West Coast Of South Island Research Articles

Post-seismic aggradation history of the West Coast, South Island, Aotearoa/New Zealand; dendrogeomorphological evidence and disaster recovery implications

In the active tectonic setting of Aotearoa/New Zealand, large earthquakes are a relatively frequent occurrence and pose particular threats to infrastructure and society in Westland, on the west coast of South Island. In order to better define the medium- and long-term (annual to decadal) implications of these threats, existing dendrochronological data were supplemented by several hundred tree-ring analyses from 14 hitherto unstudied living tree stands in five catchments; these were combined to compile a regional picture of the location, extent, and timing of major prehistoric reforestation episodes on the floodplains of the area. These episodes correspond well with known dates of large earthquakes in the area (ca. 1400, ca. 1620, 1717 and 1826 AD), and their extents are thus interpreted to reflect the sediment deliveries resulting from coseismic landsliding into mountain valleys, and their reworking by rivers to generate widespread avulsion, aggradation, floodplain inundation and forest death. This regional aggradation picture can underpin anticipation of, and planning for, the medium- to long-term societal impacts of future major West Coast earthquakes. The source location of the next major earthquake in the region is unknown, so any of the Westland floodplains could be affected by extensive, up to metre-scale river aggradation, together with avulsion and flooding, in its aftermath, and these could continue for decades. Re-establishment and maintenance of a functioning economy under these conditions will be challenging because roads, settlements and agriculture are mostly located on the floodplains. The differences in floodplain vegetation between prehistoric and future episodes will affect the rapidity and distribution of aggradation; response and recovery planning will need to consider this, together with the impacts of climate changes on river flows.

Genomic Stock Structure of the Marine Teleost Tarakihi (Nemadactylus macropterus) Provides Evidence of Potential Fine-Scale Adaptation and a Temperature-Associated Cline Amid Panmixia

Tarakihi (Nemadactylus macropterus) is an important fishery species with widespread distribution around New Zealand and off the southern coasts of Australia. However, little is known about whether the populations are locally adapted or genetically structured. To address this, we conducted whole-genome resequencing of 175 tarakihi from around New Zealand and Tasmania (Australia) to obtain a dataset of 7.5 million genome-wide and high-quality single nucleotide polymorphisms (SNPs). Variant filtering, FST-outlier analysis, and redundancy analysis (RDA) were used to evaluate population structure, adaptive structure, and locus-environment associations. A weak but significant level of neutral genetic differentiation was found between tarakihi from New Zealand and Tasmania (FST = 0.0054–0.0073, P ≤ 0.05), supporting the existence of at least two separate reproductive stocks. No clustering was detected among the New Zealand populations (ΦST < 0.001, P = 0.77). Outlier-based, presumably adaptive variation suggests fine-scale adaptive structure between locations around central New Zealand off the east (Wairarapa, Cape Campbell, and Hawke’s Bay) and the west coast (Tasman Bay/Golden Bay and Upper West Coast of South Island). Allele frequencies from 55 loci were associated with at least one of six environmental variables, of which 47 correlated strongly with yearly mean water temperature. Although genes associated with these loci are linked to various functions, the most common functions were integral components of membrane and cilium assembly. Projection of the RDA indicates the existence of a latitudinal temperature cline. Our work provides the first genomic insights supporting panmixia of tarakihi in New Zealand and evidence of a genomic cline that appears to be driven by the temperature gradients, together providing crucial information to inform the stock assessment of this species, and to widen the insights of the ecological drivers of adaptive variation in a marine species.

South Island West Coast orographic rainfall – a polarimetric radar view

South Island West Coast orographic rainfall – a polarimetric radar view

Probabilistic cascading multi-hazard risk assessment methodology using graph theory, a New Zealand trial

Probabilistic multihazard risk assessment from natural hazard is still a challenge today. Current limitations are the number of different hazards that can be included in the assessment, the capacity to output detailed spatial results and access to data for inverse fitting models. A novel quantitative multi-hazard framework is proposed which permit to model the interactions and triggering of perils of different types. Franz Josef on the West Coast of South Island, New Zealand, is used as a case study where the interactions and impacts of earthquake, rainfall, landslide, landslide dam and flooding hazards on the road network, stopbanks and housing is stochastically quantified. The results show that losses are earthquake-dominated, while rarer events show an influence of landsliding on the losses. Due to the complex interaction between hazards allowed by the modelling framework, while initial perils reach a “loss ceiling” with reducing probabilities, it also supercharges secondary perils that can cause greater and greater losses. Combining a network framework with iterative simulations is shown to provide inherent advantages by its discrete nature. In-depth exploration of the data outputs grants insight into the interconnected disaster system on a granular level. The risk assessment herein pointed out the seriousness of the multihazard threat to the Franz Josef township.

Deep soil flipping increases carbon stocks of New Zealand grasslands.

Sequestration of soil organic carbon (SOC) has been recognized as an opportunity to off‐set global carbon dioxide (CO2) emissions. Flipping (full inversion to 1–3 m) is a practice used on New Zealand's South Island West Coast to eliminate water‐logging in highly podzolized sandy soils. Flipping results in burial of SOC formed in surface soil horizons into the subsoil and the transfer of subsoil material low in SOC to the “new” topsoil. The aims of this study were to quantify changes in the storage and stability of SOC over a 20‐year period following flipping of high‐productive pasture grassland. Topsoils (0–30 cm) from sites representing a chronosequence of flipping (3–20 years old) were sampled (2005/07) and re‐sampled (2017) to assess changes in topsoil carbon stocks. Deeper samples (30–150 cm) were also collected (2017) to evaluate the changes in stocks of SOC previously buried by flipping. Density fractionation was used to determine SOC stability in recent and buried topsoils. Total SOC stocks (0–150 cm) increased significantly by 69 ± 15% (179 ± 40 Mg SOC ha‐1) over 20 years following flipping. Topsoil burial caused a one‐time sequestration of 160 ± 14 Mg SOC ha‐1 (30–150 cm). The top 0–30 cm accumulated 3.6 Mg SOC ha‐1 year‐1. The chronosequence and re‐sampling revealed SOC accumulation rates of 1.2–1.8 Mg SOC ha‐1 year‐1 in the new surface soil (0–15 cm) and a SOC deficit of 36 ± 5% after 20 years. Flipped subsoils contained up to 32% labile SOC (compared to <1% in un‐flipped subsoils) thus buried SOC was preserved. This study confirms that burial of SOC and the exposure of SOC depleted subsoil results in an overall increase of SOC stocks of the whole soil profile and long‐term SOC preservation.

Otolith microchemistry indicates regional phylopatry in the larval phase of an amphidromous fish (Gobiomorphus hubbsi)

ABSTRACTKnowledge of stock structure is key for the effective management of any fish species. Amphidromous fish, which live and spawn in freshwater but spend a pelagic larval period at sea, have typically been assumed to disperse widely during their larval phase, resulting in populations being sourced from a single unstructured larval pool. We used otolith microchemical analysis to examine the stock structure of bluegill bully (Gobiomorphus hubbsi), a declining amphidromous eleotrid endemic to New Zealand, along the west coast of South Island, New Zealand. Some drainages – even those in close proximity (c. 20 km) – were readily distinguishable based on otolith trace element concentrations, while little structure was evident between other geographically disparate locations. These results indicate that, at least in some cases, locally retained larvae, rather than a single unstructured larval pool, dominates recruitment. Management of bluegill bully and other amphidromous species must therefore consider the possibility of regionally distinct populations.

Biological control of ragwort in the New Zealand dairy sector: an ex-post economic analysis

ABSTRACTRagwort flea beetle, released in New Zealand in 1983, successfully controls ragwort, except in regions that receive very high rainfall such as the West Coast of South Island. If biocontrol had not been instigated, expenditure on ragwort control across New Zealand dairy farms in 2015 would have been an estimated NZ$64 million (adjusted for inflation and national herd size). Data on the impact of the flea beetle were used to estimate the national benefit from reduced control costs to dairy farms from biocontrol which, in 2015, was NZ$44 million. Ragwort biocontrol in New Zealand was attempted from 1926, and a net present value (NPV) analysis gave a 14:1 benefit:cost ratio, which remained positive in robust sensitivity testing. In New Zealand, the flea beetle was rejected as a biocontrol agent in 1933 on anecdotal evidence of its low impact on ragwort. This poor decision cost the dairy industry NZ$8.6 billion (NPV) from 1945 to 1999.

New Zealand Blue Whales: Residency, Morphology, and Feeding Behavior of a Little-Known Population

Abstract: Blue whales are infrequently reported from New Zealand and their taxonomic status is unclear. Here we present new information on the residency, external morphology, and habitat use of blue whales encountered in New Zealand waters. Thirty-one blue whales were photo-identified around the North and South Islands of New Zealand from 2004 to 2014 in seven different months of the year. One photographic match was found between June 2011 and March 2013: the first evidence that an individual blue whale has remained in or returned to New Zealand waters in different years and seasons. Observations of the external morphology of blue whales encountered off the South Island confirm that there is a shorter, non-Antarctic form of blue whale occurring near New Zealand. Body length and proportion, head shape, body condition, and skin condition were similar to Australian but not Antarctic blue whales. In 2013, feeding behavior was observed off the South Island's west coast and strong evidence of feeding was observ...

The phylogeography and population genetics of Polyprion oxygeneios based on mitochondrial DNA sequences and microsatellite DNA markers

A 488 base pair portion of the mitochondrial DNA (mtDNA) control region sequence from 294 individuals, and genotypes from 259 individuals using nine polymorphic microsatellite DNA loci, were used to investigate the phylogeography and population genetic structure of hapuku Polyprion oxygeneios from around New Zealand. The mtDNA data failed to detect any significant level of differentiation among sample sites. However, the microsatellite DNA analyses showed that individuals sampled from the west coast of the South Island (Hokitika) were genetically distinct from individuals sampled at all other New Zealand sites. These two groups might be representative of two separate populations of P. oxygeneios within New Zealand's Exclusive Economic Zone. Our results suggest that the west coast South Island P. oxygeneios fishery should continue to be managed as a separate stock.

Place invaders: Identity, place attachment and possum control in the South Island West Coast of New Zealand

The pesticide 1080 (sodium fluoroacetate) is used in New Zealand as the primary means of controlling the Australian brushtail possum, a problem pest. This study identified place and its role in identity as an important mediator of the perspectives of those that either strongly supported or opposed its use. Individuals' differing constructions of place influenced the way they perceived ‘others’ as a threat to their place and their views on control of its management and protection. This study may contribute to a new understanding of the importance of place in this and other similar natural resource disputes.

Late Pleistocene glacial stratigraphy of the Kumara-Moana region, West Coast of South Island, New Zealand

On the South Island of New Zealand, large piedmont glaciers descended from an ice cap on the Southern Alps onto the coastal plain of the West Coast during the late Pleistocene. The series of moraine belts and outwash plains left by the Taramakau glacier are used as a type section for interpreting the glacial geology and timing of major climatic events of New Zealand and also as a benchmark for comparison with the wider Southern Hemisphere. In this paper we review the chronology of advances by the Taramakau glacier during the last or Otira Glaciation using a combination of exposure dating using the cosmogenic nuclides 10Be and 36Cl, and tephrochronology. We document three distinct glacial maxima, represented by the Loopline, Larrikins and Moana Formations, separated by brief interstadials. We find that the Loopline Formation, originally attributed to Oxygen Isotope Chronozone 4, is much younger than previously thought, with an advance culminating around 24,900 ± 800 yr. The widespread late Pleistocene Kawakawa/Oruanui tephra stratigraphically lies immediately above it. This Formation has the same age previously attributed to the older part of the Larrikins Formation. Dating of the Larrikins Formation demonstrates there is no longer a basis for subdividing it into older and younger phases with an advance lasting about 1000 years between 20,800 ± 500 to 20,000 ± 400 yr. The Moana Formation represents the deposits of the last major advance of ice at 17,300 ± 500 yr and is younger than expected based on limited previous dating. The timing of major piedmont glaciation is restricted to between ∼25,000 and 17,000 yr and this interval corresponds to a time of regionally cold sea surface temperatures, expansion of grasslands at the expense of forest on South Island, and hemisphere wide glaciation.

Pasture growth and quality on West Coast dairy farms

Variation in rainfall, soil type and growing degree days across the West Coast creates wide variation in pasture growth rates. Farmers require pasture growth rate and quality information local to their environment to assist them with their on-farm decision making. Four farms in different geographical regions of the South Island's West Coast were monitored for four years to measure pasture growth rate (weekly, plate meter), nutrient composition (fortnightly, pre-grazing) and soil temperature (weekly, 10 cm depth). Average monthly pasture growth rate varied between the farms, however the seasonal trends were similar in all regions. There was significant variation in average monthly growth rate between years for individual farms. Soil temperature explained some of the trends in pasture growth rate, particularly in winter and early spring. Pasture quality was lowest during the summer months when neutral detergent fibre concentrations were greater. Pasture crude protein concentration exceeded 25% in 63% of the samples collected. Information reported will allow dairy farmers and their advisors to develop feed budgets and assess the appropriateness of the stocking rate and calving date of the farm relative to the annual pasture growth patterns. Times of year when the greatest variability occurs have now been identified for each sub-region. Keywords: West Coast, pasture growth, pasture quality, dairy

Pedogenesis, soil mass balance, phosphorus dynamics and vegetation communities across a Holocene soil chronosequence in a super-humid climate, South Westland, New Zealand

This study quantifies progressive pedogenesis under a super-humid climate on the west coast of South Island, New Zealand. It focuses on soil morphology, pedogenic oxides, soil mass balance, phosphorus transformation and linking pedogenesis trajectories to vegetation communities. The study comprises a set of dune ridges of a coastal sand dune complex covered by unmodified conifer (podocarp)-angiosperm forest. The surface ages of the chronosequence range from 370 y to 6500 y. Rapid podzolisation is characteristic for the study area. Within 1000 y, soils reach the Spodosol stage with typical eluvial–illuvial horizons and mobilisation of Fe and Al. This period is also characterised by the most rapid losses of total phosphorus at a rate of 110 g m − 2 ky − 1 , a relative loss of 41%. Beyond 3000 y changes in soil chemistry and losses for all nutrients markedly slow. Soil mass balance shows that the 6500 y soil has lost 75% total P, 62% K, 52% Ca and 54% Na. Soil P fractions substantially change across the gradient. High leaching losses of apatite and non-occluded P in the first hundreds of years coincide with accumulation of organic and occluded inorganic forms in the topsoil and subsoil, which mitigate total P loss. Beyond 1000 y of pedogenesis, all P fractions decline at similar rates to low, more persistent levels with apatite/non-occluded P being the dominant P form after 6500 y of pedogenesis. This incipient steady state is assumed to be sustained by the advection of parent material-derived P through surface lowering and reduced biological cycling. Vegetation communities change from more diverse communities on young and less impoverished soils in the first 1000 y to less diverse and less variable communities beyond 1000 y of ecosystem development. The soil evolution-correlated vegetation changes documented in this study are consistent with general schemes of vegetation succession for the west coast of South Island.

Distribution of Hector's dolphin (Cephalorhynchus hectori) off the west coast, South Island, New Zealand, with implications for the management of bycatch

AbstractTo support decision making on placement of protected areas for Hector's dolphin on New Zealand's South Island west coast, we conducted three aerial surveys documenting the species’ distribution in this area. The first survey was designed to quantify alongshore distribution and abundance, and revealed a patchy distribution with a central zone of high density. Two further surveys, in summer and winter, focused on this central zone to quantify offshore distribution in detail. Dolphin density decreased with increasing distance offshore, with no dolphins sighted more than 6 nmi from the coast or in water deeper than 60 m. There was no significant difference in offshore distribution between summer and winter surveys conducted in 2003 (G= 2.15, df = 5, P= 0.83). Partial Mantel tests showed that dolphin distribution was best explained by distance from the coast, in both summer (rM= 0.088, P= 0.0001) and winter (rM= 0.054, P= 0.0004). Spatial contouring techniques showed that small (ca. 5 km) and medium scale (ca. 50 km) patterns of density in the central zone were remarkably consistent, suggesting year‐round residency. Based on these data, the current restrictions on commercial gillnetting protect 60% or less of the dolphin population for 3 mo of the year.

Sedimentology of latero-frontal moraines and fans on the west coast of South Island, New Zealand

Exposures through the LGM latero-frontal moraine loops at sites along the west coast of South Island, New Zealand reveal a depositional environment that was dominated by the progradation of steep fronted, debris flow-fed fans, manifest in crudely stratified to massive diamictons, arranged in sub-horizontal to steeply dipping clinoforms and containing discontinuous bodies of variably sorted, stratified sediment (LFA 1). The fans were constructed by debris-covered glaciers advancing over outwash plains, as recorded by well stratified and horizontally bedded gravels, sands and diamicts (LFA 0). The ice-contact slopes of the fans are offlapped by retreat phase deposits in the form of glacilacustrine depo-centres (LFA 2), which record the existence of moraine-dammed lakes. Interdigitation of lake rhythmites and subaerial to subaqueous sediment gravity flow deposits documents intense debris-flow activity on unstable moraine/fan surfaces. Glacier readvances in all catchments are documented by glacitectonic disturbance and localized hydrofracturing of LFA 2, followed by the emplacement of schist-dominated debris flow-fed fans (LFA 3) inside and over the top of the earlier latero-frontal moraine/fan loops. Contorted and disturbed bedding in LFA 3 reflects its partial deposition in supraglacial positions. Clast lithologies in LFAs 1 and 3 reveal that two distinct transport pathways operated during moraine construction, with an early period of latero-frontal fan construction involving mixed lithologies and a later period of ice-contact/supraglacial fan construction dominated by schist lithologies from the mountains. These two periods of deposition were separated by a period of moraine abandonment and paraglacial reworking of ice-contact slopes to produce LFA 2. The occurrence of LFA 3 at all sites indicates that the glacier readvance phase responsible for its deposition was not localized or glacier-specific, and involved the transfer of large volumes of schist, possibly due to rock slope failures, onto glacier surfaces. The absence of any sediment that could be unequivocally classified as subglacial till reflects the dominance of debris flow and glacifluvial processes in latero-frontal moraine construction in this hyper-humid west coast setting.

Assessing the effectiveness of conservation management decisions: likely effects of new protection measures for Hector's dolphin (Cephalorhynchus hectori)

Abstract Fisheries bycatch affects many species of marine mammals, seabirds, turtles and other marine animals. New Zealand's endemic Hector's dolphins overlap with gillnet and trawl fisheries throughout their geographic range. The species is listed as Endangered by the IUCN. In addition, the North Island subspecies has been listed as Critically Endangered. Estimates of catch rates in commercial gillnets from an observer programme (there are no quantitative estimates of bycatch by amateur gillnetters or in trawl fisheries) were used in a simple population viability analysis to predict the impact of this fishery under three scenarios: Option (A) status‐quo management, (B) new regulations announced by the Minister of Fisheries in 2008 and (C) total protection. Uncertainty in estimates of population size and growth rate, number of dolphins caught and other model inputs are explicitly included in the analysis. Sensitivity analyses are carried out to examine the effect of variation in catch rate and the extent to which fishing effort is removed from protected areas but displaced to unprotected areas. These methods are applicable to many other situations in which animals are removed from populations, whether deliberately (e.g. fishing) or not (e.g. bycatch). The current Hector's dolphin population is clearly depleted, at an estimated 27% of the 1970 population. Population projections to 2050 under Options A and B predict that the total population is likely to continue declining. In the case of Option B this is driven mainly by continuing bycatch due to the much weaker protection measures on the South Island west coast. Without fishing mortality (Option C) all populations are projected to increase, with the total population approximately doubling by 2050 and reaching half of its 1970 population size in just under 40 years. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Phylogeography and ecological niche modelling implicate coastal refugia and trans‐alpine dispersal of a New Zealand fungus beetle

The Last Glacial Maximum (LGM) severely restricted forest ecosystems on New Zealand's South Island, but the extent of LGM distribution for forest species is still poorly understood. We used mitochondrial DNA phylogeography (COI) and ecological niche modelling (ENM) to identify LGM refugia for the mycophagous beetle Agyrtodes labralis (Leiodidae), a forest edge species widely distributed in the South Island. Both the phylogenetic analyses and the ENM indicate that A. labralis refuged in Kaikoura, Nelson, and along much of the South Island's west coast. Phylogeography of this species indicates that recolonization of the largely deforested east and southeast South Island occurred in a west-east direction, with populations moving through the Southern Alps, and that the northern refugia participated little in interglacial population expansion. This contradicts published studies of other New Zealand species, in which recolonization occurs in a north-south fashion from many of the same refugia.

Catch-quota balancing in mixed-fisheries: a bio-economic modelling approach applied to the New Zealand hoki (Macruronus novaezelandiae) fishery

Managing adequately the exploitation of commercial species subject to technical interactions is a key step towards the ecosystem approach to fisheries. We evaluate here, using a bio-economic modelling approach building on the ISIS-Fish simulation platform, the relative impact of total allowable commercial catches (TACC) and of taxes appli- cable to over-quota landings (deemed value) on the sustainability of a selection of species exploited by the New Zealand hoki (Macruronus novaezelandiae) fishery. We investigate some aspects of the hoki mixed fisheries, consisting of four fleets and nineteen metiers, by considering the technical interactions between hoki and Southern hake (Merluccius aus- tralis). The dynamics of effort allocation were modelled using gravity model, using value per unit of effort (VPUE) as attractivity coefficient. Several management scenarios, based on different levels of TACC, effort limits and deemed value have been defined. The impact of these strategies on spawning biomass and catches has been investigated. The results confirm that the deemed value may, in combination with TACC, be an efficient management tool. By increasing the hoki deemed value, we could somehow limit the decrease in the hoki TACC needed to harvest Western hoki sustain- ably. Constraining hoki fishing also restricts Southern hake fishing in the Chatham Rise and in the West Coast South Island, but leads to increased targeting of this species in the Sub-Antarctic area. The relative costs of renting/buying quota or paying the deemed value are most constraining when the hoki TACC is at relatively low level and when the hoki deemed value is more than 1.5 times the current value.

Unreported bycatch in the New Zealand West Coast South Island hoki fishery

Abstract There are recognised benefits to managing fisheries by individual transferable quotas (ITQs), but ITQs may increase incentives to discard fish. Trawl data from government-observed trawlers in the New Zealand hoki fishery were used to predict catches of unobserved vessels. These predictions were compared with the catches unobserved vessels reported. Unobserved vessels’ reported catches were significantly different to observed vessels’ catches. There was clear evidence of misreporting in the hoki fishery. Misreporting deprives stakeholders of rentals, distorts catch statistics, and threatens the integrity of ITQ systems. If reporting is similarly biased in other fisheries, the issue cannot be safely ignored.

Isolation and identification of a cis-C 8-diol-ester of okadaic acid from Dinophysis acuta in New Zealand

A cis-isomer of a C 8-diol ester of okadaic acid ( 1) was isolated during large-scale purification of pectenotoxins (PTXs) from extracts of Dinophysis acuta collected from the west coast of South Island, New Zealand. The compound was identified by NMR spectroscopic and liquid chromatography-mass spectrometry (LC-MS) studies, and is the first reported cis-isomer of an okadaic acid C 8-diol-ester identified in Dinophysis. The more abundant trans-C 8-diol ester of okadaic acid ( 2) isolated from the same Dinophysis extract was rapidly hydrolyzed to okadaic acid in vitro by the supernatant from green-lipped mussel hepatopancreas.