Biology subjects

Schiel, D. R.

Publications and source records attributed to Schiel, D. R..

5 recordsLinked to original sources

bioRxiv2023

Re-thinking recreational fishing - how a natural disaster presents insights and opportunities for achieving sustainability and equity objectives

P[a]ua (abalone) are a treasured natural resource that supports a recreational fishery worth $2 million annually to the local economy of the Kaik[o]ura district in New Zealand. From 2016, the fishery was closed for 5 years in response to widespread mortality caused by co-seismic uplift in the 7.8 Mw Kaik[o]ura earthquake. The fishery re-opened in 2021 for an initial 3-month open season with a recreational fishing allocation of 5 tonnes. We constructed scenario models informed by fishing pressure observations and show that this catch target was severely exceeded (by a factor of 9-10). We then evaluated a range of alternative management settings involving daily bag limit adjustments and temporal controls that shift opening times away from high visitation periods and favourable weather conditions as a means to reduce peaks in fishing pressure. Temporal control strategies reduced seasonal catch by up to 45% in comparative analyses using the 2021 fishing effort as a base-case scenario, and can be used in combination with daily bag limit adjustments and longer-term protected areas. When applied to a Total Allowable Catch, these solutions also produce equity effects that increase the proportional allocation accruing to local fishers. We discuss the potential role of these insights in designing temporal controls for managing seasonal influxes of fishing effort driven by tourism, and highlight the role of natural disasters and recovery periods as a trigger for new policy directions. In this case, they were needed to address an unexpected loss that illustrates a more general need for reliable fishery management that is responsive to environmental change in the long term.

ecology↗

bioRxiv2022

Managing beach access and vehicle impacts following reconfiguration of the landscape by a natural hazard event

After New Zealands 7.8 Mw Kaik[o]ura earthquake in late 2016 an unexpected anthropogenic effect involved increased motorised vehicle access to beaches. We show how these effects were generated by landscape reconfiguration associated with coastal uplift and widening of high-tide beaches, and present analyses of the distribution of natural environment values in relation to vehicle movements and impacts. Access changes led to extensive vehicle tracking in remote areas that had previously been protected by natural barriers. New dunes formed seaward of old dunes and have statutory protection as threatened ecosystems, yet are affected by vehicle traffic. Nesting grounds of nationally vulnerable banded dotterel (Charadrius bicinctus bicinctus) co-occur with vehicle tracking. An artificial nest experiment showed that vehicle strikes pose risks to nesting success, with 91% and 83% of nests destroyed in high and moderate-traffic areas, respectively, despite an increase in suitable habitat. Despite gains for recreational vehicle users there are serious trade-offs with environmental values subject to legal protection and associated responsibilities for management authorities. In theory, a combination of low-impact vehicle access and environmental protection could generate win-win outcomes from the landscape changes, but is difficult to achieve in practice. Detailed information on sensitive areas would be required to inform designated vehicle routes as a potential solution, and such sensitivities are widespread. Alternatively, vehicle access areas that accommodate longstanding activities such as boat launching could be formally established using identified boundaries to control impacts further afield. Difficulties for the enforcement of regulatory measures in remote areas also suggest a need for motivational strategies that incentivise low-impact behaviours. We discuss options for user groups to voluntarily reduce their impacts, the importance of interactions at the recreation-conservation nexus, and need for timely impact assessments across the social-ecological spectrum after physical environment changes -- all highly transferable principles for other natural hazard and disaster recovery settings worldwide.

ecology↗

bioRxiv2021

Predicting biomass of resident kokopu (Galaxias) populations using local habitat composition

With the global decline of freshwater fishes, quantifying the body size-specific habitat use of vulnerable species is crucial for accurately evaluating population health, identifying the effects of anthropogenic stressors, and directing effective habitat restoration. Populations of New Zealands endemic k[o]kopu species (Galaxias fasciatus, G. argenteus, and G. postvectis) have declined substantially over the last century in response to anthropogenic stressors, including habitat loss and fragmentation, invasive species, and over-exploitation. Despite well-understood habitat associations, key within-habitat features driving the reach-scale biomass of small and large k[o]kopu remain unclear. Here, we investigated whether the total biomass of small ([≤] 90 mm) and large (> 90 mm) k[o]kopu was associated with total pool area, average pool depth, total bank cover, average substrate size, and average forest canopy cover across fifty-seven 50 m reaches. These features were selected because generally pool habitats are productive feeding areas, bank cover and substrate interstices are important refuges, and forest cover provides greater food availability. Because k[o]kopu are nocturnal, populations were sampled with removal at night using headlamps and hand-nets until reaches were visually depleted. Using Akaikes information criterion, it was found that increases in large k[o]kopu biomass were most parsimoniously explained by greater pool area and bank cover, whereas increases in small k[o]kopu biomass were best explained by low bank cover and greater average forest cover. This study demonstrated the importance of considering the ontogenetic shift in species habitat use and provided an effective modelling approach for quantifying the size-specific habitat use of these stream-dwelling fish.

ecology↗

bioRxiv2020

Whitebait conservation and protected areas at non-tidal rivermouths: integrating biogeography and environmental controls on inanga (Galaxias maculatus) spawning grounds

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.

ecology↗

bioRxiv2017

Earthquake-induced habitat migration in a riparian spawning fish: implications for conservation management

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 rivermouths. This study reports changes to the spawning habitat following a series of large earthquakes that resulted in widespread deformation of ground surfaces in the vicinity of waterways. Assessments of habitat recovery focussed on two rivers 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 GIS. Habitat migration of up to 2 km occurred in comparison to all previous records and several anthropogenic land uses have become threats due to 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 exposure 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.

ecology↗