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Results for “Pacific Cooperative Studies Unit Technical Report”

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6 recordsLinked to original sources
USGS2012

A preliminary study of effects of feral pig density on native Hawaiian montane rainforest vegetation

This study aimed to examine the effects of different levels of pig density on native Hawaiian forest vegetation. Pig sign was measured across four pig management units in the 'Öla'a Forest from 1998 through 2004 and pig density estimated based upon pig activity. Six paired vegetation monitoring plots were established in the units, each pair straddling a pig fence. Percent cover and species richness of understory vegetation, ground cover, alien species, and preferred pig forage plants were measured in 1997 and 2003 and compared with pig density estimates. Rainfall and hunting effort and success by management personnel were also tracked over the study period. Vegetation monitoring found a higher percentage of native plants in pig-free or low-pig areas compared to those with medium or high pig densities, with no significant change in the percent native plant species between the first and second monitoring periods. Differences between plots were strongly affected by location, with a higher percentage of native plants in western plots, where pig damage has historically been lower. Expansion of this survey with more plots would help improve the statistical power to detect differences in vegetation caused by pigs. Because of the limited vegetation sampling in this study, the results must be viewed as descriptive. We compare the vegetation within 30 x 30 m plots across three thresholds of historical pig density and show how pig densities can change in unanticipated directions within management units. While these results cannot be extrapolated to area-wide effects of pig activity, these data do contribute to a growing body of information on the impacts of feral pigs on Hawaiian plant communities.

Hawai'i↗
USGS2025

Photographic guide to the leaf litter arthropod community of the lowland wet forest ecosystem of the Island of Hawaiʻi

Leaf litter arthropods are important components of the food web in forests, and their presence and diversity can provide information on forest health. There has been very little documentation of the leaf litter arthropods in Hawaiian forest ecosystems. This technical report is a photographic guide to some common arthropods collected from forest leaf litter at the Liko Nā Pilina Hybrid Ecosystems Project study site, a lowland wet forest in Hilo, Island of Hawaiʻi, USA. Leaf litter samples were collected from plots of invaded and experimental restoration communities using two complementary methods (litterbags and quadrats), and arthropods were extracted using Berlese funnels. The field site contained many morphospecies that were rare and locally distributed across plots, and only a few that were very common and widely distributed. The majority of the morphospecies identified were mites. This photoguide is designed to help identify arthropods found in plant litter in Hawaiian lowland forests and it may assist with research and education efforts concerned with the diversity, ecology, or conservation of litter arthropods across the Hawaiian archipelago and other Pacific islands.

Hawaii↗
USGS2025

Wake Atoll: Evaluation of plant biosecurity

Introduced organisms can cause substantial effects across most landscapes. Island ecosystems, especially tropical islands, are at elevated risk from introduced organisms. The risks are even higher for tropical islands with moderate or high levels of transit, yet this can be minimized by application of appropriate biosecurity requirements. In this study, we examined the potential for non-native plant species introductions, especially invasive plants, via shipping containers to be transported to Wake Atoll, one of the most remote terrestrial land masses in the Pacific Ocean. We sowed debris collected from 30 shipping containers in a greenhouse experiment to determine if any live plants could be germinated, identify any species that germinated, and ascertain if they posed a threat if they were to be transported to Wake Atoll and became established there. During this study 23 plant species were identified, including ferns, monocots, and dicots. Fifteen of these species reached reproductive maturity over the course of seven months. From previous plant surveys on the atoll, we know that 13 of the 23 identified species were not previously recorded, and four species are already known to be invasive on Wake Atoll. This study provides insight into the potential for debris found in shipping containers to contribute to the spread of non-native, possibly invasive species. This information may help with the refinement of biosecurity strategies to prevent the accidental introduction of invasive species into sensitive natural areas such as Wake Atoll.

Hawaii Cooperative Studies Unit Technical Report↗
USGS2021

Estimating detection and occupancy coefficients for the Pacific Islands coral reef fish species

The data-limited stock assessment models used to monitor the status of coral reef fish species in the Western Pacific region are dependent upon accurate estimates of standing stock biomass generated from underwater visual surveys of reefs. However, the imperfect detection of and variable occupancy of habitat by reef fishes are not currently accounted for in these estimates. Therefore, the objective of this project was to estimate detection and occupancy coefficients for the species listed in the Western Pacific Regional Fishery Management Council’s Fishery Ecosystem Plans by analyzing the Pacific Island Fishery Science Center-Coral Reef Ecosystem Program Reef Fish Dataset. These detection and occupancy coefficients would then be applied to refine standing stock biomass estimates. In general, species with higher detection probabilities and/or lower occupancy rates tended to exhibit the greatest differences in the estimates of standing stock biomass calculated with and without accounting for detection and occupancy. The standing stock biomass of most reef fish species seem to be underestimated when detection and occupancy are not accounted for. However, the standing stock biomass of larger-bodied targeted species, such as jacks, snappers, and groupers, seem to be over-estimated relative to the estimates generated when accounting for occupancy and detection. While there are still issues to resolve regarding how well the current data collection methods meet the underlying assumptions of the detection and occupancy modeling approach, the inclusion of detection and occupancy coefficients seems likely to improve estimates of standing stock biomass of coral reef fish species.

Hawaii↗
USGS2013

Dynamics of seabird colonies vulnerable to sea-level rise at French Frigate Shoals, Hawai`i

Globally, seabirds are vulnerable to anthropogenic threats both at sea and on land. Seabirds typically nest colonially and show strong site fidelity; therefore, conservation strategies could benefit from an understanding of the population dynamics and vulnerability of breeding colonies to climate change. More than 350 atolls exist across the Pacific Ocean; while they provide nesting habitat for many seabirds, they are also vulnerable to sea-level rise. We used French Frigate Shoals, the largest atoll in the Hawaiian Archipelago, as a case study to explore seabird colony dynamics and the potential consequences of sea-level rise. We compiled a unique combination of data sets: historical observations of islands and seabirds, a 30-year time series of population abundance, LiDAR- (light detection and ranging) derived elevations, and satellite imagery. To model population dynamics for ten species at Tern Island from 1980 to 2009, we used the Gompertz model with parameters for the population growth rate, density dependence, process variation, and observation error. We used a Bayesian approach to estimate the parameters. All species increased in a pattern that provided evidence of density dependence. Density dependence may exacerbate the consequences of sea-level rise on seabirds because species that are already near the carrying capacity of the nesting habitat will be limited more than species that still have space for population growth. Laysan Albatross ( Phoebastria immutabilis ), Great Frigatebird ( Fregata minor ), Red-tailed Tropicbird ( Phaethon rubricauda ), Masked Booby ( Sula dactylatra ), Gray-backed Tern ( Onychoprion lunatus ), and White Tern ( Gygis alba ) are likely already at carrying capacity at Tern Island and therefore are most likely to be negatively impacted by sea-level rise. We project 12% of French Frigate Shoals (excluding La Perouse Pinnacle) will be inundated with +1.0 m sea-level rise or 32% with +2.0 m. Gray-backed Terns that nest along the coastal perimeters of islands and shrub-nesting species that are habitat limited are especially vulnerable to sea-level rise. However, at Tern Island, seawalls and habitat creation may mitigate projected seabird population declines due to habitat loss. We predict substantial losses in seabird nesting habitat across the low-lying Hawaiian Islands by 2100 and emphasize the need to restore higher elevation seabird colonies.

Hawai'i↗
USGS2024

Distribution of yellow crazy ants (Anoplolepis gracilipes) and notes on other ant species at Wake Atoll, 6-21 October, 2023

Wake Atoll, located in the central Pacific Ocean, is a tropical coral atoll comprised of three islands totaling 696 ha of emergent land. Wake Atoll supports at least 17 species of non-native ants, but one species, the yellow crazy ant ( Anoplolepis gracilipes ), is especially harmful to ecosystems, including seabirds, which are federally protected species and nest throughout Wake Atoll. Our objective was to map the distribution of yellow crazy ants (YCA) across Wake Atoll to provide U.S. Air Force managers with information that could inform an eradication strategy for this species. In addition, we documented the presence of other ant species identified during our survey. We used a 50 x 50-m cell-based sampling grid to survey for YCA and other ant species. YCA were widespread across the atoll, occupying all three islands and were detected in 566 of the 3,675 (15.4%) cells surveyed, covering an area of about 142 ha. The highest proportion of cells containing YCA was on Wilkes Island (99 of 400 cells or 24.8%), followed by Wake Island (395 of 2,760 cells or 14.3%) and Peale Island (72 of 518 cells or 14.0%). YCA detections on Wilkes Island were restricted to Wilkes South (99 of 202 cells or 49.0%); no YCA were found on Wilkes North, an important area that supports the most diverse assemblage of nesting seabirds on Wake Atoll. Based on technologies developed to eradicate YCA from Johnston Atoll and elsewhere, eradicating YCA from Wake Atoll appears technically feasible. The occurrence of discrete populations (i.e., clusters of occupied cells separated from other clusters of occupied cells) within and among islands could allow a stepwise strategy where the short-term outcome of the treatment of one population is independent of the outcome of another treatment. Without action, the high-density YCA population on Wilkes South could breach the narrow (~50 m), sometimes dry, channel separating Wilkes North and South, posing a serious threat to nesting seabirds present on Wilkes North. Eradicating YCA from Wilkes South would create a buffer from YCA and reduce the threat of northward movement of YCA. We also detected 12 ant species other than YCA during our survey, including Lepisiota frauenfeldi , a new record for the atoll.

Hawaii Cooperative Studies Unit Technical Report↗