Pacific Science, vol. 63, no. 1 (2009)

Habitat-Mediated Use of Space by Juvenile and Mating Adult Port Jackson Sharks, Heterodontus portusjacksoni, in Eastern Australia
David Mark Powter and William Gladstone, 1

Studies of spatial ecology of demersal sharks are critical to understanding the significance of habitat variation; however, limited information exists. Spatial ecology of adult Heterodontus portusjacksoni was studied at three locations on the central and southern coast of New South Wales, Australia, from January 2002 to December 2005. Juveniles within a nursery area were studied from December 2002 to December 2005. Tag-recapture, day and night underwater visual census, and acoustic tagging were used. Adults returned annually to the same coastal breeding reefs for up to four consecutive years. Individual juveniles resided within a sea-grass nursery area for at least 2 yr and were not uniformly distributed throughout the nursery. Adult females often sheltered in aggregations in gutters as a male avoidance strategy, and both sexes utilized the sand/reef interface in the absence of gutters. Juveniles aggregated infrequently due to absence of habitat features that mediated aggregation. Acoustic tracks of adults revealed periods of inactivity up to 27 hr. Juveniles spent significant amounts of time inactive, punctuated with short bouts of swimming. Juveniles utilized moderate activity spaces (3,510–583,990 m²) centered over a core area of the sea-grass bed but also ranged over much larger areas of the bay. Use of space by H. portusjacksoni is strongly influenced by habitat characteristics throughout its life history.

Characteristics of Scylla spp. (Decapoda: Portunidae) and their Mangrove Forest Habitat in Ngaremeduu Bay, Republic of Palau
Katherine C. Ewel, Stacy Rowe, Blake NcNaughton, and Kimberly M. Bonine, 15

Three species of mangrove crabs (Scylla spp.) were captured in live traps in Ngaremeduu Bay on the island of Babeldaob, Republic of Palau. Most were S. serrata, but one individual each of S. olivacea and S. paramamosain was also trapped, establishing existence of a biogeographic gradient in mangrove crab species diversity across the Micronesian archipelago. Species composition of mangrove trees along transects around the bay and along the three major tributaries was similar to that of other Micronesian islands, although trees are smaller in Palau. For 17 months in 1999–2000, crabs were trapped in the bay and captured by hand along the transects; they were trapped again for 1 month in 2004. Characteristics of the crabs and of burrows encountered along the transects suggested that only S. serrata was captured in 1999–2000 and that population density of this species was 40 crabs ha­-¹. Carapace widths for the 159 crabs captured during the entire study did not differ significantly over the 4-yr span, and averaged 153 mm for males and 137 mm for females. However, average carapace widths for the largest quartile of crabs declined significantly from 174 mm to 171 mm across the study period. Catch per unit effort was 0.28 crab per trap night in 1999–2000 and 0.45 in 2004. Although large crabs are still available in Ngaremeduu Bay, current regulations may not be sufficient to keep populations from decreasing gradually in size, especially in the face of increasing harvest pressure on the island of Babeldaob.

Behavioral Responses of the Endemic Shrimp Halocaridina rubra (Malacostraca: Atyidae) to an Introduced Fish, Gambusia affinis (Actinopterygii: Poeciliidae) and Implications for the Trophic Structure of Hawaiian Anchialine Ponds
Krista A. Capps, Caroline B. Turner, Michael T. Booth, Danica L. Lombardozzi, Scott H. McArt, David Chai, and Nelson G. Hairston Jr., 27

In the Hawaiian Islands, intentionally introduced exotic fishes have been linked to changes in native biodiversity and community composition. In 1905, the mosquito fish Gambusia affinis was introduced to control mosquitoes. Subsequently, G. affinis spread throughout the Islands and into coastal anchialine ponds. Previous studies suggest that presence of invasive fishes in anchialine ponds may eliminate native species, including the endemic shrimp Halocaridina rubra. We examined effects of G. affinis on H. rubra populations in anchialine ponds on the Kona-Kohala coast of the island of Hawai‘i. In the presence of G. affinis, H. rubra exhibited a diel activity pattern that was not seen in fishless ponds. Shrimp in ponds with fish were active only at night. This pattern was evident in anchialine ponds and in laboratory experiments. In laboratory predation experiments, G. affinis preferentially consumed smaller H. rubra, and in the field the H. rubra collected from invaded sites were larger than those from fishless ponds. Analysis of trophic position using stable isotope analyses showed that feeding of H. rubra was not significantly distinct from that of snails, assumed to feed at trophic level 2.0 on epilithic algae, but G. affinis was slightly omnivorous, feeding at tropic level 2.2. The mosquito fish diet was apparently composed primarily of algae when the defensive behavior of H. rubra made them substantially unavailable as prey. The effect of successful establishment of G. affinis on shrimp behavior has the potential to alter abundance of benthic algae and processing and recycling of nutrients in anchialine pond ecosystems.

Expressions of 1976–1977 and 1988–1989 Regime Shifts in Sea-Surface Temperature off Southern California and Hawai‘i
Laurence C. Breaker and Stephanie J. Flora, 39

Sea-surface temperatures off southern California from Scripps Pier and from Koko Head, Hawai‘i, were examined to determine what impact regime shifts that occurred in 1976–1977 and 1988–1989 had on environmental conditions at each location. Cumulative sums were employed to enhance the detection process. The cumulative sum time histories revealed major turning points at both locations at the time of the 1976–1977 event. At both locations, increases in temperature were indicated, consistent with the phase change in the Pacific Decadal Oscillation that took place at that time. The cumulative sums also indicated major turning points at both locations during the 1988–1989 event. A new procedure called the method of expanding means was employed to determine the long-term impact of these events. By comparing means before and after a given event it is possible to observe the magnitude of the change and to what extent it is sustained. For the 1976–1977 regime shift, temperatures increased rapidly and remained consistently higher, by ~1°C for 2–3 yr at Scripps Pier. This increase occurred over a period of approximately 7 months and accounts for more than half of the total warming that has occurred at that location since 1920. At Koko Head, a similar response was observed with a sustained increase of approximately +0.5°C. The oceanic response to the 1988–1989 event was quite different. At Scripps Pier, temperatures before and after this event did not show any tendency to converge to significantly different values out to periods of 2–3 yr. At Koko Head, mean temperatures did converge to slightly different values after 1 yr, with mean values being consistently lower after this event (~–0.4°C). It was shown that in some cases changes associated with these events could be identified in the original data, but without the help of cumulative sums, it is usually not possible to make a clear distinction between changes of interest and other sources of variability. Finally, decorrelation time scales for the records at both locations were estimated and found to be on the order of a year, implying spatial scales that are at least synoptic (tens to hundreds of kilometers).

Reef-Top Sediment Bodies: Windward O‘ahu, Hawai‘i
Christopher Bochicchio, Charles Fletcher, Matthew Dyer, and Thomas Smith, 61

Hawaiian fringing reefs display sand bodies on their surfaces that are potentially important components of littoral sediment budgets. This work provides a regional survey of modern reef-top sediment storage and investigated geologic controls on sediment storage potential. Sand bodies are formed when sediment accumulates in topographic depressions that are the result of meteoric water eroding the emerged carbonate reef platform during periods of lower sea level. The relief of some depressions may be modified by Holocene reef accretion. Depression morphology exerts a strong control on volume and internal distribution of sediment. In this study a total of 205 jet probe thickness measurements was collected from 54 major sand bodies on the fringing reef (0–20 m depth) adjacent to 22 km of Southeast O‘ahu coastline (Kailua, Lanikai, and Waimānalo). Volumes were determined and synthesized with previous volume estimates of coastal subaerial and deeper submarine sediment bodies (20–200 m depth), giving the total sediment storage within the coastal system. Sand bodies range from 50 to 2,800 m from shore. Measured thickness varied from 0 to greater than 3.0 m with a mean of 0.95 m. For this study sand bodies were classified into three dominate morphologies: channel, field, and karst depression. The volume of sediment stored in channels was 58,253±618×10³ m³, fields contained 171±6×10³ m³, and karst depressions contained 1,332±248×10³ m³. Correlation of sediment body distribution with reef and coastal plain morphology revealed potential geologic controls on sand body formation in this region. Meteoric runoff and reef slope are important controls on spatial distribution of sand bodies.

Hyperiid Amphipods (Crustacea: Peracarida) in Mexican Waters of the Pacific Ocean
Rebeca Gasca, 83

Information on regional diversity of hyperiid amphipods of the eastern Pacific Ocean is still largely incomplete. Recent surveys of hyperiid fauna from the Mexican Pacific motivated a revision of extant faunistic accounts. This revised list includes all records from Mexican waters of the eastern Pacific (MP) from Baja California to the southern border with Central America. A total of 150 species belonging to 19 families and 48 genera of the Hyperiidea was included in this account; seven are new records in the MP. Up to 31 nominal species were excluded from previous listings. Overall, the epipelagic infraorder Physocephalata is highly diverse in the MP (119 species); Physosomata, containing deep-living forms, are less diverse (31 species). The northern part of the MP (including the gulf and off the Baja California peninsula) harbors the highest number of species/records, whereas nearly half of the species are known from the central areas and six from the southernmost sector of the MP. This pattern reflects current knowledge of the group in these areas and also geographic differences in the sampling/research efforts, but it is not a diversity gradient. Species richness of the MP is comparable with that known from other Pacific subregions. The epipelagic hyperiid fauna of the tropical MP remains relatively unknown and should be studied further to reveal regional patterns of diversity. The deep-living hyperiid community of the tropical eastern Pacific harbors a diversity that is deserving of further study.

Evidence for a Correlation between Systematics and Bioactivity in New Caledonian Cunoniaceae and Its Implications for Screening and Conservation
Yohan Pillon and Bruno Fogliani, 97

It is generally assumed that there is a good correlation between systematics and the secondary compounds found in plants. However because of the frequent homoplasy of chemical characters this has been difficult to test using statistical methods. Here we applied two nonparametric tests on a published data set, where 50 species of New Caledonian Cunoniaceae were screened for bioactivity against several pathogenic strains. Using Moran’s I index we showed that in two of nine tests against pathogenic strains there was a significantly higher similarity than expected in bioactivities between species belonging to the same genus and a significantly higher than expected dissimilarity in bioactivity between species belonging to different tribes. When considering the bioactivities against all pathogenic strains with Mantel tests, we also found significant correlation between bioactivity and phylogenetic distance in two of four tests. This has implications in screening and conservation. Searches for new molecules and bioactivity should preferentially be made on species spread across the tree of life. There is also a need to preserve as much phylogenetic diversity as possible to make sure that the widest reservoir of natural compounds remains available for future generations.

Subfossil Land Snails from Easter Island, Including Hotumatua anakenana, New Genus and Species (Pulmonata: Achatinellidae)
Patrick V. Kirch, Carl C. Christensen, and David W. Steadman, 105

The depauperate modern terrestrial biota of Easter Island contrasts with that of most other southeastern Polynesian high islands, which characteristically support a number of endemic species of insects, land snails, birds, and plants. We investigated cultural and noncultural late Holocene deposits at Anakena, Easter Island, establishing the former presence of endemic land snails on the island. These include an unidentified helicinid, a Nesopupa species, and a previously undescribed extinct achatinellid land snail, Hotumatua anakenana Kirch, Christensen & Steadman, n. genus and n. sp. A human-introduced achatinellid, Pacificella variabilis, occurs in later stratigraphic contexts of the same site. Prehistoric deforestation may have been the primary cause of the extinction of Hotumatua, although predation by rats or other alien species may have been involved as well. Along with recently discovered extirpated species of angiosperms, seabirds, and land birds, the extinction of Hotumatua reflects the nearly complete loss of the native biota of Easter Island after Polynesian colonization about 1,000 yr ago.

A New Live-Bearing Species of Scincid Lizard (Reptilia: Scincidae) from New Caledonia, Southwest Pacific
Ross A. Sadlier, Sarah A. Smith, Anthony Whitaker, and Aaron M. Bauer, 123

A new species of skink, Kanakysaurus zebratus, is described from the ultramafic Massif de Kopéto and Massif de Koniambo on the northwestern coast of Grande Terre, New Caledonia. Although this new species is similar in overall appearance to its congener K. viviparus from the far northwest of Grande Terre and the Îles Belep, it can be distinguished by features of scalation and coloration. It is also identified as being genetically distinct from and reciprocally monophyletic with respect to populations of K. viviparus from Rivière Néhoué (type population), the Îles Belep, and a recently discovered population from Sommet Poum (reported here for the first time). The population of Kanakysaurus on Dôme de Tiébaghi (5 km southeast of Rivière Néhoué) is problematic: in morphology it is closest to K. viviparus, but DNA sequence data group part of the population with K. viviparus and part with K. zebratus, n. sp. On Kopéto the new species was found only in maquis shrubland at 500–1,000 m in elevation and on Koniambo in Gymnostoma-dominated closed forest at 700 m. Adult females collected on the Massif de Kopéto in February during the height of the wet season had well-developed embryos, confirming a live-bearing mode of reproduction for the new species, and for the genus as a whole. The summit area of Kopéto is the site of a large nickel mine and substantial portions of the known range of the new species are projected to be cleared to extract nickel-bearing ore in the future; extensive development for nickel mining is also forecast in the immediate future for Koniambo. Because of the apparently restricted range and projected degradation of habitat of this new species, it is here regarded as assignable to IUCN Red List Category Endangered and considered a high priority for conservation management.

Grammonus nagaredai, a New Viviparous Marine Fish (Ophidiiformes: Bythitidae) from the Hawaiian Islands
John E. Randall and Marc James Hughes, 137

Grammonus nagaredai is described as a new species of viviparous bythitid fish from two specimens collected from caves off O‘ahu and Hawai‘i at depths of 6–9 m. Grammonus yunokawai Nielsen, known from one specimen from a cave in 20 m in the Ryukyu Islands, is the most similar species, differing in having a deeper body, more convex nape, broader maxilla, longer predorsal length, and shorter pectoral fins.

Association Affairs, 147

Advertisements

Comments are closed.