Pacific Science, vol. 62, no. 4 (2008)

Historical Tropical Cyclone Activity and Impacts in the Cook Islands
Fes A. de Scally, 443

Analysis of a recently completed database of 143 tropical cyclones in the Cook Islands revealed a minimum average frequency of 0.8 cyclones per cyclone season between 1820 and 2006, with a more-precise frequency of 1.8 cyclones per season with the beginning of satellite monitoring of cyclones in 1970. Since 1970, 31% of cyclones have reached hurricane intensity. The Southern Cooks have been more than twice as frequently affected by cyclones as the Northern Cooks, with the island of Palmerston having the greatest number of encounters. Since 1820, 96% of cyclones have occurred during the official November–April cyclone season, with February alone accounting for 29%. Since 1970, 46% of cyclones achieving hurricane status have occurred in February. Nevertheless, Cyclone Martin in October–November 1997 demonstrated the dangers of a cyclone occurring outside the official season. An increase in cyclone occurrences since the mid-1970s is probably attributable to satellite monitoring, but it is noteworthy that all six cyclones known for certain to have achieved major hurricane status have occurred since 2002. Since 1970, 56% of cyclones have occurred during El Niño events, an increase of 15% from the 1870–1969 period. Since 1891, cyclones with moderate and major human impacts have occurred on average at least every 3.8 and 8.8 yr, respectively, with the Southern Cooks more than twice as frequently affected as the Northern Cooks. However, past cyclone disasters in the latter group suggest that risk to human life is greater there due to the potential for inundation of the atolls by storm surges. Half of cyclones with human impacts have occurred during El Niño events, with weak to moderate El Niños almost as important in this respect as strong El Niños. Only 13% of cyclone impacts have occurred during La Niña events.

Was Tropical Cyclone Heta or Hunting by People Responsible for Decline of the Lupe (Ducula pacifica) (Aves: Columbidae) Population on Niue during 1994–2004?
R. G. Powlesland, D. J. Butler, and I. M. Westbrooke, 461

On 6 January 2004, Tropical Cyclone Heta devastated much of the South Pacific island nation of Niue. The forest suffered extensive damage, particularly to the north-western sector, with many trees uprooted and others stripped of branches and foliage. Even though some patches of forest in the southeast sustained little damage, many lupe (Pacific pigeon, Ducula pacifica) and kulukulu (purple-crowned fruit dove, Ptilinopus porphyraceus) entered eastern villages in search of food and water after the cyclone, a very unusual behavior. This paper details our findings from a survey of some of Niue’s forest birds carried out during September 2004 and compares these with results from a similar survey in September 1994. Five-minute point count data, an index of conspicuousness, from three transects showed that heahea (Polynesian triller, Lalage maculosa) were more abundant in 2004 than in 1994, that the results were variable from transect to transect for miti (Polynesian starling, Aplonis tabuensis) and kulukulu, but that significantly fewer lupe were detected along all three transects in 2004 than previously. We tentatively suggest that the decline in the lupe population was caused mainly by unsustainable human hunting during 1994–2004, rather than mortality caused by the cyclone.

Ecological Partitioning and Invasive Ants (Hymenoptera: Formicidae) in a Tropical Rain Forest Ant Community from Fiji
Darren Ward, 473

Determining composition and structure of ant communities may help understand how niche opportunities become available for invasive ant species and ultimately how communities are invaded. This study examined composition and structure of an ant community from a tropical rain forest in Fiji, specifically looking at spatial partitioning and presence of invasive ant species. A total of 27 species was collected, including five invasive species. Spatial partitioning between arboreal (foliage beating) and litter (quadrat) samples was evident with a relatively low species overlap and a different composition of ant genera. Composition and abundance of ants was also significantly different between litter and arboreal microhabitats at baits, but not at different bait types (oil, sugar, tuna). In terms of invasive ant species, there was no difference in number of invasive species between canopy and litter. However, the most common species, Paratrechina vaga, was significantly less abundant and less frequently collected in the canopy. In arboreal samples, invasive species were significantly smaller than endemic species, which may have provided an opportunity for invasive species to become established. However, taxonomic disharmony (missing elements in the fauna) could also play an important role in success of invasive ant species across the Pacific region. Invasive ants represent a serious threat to biodiversity in Fiji and on many other Pacific islands. A greater understanding of habitat susceptibility and mechanisms for invasion may help mitigate their impacts.

Ecology of the Endemic Land Crab Johngarthia malpilensis (Decapoda: Brachyura: Gecarcinidae), a Poorly Known Species from the Tropical Eastern Pacific
Mateo López-Victoria and Bernd Werding, 483

Johngarthia malpilensis (Faxon, 1893) is the least studied of the eight American species of Gecarcinidae. This land crab is considered endemic to Malpelo, an oceanic island of the Colombian Pacific. Several aspects of its ecology were investigated between 2003 and 2006. We estimated its population density, distribution, daily activity, reproduction, interactions, and diet by marking and monitoring 909 individuals. During our visits we recorded crabs of sizes from 5 to 82 mm carapace width. Johngarthia malpilensis shelters mainly in fissures and hollows between rocks. It is distributed all over the main island except in very steep sectors. An average density of 0.41 adults m-2 and 0.55 juveniles m-2 produced an estimated total population of 833,000. Johngarthia malpilensis showed high mobility, with crabs covering distances over 450 m in a few days on highly irregular surfaces. Activity was higher from dusk till dawn and lowest around noon. Release of larvae took place during the high tides associated with the new moon, at least during the rainy season. It is omnivorous and opportunistic, consuming practically every available resource. The crab is occasionally preyed upon by an endemic lizard and migratory birds. Its general ecology is very similar to that of J. planatus, a closely related species. As a voracious omnivore J. malpilensis is one of the most important components of Malpelo’s food web.

First Records of Butterflies (Lepidoptera) from the Republic of Nauru
Donald W. Buden and W. John Tennent, 495

Four species of butterflies are reported from Nauru for the first time and as first records of butterflies from the island republic. None is endemic. Three of the four species are widespread in Oceania: Badamia exclamationis (Fabricius), Danaeus plexippus (Linnaeus), and Hypolimnas bolina (Linnaeus). The other, Petrelaea tombugensis (Röber), belongs to a genus that also is widespread in the Pacific. The small number of widespread species found on Nauru is comparable with the situation encountered on other small, remote, low-lying Pacific islands.

The Reptiles of Nauru
Donald W. Buden, 499

Eleven species of reptiles are reported from Nauru in the first systematic treatment of the herpetofauna. Four of the species are marine; the seven others include six lizards (four geckos, two skinks) and one snake. Gehyra mutilata (Wiegman), G. oceanica (Lesson), Pelamis platura (Linnaeus), and Ramphotyphlops braminus (Daudin) are recorded on Nauru for the first time. With the exception of Emoia arnoensis Brown & Marshall, which is endemic to eastern Micronesia, the herpetofauna consists of species that range widely among the west-central Pacific Ocean islands. The only known record of E. arnoensis from Chuuk possibly is based on a misassigned locality, in which case the range of the species would be limited to the Marshall Islands, Nauru, and Kosrae. There is no evidence to suggest that habitat modification on Nauru stemming largely from more than a century of phosphate mining has reduced the number of reptile species.

Inventory of Thysanoptera Collected from French Polynesia
Mark S. Hoddle, Christina D. Hoddle, and Laurence A. Mound, 509

A survey for Thysanoptera was conducted in the Society (Tahiti, Moorea, and Raiatea), Marquesas (Hiva Oa, Nuku Hiva, Ua Huka, and Ua Pou), and Austral islands (Rurutu and Tubuai) archipelagos in French Polynesia from September 2003 to November 2005. At least 55 thrips species in 36 genera and three families were identified from 823 slide-mounted specimens that were collected from 61 host plants in 33 families. Twelve species are considered to be important pests. The greatest diversity of species, 43 (77%), was collected from the Society Islands, with 60% being recorded from Tahiti alone. Species diversity was intermediate in the Marquesas Islands at 43% (24 species collected), with 35% or 19 species being recorded from Nuku Hiva. Lowest diversity was recorded for the Austral Islands, with 38% or 21 species being found in that archipelago. Less than 10% of collected species are likely to be native, with the majority of identified thrips (>90%) in French Polynesia representing a high diversity of exotic species (leaf, flower, and fungus feeders, and four predatory species) that have successfully infiltrated other island groups in the South Pacific. Survey results and subsequent estimates of thrips species diversity in French Polynesia should be interpreted with caution due to uncontrolled variation in sampling intensity that was affected by survey duration, time of year, and visitation frequency to islands.

Attempt to control the Invasive Red Alga Acanthophora spicifera (Rhodophyta: Ceramiales), in a Hawaiian Fishpond: Assessment of Removal Techniques and Management Options
Mariska Weijerman, Rebecca Most, Kristy Wong, and Sallie Beavers, 517

Acanthophora spicifera (Vahl) Børgesen was unintentionally introduced to Hawai‘i in 1950 and has since become the most common nonindigenous algal species in the main Hawaiian Islands. On the west coast of Hawai‘i Island it has been documented at three sites, including Kaloko Fishpond in Kaloko-Honokōhau National Historical Park. The fishpond has an open connection to the sea, increasing the risk that A. spicifera will establish itself on neighboring shallow coral reefs and rocky intertidal habitats. To diminish that risk and to develop an efficient management strategy, a range of approaches was assessed to control this invasive alga in Kaloko Fishpond. Removal techniques were labor intensive and had limited effect. All experiments showed a substantial initial decrease in algal density, but the long-term effect was minimal because of rapid regrowth. The most promising removal method was the use of submerged shelters to raise local densities of herbivorous fishes. Fishes grazed the alga and quickly reduced the biomass. However, the large number of predators and absence of topographical structure will make it challenging to provide sufficient shelters to increase the herbivorous fish population in the entire fishpond. A management strategy to substantially reduce the algal biomass in the fishpond includes a combination of biological control and periodic manual removal of the alga.

Relationships Between Otolith Size and Body Size for Hawaiian Reef Fishes
Ken Longenecker, 533

Estimating body size of fishes from remains recovered from piscivores, archaeological sites, and sedimentary deposits is desirable but rarely accomplished because the relationships between the size of a fish and its durable anatomical structures are largely unknown. Regression equations to predict the size or weight of 41 common Hawaiian reef fishes from sagittae (saccular otoliths) are presented. Data are also grouped into higher taxa to permit size predictions when otoliths cannot be assigned to species.

Maximum Annually Recurring Wave Heights in Hawai‘i
Sean Vitousek and Charles H. Fletcher, 541

The goal of this study was to determine the maximum annually recurring wave height approaching Hawai‘i. The motivation was scientific as well as administrative: to enhance understanding of the recurring nature of dominant swell events, as well as to inform the Hawai‘i administrative process of determining the “upper reaches of the wash of the waves” (Hawai‘i Revised Statutes [H.R.S.] § 205-A), which delineates the shoreline. We tested three approaches to determine the maximum annually recurring wave, including log-normal and extremal exceedance probability models and Generalized Extreme Value (GEV) analysis using 25 yr of buoy data and long-term wave hindcasts. The annual recurring significant wave height was found to be 7.7 ± 0.28 m (25 ft ± 0.9 ft), and the top 10% and 1% wave heights during this annual swell was 9.8 ± 0.35 m (32.1 ft ± 1.15 ft) and 12.9 ± 0.47 m (42.3 ft ± 1.5 ft), respectively, for open North and Northwest Pacific swell. Directional annual wave heights were also determined by applying hindcasted swell direction to observed buoy data lacking directional information.

Demographic Parameters of Yellowfin Croaker, Umbrina roncador (Perciformes: Sciaenidae), from the Southern California Bight
Daniel J. Pondella II, John T. Froeschke, Lynne S. Wetmore, Eric Miller, Charles F. Valle, and Lea Medeiros, 555

The yellowfin croaker, Umbrina roncador Jordan & Gilbert, 1882, is a common nearshore and surf-zone species in the southern California bight. Age was determined for individuals (n = 1,209) using annual increments in otoliths, and size at age was modeled using the von Bertalanffy growth curve (L∞ = 307.754 mm, k = 0.278 yr-1, t0 = -0.995 yr; maximum age = 15 yr). Females (L∞ = 313.173 mm, k = 0.307 yr-1, t0 = -0.771 yr) grew significantly faster and larger than males (L∞ = 298.886, k = 0.269 yr-1, t_0 = -1.072 yr). Age and growth modeling based upon otolith length (OL) and width (OW) measurements were assessed and were consistent with body measurements. Males and females were found in all size classes and in an overall 51:49 ratio that was not significantly different from a 50% sex ratio, suggesting that these fish are gonochores. Fish were reproductive during summer months, with gonadosomatic indices (females, 5.65%; males, 5.51%) consistent with group-spawning fishes. Data from two separate monitoring programs indicated that yellowfin croaker catch-per-unit-effort (CPUE) fluctuated appreciably from 1992 to 2006 on both spatial and temporal scales. CPUE also declined significantly in the latter years of these programs. Based on samples collected between 2003 and 2004, an estimate of overall annual total mortality was A = 0.4492, and instantaneous coefficient of total mortality was estimated at Z = 0.5964. Recruitment year classes were back calculated using annual survivorship. Year class strength was variable and declined significantly by the end of this study. Considering the high temporal and spatial variation in estimates of abundance and recruitment, coupled with the likelihood that these fish employ a probable group-spawning reproductive behavior, we recommend a cautious approach for the future management of this species.

Acropora (Anthozoa: Scleractinia) Reproductive Synchrony and Spawning Phenology in the Northern Line Islands, Central Pacific, as Inferred from Size Classes of Developing Oocytes
Jean C. Kenyon, 569

Little is known of the timing of reproduction in central Pacific coral populations near the equator. Oocyte pigmentation and size comparison with sizes of mature eggs reported in published literature were used to infer intra- and interspecific synchrony and probable spawning phenology in 15 species of Acropora from Palmyra and Kingman atolls in the northern Line Islands. Sampling at both atolls took place in March–April 2002 and 2004. Oocyte sizes were determined from microdissections of fixed, decalcified samples. The majority (91.2%) of samples (n = 209) were gravid, with high levels of fertility in most (84.3%) samples. Statistically discrete oocyte size classes could be distinguished in most taxa at each atoll in each year. These discrete oocyte size classes suggest that several episodes of spawning, involving multiple species, take place over 2 or 3 months beginning in early spring. These data, which are the first observations of coral reproductive synchrony in the Line Islands, support the results of other recent studies, suggesting that reproductive synchrony can be a feature of equatorial reef assemblages where the annual ranges of sea-surface temperature and tidal amplitude are small.

Seasonal Occurrence and Aggregation Behavior of the Sea Urchin Astropyga pulvinata (Echinodermata: Echinoidea) in Bahía Culebra, Costa Rica
Juan José Alvarado, 579

Between October 2003 and July 2005, aggregation behavior of the sea urchin Astropyga pulvinta Lamarck was studied in Bahía Culebra, Costa Rica. This sea urchin forms aggregations during part of the year and then disappears. I quantified the number of individuals present in a defined area each month, their aggregation behavior between day and night, and their size. Also, temperature and nutrient concentrations of the water were sampled. There were significantly more individuals in aggregations during the colder, upwelling season (December to April). Aggregations consisted of adult individuals that exploit food during the upwelling season. Moreover, these aggregations were used as a refuge by several fish species of high commercial value for the aquarium trade. These sea urchin populations could suffer as extraction of ornamental fishes and urchins increases. Their abundance and behavior should continue to be monitored as an indication of the ecological health of the community.

First Record of a Pearlfish, Carapus mourlani, Inhabiting the Aplysiid Opisthobranch Mollusc Dolabella auricularia
Peter W. Glynn, Ian C. Enochs, John E. McCosker, and Abigail N. Graefe, 593

Adult individuals of the pearlfish Carapus mourlani (Petit, 1934) occur commonly in the mantle cavity of the opisthobranch mollusc Dolabella auricularia (Lightfoot, 1786) in shallow marine waters of the Gulf of Chiriquí, Pacific Panamá. Nearly 30% of the molluscan hosts collected during the day on a coral reef contained one or two fish. Feeding observations of a captive fish as well as the intact condition of the host’s ctenidium and other internal organs suggest that C. mourlani is an inquiline commensal and not parasitic. Fish curl around the ctenidium during the day and capture microcrustaceans when the fish emerge from their host at night to feed. From low-light infrared video recordings, Carapus was observed to accurately grasp rapidly swimming amphipods in nearly total darkness and ingest them. This symbiotic relationship appears to benefit Carapus by allowing the fish to avoid predators during the day and to forage at night.

Two New Indo-Pacific Sand Lances of the Genus Ammodytoides (Perciformes: Ammodytidae)
John E. Randall and John L. Earle, 603

One new sand lance, Ammodytoides idai Randall & Earle, n. sp., is described from 10 specimens, 67.2–121.3 mm standard length, collected on sand substratum in the depth range of 8–25 m from the D’Entrecasteaux Islands, Papua New Guinea. It is characterized by 44–46 dorsal rays, 21–22 anal rays, 14–16 pectoral rays, 103–107 pored lateral-line scales, two or three small scales dorsally on the opercle, 5–6 + 21–23 gill rakers, 55–58 vertebrae; a series of black spots distally in the dorsal fin, and a blackish posterior border on the caudal fin (at least on adult males), broadening toward lobe tips. A second similar species, A. praematura Randall & Earle, n. sp., is described from a single 61 mm specimen from the Chagos Archipelago, differing in having 48 dorsal rays, 24 anal rays, black dots in the dorsal and anal fins, no submarginal black spots in the dorsal fin, and a curved blackish bar across each lobe of the caudal fin. A key is provided for the eight known species of Ammodytoides.

Association Affairs, 613

Index to Volume 62, 617

Advertisements

Comments are closed.