Pacific Science, vol. 66, no. 3 (2012)

Pacific Science, vol. 66, issue 3 cover

Biology and Impacts of Pacific Island Invasive Species. 8. Eleutherodactylus planirostris, the Greenhouse Frog (Anura: Eleutherodactylidae)
Christina A. Olson, Karen H. Beard, and William C. Pitt, 255–270

The greenhouse frog, Eleutherodactylus planirostris, is a direct-developing (i.e., no aquatic stage) frog native to Cuba and the Bahamas.It was introduced to Hawai‘i via nursery plants in the early 1990s and then subsequently from Hawai‘i to Guam in 2003. The greenhouse frog is now widespread on five Hawaiian Islands and Guam. Infestations are often overlooked due to the frog’s quiet calls, small size, and cryptic behavior, and this likely contributes to its spread. Because the greenhouse frog is an insectivore, introductions may reduce invertebrates. In Hawai‘i, the greenhouse frog primarily consumes ants, mites, and springtails and obtains densities of up to 12,500 frogs ha-1. At this density, it is estimated that they can consume up to 129,000 invertebrates ha-1 night-1. They are a food source for the nonnative brown tree snake in Guam and may be a food source for other nonnative species. They may also compete with other insectivores for available prey. The greatest direct economic impacts of the invasions are to the nursery trade, which must treat infested shipments. Although various control methods have been developed to control frogs in Hawai‘i, and citric acid, in particular, is effective in reducing greenhouse frogs, the frog’s inconspicuous nature often prevents populations from being identified and managed.

From Early Polynesian Settlements to the Present: Bird Extinctions in the Gambier Islands
Jean-Claude Thibault and Alice Cibois, 271–281

Located in the South Pacific Ocean, the Gambier Islands are sometimes presented as an example, with Easter Island, of biodiversity collapse provoked by overexploitation of the natural resources by the Polynesian people during the course of several centuries. However, when comparing the list of bird bones obtained from archaeological sites with the data obtained and specimens collected by naturalists from the end of the eighteenth century to the mid-
twentieth century, we show that land-bird extinction continued uninterrupted, mostly due to introduced predators and the continuous loss of wooded areas. Conversely, the list of breeding seabirds has remained relatively stable, but the number of breeding sites has decreased owing to introduction of predators, especially the cat and black rat. Today these sites are restricted to cliffs on the main islands and to remote islets.

Bird Populations on the Island of Tinian: Persistence despite Wholesale Loss of Native Forests
Richard J. Camp, Frederick A. Amidon, Ann P. Marshall, and Thane K. Pratt, 283–298

Bird habitat on the island of Tinian, Mariana Islands, has been substantially altered, and only around 5% of the island has native forest today. The modern bird fauna is likely to be a subset of the original avifauna where only species tolerant to native forest loss and human disturbance have survived. Avian surveys were conducted on the island in 2008 by the U.S. Fish and Wildlife Service to provide current densities and abundances of the remaining species, and assess population trends using data collected from previous surveys. During the three surveys (1982, 1996, and 2008), 18 species were detected, and abundances and trends were assessed for 11 species. Five of the nine native species and one alien bird have increased since 1982. Three native birds—Mariana Fruit-Dove (Ptilinopus roseicapilla), Micronesian Honeyeater (Myzomela rubratra), and Tinian Monarch (Monarcha takatsukasae)—have decreased since 1982. Trends for the remaining two birds (one native and one alien) were considered relatively stable. Only five birds, including the Tinian Monarch, showed significant differences among regions of Tinian by year. Increased development on Tinian may result in increases in habitat clearing and expansion of human-dominated habitats, and declines in some bird populations would likely continue or be exacerbated with these actions. Expanded development activities on Tinian would also mean increased cargo movement between Guam and Tinian, elevating the probability of transporting the Brown Tree Snake (Boiga irregularis) to Tinian, which would lead to precipitous decreases and extinctions.

Survival Estimates for Two Hawaiian Honeycreepers
John P. Vetter, Kirsty J. Swinnerton, Eric A. VanderWerf, Julia C. Garvin, Hanna L. Mounce, Haley E. Breniser, David L. Leonard, and J. Scott Fretz, 299–309

Most Hawaiian forest birds are endangered by habitat loss and degradation, predation by introduced mammals, and introduced diseases, but species recovery planning has been hampered by lack of demographic information, such as annual survival rates. To address this knowledge gap, we analyzed mark-
recapture data using the program MARK to estimate apparent survival in the endangered Maui parrotbill (Pseudonestor xanthophrys) and Maui ‘alauahio (Paroreomyza montana). Annual survival estimates were high in adult Maui parrotbills (0.84 ± 0.04) and Maui ‘alauahio (0.78 ± 0.15). Survival was lower in hatch-year parrotbills (0.76 ± 0.09) and hatch-year ‘alauahio (0.64 ± 0.13), and survival of ‘alauahio also varied among years (0.51 ± 0.18 to 0.95 ± 0.06 in adults). These results provide important baseline data for two little-known species of honeycreepers and, together with ongoing nest success and productivity studies, will enable assessment of population trends and inform management decisions. Mark-recapture methods are a useful tool for monitoring populations of rare and cryptic species that are difficult to monitor using traditional survey methods.

Hydroacoustical Survey of Near-Surface Distribution, Abundance, and Biomass of Small Pelagic Fish in the Gulf of California
José Francisco Domínguez-Contreras, Carlos J. Robinson, and Jaime Gómez-Gutiérrez, 311–326

Near-surface distribution (10–40 m depth), abundance, and biomass of small pelagic fish were estimated using an echo sounder (EY-60, 120 kHz) during January 2007 in central and northern areas of the Gulf of California. Small pelagic fish distribution was spatially correlated with simultaneous, continuous, high-resolution measurements of 4 m depth temperature, salinity, turbidity, chlorophyll a, and dissolved oxygen concentration to characterize water and habitat conditions. Small pelagic fish shoals were concentrated in five areas of northern and central parts of the gulf, along the coast of Sonora, and south of Isla Tiburón. About 62% of small pelagic fish abundance and 57% of the biomass was echo-detected during the night, when small pelagic fish tend to assemble near the surface. Fish abundance in these areas (11,210 km2) was estimated at 6.16 × 109 individuals. Echo- integrated median biomass was 2.6 × 105 t. Projecting this biomass to the surveyed area (80,102 km2), median biomass of multispecific small pelagic fish shoals could be up to 1.92 × 106 t. Fish shoals were significantly associated with areas at 15.0°C–17.5°C, >2 nephelometric turbity units, and dissolved oxygen concentrations >5 mg O2 liter-1 at depths of 4 m. These areas were not associated with specific chlorophyll a concentration or salinities. Distribution of fish shoals was highly concentrated during winter despite apparently homogeneous environmental conditions.

Lethal Ramming of Sharks by Large Jacks (Carangidae) in the Palau Islands, Micronesia
Diana L. McPherson, Kautchang Vince Blaiyok, and W. Bruce Masse, 327–333

We observed a Giant Trevally (Caranx ignobilis) ramming and mortally injuring a pair of adult Blacktip Reef Sharks (Carcharhinus melanopterus) in the Palau Islands of Micronesia. Such ramming behavior is known to Palauan and Marshallese fishermen for large-sized individuals of several different species of jacks (Carangidae). In addition, we interviewed knowledgeable Palauan subsistence fishermen regarding episodes of ramming that they had witnessed. Our observations suggest that ramming of sharks may be a normal aspect of jack aggressive behavior. These observations expand our knowledge of social behavior between sharks and large jacks.

Life History Characteristics of the Surf Clam Mactra veneriformis (Bivalvia: Veneroida: Mactridae) on a Sandy Tidal Flat in Tokyo Bay, Japan
Kazuyoshi Hashizume, Norihisa Tatarazako, Kunio Kohata, Yasuo Nakamura, and Masatoshi Morita, 335–346

Life history and growth of the surf clam, Mactra veneriformis, were examined in a tidal flat area of Tokyo Bay from November 2002 to November 2004. Gonads of both sexes began to develop in March, and animals with mature gonads (ripe phase) were observed from spring to summer (April–August). Most of the animals showed signs of having finally spawned by September, indicating that spawning occurs from spring to summer. Moreover new cohorts were established several times in both years, with the largest settlement occurring in July. These findings suggest that surf clams in this area spawn several times a year. By monitoring increase in shell length of these cohorts, we found that shell growth was rapid in the first year, reaching approximately 35–40 mm 1 yr after settlement. In the second year, shell lengths exceeded 40 mm. Most of the animals died after the spawning season in the second year. The observation of several settlement events per year and a short life span differed considerably from characteristics of M. veneriformis along the Korean coast.

Polychaetes (Annelida: Polychaeta) of Cocos Island National Park, Pacific Costa Rica
Harlan K. Dean, Jeffrey A. Sibaja-Cordero, and Jorge Cortés, 347–386

An extensive collecting effort resulted in identification of 106 species of polychaetes from the intertidal and shallow subtidal of Isla del Coco, Costa Rica. One hundred and three of the species reported here are new records. Only two species had not been previously collected from the Pacific coastline between Mexico and Chile. Transport of polychaetes to the island either as larvae, adults, or by rafting is discussed. Comparisons are made with the less well-analyzed polychaete fauna of the Galápagos Islands, with lower species richness on the smaller and ecologically less variable Isla del Coco. Relative lack of isolation between the polychaetes of Isla del Coco and the mainland is discussed.

Veleroa setteana, n. sp. (Rhodophyta: Rhodomelaceae) from the Hawaiian Archipelago, including Notes on the Generitype
Isabella A. Abbott and David L. Ballantine, 387–395

A new species of Veleroa, V. setteana Abbott & Ballantine, has been collected from the Northwestern Hawaiian Islands. Veleroa setteana is among the larger of the Veleroa species, reaching a height of 30 cm. The new species is highly corticated with cortication beginning in young thallus portions. Tetrasporangia, which measure up to 60 μm in diameter, possess three cover cells and are produced in principal indeterminate axes and more commonly in short indeterminate laterals. The genus Veleroa is properly placed in the Brongniartelleae.

Diet of the Invasive Lizard Chamaeleo jacksonii (Squamata: Chamaeleonidae) at a Wet-Forest Site in Hawai‘i
Fred Kraus and David Preston, 397–404

We assessed diet from a sample of Jackson’s chameleons inhabiting wet forest in Volcano Village, Hawai‘i Island, Hawai‘i. Most lizards contained food in their gastrointestinal tract, diet was broad, and large numbers of invertebrates, mostly insects, were consumed. Native insects composed the largest component of dietary items, and these spanned most of the body-size range found in the native invertebrate community. Taxonomic composition of diets does not conform to expectations for iguanian lizards inasmuch as hymenopterans form only a small portion of consumed items. Insect chemical or stinging defenses did not preclude consumption by lizards. The study site is a mixture of native and alien vegetation. Chameleons collected from alien plants contained larger numbers of native prey items than did those lizards removed from native plants, suggesting that lizard residency on non-native plants will not reduce their predation impact on native invertebrates in mixed forest. Our results confirm the finding of a similar study in dry-forest habitat on Maui that Jackson’s chameleons are likely to pose a substantial threat to a broad range of native invertebrate biodiversity in Hawai‘i.

Association Affairs

Comments are closed.