Using diversity indices to measure changes in prey choice at the Shag River Mouth site, southern New Zealand

2001 ◽  
Vol 11 (1-2) ◽  
pp. 101-111 ◽  
Author(s):  
Lisa Nagaoka
Keyword(s):  
New Zealand ◽  
River Mouth ◽  
Diversity Indices ◽  
Prey Choice

Marine Terraces Reveal Complex Near-Shore Upper-Plate Faulting in the Northern Hikurangi Margin, New Zealand

2020 ◽  
Vol 110 (2) ◽  
pp. 825-849 ◽  
Author(s):  
Nicola J. Litchfield ◽  
Kate J. Clark ◽  
Ursula A. Cochran ◽  
Alan S. Palmer ◽  
Joshu Mountjoy ◽  
...  
Keyword(s):  
New Zealand ◽  
Plate Boundary ◽  
River Mouth ◽  
Seismic Reflection Data ◽  
Subduction Earthquakes ◽  
Reflection Data ◽  
Marine Terraces ◽  
Need To Evaluate ◽  
Near Shore ◽  
Recent Earthquakes

ABSTRACT Recent earthquakes involving multiple fault ruptures highlight the need to evaluate complex coastal deformation mechanisms, which are important for understanding plate boundary kinematics and seismic and tsunami hazards. We compare ages and uplift of the youngest Holocene marine terraces at Puatai Beach and Pakarae River mouth (∼10  km apart) in the northern Hikurangi subduction margin to examine whether uplift is the result of subduction earthquakes or upper-plate fault earthquakes. From stepped platform-cliff morphology, we infer uplift during 2–3 earthquakes and calculate an average uplift-per-event of 2.9±0.5  m at Puatai Beach and 2.0±0.5  m at Pakarae River mouth. Radiocarbon ages from the youngest beach deposit shells on each terrace and a tephra coverbed on one terrace constrain the timing of earthquakes to 1770–1710, 1100–910, and 420–250 cal. B.P. at Puatai Beach, and 1490–1290 and 660–530 cal. B.P. at Pakarae River mouth. The ages differ at each site indicating uplift is neither the result of subduction earthquakes nor single upper-plate fault earthquakes. A reinterpretation of new and existing bathymetry and seismic reflection data, combined with dislocation modeling, indicates that near-shore fault segmentation is more complex than previously thought and ruptures likely involve multiple upper-plate faults. Future updates of the New Zealand National Seismic Hazard Model should revise the northern Hikurangi subduction seismic sources so that rupture does not uplift Puatai Beach and Pakarae River mouth and include new near-shore upper-plate faults as multifault sources.

scholarly journals Diet-Derived Variations in Radiocarbon and Stable Isotopes: A Case Study from Shag River Mouth, New Zealand

Radiocarbon ◽  
2005 ◽  
Vol 47 (3) ◽  
pp. 367-375 ◽  
Author(s):  
Thomas Higham ◽  
Atholl Anderson ◽  
Christopher Bronk Ramsey ◽  
Christine Tompkins
Keyword(s):  
New Zealand ◽  
River Mouth ◽  
Freshwater Species ◽  
Faunal Remains ◽  
Cultural Sites ◽  
Wide Range ◽  
Dietary Variation ◽  
Early Human ◽  
Dietary Food

Accelerator mass spectrometry (AMS) determinations of rat bones from natural and cultural sites in New Zealand have produced ages at odds with the accepted date for early human settlement by over 1000 yr. Since rats are a human commensal, this implies either an earlier visitation by people or problems with the reliability of the AMS determinations. One explanation for the extreme ages is dietary variation involving movement of depleted radiocarbon through dietary food chains to rats. To investigate this, we 14C dated fauna from the previously well-dated site of Shag River Mouth. The faunal remains were of species that consumed carbon derived from a variety of environments within the orbit of the site, including the estuary, river, land, and sea. The 14C results showed a wide range in age among estuarine and freshwater species. Terrestrial and marine organisms produced ages within expectations. We also found differences between bone dated using the Oxford ultrafiltration method and those treated using the filtered gelatin method. This implies that contamination could also be of greater importance than previously thought.

scholarly journals Macrofauna Communities In The Marine Section Of Ba Lai Estuary, Ben Tre Province

2020 ◽  
Vol 4 (1) ◽  
pp. first
Author(s):  
Thai Thanh Tran ◽  
Nguyen Thi My Yen ◽  
Tran Thi Hoang Yen ◽  
Pham Thanh Luu ◽  
Ngo Xuan Quang
Keyword(s):  
Distribution Pattern ◽  
Environmental Changes ◽  
Economic Value ◽  
River Mouth ◽  
Wiener Index ◽  
Diversity Indices ◽  
Left Bank ◽  
Dam Impact ◽  
The Right ◽  
Macrofauna Communities

Macrofauna communities in Ba Lai estuary, Ben Tre province were investigated in three transects from the river mouth to the dam construction, in the order from the right, middle to the left bank. The community characteristics such as the composition, density, biodiversity, and the distribution pattern were recorded and analyzed. The results showed that the macrofauna communities in the marine section part of Ba Lai river consisted of 76 species belonging to 3 phyla: Mollusca, Arthropoda, and Annelida. In this study, it was notable that a high economic value of Ben Tre Clam (Meretrix lyrata) presented in the Ba Lai estuary with a density of 3160 ind /m2 on the right bank. The highest density was recorded in the mid transect of the river, followed by the right and the left (2907 +/- 4298, 1813 +/- 2056; 1730 +/- 1590 ind /m2, respectively). The biodiversity of macrofauna communities was measured by the species richness, Shannon – Wiener index, and Pielou's evenness. Diversity indices illustrated that the middle bank had the highest biodiversity. However, the statistical analysis results showed that the density and biodiversity indices in these transects were not significantly different. The main reason might be due to Ba Lai dam impact, which has been accreting alluvial, causing these locations gradually being similar in the environmental conditions. The distribution pattern of benthic macrofauna communities in this study should be considered as a typical distribution of benthos in rivers affected by dams. Macrofauna communities which gave rapid responses to environmental changes should be used as a bioindicator.

Challenges for Diadromous Fishes in a Dynamic Global Environment

2009 ◽  
Keyword(s):  
Growth Rate ◽  
New Zealand ◽  
River Mouth ◽  
Fish Length ◽  
The South ◽  
Growth Rings ◽  
Daily Growth ◽  
The North ◽  
Average Size ◽  
Feeding Grounds

<em>Abstract</em>.- Juvenile inanga <em>Galaxias maculatus </em>are the main species in the New Zealand whitebait fishery. Whitebait were sampled throughout the spring fishing season (August-November 2002) as they entered the mouths of two New Zealand rivers, one in the North Island and the other more than 500 km south in the South Island. Fish length, date of arrival at the river mouth, and the number of daily growth rings in otoliths were used to determine age, hatch date, and mean growth rate at sea. Backdating indicated that whitebait hatched between mid-March and late July 2002, spent 104-168 d at sea, and experienced overall growth rates ranging from 0.24 to 0.41 mm/d. Mean length on return to the river mouth ranged from 45 to 55 mm total length and varied among months as well as between rivers. The duration of the oceanic rearing period (in days) was inversely related to growth rate, implying that the time of return to freshwater is endogenously determined. However, average size at river entry was larger for the South Island than for the North Island fish because, on average, the South Island fish remained at sea for a further 10 d. A longer journey from marine feeding grounds back to the coast rather than a delay at the river mouth before entry would account for this difference, but colder oceanic waters in the south may also play a role.

scholarly journals Problems Associated with the AMS Dating of Small Bone Samples: The Question of the Arrival of Polynesian Rats to New Zealand

Radiocarbon ◽  
2004 ◽  
Vol 46 (1) ◽  
pp. 207-218 ◽  
Author(s):  
T F G Higham ◽  
R E M Hedges ◽  
A J Anderson ◽  
C Bronk Ramsey ◽  
B Fankhauser
Keyword(s):  
New Zealand ◽  
River Mouth ◽  
Important Variable ◽  
Bone Collagen ◽  
Late Archaic ◽  
Potential Influence ◽  
15Th Century ◽  
Amino Acid Profiles ◽  
Ams Dating ◽  
Small Bone

We have AMS dated samples of Pacific rat (Rattus exulans) bone “collagen” and filtered gelatin samples from the prehistoric site of Shag River Mouth, New Zealand. The age of occupation of this site has previously been determined based on 50 radiocarbon measurements. The site dates to the late Archaic phase of southern New Zealand prehistory (about 650–500 BP; 14th–15th century AD). The results of rat bones which we have dated produce a range in ages, from about 980–480 BP, a difference we attribute to a combination of effects. Pretreatment appears to be an important variable, with results showing differences in 14C age between the progressive “collagen” and filtered gelatin chemical treatment stages. Amino acid profiles suggest there is a proteinaceous but non-collagenous contaminant which is removed by the more rigorous pretreatment. Stable isotopes vary between pretreatments, supporting the removal of a contaminant, or contaminants. Variation in δ15N values imply a range in uptake of dietary protein, and might suggest a potential influence from the local aquatic environment or the consumption of marine-derived protein. Rats are opportunistic, omnivorous mammals, and, therefore, obtain carbon from a variety of reservoirs and so we ought to expect that in environments where there is a variety of reservoirs, these will be exploited. Taken together, the results show that rat bone AMS 14C determinations vary in comparison with the established age of the site, but are in notably better agreement with non-collagenous data than in previously published determinations (Anderson 1996).

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