Tectonic effects of a subducting aseismic ridge: The subduction of the Nazca Ridge at the Peru Trench

A 1987 survey of the offshore Peru forearc using the SeaMARC II seafloor mapping system reveals that subduction of the Nazca Ridge has resulted in uplift of the lowermost forearc by as much as 1500 m. This uplift is seen in the varied depths of two forearc terraces opposite the subducting ridge. Uplift of the forearc has caused fracturing, minor surficial slumping, and increased erosion through small canyons and gullies. Oblique trending linear features on the forearc may be faults with a strike-slip component of motion caused by the oblique subduction of the Nazca Ridge. The trench in the zone of ridge subduction is nearly linear, with no re-entrant in the forearc due to subduction of the Nazca Ridge. Compressional deformation of the forearc due to subduction of the ridge is relatively minor, suggesting that the gently sloping Nazca Ridge is able to slide beneath the forearc without significantly deforming it. The structure of the forearc is similar to that revealed by other SeaMARC II surveys to the north, consisting of: 1) a narrow zone (10 to 15 km across) of accreted material making up the lower forearc; 2) a chaotic middle forearc; 3) outcropping consolidated material and draping sediment on the upper forearc; and 4) the smooth, sedimented forearc shelf.The subducting Nazca plate and the Nazca Ridge are fractured by subduction-induced faults with offsets of up to 500 m. Normal faulting is dominant and begins about 50 km from the trench axis, increasing in frequency and offset toward the trench. These faults are predominantly trench-parallel. Reverse faults become more common in the deepest portion of the trench and often form at slight angles to the trench axis.Intrusive and extrusive volcanic areas on the Nazca plate appear to have formed well after the seafloor was created at the ridge crest. Many of the areas show evidence of current scour and are cut by faulting, however, indicating that they formed before the seafloor entered the zone of subduction-induced faulting.     

From oblique subduction to intra-continental transpression: Structures of the southern Kermadec-Hikurangi margin from multibeam bathymetry,side-scan sonar and seismic reflection

The southern Kermadec-Hikurangi convergent margin, east of New Zealand, accommodates the oblique subduction of the oceanic Hikurangi Plateau at rates of 4–5 cm/yr. Swath bathymetry and sidescan data, together with seismic reflection and geopotential data obtained during the GEODYNZ-SUD cruise, showed major changes in tectonic style along the margin. The changes reflect the size and abundance of seamounts on the subducting plateau, the presence and thickness of trench-fill turbidites, and the change to increasing obliquity and intracontinental transpression towards the south. In this paper, we provide evidence that faulting with a significant strike-slip component is widespread along the entire 1000 km margin. Subduction of the northeastern scrap of the Hikurangi Plateau is marked by an offset in the Kermadec Trench and adjacent margin, and by a major NW-trending tear fault in the scarp. To the south, the southern Kermadec Trench is devoid of turbidite fill and the adjacent margin is characterized by an up to 1200 m high scarp that locally separates apparent clockwise rotated blocks on the upper slope from strike-slip faults and mass wasting on the lower slope. The northern Hikurangi Trough has at least 1 km of trench-fill but its adjacent margin is characterized by tectonic erosion. The toe of the margin is indented by 10–25 km for more than 200 km, and this is inferred to be the result of repeated impacts of the large seamounts that are abundant on the northern Hikurangi Plateau. The two most recent impacts have left major indentations in the margin. The central Hikurangi margin is characterized by development of a wide accretionary wedge on the lower slope, and by transpression of presubduction passive margin sediments on the upper slope. Shortening across the wedge together with a component of strike-slip motion on the upper slope supports an interpretation of some strain partitioning. The southern Hikurangi margin is a narrow, mainly compressive belt along a very oblique, apparently locked subduction zone.     

The application of multivariate statistical methods to phytoplankton counts from the Hauraki Gulf,New Zealand

The phytoplankton population from a station in the Jellicoe Channel area of the Hauraki Gulf, New Zealand, was fairly constant, in terms of total population and species composition, throughout the year. Correspondence analysis enabled us to identify 3 groups of species. The largest of these comprised the core species which were present most of the time and included some, such as the coccolithophores, with a strongly seasonal occurrence. The species in the second group were mainly large centric diatoms and appeared for short periods during the winter months, apparently brought in by incursions of oceanic water. The third group of species occurred between April 1970 and October 1971 when there was a period of unusually warm weather: the winds were lighter and more often blowing onshore and this perhaps led to warmer, less nutrient‐rich surface waters being brought into the Gulf.     

From Vagrant to Resident: occurrence,residency and births of leopard seals (Hydrurga leptonyx) in New Zealand waters

ABSTRACT

In contrast to previous reports that leopard seals (Hydrurga leptonyx) are rare vagrants to New Zealand, we show that this species is a regular member of the marine fauna of this region. We present a first analysis from the New Zealand Leopard Seal Database – an extensive collation of 2,711 records of leopard seals within New Zealand between 1200 and 2018. Of these records, 51.2% (n?=?1,408) were photographic. Leopard seal sightings have increased over time and been reported in all seasons and regions of New Zealand. Sightings are predominantly of adult individuals of good or excellent body condition, which differs to previous hypotheses suggesting that leopard seals visiting New Zealand shores are primarily juvenile animals in poor health condition. A total of 176 unique individuals have been identified in the New Zealand Leopard Seal Catalogue between 2014 and 2018 and preliminary results indicate that numbers per annum have continued to increase over time. Three leopard seal births and a number of juvenile animals (34% of the NZ records) have been documented. Considering the information presented here and the current definitions in the New Zealand Threat Classification System, the threat status of leopard seals within New Zealand waters should be reclassified from Vagrant to Resident.     

Input of river-derived sediment to the New Zealand continental shelf: I. Mass

The input of river-borne sediments to the New Zealand continental shelf has been calculated for all the major rivers and basins in New Zealand. South Island yields 284 ± 40 × 10⁶ tonnes per year of sediment from a land area of 152 977 km² and North Island yields 105 ± 9·4 × 10⁶ tonnes per year from a land area of 114 621 km². Particularly high discharges are noted off the west coast of South Island and east coast of North Island and result in higher offshore sedimentation there. The data are compatible with measured sedimentation rates on the New Zealand continental shelf. The specific sediment yield from South Island is amongst the highest previously recorded.     

Compliance costs and the small fisher: A study of exiters from the New Zealand fishery

Over 3000 predominantly small-scale fishers have exited the New Zealand's quota management system (QMS) between its inception in 1986 and 2000. This study, based on the Ministry of Fisheries database and a questionnaire sent to the exiters, establishes that compliance costs in general, and those specifically related to the QMS, were one of the most consistent reasons for exit. Uncertainty about future QMS policy and the high cost of quota were also significant factors. It appears that the small fishers’ perception of high compliance cost can be supported by industry data.     

New species of benthopelagic copepod Xantharus (Calanoida: Scolecitrichidae) from the upper slope,eastern central New Zealand

Xantharus Andronov, 1981 is reported, for the first time from New Zealand, from the upper slope (306 m) off the southeastern coast of North Island (41°04.10′S, 176°22.05′E). Xantharus cryeri n. sp. females differ from the three known species by a combination of characters: antennules that extend to the distal border of pedigerous somite 2; ancestral segment XVIII of the antennule with 1 seta; mandible basis with 3 setae; maxilla endite 1 with 5 setae; leg 1 basis with inner distal border lined with small spinules; and leg 5 is squat, with all segments as long as wide and the 2 terminal spine‐like extensions of the terminal segment approximately as long as the articulated, inner, subterminal spine.     

国外对海底电缆管道违法行为处罚对我国的启示 ——以新西兰和澳大利亚为例

近年来,随着海洋油气资源的大规模开发以及跨海电力和通信需求的增加,我国海底电缆管道建设得到迅速发展,近海海底电缆管道分布愈来愈密集,同时与之相关的违法行为也日益增多。目前,我国尚未出台海底电缆管道保护法,现有的处罚规定较为分散、模糊,且处罚力度小,甚至处罚规定之间存在混乱和矛盾的问题,导致难以对海底电缆管道违法行为实施有效打击。澳大利亚和新西兰作为海洋管理经验相对成熟的国家,对海底电缆管道的法律保护较为成熟,其中对海底电缆管道违法行为的处罚分类和方式等,有诸多值得我国学习之处。基于此,文章从违法行为处罚角度深入分析我国海底电缆管道管理与保护的相关制度现状,介绍新西兰和澳大利亚海底电缆管道法律制度概况及处罚规定的特点并与我国进行比较,为完善我国海底电缆管道违法行为的处罚规定和今后的海底电缆管道立法提出了在《中华人民共和国刑法》中增设破坏海底电缆管道罪;制定《海底电缆管道法》等建议。     

Phyllosoma larvae of Jasus edwardsii (Hutton) (Crustacea: Decapoda: Palinuridae) and their distribution off the east coast of the North Island,New Zealand

The complete series of phyllosoma larval stages of spiny lobster lasus edwardsii are described. Eleven stages are recognised from specimens captured in plankton samples collected along a transect extending 185 km east of Castlepoint, North Island, New Zealand between July 1969 and December 1971. A table of distinguishing characteristics and a key for identification of stages are presented. First stage larvae occur between August and October and last stage larvae about 15 months later. Mortality through the phyllosoma stages is estimated to be 98%. Early stage larvae occur mainly inshore in Southland Current water in the upper 5 m, and later stage larvae occur more frequently offshore in East Cape Current water at 40–60 m depth.     

Catastrophic reduction of the oyster,Tiostrea chilensis (Bivalvia: Ostreidae), in Foveaux Strait,New Zealand,due to infestation by the protistan Bonamia sp.

Between 1985 and 1992, mortality due to infestation by the protistan Bonamia sp. severely reduced the numbers of the oyster, Tiostrea chilensis in Foveaux Strait, New Zealand. In 1990, two dredge surveys gave relative estimates, and a dive survey an absolute estimate, of the size of this oyster population; this allowed us to estimate dredge efficiency precisely. This estimate was used to re‐evaluate the dredge survey of 1975–76 and relate the size of the population in 1990 to that in 1975. By 1990 the population density had declined by 67% while a dredge survey in 1992 showed that the population density had declined by 91% from 1975. A dredge survey in 1993 showed that the population had increased slightly (but not significantly) over the 1992 level. By 1992 the population had probably been reduced below 10% of the virgin level. The fishery was closed in 1993 to allow the population to rebuild. The population surveys have followed stratified random and grid pattern sampling designs and the merits of the designs and methodology are discussed.