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Earthquake-induced habitat migration in a riparian spawning fish has implications for conservation management
Abstract
• Galaxias maculatus is a riparian spawning fish that supports an important recreational fishery in New Zealand, with spawning habitat requirements strongly structured by salinity gradients at river mouths. This study reports changes to the spawning habitat following a series of large earthquakes that resulted in the widespread deformation of ground surfaces in the vicinity of waterways.
• Assessments of habitat recovery focused on two river systems, the Avon and Heathcote, with pre‐disturbance data available over a 20‐year period. Recovery dynamics were assessed by field survey and mapping of spawning habitat prior to and on seven occasions after the disturbance event. Riparian land‐use and management patterns were mapped and analysed using overlay methods in a geographical information system (GIS).
• Habitat migration of up to 2 km occurred in comparison with all previous records, and several anthropogenic land uses have become threats because of changed patterns of co‐occurrence. Incompatible activities now affect more than half of the spawning habitat in both rivers, particularly in areas managed for flood control purposes and recreational use.
• The results are an example of landscape‐scale responses to salinity and water‐level changes driven by tectonic dynamics. These dynamics are not the source of the stress per se; rather, they have increased the exposure of the species to pre‐existing stressors.
• The case illustrates important principles for managing subtle, yet widespread, change. Adaptive conservation methods and investments in information are priorities for avoiding management failure following environmental change.
Supplementary resource (1)
Data
November 2020
... six months before migrating back into fresh water to mature into adults (McDowall & Eldon 1980). These characteristics have pronounced implications for conservation around the need to ensure connectivity between life stages and their associated the habitat requirement, which are susceptible to changes over time (McDowall 1992(McDowall , 1999Orchard et al. 2018b).. ...
... The reduction of lowland aquatic habitat through historical drainage (Ausseil et al. 2008;Larned et al. 2018), has undoubtedly contributed to īnanga decline. Īnanga are also reliant on riparian habitat for spawning (Benzie 1968), and this contributes to their vulnerability to land-use change (Hickford et al. 2010;Hickford & Schiel 2011;Orchard et al. 2018b). Important considerations for the recovery of īnanga populations in the contemporary environment include the condition and accessibility of instream habitat for adult fish, and the protection of spawning grounds as critical habitat for this particular life stage. ...
... Many of the known spawning sites are located close to the upstream limit of salt water in lowland tidal waterways (Burnet 1965;Taylor 2002). Recent research has found that spawning may occur over a relatively large salinity range (Orchard et al. 2018b). In some rivers this increases the size of the area that requires protection for spawning (Orchard & Hickford 2020), and is also reflected in the spatio-temporal dynamics of spawning locations which may 'move around' within a rivermouth system. ...
A range of literature was reviewed and summary information compiled to support the development of a conservation prioritisation strategy for two migratory fish species (īnanga and shortjaw kōkopu) on the South Island’s West Coast. This strategy will support the development of migratory species recovery plans under the government-funded Bio18 programme being implemented by the Department of Conservation. Existing datasets were evaluated and a desktop assessment completed to provide an initial characterisation of conservation value and threat intensity at regional scale. Recommendations are provided for a progressive conservation prioritisation strategy using the best available data. Results of the desktop assessment are presented in this summary report and include a set of spatial data and maps prepared for the use of operational staff who will lead implementation of this project in the coming years.
Findings of the desktop analyses included the characterisation of existing information on conservation value and the distribution of threats to the security of these species. Spatial disparities between species distribution models (SDMs) produced on different versions of the River Environment Classification were identified and are described. Model discrepancies may indicate the influences of differences in environmental predictor variables, areas of heightened uncertainty due to environmental conditions, or both.
Since both models were able to simulate training data with high levels of accuracy, the uncertainties relate mostly to their ability to extrapolate into new spatial domains. This suggests a useful role for targeted ground-truthing surveys, both within areas of model congruence and also model discrepancy, and is recommended for inclusion in the Bio18 operational work. For the purposes of prioritising actions, these results also indicate challenges for the adoption of model predictions as indicators of conservation value. To address this, a linked-model approach is proposed that takes into account both data sources. A four-tier ‘priority class’ classification is assigned based on the strength of evidence for species presence.
... Unfortunately, the specific location of īnanga spawning habitat on the margins of lowland waterways often results in spatial overlap with human activities. During the spawning season, these may pose threats to successful spawning by reducing the availability of suitable habitat or impact on the survival rate of eggs after spawning has occurred (Hickford & Schiel 2011a;Orchard et al. 2018a). Common examples include riverbank engineering, drainage and other hydrological modifications, and disturbance activities such as vegetation clearance and grazing. ...
... Salinity effects also have the potential to drive spatial variability in spawning locations. For example, Orchard et al. (2018a) found a strong relationship between the upstream limit of salt water and the upstream limit of spawning in Christchurch waterways, despite that there is no physiological barrier to spawning taking place in entirely fresh water (Orchard et al. 2018a). In this study, the re-routing of Flowery Creek since the December 2019 storms may have generated movement in the preferred locations of spawning due to salinity effects in consideration of the major changes to waterway connections in this location (Fig. 10). ...
... Salinity effects also have the potential to drive spatial variability in spawning locations. For example, Orchard et al. (2018a) found a strong relationship between the upstream limit of salt water and the upstream limit of spawning in Christchurch waterways, despite that there is no physiological barrier to spawning taking place in entirely fresh water (Orchard et al. 2018a). In this study, the re-routing of Flowery Creek since the December 2019 storms may have generated movement in the preferred locations of spawning due to salinity effects in consideration of the major changes to waterway connections in this location (Fig. 10). ...
This report summarises results from field surveys of the Arahura River lagoon system to support the Arahura River Restoration Project on the South Island’s West Coast. The focus of these surveys was to improve the understanding of locations used by īnanga (Galaxias maculatus) for spawning. Īnanga is a migratory fish that is the most abundant of the five galaxiid species that support New Zealand’s whitebait fishery. At the Arahura River the fishery has important cultural values for Te Rūnanga o Ngāti Waewae and the Arahura Marae is located close to the river a short distance from the coast. Investigations were undertaken to characterise the tidal range and locate spawning sites to provide a baseline for future monitoring and support restoration work. Prior to this project, there were no previously reported spawning sites in the river system despite there being an abundance of suitable habitat for adult fish.
... Although the biogeography of G. maculatus spawning grounds has been relatively well characterised in tidal rivers where they are strongly influenced by spring high tides (Benzie 1968;Taylor 2002;Orchard et al. 2018aOrchard et al. , 2018b, many nontidal rivers also support fish populations. In New Zealand, these rivers are particularly common on the east coast of the South Island and south-eastern North Island where they are often associated with mixed sand-gravel beaches at the coast (Kirk 1980(Kirk , 1991. ...
... In the first month of the study (February 2019) intensive eggs searches and environmental measurements were completed in all catchments by a team of three researchers in all catchments beginning at the rivermouth and working upstream, with the distribution of spawning sites (if any) being unknown. Although March and April were expected to be the months of peak spawning activity based on previous work in tidal waterways in the Canterbury region (Orchard et al. 2018a(Orchard et al. , 2018b, significant spawning activity was detected in February that was apparently triggered by a rain event. This finding helped to establish the general location of spawning in the study catchments and define areas for repeat surveys in the following months. ...
... This highlights the need for further research on the characteristics of recruitment sources, and in turn emphasises the need for a solid understanding of the biogeography of spawning grounds, which are the ultimate larval source (McDowall 2010b). In New Zealand, there is a noticeable information gap on the characteristics of non-tidal rivers despite a considerable body of work on G. maculatus spawning in estuarine locations (McDowall 1968(McDowall , 1991Hickford and Schiel 2011;Orchard et al. 2018a), and contrasts with numerous studies on landlocked G. maculatus populations in Australian and South American rivers and lakes (Pollard 1971;Cussac et al. 2004;Chapman et al. 2006;Barriga et al. 2007). Recent advances in New Zealand have included the identification of non-diadromous recruitment in amphidromous galaxiid species, including G. maculatus, where suitable freshwater pelagic habitat was present in rivers open to the sea (Hicks et al. 2017;David et al. 2019). ...
Galaxias maculatus is a declining amphidromous fish that supports New Zealand’s culturally-important whitebait fisheries targeting the migratory juvenile stage. Spawning ground protection and rehabilitation is required to reverse historical degradation and improve fisheries prospects alongside conservation goals. Although spawning habitat has been characterised in tidal rivers, there has been no previous study of spawning in non-tidal rivermouths that are open to the sea. We assessed seven non-tidal rivers over four months using census surveys to quantify spawning activity, identify environmental cues, and characterise fundamental aspects of the biogeography of spawning grounds. Results include the identification of compact spawning reaches near the rivermouths. Spawning events were triggered by periods of elevated water levels that were often of very short duration suggesting that potential lunar cues were less important, and that rapid fish movements had likely occurred within the catchment prior to spawning events. Spawning grounds exhibited consistent vertical structuring above typical low-flow levels, with associated horizontal translation away from the river channel leading to increased exposure to anthropogenic stressors and associated management implications for protecting the areas concerned. These consistent patterns provide a sound basis for advancing protective management at non-tidal rivermouths. Attention to flood management, vegetation control, and bankside recreational activities is needed and may be assisted by elucidating the biogeography of spawning grounds. The identification of rapid responses to environmental cues deserves further research to assess floodplain connectivity aspects that enable fish movements in emphemeral flowpaths, and as a confounding factor in commonly-used fish survey techniques.
... For a large part of their development period this places the eggs in a terrestrial environment where they are vulnerable to a variety of anthropogenic threats (McDowall & Charteris 2006). Examples include disturbance effects associated with mowing, grazing and trampling, flood management activities such as vegetation clearance and dredging, and the construction of retaining walls and other engineering works (Hickford & Schiel 2011;Orchard et al. 2018a). ...
... This task is best done by the original observers (rather than a 3 rd party), potentially in association with re-establishment of the NISD. There are also other known spawning site records not addressed in this project, including a large number of sites identified in Christchurch waterways in connection with post-earthquake research (Orchard 2017;Orchard & Hickford 2016;Orchard & Hickford 2018;Orchard et al. 2018a). However, these waterways are well represented in the NISD (Taylor 2002). ...
Īnanga (Galaxias maculatus) is a highly valued diadromous fish that supports a popular recreational fishery. However, the species is currently listed in the ‘at risk - declining’ category of the New Zealand Threat Classification System in recognition of historic declines. The scope of this project included development of a draft methodology for guiding decisions on re-survey (and new survey) priority for inanga spawning sites, and a methodology for assigning conservation priorities to spawning sites. These were applied to develop a GIS shapefile layer showing conservation prioritisation results within defined spatial areas, in this case being the Department of Conservation's diadromous fish management units.
... Salinity is essential for the development of eggs, success of hatchlings, and the survival of young fish (Fonds, 1979;Spies & Steele, 2016). Moreover, large scale changes in salinity can affect the spawning area (Orchard et al., 2018). The eggs and larval abundance of M. cephalus. ...
Identifying the breeding grounds of fishes is crucial for the sustainable management of fisheries resources. The present study is aimed at identifying the potential breeding ground of Mugil cephalus along the estuary of the North Mumbai coast. A total of 1197 specimens of M. cephalus, including 546 eggs, 271 larvae, 235 juveniles, and 235 adults, were collected from four sampling stations in the Karanja estuary between January to October 2022. Water quality parameters, plankton dynamics in the estuary, and the reproductive and feeding biology of M. cephalus were also examined. The eggs, larvae, juveniles, and adults were identified using traditional morpho-meristic and DNA barcoding techniques. The results revealed a potential spawning ground of M. cephalus in the Karanja estuary. The results of reproductive biology also confirmed the occurrence of matured fishes during May–July. The abundance of eggs and larvae at the estuary’s mouth and the presence of juveniles and mature individuals of M. cephalus dominantly in the Karanja estuary from May to July infer the presence of a spawning site. It is also recorded that M. cephalus spawn in higher salinity (35 ppt) and seawater temperature (33 °C) where the hatching of offspring takes place successfully. This study emphasizes the significance of DNA barcoding in guiding routine monitoring surveys and demonstrates its usefulness when combined with these techniques in identifying fish spawning grounds. The study findings will serve as baseline information to develop effective conservation and management strategies and protect the ideal spawning stock.
... Hydrological changes also caused the loss of coastal wetlands and shorebird habitat in areas of relative sea-level rise as characteristic ecosystems moved landward [2,12,22]. In uplifted areas, impacts included shifts in the salt water intrusion characteristics of lowland waterways leading to the downstream migration of coastal zonation patterns and key habitats [23,24]. ...
Widespread mortality of intertidal biota was observed following the 7.8 Mw Kaikoura earthquake in November 2016. To understand drivers of change and recovery in nearshore ecosystems, we quantified the variation in relative sea-level changes caused by tectonic uplift and evaluated their relationships with ecological impacts with a view to establishing the minimum threshold and overall extent of the major effects on rocky shores. Vertical displacement of contiguous 50 m shoreline sections was assessed using comparable LiDAR data to address initial and potential ongoing change across a 100 km study area. Co-seismic uplift accounted for the majority of relative sea-level change at most locations. Only small changes were detected beyond the initial earthquake event, but they included the weathering of reef platforms and accumulation of mobile gravels that continue to shape the coast. Intertidal vegetation losses were evident in equivalent intertidal zones at all uplifted sites despite considerable variation in the vertical displacement they experienced. Nine of ten uplifted sites suffered severe (>80%) loss in habitat-forming algae and included the lowest uplift values (0.6 m). These results show a functional threshold of c.1/4 of the tidal range above which major impacts were sustained. Evidently, compensatory recovery has not occurred—but more notably,
previously subtidal algae that were uplifted into the low intertidal zone where they ought to persist (but did not) suggests additional post-disturbance adversities that have contributed to the overall effect. Continuing research will investigate differences in recovery trajectories across the affected area to identify factors and processes that will lead to the regeneration of ecosystems and resources.
... Studies have shown that lower or higher salinities can interfere with egg development and the hatching processes, and reduce the survival rate of larvae and juveniles [48,52]. Drastic changes in salinity can cause large-scale changes in the spawning area [53]. In the PRE, the optimum salinity for egg density was 17-35‰, and the egg density decreased when SSS was lower than 17‰ (Figure 2c). ...
Spawning grounds are important areas for fish survival and reproduction, and play a key role in the supplement of fishery resources. This study investigated environmental effects on the spatiotemporal variability of spawning ground in the Pearl River Estuary (PRE), China, using the generalized additive model (GAM), based on satellite remote sensing (sea surface temperature (SST), chlorophyll-a concentration (Chl-a), sea surface salinity (SSS), depth), and in situ observations. Results showed that 39.8% of the total variation in fish egg density was explained by these factors. Among them, the most important factor was SST, accounting for 14.3%, followed by Depth, SSS, and Chl-a, with contributions of 9.7%, 8.5%, and 7.3%, respectively. Spawning grounds in the PRE were mainly distributed in the waters with SST of 22 °C, depth of 30–50 m, SSS of 16–35 ‰, and Chl-a of 6–15 mg/m3. From spring to summer, the spawning ground moved from the outlet of the PRE to the east. The distribution of the spawning ground in the PRE was mainly affected by the Pearl River Plume (PRP), Guangdong Coastal Current (GCC), and monsoons in this area.
“Natural” disasters (also known as geophysical disasters) involve physical processes that have a direct or indirect impact on humans. These events occur rapidly and may have severe consequences for resident flora and fauna as their habitat undergoes dramatic and sudden change. Although most studies have focused on the impact of natural disasters on humans and terrestrial systems, geophysical disasters can also impact aquatic ecosystems. Here we provide a synthesis on the effects of the most common and destructive geophysical disasters on aquatic systems (life and habitat). Our approach spanned realms (i.e., freshwater, estuarine, marine) and taxa (i.e., plants, vertebrates, invertebrates, microbes) and included floods, droughts, wildfires, hurricanes/cyclones/typhoons, tornadoes, dust storms, ice storms, avalanches (snow), landslides, volcanic eruptions, earthquakes (including limnic eruptions), tsunamis, and cosmic events. Many geophysical disasters have dramatic effects on aquatic systems. The evidence base is somewhat limited for some natural disasters because transient events (e.g., tornadoes, floods) are difficult to study. Most natural disaster studies focus on geology/geomorphology and hazard assessment for humans and infrastructure. However, the destruction of aquatic systems can impact humans indirectly through loss of food security, cultural services or livelihoods. Many geophysical disasters interact in complex ways (e.g., wildfires often lead to landslides and flooding) and can be magnified or otherwise mediated by human activities. Our synthesis reveals that geophysical events influence aquatic ecosystems, often in negative ways, yet systems can be resilient provided that effects are not compounded by anthropogenic stressors. It is difficult to predict or prevent geophysical disasters but understanding how aquatic ecosystems are influenced by geophysical events is important given the inherent connection between peoples and aquatic ecosystems.
Galaxias maculatus is a declining amphidromous fish that supports culturally-important whitebait fisheries in New Zealand and elsewhere in the Pacific. As a largely annual species, the seasonal productivity of spawning grounds has a strong influence on the availability of recruits. Spawning ground protection is urgently required to reverse historical degradation and improve prospects for the maintenance of sustainable fisheries. Although spawning habitat has been well characterised in tidal rivers where it is structured by water level changes on spring high tides, there has been no previous study of spawning in non-tidal rivermouths. We assessed seven non-tidal rivers over four months using a census survey approach to quantify spawning activity, identify environmental cues, and characterise fundamental aspects of the biogeography of spawning grounds. We report conclusive results that include a) identification of compact spawning reaches near the rivermouths, b) triggering of spawning events by periods of elevated water levels that were often of very short duration, suggesting that potential lunar cues were less important and that rapid fish movements had likely occurred within the catchment prior to spawning events, and c) consistent vertical structuring of spawning grounds above typical low-flow levels with associated horizontal translation away from the river channel, leading to increased exposure to anthropogenic stressors and associated management implications for protecting the areas concerned. These consistent patterns provide a sound basis for advancing the management of non-tidal rivermouths. Attention to flood management, vegetation control, and bankside recreational activities is required and may be assisted by quantifying spawning ground biogeography. The identification of rapid responses to environmental cues deserves further research to assess implications for floodplain connectivity management to support fish movements in emphemeral flowpaths, and as a potential source of bias in commonly-used fish survey methodologies.
Earthquake experts have stated that the western coastal region of Sumatra Island is one of the most earthquake-prone areas in Indonesia. In response to this fact, disaster mitigation education programs must involve preparedness and preparedness before an earthquake occurs. This preliminary study aims to describe the profile of integration of biological studies, especially earthquake precursors in animal ecology lectures at the Biology Department of the Faculty of Natural Sciences (FMIPA) Padang State University (UNP). Data collection is done through analysis of lecture documents, surveys and interviews, and data analysis is done descriptively by referring to Hsieh and Shannon (2015) in Malekipour et al ., (2017). The instruments used were a checklist of lecture content, semi-structured questionnaires, and interview guidelines. The results of the study show that the lectures on animal ecology in the Department of Biology FMIPA UNP have included the application of basic ecological concepts in everyday life. However, the area of application of these competencies is limited to conservation goals and how to treat animals in the student environment. The study of animal behaviour as a marker of earthquakes has never been integrated and applied in lectures on theory and practicum. Students’ knowledge of animal behaviour in an earthquake event is mostly obtained independently from books and articles. From the results of the study, it can be concluded that the lecture on animal ecology is a potential lecture to examine the relationship between animal behaviour and earthquake disasters. Furthermore, it can be recommended integration of the behaviour of earthquake-related animals in animal ecology lectures for prospective biology teacher students, especially in practical learning. It aims to improve the ability and contribution of prospective teacher students involved in anticipating the impact of the earthquake on students living in disaster-prone areas, especially on the west coast of Sumatra.
This report presents the results of a cultural environmental health assessment of Te Ihutai / Avon-Heathcote Estuary and its catchment undertaken by representatives from Te Ngāi Tūāhuriri Rūnanga and Mahaanui Kurataiao Ltd between March and May 2012.
The purpose of the 2012 State of the Takiwā programme was to undertake a cultural assessment of Te Ihutai (Avon-Heathcote Estuary) and its tributaries, the Ōtākaro (Avon) and Ōpāwaho (Heathcote) rivers at 31 sites within the catchment. This mahi is a continuation of the work initiated by Pauling et al. (2007) in their previous State of the Takiwā assessment, and in addition provides an indication of the post-earthquake state of these waterways in relation to Ngāi Tahu values.
The same State of the Takiwā methodology as used in the 2007 programme was used. Two additional fishing survey techniques using hīnaki (set nets) and drag nets were employed to extend the fish survey component to a greater number of sites. In addition a new site was added in Mt Vernon valley to provide an example of a hill-country stream site within the monitoring programme since there are several such streams within the Ōpāwaho/ Heathcote catchment.
The results from this assessment indicate that the catchment is in a state of poor cultural health. As was found in the previous State of the Takiwā programme (Pauling et al., 2007) the different assessments conducted indicated that a range of culturally relevant aspects are degraded, including both in-stream and riparian values. When compared with the 2007 study the 2012 results suggest that the catchment is in a similar state of cultural health. However modest improvements noted at some sites whilst further degradation was recorded at others which in some cases was related to earthquake damage.
Although some adverse impacts associated with earthquake damage were expected, the results clearly indicated that many recommendations from the previous State of the Takiwā programme have not been implemented. Consequently, management responses needed to protect and enhance Ngāi Tahu values include all of the recommendations from the 2007 programme. In particular, improvement in water quality and habitat quality including the restoration and conservation of indigenous vegetation in the riparian zone is urgently required. In addition, there is a need to take Ngāi Tahu values into account in the planning and implementation of earthquake repair activities. This includes the need for comprehensive monitoring to establish whether important aspects of waterway recovery are being achieved as the earthquake repair process progresses.
Airborne light detection and ranging (LiDAR) data were acquired over the coastal city of Christchurch, New Zealand, prior to and throughout the 2010 to 2011 Canterbury Earthquake Sequence. Differencing of pre-and post-earthquake LiDAR data reveals land surface and waterway deformation due to seismic shaking and tectonic displacements above blind faults. Shaking caused floodplain subsidence in excess of 0.5 to 1 m along tidal stretches of the two main urban rivers, greatly enhancing the spatial extent and severity of inundation hazards posed by 100-year floods, storm surges, and sea-level rise. Additional shaking effects included river channel narrowing and shallowing, due primarily to liquefaction, and lateral spreading and sedimen-tation, which further increased flood hazard. Differential tectonic movement and associated narrowing of downstream river channels decreased channel gradients and volumetric capacities and increased upstream flood hazards. Flood mitigation along the large regional Waimakariri River north of Christchurch may have, paradoxically, increased the long-term flood hazard in the city by halting long-term aggradation of the alluvial plain upon which Christchurch is situated. Our findings highlight the potential for moderate magnitude (MW 6–7) earthquakes to cause major topo-graphic changes that influence flood hazard in coastal settings.
Anthropogenic impacts, including urbanization, deforestation, farming, and livestock grazing have altered riparian margins worldwide. One effect of changes to riparian vegetation is that the ground-level light, temperature, and humidity environment has also been altered. Galaxias maculatus, one of the most widely distributed fishes of the southern hemisphere, lays eggs almost exclusively beneath riparian vegetation in tidally influenced reaches of rivers. We hypothesized that the survival of these eggs is greatly affected by the micro-environment afforded by vegetation, particularly relating to temperature, humidity and UVB radiation. We experimentally reduced riparian vegetation height and altered shading characteristics, tracked egg survival, and used small ground-level temperature, humidity and UVB sensors to relate survival to ground-level effects around egg masses. The ground-level physical environment was markedly different from the surrounding ambient conditions. Tall dense riparian vegetation modified ambient conditions to produce a buffered temperature regime with constant high relative humidity, generally above 90%, and negligible UVB radiation at ground-level. Where vegetation height was reduced, frequent high temperatures, low humidity, and high UVB irradiances reduced egg survival by up to 95%. Temperature effects on egg survival were probably indirect, through reduced humidity, because developing eggs are known to survive in a wide range of temperatures. In this study, it was remarkable how such small variations in relatively small sites could have such a large effect on egg survival. It appears that modifications to riparian vegetation and the associated changes in the physical conditions of egg laying sites are major mechanisms affecting egg survival. The impacts associated with vegetational changes through human-induced disturbances are complex yet potentially devastating. These effects are particularly important because they affect a very small portion of habitat that is required to complete the life history of a species, despite the wide distribution of adults and juveniles across aquatic and marine environments.
Many species traverse multiple habitats across ecosystems to complete their life histories. Degradation of critical, life stage-specific habitats can therefore lead to population bottlenecks and demographic deficits in sub-populations. The riparian zone of waterways is one of the most impacted areas of the coastal zone because of urbanisation, deforestation, farming and livestock grazing. We hypothesised that sink populations can result from alterations of habitats critical to the early life stages of diadromous fish that use this zone, and tested this with field-based sampling and experiments. We found that for Galaxias maculatus, one of the most widely distributed fishes of the southern hemisphere, obligate riparian spawning habitat was very limited and highly vulnerable to disturbance across 14 rivers in New Zealand. Eggs were laid only during spring tides, in the highest tidally influenced vegetation of waterways. Egg survival increased to >90% when laid in three riparian plant species and where stem densities were great enough to prevent desiccation, compared to no survival where vegetation was comprised of other species or was less dense. Experimental exclusion of livestock, one of the major sources of riparian degradation in rural waterways, resulted in quick regeneration, a tenfold increase in egg laying by fish and a threefold increase in survival, compared to adjacent controls. Overall, there was an inverse relationship between river size and egg production. Some of the largest rivers had little or no spawning habitat and very little egg production, effectively becoming sink populations despite supporting large adult populations, whereas some of the smallest pristine streams produced millions of eggs. We demonstrate that even a wide-ranging species with many robust adult populations can be compromised if a stage-specific habitat required to complete a life history is degraded by localised or more diffuse impacts.
Here, we describe a methodology for quantifying the spawning habitat of īnanga (Galaxias maculatus), a protected native fish species. Our approach is demonstrated with a survey of the Heathcote/Ōpāwaho following the Canterbury earthquakes that produced unexpected findings. Spawning habitat was detected over a 2.5 km reach and the area occupied by spawning sites (75m²) was much larger than in previous records (ca. 21m²). Sites dominated by the invasive Phalaris arundinaceae were found to support high egg numbers. Spawning has not previously been recorded on this species and it is identified in the literature as a threat to spawning habitat. Considerable spatio-temporal variation was also detected in the location of spawning sites and pattern of egg production. Together, these aspects illustrate the need for a comprehensive survey methodology to reliably quantify spawning habitat. The Heathcote/Ōpāwaho example shows the utility of our census approach for achieving this, and supporting habitat conservation objectives.
Seismic shaking and tectonic deformation during strong earthquakes can trigger widespread environmental effects. The severity and extent of a given effect relates to the characteristics of the causative earthquake and the intrinsic properties of the affected media. Documentation of earthquake environmental effects in well-instrumented, historical earthquakes can enable seismologic triggering thresholds to be estimated across a spectrum of geologic, topographic and hydrologic site conditions, and implemented into seismic hazard assessments, geotechnical engineering designs, paleoseismic interpretations, and forecasts of the impacts of future earthquakes. The 2010-2011 Canterbury earthquake sequence (CES), including the moment magnitude (Mw) 7.1 Darfield earthquake and Mw 6.2, 6.0, 5.9, and 5.8 aftershocks, occurred on a suite of previously unidentified, primarily blind, active faults in the eastern South Island of New Zealand. The CES is one of Earth’s best recorded historical earthquake sequences. The location of the CES proximal to and beneath a major urban centre enabled rapid and detailed collection of vast amounts of field, geospatial, geotechnical, hydrologic, biologic, and seismologic data, and allowed incremental and cumulative environmental responses to seismic forcing to be documented throughout a protracted earthquake sequence. The CES caused multiple instances of tectonic surface deformation (≥ 3 events), surface manifestations of liquefaction (≥ 11 events), lateral spreading (≥ 6 events), rockfall (≥ 6 events), cliff collapse (≥ 3 events), subsidence (≥ 4 events), and hydrological (10s of events) and biological shifts (≥ 3 events). The terrestrial area affected by strong shaking (e.g. peak ground acceleration (PGA) ≥ 0.1-0.3 g), and the maximum distances between earthquake rupture and environmental response (Rrup), both generally increased with increased earthquake Mw, but were also influenced by earthquake location and source characteristics. However, the severity of a given environmental response at any given site related predominantly to ground shaking characteristics (PGA, peak ground velocities) and site conditions (water table depth, soil type, geomorphic and topographic setting) rather than earthquake Mw. In most cases, the most severe liquefaction, rockfall, cliff collapse, subsidence, flooding, tree damage, and biologic habitat changes were triggered by proximal, moderate magnitude (Mw ≤ 6.2) earthquakes on blind faults. CES environmental effects will be incompletely preserved in the geologic record and variably diagnostic of spatial and temporal earthquake clustering. Liquefaction feeder dikes in areas of severe and recurrent liquefaction will provide the best preserved and potentially most diagnostic CES features. Rockfall talus deposits and boulders will be well preserved and potentially diagnostic of the strong intensity of CES shaking, but challenging to decipher in terms of single versus multiple events. Most other phenomena will be transient (e.g., distal groundwater responses), not uniquely diagnostic of earthquakes (e.g., flooding), or more ambiguous (e.g. biologic changes). Preliminary paleoseismic investigations in the CES region indicate recurrence of liquefaction in susceptible sediments of ~ 100 to 300 yr, recurrence of severe rockfall event(s) of ca. 6,000 to 8,000 yr, and recurrence of surface rupturing on the largest CES source fault of ca. 20,000 to 30,000 yr. These data highlight the importance of utilizing multiple proxy datasets in paleoearthquake studies. The severity of environmental effects triggered during the strongest CES earthquakes was as great as or equivalent to any historic or prehistoric effects recorded in the geologic record. We suggest that the shaking caused by rupture of local blind faults in the CES comprised a ‘worst case’ seismic shaking scenario for parts of the Christchurch urban area. Moderate Mw blind fault earthquakes may contribute the highest proportion of seismic hazard, be the most important drivers of landscape evolution, and dominate the paleoseismic record in some locations on Earth, including locations distal from any identified active faults. A high scientific priority should be placed on improving the spatial extent and quality of ‘off-fault’ shaking records of strong earthquakes, particularly near major urban centres.
New Zealand whitebait comprises the migratory juveniles of five species of native Galaxias. The most abundant of these is inanga, Galaxias maculatus. In 1987, the Department of Conservation (DOC) commissioned nationwide field surveys to identify (with the aim of protecting) inanga spawning sites, with data to be collated into a database administered by the National Institute of Water and Atmospheric Research Ltd (NIWA). The database currently holds 562 records from a total of 194 inanga spawning sites. Spawning sites have been located in every coastal DOC conservancy except Auckland. Further work to identify spawning sites is required, particularly in Northland, Auckland, Waikato, Wellington and Southland Conservancies. At least some protection work has been carried out in every conservancy where spawning has been located. Inanga spawning usually occurs on autumnal spring tides, with the nationwide peak spawning activity taking place 2 or 3 days after the new or full moon; however, some spawning may also occur in spring. Preferred spawning sites appear to be the banks of tidally-influenced flow-stable waterways, and tributaries and small creeks in very large catchments, often where there are embayments and confluences. Inanga spawn gregariously amongst inundated bankside vegetation. Consequently, spawning sites and eggs are prone to damage by cattle trampling or grazing. Exotic vegetation commonly associated with inanga spawning includes a number of grass and herb communities, often dominated by tall fescue (Festuca arundinacea). A wide variety of native plants are also associated with inanga spawning. These include New Zealand rush (wiwi, Juncus gregiflorus), bull rush (raupo, Typha orientalis), flax (harakeke, Phormium tenax) and toetoe (Cortaderia richardii). The spread of reed sweet grass (Glyceria maxima) and other exotic grass species unfavourable for fish spawning into spawning areas is of concern.
Riparian vegetation has been compromised worldwide by anthropogenic stressors, including urbanization and livestock grazing. In New Zealand, one consequence has been a reduction in the obligate riparian spawning habitat of Galaxias maculatus. This diadromous species forms the basis of an important fishery where juveniles are caught as they migrate into freshwater. Spawning success of G. maculatus is closely associated with the nature of available riparian habitat. We used a field experiment in a rural stream to test whether livestock grazing limits egg production and whether there is a lag in increased egg production after protection from grazing because of the recovery time of riparian vegetation. In a separate experiment in an urban stream we tested whether improved riparian management can increase egg production. Livestock exclusion produced an immediate and long-lasting increase in the height and density of riparian vegetation with reduced fluctuations in the ground-level physical environment, and positive changes to the density and survival of eggs. After 4 years, egg densities in exclosures were 400 times greater than in grazed controls and egg survival had doubled. Mowing riparian vegetation 2 months prior to spawning reduced egg densities by 75% and survival by 25%. Our experiments showed that altering grazing and mowing in spawning sites produced dense riparian vegetation, that this improved the microsite environment and resulted in greatly increased egg deposition and survival over several years. This clearly indicates that the single most effective step in rehabilitating G. maculatus spawning habitat is a simple reduction in grazing/mowing pressure.
1. Known diadromous fish number <250 species, and <1.5% of fish species.
2. They comprise ca. 3% of species regarded as ‘endangered’.
3. Amongst them are species of great importance to fisheries, and out of proportion to their number.
4. They occupy complexes of connected habitats between or through which passage is needed at two or more life history phases.
5. They therefore pose special problems for conservation which relate to: a. diversity of habitats; b. huge areas occupied; c. the spatial separation of the various habitats used; d. need for fish passage; e. often heavy exploitation.
6. These problems are often the opposite of those experienced with species that occupy local habitats and which are in danger of local extirpation.
Several diadromous New Zealand and Australian species of Galaxias are now known, or suspected, to deposit their eggs amongst riparian vegetation or substrates either supratidally in estuaries or in forested streams in locations that are only temporarily submerged by elevated water levels. The eggs develop in a humid atmosphere and hatch when the egg deposition sites are resubmerged; a significant role for agitation in stimulating hatching seeming likely. There are risks from the eggs becoming dehydrated, and also from a failure by water to resubmerge the eggs before they have exhausted their energy resources. Hatching is triggered by elevated flows, perhaps being an outcome of agitation of the eggs. Elevated flows may also increase the rate of downstream transport of the larvae, facilitating survival during dispersal to sea from spawning sites in streams that may be long distances inland. Hatching during flood events may favour survival of the larvae because turbid flows may provide ‘cover’ for the larvae as they emigrate to sea. Risks from egg predation by aquatic predators may be replaced by risks from terrestrial predators.
Mortality from predation during the early life-stages of most teleost fishes can be extreme, and many species have developed specialized spawning strategies to reduce predation. In the diadromous fish Galaxias maculatus there is terrestrial development of eggs which restricts aquatic predation, but exposes them to terrestrial predators and a more extreme physical environment. We hypothesised that exotic slugs (Milax gagates, Deroceras panormitanum and D. reticulatum) and mice (Mus musculus) reduce the survival of developing eggs and tested this using laboratory and field predation experiments and sampling. We also tested the effects of riparian vegetation composition and density on egg survival. We found that exotic slugs (M. gagates and D. panormitanum) reduced the survival of eggs in laboratory experiments, but that neither slugs nor mice affected egg survival in field experiments. Egg densities were positively associated with the stem density of riparian vegetation and the thickness of the aerial root-mat. Egg survival was also positively associated with stem density and aerial root-mat thickness, but was not density-dependent. Although predation by mice and slugs did not appear to be a major cause of egg mortality in our study locations, mortality dynamics could be different in areas with greater densities of predators. Abiotic factors are important in egg survival and these are heavily modified by the height and density of riparian vegetation. It is likely that G. maculatus egg survival, therefore, co-varies with the composition of riparian vegetation.
Abstract Spatial prioritization techniques are applied in conservation-planning initiatives to allocate conservation resources. Although typically they are based on ecological data (e.g., species, habitats, ecological processes), increasingly they also include nonecological data, mostly on the vulnerability of valued features and economic costs of implementation. Nevertheless, the effectiveness of conservation actions implemented through conservation-planning initiatives is a function of the human and social dimensions of social-ecological systems, such as stakeholders' willingness and capacity to participate. We assessed human and social factors hypothesized to define opportunities for implementing effective conservation action by individual land managers (those responsible for making day-to-day decisions on land use) and mapped these to schedule implementation of a private land conservation program. We surveyed 48 land managers who owned 301 land parcels in the Makana Municipality of the Eastern Cape province in South Africa. Psychometric statistical and cluster analyses were applied to the interview data so as to map human and social factors of conservation opportunity across a landscape of regional conservation importance. Four groups of landowners were identified, in rank order, for a phased implementation process. Furthermore, using psychometric statistical techniques, we reduced the number of interview questions from 165 to 45, which is a preliminary step toward developing surrogates for human and social factors that can be developed rapidly and complemented with measures of conservation value, vulnerability, and economic cost to more-effectively schedule conservation actions. This work provides conservation and land management professionals direction on where and how implementation of local-scale conservation should be undertaken to ensure it is feasible.
Conservation assessment is a rapidly evolving discipline whose stated goal is the design of networks of protected areas that represent and ensure the persistence of nature (i.e., species, habitats, and environmental processes) by separating priority areas from the activities that degrade or destroy them. Nevertheless, despite a burgeoning scientific literature that ever refines these techniques for allocating conservation resources, it is widely believed that conservation assessments are rarely translated into actions that actually conserve nature. We reviewed the conservation assessment literature in peer-reviewed journals and conducted survey questionnaires of the authors of these studies. Two-thirds of conservation assessments published in the peer-reviewed scientific literature do not deliver conservation action, primarily because most researchers never plan for implementation. This research–implementation gap between conservation science and real-world action is a genuine phenomenon and is a specific example of the “knowing–doing gap” that is widely recognized in management science. Given the woefully inadequate resources allocated for conservation, our findings raise questions over the utility of conservation assessment science, as currently practiced, to provide useful, pragmatic solutions to conservation planning problems. A reevaluation of the conceptual and operational basis of conservation planning research is urgently required. We recommend the following actions for beginning a process for bridging the research–implementation gap in conservation planning: (1) acknowledge the research–implementation gap is real, (2) source research questions from practitioners, (3) situate research within a broader conservation planning model, (4) expand the social dimension of conservation assessments, (5) support conservation plans with transdisciplinary social learning institutions, (6) reward academics for societal engagement and implementation, and (7) train students in skills for “doing” conservation.
Resumen: La evaluación de la conservación es una disciplina que evoluciona rápidamente y cuya meta es el diseño de redes de áreas protegidas que representen y aseguren la persistencia de la naturaleza (i.e., hábitats de especies y procesos ambientales) mediante la separación de áreas prioritarias de las actividades que las degradan o destruyen. Sin embargo, no obstante una creciente literatura científica que refina estas técnicas para la asignación de recursos para la conservación, es amplia la creencia de que las evaluaciones de la conservación raramente se traducen en acciones que realmente conservan la naturaleza. Revisamos la literatura sobre evaluación de la conservación en revistas con revisión por pares y aplicamos cuestionarios a los autores de estos estudios. Dos tercios de las evaluaciones de conservación publicadas en la literatura científica revisada por pares no consideran acciones de conservación, primariamente porque la mayoría de los investigadores nunca planean la implementación. Esta brecha investigación-implementación entre la ciencia de la conservación y la acción en el mundo real es un fenómeno genuino y es un ejemplo específico de la “brecha conocer-actuar” que es ampliamente reconocida en la ciencia del manejo. Debido a los recursos tristemente inadecuados que se asignan a la conservación, nuestros resultados originan preguntas sobre la utilidad de la evaluación de la conservación, como es practicada actualmente, para proporcionar soluciones pragmáticas a los problemas de planificación de la conservación. Se requiere urgentemente una reevaluación de las bases conceptuales y operativas de la investigación para la planificación de la conservación. Recomendamos las siguientes acciones para iniciar un proceso para reducir la brecha investigación-implementación en la planificación de la conservación (1) reconocer que la brecha investigación-implementación es real, (2) obtener preguntas de investigación con profesionales, (3) situar la investigación en un modelo de planificación de la conservación más amplio, (4) expandir la dimensión social de las evaluaciones de la conservación, (5) apoyar los planes de conservación con instituciones de aprendizaje social transdisciplinarias, (6) recompensar a académicos por compromisos con la sociedad y su implementación y (7) entrenar a estudiantes en habilidades para ‘hacer’ conservación.
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