Ningaloo Marine Park Research Articles

Stable isotopes reveal sargassum rafts provide a trophic subsidy to juvenile pelagic fishes

Floating macroalgal rafts can form extensive habitat in coastal waters and support abundant and diverse communities of juvenile fishes. Rafts comprised predominantly of Sargassum spp. are common within the Ningaloo Coast World Heritage Area, Western Australia, and may be an important transitional habitat for pre-settlement coastal fishes. We had three aims: 1) to quantify the diversity and abundance of fishes associated with Sargassum rafts; 2) to use stable isotopes to determine whether fishes associating with rafts preyed on nearby plankton or on prey associated with Sargassum; and 3) to determine whether the food web fishes relied upon was ultimately supported by primary production of Sargassum or planktonic phytoplankton (measured as seston). Fishes and macroinvertebrates associating with Sargassum rafts, zooplankton, and seston were collected at six sites in the Ningaloo Marine Park and analysed for δ15N and δ13C, and the diets of the most common fishes were analysed using MixSIAR. Fishes were more abundant around macroalgal rafts than in open water. Eleven species of juvenile fishes associated with Sargassum rafts, with one species (Histrio histrio (Antennariidae)) represented by juveniles and adults. Four of the five fishes most sampled around Sargassum spp. rafts, (Abudefduf vaigiensis (Pomacentridae), Helotes sexlineatus (Terapontidae), Colurodontis paxmani (Monacanthidae) and Petroscirtes breviceps (Blenniidae)) had generalist diets whose food webs were ultimately supported by greater contributions of primary production from Sargassum spp. (55–72%) than planktonic seston. H. histrio was predominantly piscivorous but still derived most (64%) of its organic matter indirectly from Sargassum spp. Our results reveal the importance of Sargassum rafts as habitat that provides shelter and food for juvenile fishes and adult H. histrio. Moreover, the prevalence of juvenile fishes associating with Sargassum rafts highlights a bidirectional form of benthic-pelagic coupling whereby macroalgae that detach from the benthos provide habitat and a trophic subsidy for pelagic juvenile fishes before they the transition into benthic coastal habitats.

Stereo-ROV surveys of tropical reef fishes are comparable to stereo-DOVs with reduced behavioural biases

Cumulative anthropogenic impacts such as overfishing, and climate change are placing marine ecosystems under increasing pressure. This includes the loss or degradation of marine habitats and reductions in fish stocks, with conservation and fisheries management strategies aiming to mitigate, or reverse the effects. Measuring the effectiveness of management actions on fish requires accurate data on the abundance and size of fishes. Diver operated stereo-video systems (stereo-DOVs) have become a widely accepted method for surveying reef fish but have known biases and constraints. A new generation of small and affordable remotely operated vehicles (ROVs) can carry a stereo-video system to collect reef fish data without the need for divers. However, before ROVs are adopted there is a need to understand how they compare to other conventional survey methods. We compared how stereo-DOVs and stereo-ROVs influenced fish behaviour and sampled coral reef fish assemblages inside and outside sanctuary zones in the Ningaloo Marine Park, Northern Western Australia. In general, the numbers of species, individuals and the assemblage composition did not differ significantly between survey techniques and detected consistent patterns in the assemblage composition across locations and inside and outside sanctuary zones. Both methods recorded similar proportions of length measurements (68% and 70% for stereo-DOV and stereo-ROV respectively). Fishes were significantly more wary and exhibited more flight responses towards stereo-DOVs when compared to stereo-ROVs. The use of ROVs has the potential to be a cost-effective method of surveying reef fish while eliminating the health and safety risks involved with SCUBA diving. Given the comparable metrics as well as reduced behavioural bias and logistical advantages of using stereo-ROVs, we recommend stereo-ROVs as a viable alternative to stereo-DOVs surveys.

Australia, Western Australia, Ningaloo Marine Park, Indian Ocean Coast

Australia, Western Australia, Ningaloo Marine Park, Indian Ocean Coast

Foraging microhabitat preferences of invertivorous fishes within tropical macroalgal meadows: identification of canopy specialists

Invertivorous fishes are key middle-order consumers that connect energy flows across different trophic levels. However, the potential for distinct functional roles to exist within this trophic guild has not been satisfactorily explored to date, meaning that current assessments of ecosystem resilience are likely to over-estimate the level of functional redundancy within a given invertivorous fish assembly. Our study examined the foraging behaviour and microhabitat preferences of invertivorous fish communities within the productive canopy macroalgal meadows of Ningaloo Marine Park, Western Australia. Our aim was to identify foraging specialisations that could yield distinct functional roles for species belonging to the guild. We found that invertivorous fishes at this location were chiefly represented by species belonging to the Labridae, Lethrinidae and Mullidae families. Individual species demonstrated strong preferences for foraging within specific microhabitat types, suggesting that the guild can be grouped into three categories of foraging specialists: ‘canopy forager’, ‘generalist’ and ‘abiotic forager’. Our results highlight subtle niche partitioning of foraging microhabitats within the trophic guild of invertivorous fishes associated with tropical macroalgal meadows. Moreover, this partitioning is consistent across seasons, despite significant fluctuations in canopy structure and biomass. The resulting refinement of foraging specialisations allows us to identify the functional roles of invertivorous fishes and afford greater protection to individual species that might otherwise be considered functionally redundant. Our results will help to inform knowledge of the functional impact of particular species and their ecological specialisations and improve our understanding of trophic flows in marine food webs for appropriate management and conservation.

Recreational Fishing Impacts in an Offshore and Deep-Water Marine Park: Examining Patterns in Fished Species Using Hybrid Frequentist Model Selection and Bayesian Inference

No-take marine reserves are often located in remote locations far away from human activity, limiting perceived impact on extractive users but also reducing their use for investigating impacts of fishing. This study aimed to establish a benchmark in the distribution of fished species across the Ningaloo Marine Park – Commonwealth (NMP-Commonwealth), and adjacent comparable habitats within the Ningaloo Marine Park - State (NMP-State), in Western Australia to test if there was evidence of an effect of recreational fishing, as no commercial fishing is allowed within either marine park. We also examined whether the remote location of the newly established (2018) No-take Zone (NTZ), in NMP-Commonwealth, limits its use for studying the effects of fishing. Throughout the NMP-Commonwealth and NMP-State, where recreational fishing is permitted, we expected the abundance of recreationally fished fish species to increase with increasing distance to the nearest boat ramp, as a proxy of recreational fishing effort. Conversely, we did not expect the abundance of non-fished species and overall species richness to vary in response to the proxy for human activity. Distance to the nearest boat ramp was found to be a strong predictor of fished species abundance, indicating that the effect of recreational fishing can be detected across the NMP-Commonwealth. The effect of the NTZ on fished species abundance was weakly positive, but this difference across the NTZ is expected to increase over time. Habitat composition predictors were only found to influence species richness and non-fished species abundance. This study suggests a clear footprint of recreational fishing across the NMP-Commonwealth and as a result the new NTZ, despite its remote location, can act as a control in future studies of recreational fishing effects.

Understanding visitor awareness and knowledge of marine parks: Insights from the Ningaloo Coast, Australia

Marine Protected Areas (MPAs) are a key policy instrument used for the protection of ocean and coastal environments. However, many MPAs are currently falling short of their intended objectives. Studies show that meaningful public engagement can assist in optimising the outcomes of an MPA by improving stakeholder knowledge, support, and social license, and thus improving voluntary compliance with local MPA regulations. Ensuring more meaningful engagement, however, requires a context specific understanding of how different stakeholder groups understand the MPA, how they acquire that knowledge, and how information delivery can be tailored more effectively to reach the target audience. To that end, this study employed a quantitative survey to explore stakeholder awareness and knowledge of the Ningaloo Marine Park (NMP), a multi-use marine park on the west Australian coastline. Specifically, we surveyed visitors (i.e., tourists) to the Ningaloo region to understand their awareness of the NMP, their knowledge of the marine zoning regulations, and their access to information (N = 169). Results suggest that visitors to the region exhibit low levels of awareness of the primary management bodies, and of the presence of zoning regulations in the NMP. There was also a significant gap in the perceived level of protection afforded by the NMP compared to the actual protection, with visitors believing that the MPA provides more protection of the marine environment than it does in practice. These findings highlight a need for future regional communication strategies to be focused on improving the overall awareness and knowledge of the NMP among visitors through clear, consistent and accessible information. Specifically, visitors indicated that moving forwards, they would like to access this information through visitor centres, on local signage and on websites. The results of this study provide valuable insights for local marine park managers and decision-makers to improve existing communication strategies in order to maximise the ecological, social and economic outcomes of the NMP. These insights also have a wider application for improving ongoing public engagement with MPAs globally, which is particularly important given the rapid designation of MPAs to meet the global target of 30% of global oceans protected by 2030.

Baited video, but not diver video, detects a greater contrast in the abundance of two legal-size target species between no-take and fished zones

Inherent differences between baited remote video versus diver-operated video survey methodologies may influence their ability to detect effects of fishing. Here, the ability of no-take zones (NTZs) to provide protection for legal-sized fish from targeted species within the Ningaloo Marine Park (NMP) was assessed using both baited remote underwater stereo-video (stereo-BRUV) and diver-operated stereo-video (stereo-DOV). The relative abundance of legal-sized individuals of three recreationally targeted fish species, spangled emperor Lethrinus nebulosus, chinaman cod Epinephelus rivulatus and goldspotted trevally Carangoides fulvoguttatus, were examined using both methodologies inside and outside six NTZs across the NMP. Stereo-BRUVs found positive effects of protection on the relative abundance of legal-size C. fulvoguttatus and L. nebulosus in NTZs. Stereo-DOVs, however, did not detect any differences in relative abundances and sizes of these species between areas opened and closed to fishing. These contrasting results suggest that choice of sampling methodology can influence interpretations of the ability of NTZs to provide adequate levels of protection for target species. Our results suggest that stereo-BRUVs are a superior technique to stereo-DOVs for assessing the effectiveness of no-take zones for protection of fishery target species, reflecting bait attraction and an absence of diver influence on fish behaviour.

Fine‐scale movement and habitat use of juvenile, subadult, and adult green turtles (Chelonia mydas) in a foraging ground at Ningaloo Reef, Australia

Abstract The residence, home range, and habitat use of juvenile (42.0–63.5 cm midline curved carapace length, CCL), subadult (68.6–84.6 cm CCL), and adult (81.9–104.2 cm CCL) green turtles (Chelonia mydas) was investigated using passive acoustic telemetry in Ningaloo Marine Park, north‐western Australia. Eighty‐one turtles ranging in size from 42 to 104 cm CCL were captured on their foraging grounds and tagged with acoustic tags. Individuals were monitored for up to 913 days (range 48–913 days, median 367 days). Turtles of all sizes demonstrated very high fidelity to their foraging area. Residence declined with turtle body size and home range increased with turtle body size, with an average 50% kernel utilization distribution (KUD) area of 0.29, 0.47, and 0.57 km2 for juveniles, subadults, and adults, respectively. Juveniles occurred only in shallow inshore habitat dominated by seagrass and macroalgae‐covered pavement. Subadults and adults selected macroalgae‐covered pavement, sandy areas of the lagoon, and macroalgae‐dominated patch reefs within the lagoon. At high tide, juveniles were approximately 200 m closer to the shore than at low tide, but there was no tidal pattern of space use in subadult and adult turtles. Less than 5% of turtles departed the array within 6 months and there was no evidence of developmental migrations in subadults. The results highlight the conservation potential for go‐slow areas to minimize boat strike in areas of high turtle density, given the small and stable home ranges. Furthermore, the spatial segregation of juveniles, subadults, and adults will result in variability in the susceptibility of individuals to boat strike. The influencing factors that drive the developmental migrations of turtles to consecutive habitats as they grow, as well as movement away from foraging grounds in response to changes in habitat quality, are complex. The ability of acoustic telemetry to provide long‐term data on all size classes of turtles within foraging areas provides a tool to enable the long‐term monitoring of turtle populations, which is required for at‐risk populations and/or habitats.

The Spatial Variation of Acoustic Water Column Data and Its Relationship with Reef-Associated Fish Recorded by Baited Remote Underwater Stereo-Videos off the Western Australia Coast

Spatially explicit information on coral fish species abundance and distribution is required for effective management. Nonextractive techniques, including echosounders and video census, can be particularly useful in marine reserves where the use of extractive methods is restricted. This study aimed to investigate the possibility of combining echosounders and baited remote underwater stereo-videos (stereo-BRUVs) in providing more holistic information on the distribution of demersal and semidemersal reef-associated fish. The spatial distribution of fish biomass was assessed using both methods in two small areas, one in Cockburn Sound (CS), a temperate body of water, and the other in the tropical waters of the Ningaloo Marine Park (NMP). The results showed high correlations between the acoustic and stereo-BRUV data in CS, suggesting the potential use of both for a better estimation of biomass in the area. The results for the NMP showed weaker correlations between the two datasets and highlighted the high variability of the system. Further studies are required, but our initial findings suggest a potential benefit of combining both techniques in the reef-associated fish distribution assessment.

Low quantities of marine debris at the northern Ningaloo Marine Park, Western Australia, influenced by visitation and accessibility

Marine debris (MD) is a serious environmental concern globally. Yet, few studies have reported on MD in sanctuary zones of the Indian Ocean. Consequently, coastal transects were conducted to determine MD quantity, composition and distribution at northern Ningaloo Marine Park, Western Australia. Debris density ranged between 0.004 and 0.02 items m−2 with the greatest density near Exmouth township. Composition was predominantly plastic (61%) with fishing-related items (25.5%) and plastic fragments/remnants (16%) the most numerous overall. Land-based and general sourced MD accounted for 88% of all debris. Debris levels were significantly lower at sites with higher visitation and increased distance from access points. There was no significant difference between sanctuary and non-sanctuary zones. Although not immune to MD, this study suggests its remote location, environmental awareness and management strategies implemented at Ningaloo Marine Park may be key to its low MD levels.

Coastal dolphins and marine megafauna in Exmouth Gulf, Western Australia: informing conservation management actions in an area under increasing human pressure

Context Exmouth Gulf is adjacent to the Ningaloo Marine Park, a UNESCO-listed area in Western Australia. The gulf remains largely unprotected, and is under increasing anthropogenic pressure from proposed industrial activities that pose threats to marine megafauna inhabiting the gulf. Threatened and near threatened species, such as the Australian humpback dolphin (Sousa sahulensis) and Indo-Pacific bottlenose dolphin (Tursiops aduncus), reside in the gulf; however, detailed information on their ecology and behaviour is lacking. Aims The aim was to (1) provide baseline data on the distribution, encounter rate, group size and behaviour of coastal dolphins over an area where current industrial developments are proposed, and (2) report on the occurrence of other marine megafauna within this area. Methods Boat-based photo-identification surveys were conducted on the western coastline of Exmouth Gulf along pre-determined line transects (150 km2) over austral autumn/winter 2021. Key results Across 809.35 km of surveyed waters (181 h), a total of 93 bottlenose dolphin, 15 humpback dolphin, and six interspecific dolphin groups were sighted. Bottlenose dolphin groups were encountered at a rate of 0.077/km, humpback dolphin groups at 0.015/km and interspecific dolphin groups at 0.005/km. Dolphins were predominantly recorded in shallow (mean 10 m) and warm (mean 21°C) waters, and were commonly travelling and foraging. In total, 199 individual bottlenose dolphins and 48 humpback dolphins were photo-identified (excluding calves). There were 30 bottlenose dolphin calves (including three newborns) and four humpback dolphin calves (including two newborns) identified. Other marine megafauna group sightings included humpback whales (Megaptera novaeangliae; n = 32), southern right whales (Eubalaena australis, n = 1), dugongs (Dugong dugon, n = 25), turtles (n = 54), sea snakes (n = 27), manta rays (Mobula alfredi, n = 13) and sharks (n = 2). Conclusions The presence of threatened marine species feeding, socialising, and resting highlights the importance of these waters for the identified species. Implications The information provided is applicable for the spatial management and conservation efforts of these species, and aids in informing environmental impact assessments of individual and cumulative pressures.

Testing the Improvement of Coral Reef Associated Fish Distribution Models Based on Multibeam Bathymetry by Adding Seafloor Backscatter Data

Demersal fishes constitute an essential component of the continental shelf ecosystem, and a significant element of fisheries catch around the world. However, collecting distribution and abundance data of demersal fish, necessary for their conservation and management, is usually expensive and logistically complex. The increasing availability of seafloor mapping technologies has led to the opportunity to exploit the strong relationship demersal fish exhibit with seafloor morphology to model their distribution. Multibeam echo-sounder (MBES) systems are a standard method to map seafloor morphology. The amount of acoustic energy reflected by the seafloor (backscatter) is used to estimate specific characteristics of the seafloor, including acoustic hardness and roughness. MBES data including bathymetry and depth derivatives were used to model the distribution of Abalistes stellatus, Gymnocranius grandoculis, Lagocephalus sceleratus, Lethrinus miniatus, Loxodon macrorhinus, Lutjanus sebae, and Scomberomorus queenslandicus. The possible improvement of model accuracy by adding the seafloor backscatter was tested in three different areas of the Ningaloo Marine Park off the west coast of Australia. For the majority of species, depth was a primary variable explaining their distribution in the three study sites. Backscatter was identified to be an important variable in the models, but did not necessarily lead to a significant improvement in the demersal fish distribution models’ accuracy. Possible reasons for this include: the depth and derivatives were capturing the significant changes in the habitat, or the acoustic data collected with a high-frequency MBES were not capturing accurately relevant seafloor characteristics associated with the species distribution. The improvement in the accuracy of the models for certain species using data already available is an encouraging result, which can have a direct impact in our ability to monitor these species.

Distribution and Habitat Preferences of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) Inhabiting Coastal Waters With Mixed Levels of Protection

Assessments of species distributions are crucial for informing conservation and management action. In this study, we used ensemble modelling to explain the distribution of Near Threatened Indo-Pacific (IP) bottlenose dolphins (Tursiops aduncus) in coastal waters at the North West Cape (NWC), Western Australia (WA), an area encompassing a marine protected area (MPA) and adjacent unprotected coastal waters. Analyses used dolphin sighting data collected during boat-based surveys conducted from 2013 to 2015 and 2018 to 2019. Overall, the distribution of IP bottlenose dolphins was best explained by distance to coast (up to 2,000 m) and distance to boat ramp (up to 7,000 m). Areas of high probability of occurrence for dolphins extended from the tip and down the eastern side of the NWC and overlapped with designated sanctuary zones as well as waters beyond the boundaries of the Ningaloo Marine Park (NMP). Distribution and habitat preferences varied slightly with season. In autumn, dolphin distribution was best explained by distance to coast and water depth with a higher likelihood of observing dolphins 1,000–2,000 m from the coast and in water depths of 7–10 m deep. During winter months, distance to coast (1,000–2,000 m) and sea surface temperature (SST) (21.5–23.5°C) were the most important explanatory variables, with presence in coastal lagoons to the west of the NWC more likely than other seasons. During spring, areas of moderate to high probability of dolphin occurrence were mainly located outside the NMP, with marine park zone (outside the NMP and Sanctuary zones within the NMP, the two zones with the highest probability of IP bottlenose dolphin occurrence) and water depth (waters 7–13 m deep) best explaining dolphin distribution. This study highlights the importance of inshore areas of the NWC for IP bottlenose dolphins and the potential vulnerability of this species to increasing and cumulative anthropogenic stressors associated with these areas. Results of this study should be considered in future zoning reviews and adaptive management efforts of the NMP allowing for effective management of this Near Threatened species.

ENSO feedback drives variations in dieback at a marginal mangrove site

Ocean–atmosphere climatic interactions, such as those resulting from El Niño Southern Oscillation (ENSO) are known to influence sea level, sea surface temperature, air temperature, and rainfall in the western Pacific region, through to the north-west Australian Ningaloo coast. Mangroves are ecologically important refuges for biodiversity and a rich store of blue carbon. Locations such as the study site (Mangrove Bay, a World Heritage Site within Ningaloo Marine Park and Cape Range National Park) are at the aridity range-limit which means trees are small in stature, forests small in area, and are potentially susceptible to climate variability such as ENSO that brings lower sea level and higher temperature. Here we explore the relationship between mangrove dieback, and canopy condition with climatic variables and the Southern Oscillation Index (SOI)—a measure of ENSO intensity, through remote sensing classification of Landsat satellite missions across a 29 year period at a north-west Australian site. We find that the SOI, and seasonal mean minimum temperature are strongly correlated to mangrove green canopy (as indicator of live canopy) area. This understanding of climate variations and mangrove temporal heterogeneity (patterns of abundance and condition) highlights the sensitivity and dynamics of this mangrove forest and recommends further research in other arid and semi-arid tropical regions at mangrove range-limits to ascertain the extent of this relationship.

Environmental factors and predator abundance predict the distribution and occurrence of two sympatric urchin species at Ningaloo Reef, Western Australia

Sea urchins can play a critical ecological role in the functioning of marine benthic ecosystems, mediating competitive interactions between corals and algae. Yet, little is known about factors affecting urchin distribution in intact coral reef systems. This study aims to determine the spatial distribution of two sympatric urchin species, Echinometra mathaei and Echinostrephus molaris, and potential factors contributing to this, within the intact coral reef system of Ningaloo Marine Park, north-western Western Australia. Benthic photographs and surveys were conducted on SCUBA at 126 sites across the Park to determine urchin presence, rugosity, substrate cover, water velocity, and fish predation for each site. Generalised additive models found that E. mathaei presence was positively related to algal cover, rugosity and non-sanctuary zones, suggesting that distribution may be driven by foraging behaviour, habitat complexity and predation. Echinostrephus molaris presence was positively related to habitat and region, suggesting its distribution may be largely driven by hydrodynamics, feeding strategy and regional variation. This study highlighted species-habitat associations and the complexities of these in structuring urchin communities. Although occupying similar niches, the predominantly non-overlapping feeding preferences, and morphological and behavioural differences between E. mathaei and E. molaris enable these species to coexist within the intact reef system of Ningaloo Marine Park.

Identifying priority habitat for conservation and management of Australian humpback dolphins within a marine protected area

Increasing human activity along the coast has amplified the extinction risk of inshore delphinids. Informed selection and prioritisation of areas for the conservation of inshore delphinids requires a comprehensive understanding of their distribution and habitat use. In this study, we applied an ensemble species distribution modelling approach, combining results of six modelling algorithms to identify areas of high probability of occurrence of the globally Vulnerable Australian humpback dolphin in northern Ningaloo Marine Park (NMP), north-western Australia. Model outputs were based on sighting data collected during systematic, boat-based surveys between 2013 and 2015, and in relation to various ecogeographic variables. Water depth and distance to coast were identified as the most important variables influencing dolphin presence, with dolphins showing a preference for shallow waters (5–15 m) less than 2 km from the coast. Areas of high probability (> 0.6) of dolphin occurrence were primarily (90%) in multiple use areas where extractive human activities are permitted, and were poorly represented in sanctuary (no-take) zones. This spatial mismatch emphasises the need to reassess for future spatial planning and marine park management plan reviews for NMP. Shallow, coastal waters identified here should be considered priority areas for the conservation of this Vulnerable species.

A novel experimental approach to investigate the potential for behavioural change in sharks in the context of depredation

Baited video systems have been widely used to assess the relative abundance and diversity of sharks in locations around the world, however they provide limited information on behaviour. We developed and pilot tested a novel experimental approach to investigate whether repeated deployments of baited video systems in the same location could generate quantitative data on shark behavioural patterns, in the context of shark depredation (where sharks consume hooked fish). Specifically, we sought to test whether repeated exposure to boats and food in the same location would lead to a change in the arrival time and first feeding time of sharks, over a short timescale. We used the Ningaloo Marine Park (NMP) in Western Australia, a location where higher shark depredation rates have been identified in consistently fished areas, as a case study. A modified Baited Remote Underwater Video (BRUV) system was repeatedly deployed at two fished sites and two sites within a no-take marine reserve in the NMP, over six consecutive days, to mimic repeated recreational fishing and the availability of hooked fish for sharks to depredate. This approach was designed to investigate and disentangle the potential role of changes in behaviour versus variation in shark abundance, as a mechanism for how and why shark depredation can occur. Here, we report preliminary results from this methodological approach, where time of arrival and time of first feeding declined markedly in the fished site over 6 days of BRUV deployments, compared to the control site in the no-take marine reserve. A greater number of individuals from four carcharhinid species were observed at the fished site, compared to only three individuals from two species in the no-take marine reserve. The preliminary results from pilot testing of this novel experimental approach suggest that, with further modifications to identify individual sharks, and a greater spatial and temporal replication of sampling, it may be possible to identify behavioural changes occurring in sharks in the context of shark depredation. Understanding this mechanism can bring important benefits for fishers and managers, as it can lead to modifications in fishing methods designed at reducing the occurrence of behavioural changes in sharks, and thus mitigating shark depredation.

Multi-year patterns in scarring, survival and residency of whale sharks in Ningaloo Marine Park, Western Australia

Multi-year patterns in scarring, survival and residency of whale sharks in Ningaloo Marine Park, Western Australia

The diversity and distribution of mesophotic benthic invertebrates at Ningaloo Reef, Western Australia

The effective management of marine species relies on a comprehensive understanding of how the environment can influence biodiversity and distributions. This study quantified the biodiversity of invertebrates across the phyla Arthropoda, Echinodermata, Mollusca and Porifera from 132 sampling stations along the coast of the Ningaloo Marine Park (NMP) and across depths ranging from 30 to 123 m, providing a broad assessment of the biodiversity of marine invertebrates in mesophotic habitats of the NMP. Benthic sleds were used to sample biodiversity and specimens identified to the highest taxonomic resolution. Single-beam and multibeam surveys of the seabed were performed to derive 58 spatial and bathymetric variables used to assess their relevance to the distributions of benthic diversity. A total of 787 taxa were identified across the four phyla, of which 51% were rare and sampled from a single station. Latitude and depth were significant in structuring the invertebrate diversity in the mesophotic, with Point Cloates notably identified as a significant geographical feature in partitioning diversity to the north and south of the NMP. Depth was more influential at structuring diversity in the northern section of the NMP due to the narrower Ningaloo Shelf, and southern localities including Turtles and Red Bluff were identified as biodiversity hotspots for benthic invertebrates. Importantly, comparisons of diversity within ‘no-take’ and ‘general use’ zones along the NMP indicate that sanctuary zones represent the diversity contained in the marine park, thus highlighting their importance in the protection and conservation of invertebrate diversity for the region.

Behavioural responses of migrating humpback whales to swim-with-whale activities in the Ningaloo Marine Park, Western Australia

Swim-with-whale tourism is a lucrative and rapidly growing industry worldwide. Whale-watching can cause negative effects on the behaviour of targeted animals. Although this is believed to be particularly true for close-up interactions, such as swim-with operations, few empirical studies have investigated this. In 2016, the Western Australian State Government commenced a swim-with humpback whale (Megaptera novaeangliae) trial in the Ningaloo Marine Park, where 11 commercial licences were granted. The swim-with trial was conducted during both the northern and southern whale migration (August to November), during which we assessed potential short-term behavioural effects on humpback whales to swim-with activities. From both an independent research vessel (n = 300 h) and on-board commercial swim-with vessels (n = 357 h), we collected group-follow data (n = 224) on whale behaviour before, during and after swim-with activities. Behavioural effects on whales were investigated, including movement patterns (deviation and directness index, heading, swim speed), surfacing patterns (dive duration and respiration rate) and occurrence of agonistic behaviours. Results showed that the most common type of vessel approach to place swimmers in the water was in the path of whales (89.8% of interactions). During in-path approaches, vessels travelled significantly faster (P = .002) compared to when approaching from the side (side/line abreast approaches). When vessels approached in the whales' path, whales exhibited horizontal and vertical avoidance strategies by adopting a less predictable path (deviating from 32° to 46°), increasing turning angles away from the vessel (heading from 73° to >90°), increasing swim speeds (from 1.68 to 1.89 ms−1), and decreasing the duration of their dives (from 224 to 194 s). Whales displayed a higher frequency of agonistic behaviours when a swim-with vessel was <100 m distance from them compared to >100 m away (P = .011). Young-of-year calves were present during 19.6% (18 of 92) of group-follows that included swim attempts. To reduce potential impacts on whales and increase swimmer safety, we recommend to avoid in-path vessel approaches, not place swimmers in the water with groups of whales that perform agonistic behaviours, and avoid swimming with young-of-year calves.