Thirteen commonly consumed types of fish caught in the North Pacific and locally available in Hawai‘i were analyzed using gamma spectroscopy to measure Fukushima-derived and historic ¹³⁴Cs and ¹³⁷Cs isotopes. All fish samples had detectable ¹³⁷Cs above 95% confidence intervals. Three out of the thirteen samples had ¹³⁴Cs, an isotope indicative of Fukushima releases, detected above 95% confidence intervals. The highest ¹³⁴Cs and ¹³⁷Cs concentration in the examined species was in ‘ahi tuna, carrying 0.10 ± 0.04 Bq/kg and 0.62 ± 0.05 Bq/kg, respectively. Other samples with ¹³⁴Cs activities found above their 2-sigma uncertainty were albacore tuna and swordfish. Historic and Fukushima-derived contributions were evaluated, and in several samples the Fukushima-derived radiocesium dominated the total radiocesium inventory with up to 61% contribution. All activities were below derived intervention limits of 1,200 Bq/kg, and the doses to humans from consuming the fish attributable to radiocesium were 0.02–0.2 µ Sv, in comparison to 6–20 µ Sv contributed by the natural ⁴⁰K present in the same fish.

C₃ and C₄ plants are often reported to differ in functional traits and resource-use strategies, whereas nonnative plants may differ from native plants in functional traits, leading to different resource-use strategies that facilitate their invasion. In this study, we compared root functional traits of native and nonnative C₃ and C₄ grasses with the prediction that different resource acquisition strategies would be observed among these groups. We examined five root functional traits [mean diameter, specific root length, root tissue density, fine root percentage (diameter <0.2 mm), and root length density] among natural communities of C₃ and C₄ grass species along an elevation gradient in Hawai‘i to classify resource-use strategies. We also examined how root functional traits were related to environmental characteristics (mean annual, seasonal, and July soil moisture; mean annual precipitation and temperature; and soil nitrogen percentage) along this elevation gradient. Root traits corresponded broadly to differences in photosynthetic pathway [C₃ versus C₄ (P < .05)]. However, significant variation occurred within the C₃ functional group (P < .05), whereas all C₄ species had similar root functional traits. Grass assemblages were associated with differences in seasonal soil moisture, but root traits did not sort consistently along any environmental gradient. Principal component and cluster analyses of root functional traits showed that nonnative C₃ species tended to be resource acquisitive whereas the native C₃ species was resource conservative, similar to native and nonnative C₄ species. Evaluating functional traits of native versus nonnative species will provide a better understanding of invasion dynamics and suggest possible restoration and conservation strategies in grassland communities where native species still persist.

Garden eels occur worldwide in the tropics, but little is known about their biology and ecology. We studied Hawaiian garden eel (Gorgasia hawaiiensis) colonies near Kawaihae, Hawai‘i, to investigate multiple aspects of basic biology of this species. Colonies of G. hawaiiensis occurred at depths from 16 to 36 m in soft-bottom habitat adjacent to rocky reefs. Highest burrow densities (up to 40 eels m^-2) were in shallower water, and large (~10 mm diameter) burrows were more abundant, less dense, and commonly found in pairs in deeper water. Eels emerged around sunrise and withdrew and covered burrow entrances around sunset. Age was estimated from annual rings in sectioned otoliths (n = 17) and modeled to suggest fast growth to a maximum size of ~600 mm total length and a maximum age of 6 yr. Prey size and eel anatomy suggest that these fish feed by ingesting planktonic prey and processing them in the esophagus. The most common food items were small (<0.5 mm) demersal harpacticoid, cyclopoid, and calanoid copepods and unidentified fish eggs. These and other observations indicate that G. hawaiiensis is abundant, has a high population turnover rate, and may enrich sandy-bottom habitat within their beds by facilitating energy flow from the water column to the benthos.

Easter Island is located in the southeastern corner of Polynesia. This 163.6 km² volcanic island is one of the most isolated places on Earth. During spring 2014 and 2015, we studied a breeding colony of Red-tailed Tropicbirds (Phaethon rubricauda) located on Rano Raraku Volcano. We specifically aimed to determine (1) main nest types used by tropicbirds, (2) nest distribution and abundance, (3) breeding success, and (4) threats faced by tropicbirds at this colony. Results showed presence of four nest types: rock caves, moai nest, rockprotected, and vegetation nests. Nests were strongly associated with unfinished moai statues. Breeding success ranged from 37% in 2014 to 26% in 2015. Camera traps and direct observations showed interactions with five invasive alien species: the raptor Chimango Caracara (Milvago chimango) was the most severe predator of unattended eggs and chicks; cats were observed close to adult birds; dogs killed fledglings; ants preyed on newborn chicks; rats were recorded inspecting both occupied and unoccupied nests. We suggest that this is a relatively new and expanding colony. Urgent measures to control and/or eradicate invasive alien species on Rano Raraku are needed to improve breeding success and persistence of this colony in the future.

The Red-headed Wood Pigeon, Columba janthina nitens, is an endemic and endangered subspecies of the Ogasawara Islands. This pigeon moves irregularly among island habitats. However, its range and patterns of movement, particularly between the Bonin and the Volcano Islands, which are two remote island groups approximately 150 km apart, remain unclear. In this study, we conducted a survey on the uninhabited Kita-Iwojima Island of the Volcano Islands to collect direct evidence of pigeon movement between the two island groups and to reveal their food resource availability. Pigeon food composition was also analyzed. During the study period in Kita-Iwojima, we observed two individuals banded in Chichijima in the Bonin Islands. Food composition was estimated by fecal DNA analysis and compared with a fruit census of Kita-Iwojima, which differed from fruits observed in two monitored islands of the Bonin Islands, Chichijima and Hahajima. The pigeons might move among these islands to use available food resources, reflecting limitations of food resources in a single island habitat. Fruits detected in feces of the pigeons on Kita-Iwojima were not from plants observed on the island but rather derived from plants observed on Chichijima and Hahajima, likely indicating high movement capacity of pigeons among the islands. However, the foraging habitat of the Red-headed Wood Pigeon is limited to areas of low elevation in Kita-Iwojima despite apparent food sources at higher elevations. Therefore, factors beyond food abundance, such as geographical features, might affect habitat use of pigeons on the island.

To highlight adaptation of an endemic species to an oceanic island environment, adult morphological characteristics and growth patterns were compared between a mitten crab endemic to the Ogasawara Islands (Eriocheir ogasawaraensis) and a congener from mainland Japan (E. japonica). Mean carapace width of E. ogasawaraensis was nearly 1.6 times larger than that of E. japonica in both sexes. A difference was detected in the carapace length versus carapace width relationship between these two species. Comparing chela propodus height versus carapace width, a sexual difference was detected similarly in both species, but males had only one growth phase in E. ogasawaraensis, whereas males of E. japonica were dimorphic due to two growth phases. The regression line obtained for male E. ogasawaraensis (chela propodus height versus carapace width) was nearly on the extending line of small-phase male E. japonica. Female E. ogasawaraensis had relatively larger chelipeds than female E. japonica. As for ambulatory legs, E. japonica males had relatively longer legs than females, but no sexual difference was detected in E. ogasawaraensis. Eriocheir ogasawaraensis had relatively shorter legs than male E. japonica but longer legs than female E. japonica. Therefore, in E. ogasawaraensis sexual dimorphism was not as differentiated as in E. japonica, and the adult male dimorphism recognized in E. japonica was absent. The large body size of E. ogasawaraensis is consistent with island gigantism that is commonly found in response to a lack of large predators on isolated islands. Evolution of dimorphism can be explained by sexual selection, and the differences between the island and mainland species are presumed to be correlated with differences in the mating behavior and/or environmental factors in their habitats.

Among the most striking crustaceans from Rapa Nui Island (27° S, 109° 22′ W) is the endemic lobster Panulirus pascuensis, commonly known as the spiny lobster. This species is also present in Pitcairn Island and the Salas y Gómez Ridge. Larvae of this species pass through different phyllosoma stages until metamorphosis, during which they molt to a puerulus, a transitional stage adapted to benthic life. This species is an important fishery resource for inhabitants of Rapa Nui. However, there are several gaps in biological knowledge of this species, including its ontogeny. We sampled zooplankton to obtain firststage P. pascuensis phyllosoma during three oceanographic campaigns around Rapa Nui (April 2015, September 2015, and March 2016). Individuals were encountered between the surface and 200 m depth with an abundance of 1.3 indiv./1,000 m³. These individuals, along with laboratory-hatched phyllosoma, allowed us to describe the morphology of this larval stage. Panulirus pascuensis stage I phyllosoma were observed in fall, suggesting that larval development would be synchronized with the productivity cycle in the region of Rapa Nui, where maximum chlorophyll concentration is observed during austral winter.

The diversity of seven families of brachyurans occurring on Easter Island is reviewed based on historical and more recently collected specimens. Lewindromia unidentata (Rüppell, 1830) (Dromiidae) is confirmed to occur, and Dynomene hispida (Latreille, in Milbert, 1812) (Dynomenidae) and Actaeomorpha erosa Miers, 1877 (Aethridae) are recorded for the first time from the island. The sole homolid species known from Easter Island, previously identified only to family, is provisionally identified as Latreillopsis cf. okala Castro & Naruse, 2014. A new species of Daldorfia Rathbun, 1904 (Parthenopidae), previously confused with D. horrida (Linnaeus, 1758), is described. The taxonomic issues with Schizophroida Sakai, 1933 (Majidae) are reviewed: S. simodaensis Sakai, 1933, from Japan is synonymized with S. manazuruana Sakai, 1933, also from Japan, and a new species is described from Easter Island; an earlier record of Ageitomaia baeckstroemi (Balss, 1924) from Salas y Gómez is shown to be a misidentification of this new species. The presence of a Huenia, possibly H. aff. pacifica (Miers, 1879) (Epialtidae), on the island is also confirmed.

Eleven species of ranid frogs (N = 42) from Southeast Asia were examined for gastrointestinal helminths: Amolops torrentis, Chalcorana labialis, Hylarana erythraea, Hylarana taipehensis, Indosylvirana milleti, Pulchrana banjarana, Pulchrana baramica, Pulchrana glandulosa, Pulchrana picturata, Sylvirana cubitalis, Sylvirana mortensi. The helminth community consisted of eight species of Nematoda, represented by Aplectana macintoshii, Cosmocerca ornata, Cosmocercoides pulcher, Icosiella innominata, Meteterakis japonica, Seuratascaris numidica, Abbreviata sp., and a species of Acuariidae. Ranid frogs from Southeast Asia are infected by generalist helminths that also infect other frogs. Twenty new host records are reported.