French Frigate Shoals Research Articles

Humpback whale Megaptera novaeangliae song reveals wintering activity in the Northwestern Hawaiian Islands

The main Hawaiian Islands (MHI) are the principal breeding ground for humpback whales in the North Pacific. Over the past 3 decades, population recovery from whaling-era losses has resulted in a steady increase in the number of whales wintering in Hawaiian waters and a geo- graphic expansion of their distribution in the MHI. Until recently, no existing evidence showed that this expansion included the islands, atolls, and banks of the Northwestern Hawaiian Islands (NWHI). To better understand the occurrence of humpback whales in the NWHI, 9 ecological acoustic recorders (EARs) were deployed at sites throughout the archipelago to record the occurrence of humpback whale song, an indicator of winter breeding activity. Song was found to be prevalent at Maro Reef, Lisianski Island, and French Frigate Shoals but was also recorded at Kure Atoll, Midway Atoll, and Pearl and Hermes Atoll. Both the timing and abundance of song at several locations closely followed trends observed on Oahu, which is one of the MHI, strongly suggesting that humpback whales use the NWHI as a wintering area. This finding is of particular relevance in light of recent suggestions that, based on photo-identification data, a yet undocumented wintering area exists somewhere in the central North Pacific. We propose that the NWHI could be that area.

A revision of the Hawaiian and Wake Island species of the genus Conchopus Takagi (Diptera, Dolichopodidae)

Six shore-dwelling species of the rectus group of the genus Conchopus Takagi are recognized from the Hawaiian and Wake Islands, including five new species. Conchopus is restricted to this species group herein. Contrary to some earlier records, C. acrosticalis (Parent, 1937) occurs only on four of the Hawaiian Islands (Hawai‘i, Maui, Lāna‘i, and Moloka‘i). The new species are distributed as follows: C. ciliatus sp. nov. (Hawai‘i, Maui, O‘ahu and Lisianski Is.); C. crassinervis sp. nov. (Kaua‘i); C. minutus sp. nov. (Hawai‘i, Maui, Lāna‘i, O‘ahu, and French Frigate Shoals); C. menehune sp. nov. (Kaua‘i and Nihoa Is.); and C. pacificus sp. nov. (Hawai‘i, O‘ahu, Kaua‘i, and Wake Is). A key to the males of all known species of the rectus group is provided.

Estimating carrying capacity at the green turtle nesting beach of East Island, French Frigate Shoals

Many sea turtle populations are at a fraction of their historical abundance, and under- standing ecological processes, under current and climate change scenarios, is critical for establishing recovery goals. In the Hawaiian Islands, the nesting population of the green turtle Chelonia mydas on East Island, French Frigate Shoals, has been recovering at a rate of 5.7% per year. Climate change models, however, predict a loss in nesting habitat on East Island of up to 30% due to sea level rise by 2100. Therefore, the objective of the present study was to determine the carrying capacity of East Island for hatchlings and nesting females under current conditions and predictions of sea level rise. In the simulation model, density-dependent nest destruction was the primary factor regulating population size. Carrying capacity was reached between 1.9 and 2.1 million hatchlings at current conditions; carrying capacity was approached when 80 000 to 120 000 nests were laid on the beach, representing 20 000 to 30 000 nesting females. With a rise in sea level, carrying capacity was reached when 60 000 to 100 000 nests were laid on the beach. The current mean estimate of 390 nesting females per year, over the past 10 yr, at East Island represents 1.3 to 2% of the females that would nest at carrying capacity. The beach at East Island is well below carrying capacity and is capable of supporting a larger nesting population. However, the availability of suitable coastal habitats may play a bigger role in regulating the Hawaiian green turtle population than available nesting habitat.

Widespread Dispersal of the Crown-of-Thorns Sea Star,Acanthaster planci, across the Hawaiian Archipelago and Johnston Atoll

The population structure of marine species is variable along the Hawaiian Archipelago; thus, it is important to understand dispersal and recruitment patterns for economically and ecologically important taxa to inform Ecosystem-based Management. Connectivity of the coral-eating crown-of-thorns sea star,Acanthaster planci, was examined from Johnston Atoll and 12 locations across the Hawaiian Archipelago. Sequences of mitochondrial DNA from 383 individuals were analyzed to infer patterns of gene flow among the Northwestern Hawaiian Islands (NWHIs), the main Hawaiian Islands, and Johnston Atoll. Population samples were genetically similar across the Hawaiian Archipelago with the exception of the west side of the Big Island of Hawaii, which was significantly differentiated from the majority of Hawaiian samples (pairwise , ). Although differentiated, Hawai`i West shares haplotypes with every other site across the Hawaiian Archipelago. Johnston Atoll was genetically distinct from every location (pairwise , ) except French Frigate Shoals (, ), supporting connectivity between the central NWHIs and Johnston Atoll. Taken together with the lack of geographic population structure and haplotypes shared among all populations, these results indicate widespread larval dispersal with few restrictions to gene flow along the archipelago.

Marine Benthic Algae of Johnston Atoll: New Species Records, Spatial Distribution, and Taxonomic Affinities with Neighboring Islands

Forty-five of the 107 species of marine benthic algae collected during 2004 and 2006 NOAA cruises to isolated Johnston Atoll and two additional species from earlier collections represent new species records. Total number of algae is now increased to 189 species: 26 species of cyanobacteria (blue-green algae), 105 species of red algae, 15 species of brown algae, and 43 species of green algae. The macroalga Caulerpa serrulata and the epiphyte Lomentaria hakodatensis were the most widely distributed species at Johnston Atoll based on frequency of occurrence at 10 of 12 stations and 8 of 12 stations, respectively, during the 2004 NOAA cruise. Despite the atoll's isolation, the parasitic red alga Neotenophycus ichthyosteus and the cyanobacterium Borzia elongata are the only endemic algal species on Johnston Atoll. Nonmetric multidimensional scaling analyses indicate that taxonomic affinities of Johnston Atoll lie between French Frigate Shoals and Wake Atoll. In terms of atolls, biodiversity of the marine flora of Johnston Atoll (i.e., 189 species) is surpassed only by the 256 algal species of the much-larger and better-studied Enewetak Atoll in the Marshall Islands.

A multiple instrument approach to quantifying the movement patterns and habitat use of tiger (Galeocerdo cuvier) and Galapagos sharks (Carcharhinus galapagensis) at French Frigate Shoals, Hawaii

We equipped individual tiger (Galeocerdo cuvier Peron and Lesueur, 1822) and Galapagos (Carcharhinus galapagensis Snodgrass and Heller, 1905) sharks with both acoustic and satellite transmitters to quantify their long-term movements in the Papahanaumokuakea Marine National Monument (Northwestern Hawaiian Islands). Tiger sharks exhibited two broad patterns of behavior. Some individuals were detected at French Frigate Shoals (FFS) year round, whereas others visited FFS atoll in summer to forage on fledging albatross, then swam thousands of kilometers along the Hawaiian chain, or out into open ocean to the North Pacific transition zone chlorophyll front, before returning to FFS in subsequent years. These patterns suggest tiger sharks may use cognitive maps to navigate between distant foraging areas. Different patterns of spatial behavior may arise because cognitive maps are built up through individual exploration, and each tiger shark learns a unique combination of foraging sites. Galapagos shark detections were all associated with FFS, suggesting these sharks may be more resident around oceanic islands. Both Galapagos and tiger sharks primarily used the mixed layer (<100 m depth) and made occasional deeper dives through the thermocline down to 680 m. Results show reef-associated sharks utilize a wide variety of habitats ranging from shallow atoll lagoons to deep reefs and open ocean and may provide important trophic links between these habitats.

Long-Range Propagation of the Semidiurnal Internal Tide from the Hawaiian Ridge

Abstract The northeastward progression of the semidiurnal internal tide from French Frigate Shoals (FFS), Hawaii, is studied with an array of six simultaneous profiling moorings spanning 25.5°–37.1°N (≈1400 km) and 13-yr-long Ocean Topography Experiment (TOPEX)/Poseidon (T/P) altimeter data processed by a new technique. The moorings have excellent temporal and vertical resolutions, while the altimeter offers broad spatial coverage of the surface manifestation of the internal tide’s coherent portion. Together these two approaches provide a unique view of the internal tide’s long-range propagation in a complex ocean environment. The moored observations reveal a rich, time-variable, and multimodal internal tide field, with higher-mode motions contributing significantly to velocity, displacement, and energy. In spite of these contributions, the coherent mode-1 internal tide dominates the northeastward energy flux, and is detectable in both moored and altimetric data over the entire array. Phase and group propagation measured independently from moorings and altimetry agree well with theoretical values. Sea surface height anomalies (SSHAs) measured from moorings and altimetry agree well in amplitude and phase until the northern end of the array, where phase differences arise presumably from refraction by mesoscale flows. Observed variations in SSHA, energy flux, and kinetic-to-potential energy ratio indicate an interference pattern resulting from superposed northeastward radiation from Hawaii and southeastward from the Aleutian Ridge. A simple model of two plane waves explains most of these features.

Demography and Natural History of Laysan Albatross on Oahu, Hawaii

Laysan Albatross (Phoebastria immutabilis) began re-colonizing sites across the Pacific in the 1970s after severe population declines, and fledged the first chick on the island of Oahu in 1992. We report the status of Laysan Albatross populations at Kaena Point and Kuaokala on the island of Oahu, Hawaii and provide new demographic data for this species. Colonies on Oahu were monitored weekly from 2004 to 2008; all individuals were censused, banded, and genetically identified to gender. There was a population of 365 adults on Oahu in 2008 of which 47% were active breeders. The breeding population increased 27% annually since 1991. The high rate of increase was due primarily to immigration with some local recruitment. Recaptures indicate that seven birds were from French Frigate Shoals, one was from Midway Atoll, and 52 were from Oahu and returning to breed; all other adults were of unknown origin. Hatching rate (62%), fledging rate (78%), and overall reproductive success (48%) were comparable to other colonies despite occasional predation. The rate of adult dispersal was high with up to 10% of birds observed each day on Oahu visiting from Kauai. Adults occasionally changed breeding colonies between seasons, and even visited other islands while actively breeding on Oahu. While small, these colonies are at higher elevations and may serve as refugia in the event of sea level rise and, thus, should continue to be conservation priorities.

Development of microsatellite markers from four Hawaiian corals: Acropora cytherea, Fungia scutaria, Montipora capitata and Porites lobata

Comprehensive population genetic studies of coral communities are comparatively rare, because of the scarcity of population genetic markers. The Hawaiian archipelago offers a unique perspective into understanding the population genetic structuring of this ecologically important group of organisms. Here we report the development of microsatellite marker libraries from holobiont extracts of four corals: Acropora cytherea (n = 50), Fungia scutaria (n = 118), Montipora capitata (n = 140) and Porites lobata (n = 149). Blast searches indicate that these libraries contain microsatellites from both the coral host and Symbiodinium endosymbionts from each coral. In addition, we also present redesigned primers for the nuclear coding region (atpsβ) for use in M. capitata. We report testing and optimization for seven of these microsatellites from A. cytherea, and eight microsatellites and the atpsβ locus from M. capitata. Using 25 individuals per species collected from each French Frigate Shoals (FF) and Johnston Atoll (JO), the number of alleles per locus ranged from 2 to 9. Expected heterozygosities ranged from 0.38 to 0.85 and 0.08 to 0.87 for A. cytherea and M. capitata, respectively. We expect that these libraries will be a valuable resource and provide additional useful microsatellite markers for both the coral host and zooxanthellae.

Additions to the decapod crustacean fauna of the Hawaiian Islands, III. A new species of the genus Babamunida (Crustacea: Galatheidae) from Hawaii based on morphological and molecular evidence

Babamunida kanaloa n. sp., a new galatheid from approximately 250 m depth off the Northwestern Hawaiian Islands (French Frigate Shoals), is described. DNA sequence data from two gene regions (16S and CO1) corroborates the placement of this new species in the genus Babamunida. Images taken independently using the Deep Submergence Vehicle Pisces IV are almost certainly of the same species based on overall size and color pattern and provide limited ecological information. This new species brings the number of species in the genus Babamunida to six and the total number of galatheid species known from the Hawaiian Islands to four (possibly higher depending on some previous records that might be questionable).

Additions to the decapod crustacean fauna of the Hawaiian Islands, I. A review of the genus Sakaila Manning and Holthuis, 1981 (Decapoda, Brachyura, Aethridae), with the description of a new species from the Northwestern Hawaiian Islands

The brachyuran crab genus Sakaila, currently considered a member of the family Aethridae, is reviewed and revised. Illustrations are provided for all of the known species, and a new species, the fourth in the genus, is described based on one female from French Frigate Shoals, one male from Maro Reef, both in the Northwestern Hawaiian Islands, and a second male from Johnston Atoll. Previous species are known only from the eastern Atlantic off the west coast of Africa (S. africana Manning and Holthuis, 1981) and from the far western Pacific off Japan (S. japonica Sakai, 1963, and S. imperialis Sakai, 1963). The new species differs from its congeners mostly in the overall spination of the carapace and legs, which is more pronounced in the new species. A key to the known species is provided and the current status of each species is discussed.

Variation in the relationship between offspring size and survival provides insight into causes of mortality in Hawaiian monk seals

The reasons why wildlife populations decline in abundance are often unknown; thus, competing hypotheses are offered as causal factors, and research focuses on attributing relative sup- port to them. The widely documented relationship between offspring size and survival during the period following parental investment has been typically attributed to larger offspring having greater energy reserves, though size may also confer other survival advantages. Here, it is hypothesized that variation in the relationship between offspring size and survival in a population should provide insight into causes of mortality; for example, size-dependent and size-independent mortality will affect the shape of the size-survival curve differentially. This hypothesis is examined using weaning girth measurements and subsequent survival outcomes for Hawaiian monk seal Monachus schauins- landi pups, a species which is currently declining in abundance as a result of low juvenile survival. The probability of surviving the first year is strongly influenced by weaning condition (girth), as well as subpopulation and year. Comparing size-survival curves during years with high, medium, and low first-year survival suggests that an intensification of size-dependent mortality, probably related to food limitation, is commonly associated with poor survival. A notable exception at one colony, French Frigate Shoals, indicates that size-independent mortality, probably a result of a known high incidence of shark predation, is associated with high juvenile mortality. Analyzing variability in the relationship between body size and survival can be a useful tool for evaluating sources of mortality and, ultimately, aid in diagnosing population declines.

Composition of Hawaiian green turtle foraging aggregations: mtDNA evidence for a distinct regional population

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 5:37-44 (2008) - DOI: https://doi.org/10.3354/esr00101 Composition of Hawaiian green turtle foraging aggregations: mtDNA evidence for a distinct regional population Peter H. Dutton1,*, George H. Balazs2, Robin A. LeRoux1, Shawn K. K. Murakawa2, Patricia Zarate3, Laura Sarti Martínez4 1NOAA Fisheries, Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, California 92037, USA 2NOAA Fisheries, Pacific Islands Fisheries Science Center, 2570 Dole Street, Honolulu, Hawaii 96822-2396, USA 3Charles Darwin Foundation, Santa Cruz, Galapagos Islands, Ecuador 4CONANP, Camino al Ajusco No. 200, Col. Jardines en la Montaña, Tlalpan, México DF CP 14210, Mexico *Email: peter.dutton@noaa.gov ABSTRACT: To examine the stock composition of Hawaiian foraging populations and evaluate current life-history hypotheses, mtDNA control region sequences from immature and adult green turtles that forage around the Hawaiian Islands were compared to potential source nesting populations across the Pacific. We examined the stock composition of the feeding ground (FG) populations at 5 index sites across the Hawaiian Archipelago, as well as animals stranded in areas outside these index sites. Six haplotypes, based on mtDNA sequences, were observed among the 788 green turtles sampled around the Hawaiian Islands. Stock mixture analysis shows that the Hawaiian FG populations comprise one genetic stock derived from the nesting population at French Frigate Shoals (FFS), based on a mean estimate of 99.9% from FFS as opposed to other potential source stocks. We identified only 3 turtles with haplotypes not found at FFS, indicating that Hawaiian FGs might occasionally, albeit rarely, be visited by animals from rookeries outside the Hawaiian Archipelago, both in the eastern and western Pacific. These findings lead us to conclude that the numerous foraging aggregations around the Hawaiian Islands can be considered part of a distinct regional population for management. The finding that FGs scattered across a distance of over 2400 km belong to one genetic stock is unique among sea turtles, and allows Hawaiian green turtles to be assessed separately from other Pacific stocks with respect to risk. We explore the unique population ecology of Hawaiian green turtles with reference to the complex life history of this marine megaherbivore. KEY WORDS: Population genetics · Control region · Mitochondrial DNA · mtDNA · Sea turtles Full text in pdf format PreviousNextCite this article as: Dutton PH, Balazs GH, LeRoux RA, Murakawa SKK, Zarate P, Martínez LS (2008) Composition of Hawaiian green turtle foraging aggregations: mtDNA evidence for a distinct regional population. Endang Species Res 5:37-44. https://doi.org/10.3354/esr00101 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 5, No. 1. Online publication date: August 13, 2008 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2008 Inter-Research.

Foraging interaction between monk seals and large predatory fish in the Northwestern Hawaiian Islands

CRITTERCAMS were deployed on 42 Hawaiian monk seals at French Frigate Shoals, Hawaii, to assess the degree to which interaction with large predatory fish may play a role in their foraging success. Sharks, jacks, and large-bodied snappers were seen near the actively foraging seals approximately 17% of the time. Present at all but the greatest depths (>100 m), the predatory fish were most frequently observed when seals foraged at the summits of neighboring banks. Competing fish were encountered as individuals and in schools (mean 4.5, maximum 46 ind.) and often formed mixed-species assemblages that followed seals around. By traveling with foraging seals, the preda- tory fish could exploit the seals' superior ability to flush cryptic prey from bottom cover. The probing, digging, and rock-flipping activities of seals spook prey into the open, making them available to jacks, sharks, and snappers. The jacks Caranx ignobilis and Seriola dumerili were the most success- ful at obtaining prey items flushed from cover by the seals, but carcharhinid sharks were also seen competing for prey. Some adult seals appeared to feed effectively in prey-rich areas despite the pres- ence of high densities of predatory fish. It is not known if the predatory fish have a larger impact on juvenile seals, the segment of the population with the poorest survivorship.

Diving behavior of the Hawaiian green turtle ( Chelonia mydas) during oceanic migrations

The diving behavior of an adult female and two adult male green turtles was recorded during their roundtrip breeding migration from Laniakea, Oahu, to French Frigate Shoals in the Northwestern Hawaiian Islands. These data represent the first detailed records of diving behavior of green turtles as they migrate to their breeding grounds. All three turtles exhibited a biphasic diving behavior. During the daylight hours, diving depth was shallow (1–4 m) and duration was short (1–18 min). It was assumed that the turtles were moving deliberately toward their destination during this time. Between 1900 and 1930 h daily, the turtles began a diving pattern consisting of deep dives with a mean maximum dive depth of 35–55 m and a mean duration of 35 to 44 min. The shallow diurnal diving began between 0600 and 0700 h, after the nocturnal deep-diving pattern ended. The adult female made two dives in excess of 135 m and one male made several dives in excess of 100 m. These are the deepest dives ever recorded for a naturally diving green turtle. It took an average of 36 days for the turtles to make the trip to French Frigate Shoals and an average of 30 days to make the return trip. The deep nocturnal diving was unexpected and this behavior is in need of further investigation.

Distribution and morphology of growth anomalies in Acropora from the Indo-Pacific

We assessed the distribution and prevalence of growth anomalies (GAs) in Acropora from French Frigate Shoals (Hawaii, USA), Johnston Atoll and Tutuila (American Samoa), developed a nomenclature for gross morphology, characterized GAs at the cellular level and obtained preliminary indices of their spatial patterns and progression within coral colonies. Acropora GAs were found in all 3 regions, but the distribution, variety and prevalence of Acropora GAs was highest in American Samoa. GAs were grouped into 7 gross morphologies (exophytic, bosselated, crateriform, nodular, vermiform, fimbriate or annular). On histology, GAs consisted of hyperplastic basal body wall (calicodermis, mesoglea and gastrodermis apposed to skeleton) with 3 distinct patterns of necrosis. There was no evidence of anaplasia or mitotic figures (common but not necessarily required morphologic indicators of neoplasia). Compared to normal tissues, GAs had significantly fewer polyps, zooxanthellae within the gastrodermis of the coenenchyme, mesenterial filaments and gonads but significantly more necrosis. On 2 colonies with GAs monitored at 2 points over 11 mo, numbers of GAs per colony increased from 0.9 to 3 times the original number seen, and significant clustering of GAs occurred within colonies. The evidence of GAs being true neoplasias (tumors) is mixed, so a cautionary approach is urged in use of morphologic terminology.

Factors affecting marine debris deposition at French Frigate Shoals, Northwestern Hawaiian Islands Marine National Monument, 1990–2006

Data on the amount and type of small debris items deposited on the beaches of the Hawaiian Islands National Wildlife Refuge Tern Island station, French Frigate Shoals were collected over 16 years. We calculated deposition rates and investigated the relationship among deposition and year, season, El Niño and La Niña events from 1990 to 2006. In total 52,442 debris items were collected with plastic comprising 71% of all items collected. Annual debris deposition varied significantly (range 1116–5195 items) but was not influenced by season. Debris deposition was significantly greater during El Niño events as compared to La Niña events. Although often deduced to influence floating marine pollution, this study provides the first quantitative evidence of the influence of El Niño/La Niña cycles on marine debris deposition.

Using Bayesian state-space modelling to assess the recovery and harvest potential of the Hawaiian green sea turtle stock

The Hawaiian green sea turtle genetic stock is endemic to the Hawaiian Archipelago. This stock was depleted over the past century mainly due to over-exploitation that ceased during the 1970s following protection under the US Endangered Species Act. Nesting trends suggest the stock has been recovering but no formal stock assessment has been undertaken. So, we used a Bayesian state-space surplus-production model to describe Hawaiian green turtle population dynamics given limited data and uncertainty about sea turtle demography. Data series comprised commercial landings of green turtles reported from the Archipelago (1944–1973) and nester abundance recorded at the primary rookery on East Island, French Frigate Shoals (1973–2004). The model incorporated process and observation error and was fitted using Markov chain Monte Carlo simulation with a mix of informative and non-informative priors. We estimated that the Hawaiian green turtle stock was ca. 20% of pre-exploitation biomass when monitoring and protection began in the 1970s. The stock is estimated to be now ca. 83% of pre-exploitation biomass with an intrinsic growth rate ca. 5.4% pa (95% Bayesian credible interval: 3.1–8.9%). Rebound or recovery potential (also exploitation rate at MSP) of this stock was estimated to be 3.4% (1.6–6.2%), which is consistent with estimates for other long-lived late-maturing marine species. So, this once-seriously-depleted green turtle stock is well on the way to recovery and a limited harvest might now be demographically feasible. These findings are relevant for supporting informed public policy debate on the restoration of indigenous hunting rights in the Archipelago. Parameter estimates and model structure from the Bayesian surplus-production model were incorporated in an interactive easy-to-use stochastic simulation model to help support policy analysts in stock recovery planning and to explore sustainable harvest potential.

Seasonal and diel movements of giant trevally Caranx ignobilis at remote Hawaiian atolls: implications for the design of Marine Protected Areas

We need to understand the long-term movement patterns of coral reef top predators in order to design marine protected areas that will provide these animals with effective, long-term pro- tection. We used acoustic telemetry to quantify the movements of giant trevally, a large coral reef top predator, at 5 atolls in the Northwestern Hawaiian Islands Marine National Monument. We did not observe any inter-atoll movements but found that giant trevally were attached to core activity areas from which they made periodic atoll-wide excursions of up to 29 km. Within the core areas, the tagged fish exhibited diel habitat shifts. We identified Rapture Reef at French Frigate Shoals (FFS) atoll as a spawning site, where giant trevally form seasonal mating aggregations. Giant trevally that use Rapture Reef as their core daytime area live there year-round, whereas those that occupy other areas of FFS migrate to Rapture Reef in the summertime during specific phases of the moon. Although giant trevally were wide-ranging and would require large marine protected areas (e.g. entire atolls or islands) to protect their entire range, core activity areas and spawning sites for giant trevally could be contained within relatively small marine protected areas. Identification of spawning sites could assist in the establishment of focused marine protected areas that, while quite small in size, could have significant impact in preserving the spawning biomass of this species. Very large marine protected areas are not feasible in most heavily populated areas, hence effective alternative management strategies must be found for this fishery-targeted, wide-ranging top predator. We sug- gest using a combination of relatively small marine protected areas, to protect core activity areas and spawning sites for giant trevally, and conventional measures such as minimum size or 'slot' limits to further safeguard spawning stocks.

Colonization of the Hawaiian Archipelago via Johnston Atoll: a characterization of oceanographic transport corridors for pelagic larvae using computer simulation

Larval transport between Johnston Atoll and the Hawaiian Archipelago was examined using computer simulation and high-resolution ocean current data. The effects of pelagic larval duration and spawning seasonality on long-distance transport and local retention were examined using a Lagrangian, individual-based approach. Retention around Johnston Atoll appeared to be low, and there appeared to be seasonal effects on both retention and dispersal. Potential larval transport corridors between Johnston Atoll and the Hawaiian Archipelago were charted. One corridor connects Johnston Atoll with the middle portion of the Hawaiian Archipelago in the vicinity of French Frigate Shoals. Another corridor connects Johnston Atoll with the lower inhabited islands in the vicinity of Kauai. Transport appears to be related to the subtropical countercurrent and the Hawaiian Lee countercurrent, both located to the west of the archipelago and flowing to the east. A new analytical tool, termed CONREC–IRC is presented for the quantification of spatial patterns.