inconspicuous, being small and having a column covered with sand. In comparison with other species of the genus, Andvakia discipulorum, n. sp., presents distinct arrangement of mesenteries, sizes of nematocysts, and musculature. We also provide a redescription of Andvakia boninensis based on specimens collected from Saipan, Mariana Islands. These descriptions provide an opportunity to revise and update the taxonomy of Andvakia and to address the systematics of family Andvakiidae. We determine that Andvakia is the senior synonym of Decaphellia and reject earlier hypotheses of synonymy between Andvakia and Capneopsis, Ilyactis, and Octophellia. A tabular key to the species of Andvakia is provided.
A Hawaiian species of antipatharian coral previously identified as Antipathes dichotoma Pallas, 1766, is described as Antipathes griggi Opresko, n. sp. The species forms tall, bushy colonies with elongate, upright terminal branches, often arranged uniserially. Spines are conical, mostly 0.20 to 0.26 mm tall, apically bifurcated, multilobed to jagged in appearance, and covered over most of their surface with small roundish to elongate papillae. Minute secondary spines may occur on some of the thicker branches. Polyps are 1 to 1.6 mm in transverse diameter. The species resembles A. fruticosa Gray in branching pattern, size of spines, and presence of secondary spines but differs in morphology and density of the spines (thicker, more crowded primary spines and fewer secondary spines in A. griggi). Other related species differ from A. griggi in having more widely spreading and irregularly arranged branches, no secondary spines, and either smaller spines with fewer apical lobes (A. curvata van Pesch, A. arborea Dana, and A. galapagensis Deichmann) or larger spines with the apical lobes arranged in a somewhat coronate pattern [A. spinulosa (Schultze) and A. lentipinna Brook].
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