Mike Van Keulen

For some species certain biological and ecological data, such as diet, age and growth estimates can only be obtained through lethal sampling of study animals. Traditionally, commercial fishermen have provided samples of rays caught in nets for use by biologists: however, by-catch exclusion devices now prevent medium and larger-bodied rays (>100 cm disc width) from being collected in trawl nets. This means that other methods must be used for lethal sampling. We obtained a large suite of biological and ecological data from 170 wild-caught stingrays collected from Ningaloo Reef, Western Australia over two years. Our sampling program was designed to minimize or eradicate any pain and suffering to the animals, while ensuring the safety of researchers undertaking the sampling process. Small rays (<100 cm disc width: WD) were caught in beach seines and euthanized immediately by destruction of the bran and severance of the spinal cord with a reinforced, serrated steel knife. Larger rays were euthanized by firing high-powered spears directly into their brains from close range while free diving. Of the 170 rays sampled in this manner, 94 % (159) were killed instantly or within an estimated 10 - 30 seconds of capture. The design and application of this lethal sampling program was deemed successful in terms of ensuring the safety of researchers as well as minimising suffering to rays. Pain perception in elasmobranchs has been quantified by few studies: however, research suggests that certain neural apparatus associated with pain sensation is lacking in rays. Our study has provided critical data on the biology and life history of stingrays that could not be obtained by any other means.

Stingrays are an important part of the biomass of the fishes in shallow coastal ecosystems, particularly in interreefal areas. In these habitats, they are considered keystone species – modifying physical and biological habitats through their foraging and predation. Here, we quantify the effects of bioturbation by rays on sand flats of Ningaloo Reef lagoon in Western Australia. We measured the daily length, breadth and depth of 108 feeding pits over three 7-day periods, created by stingrays ( Pastinachus atrus, Himantura spp. Taeniura lymma and Urogymnus asperrimus) in Mangrove Bay. Additionally, an area of , 1km 2 of the lagoon at Coral Bay was mapped three times over 18 months, to record patterns of ray and pit presence. Over 21 days at Mangrove Bay, a total of 1.08m 3 of sediment was excavated by rays, equating to a sediment wet weight of 760.8 kg, and 2.42% of the total area sampled, or 0.03% of the whole intertidal zone. We estimate that up to 42% of the soft sediments in our study area would be reworked by stingrays each year. Based on a model predicting the probability of pit presence over time, there was a 40% probability of ray pits persisting for 4 days before being filled in but only a 15% probability of a pit being present after 7 days. Changes in pit volume over time were static, providing evidence for secondary use. Our results imply that rays play an important ecological role creating sheltered habitats for other taxa in addition to the turnover of sediments.

Stingrays are an important part of the biomass of fishes in shallow, coastal ecosystems, particularly in inter-reefal areas. In these habitats they are thought to be keystone species, responsible for modifying physical and biological habitats through their foraging and predation. Here, we quantify the effects of bioturbation by rays on sand flats of Ningaloo Reef lagoon in Western Australia. At Mangrove Bay we measured 108 pits (length, breadth, depth) on a daily basis for a week. Additionally, an area of 1,000m² of the lagoon at Coral Bay was mapped three times over 18 months, in order to record patterns of ray and pit presence. Over 21 days at Mangrove Bay a total of 1.08m³ of sediment was excavated by rays, equating to a wet weight of 760.8kg, and 2.42% of the total area sampled, or 0.03% of the whole intertidal zone. Based on these calculations we estimate that up to 42% of the soft sediments in our study area would be reworked by stingrays to an average depth of 5.6cm over a year. On average, ray pits persisted in the environment for 4-8 days before being in-filled. An analysis of the change in volume of the pits over time showed high variability in the relationship between pits and years such that only 48% of pits had a negative relationship. Rays play an important ecological role creating sheltered habitats for other taxa in addition to the turnover of sediments and change in the sediment-water interface.

For some species certain biological and ecological data, such as diet and age and growth estimates can only be obtained through lethal sampling of study animals. Traditionally, commercial fishermen have provided samples of rays caught in nets for use by biologists; however, by-catch exclusion devices now prevent medium and larger-bodied rays (>100 cm disk width) from being collected in trawl nets. This means that other methods must be used for lethal sampling. We obtained a large suite of biological and ecological data from 170 wild-caught stingrays collected from Ningaloo Reef, Western Australia over two years. Our sampling program was designed to minimize or eradicate any pain and suffering to the animals, while ensuring the safety of researchers undertaking the sampling process. Small rays (< 100 cm disc width; WD) were caught in beach seines and euthanized immediately by destruction of the brain and severance of the spinal cord with a reinforced, serrated steel knife. Larger rays were euthanized by firing high-powered spears directly into their brains from close range while free diving. Of 170 rays sampled in this manner, 94 % (159) were killed instantly or within an estimated 10 - 30 seconds of capture. The design and application of this lethal sampling program was deemed successful in terms of reducing distress and suffering to the rays caught, as well as ensuring the safety of researchers. The work has provided critical data on the biology and life history of stingrays that could not be obtained by any other means.

Stingrays are an important part of the biomass of the fishes in shallow, coastal ecosystems, particularly in inter-reefal areas. In these habitats they are thought to be keystone species, responsible for modifying physical and biological habitats through their foraging and predation. However, there have been few attempts to quantify the effects of these animals on benthic environments. Here, we examine the effects of bioturbation by rays on sand flats of the lagoon of Ningaloo Reef WA. At Mangrove Bay we surveyed 15, 10x10 m quadrats during August 2009, September 2010 and February 2011. We recorded all pits that could be identified as due to ray feeding. Of these, 98 were selected randomly to be measured (length, breadth, depth) on a daily basis for a week. Over the 21 day period, a total of 2.01 cubic m of sediment was excavated by ray pits equating to a wet weight of 1,411.3 kg and 2.42% of the total area sampled. Based on these figures, up to 42% of the soft sediments in our study area would be reworked by stingray feeding to an average depth of 5.16 cm over a year. Within the 15 quadrats, new pits were formed at a rate of 0.41/day and then maintained a clear shape for an average of 1.57 days, after which time they could no longer be measured. All evidence of the pit was lost after an average of 3.3 d. In addition to the turnover of sediment and removal of prey, pits created sheltered habitats for a range of organisms, including larval fish, crabs and gastropods. The role of stingrays is compared with that of other organisms that are seen as important ecosystem engineers in soft-sediment environments such as dugongs, crabs and callianasiid shrimps.

Sea urchins can have a significant influence upon the ecological structure of coral reefs through bioerosion of substrata and also by affecting competition for space. They are important grazers in many marine systems and can cause major ecosystem changes when their populations reach high levels (generally after a decline in the numbers of their fish predators). However, the relative importance of the role of sea urchins in influencing the composition and structure of coral reef habitats has rarely been explored. This study is linked to the CSIRO Wealth from Oceans Ningaloo Collaboration Cluster, Component 1: Habitat Mapping and Biodiversity. It has so far examined coral reef habitats and macroinvertebrate (particularly urchins) distribution and abundance within Ningaloo Marine Park. Field sampling has been undertaken at over 100 sites within the Park, focussing on near shore, lagoonal and back reef areas within Sanctuary zones and adjacent Recreation zones. Data analyses so far indicate that the distribution of urchins is not affected by the management zones of the park (i.e. no significant evidence has been found of indirect effects from fishing of urchin predators). However, habitat type has a major influence on urchin distribution, e.g. urchin populations were higher on nearshore intertidal and sub-tidal reef platforms, lagoonal patch reefs and shallow backreef platforms than other habitats. In coral reefs in other parts of the world, unusually high urchin populations can indicate overfishing. So far, this study has found no indication of fishing pressure indirectly affecting urchin densities, which suggests that the current zoning may be effective. However, further analyses of the data, particularly those from the nearshore sanctuary areas where shore based fishing activities are allowed, are yet to be completed. If fishing pressure is having an effect, it is likely to be seen in those areas where urchin abundance is predicted to be highest.

The year round visitation to Ningaloo Marine Park (NMP) of the coastal manta ray (Manta alfredi) has been investigated using the AATAMS acoustic tagging network. A total of 37 individuals were tagged with acoustic ‘pingers’, including 6 with depth tags. Over 10,000 detections were recorded along the length of the array over a three year period. Visitation patterns match photographic sighting data and confirm that manta ray visitation to NMP can be grouped into 3 broad categories, seasonal, roaming and resident. Seasonal aggregations of manta rays at NMP coincide with major reef spawning events which also attract other large planktivores such as the whaleshark. Roaming individuals largely comprise adult males, whilst true residency appears to be the domain of large breeding females. These females show strong fidelity to feeding and cleaning sites, where they interact on occasion with both roaming and seasonal individuals. Their occurrence at numerous small-scale spawning events and zooplankton blooms throughout their potential range indicates the importance of local knowledge. Such on-site knowledge may make resident manta rays key regulators of larval recruitment to the reef system and may play an important role in the reduction of potentially invasive species. The currently un-regulated and growing tourism industry appears to rely heavily on the frequent visitation to key areas of resident manta rays. Any avoidance of these high tourism areas by resident animals could be detrimental to both localized reef health and indeed the lucrative tourism industry of NMP. Acoustic tracking is proving invaluable in our understanding of habitat visitation and manta ray residency within NMP and will assist directly with future management of NMP.

Surveys were undertaken of key invertebrate and plant groups in lagoon areas throughout the Ningaloo Marine Park, focussing on identifying and quantifying soft corals, sponges, echinoderms (urchins and sea cucumbers) and seagrasses; this information was linked to the underlying habitat structure in the Ningaloo Reef lagoons, used in a parallel habitat mapping project based on hyperspectral aerial photography. The biodiversity surveys conducted throughout the Ningaloo Reef system have shown that there are clear differences in the lagoon systems in different parts of the Marine Park, with clear biogeographic separation of sponges, soft corals and seagrasses. This has important implications for the distribution and abundance of many animals, including some of commercial importance. The northern section of the Marine Park (north of Point Cloates) is more strongly tropical than the southern section, which has many temperate species present. There are also several locations within the Ningaloo Reef system that are quite unique and don’t necessarily match the surrounding lagoon environment. Examples include Coral Bay, Bateman Bay and the Point Cloates region. These observations will be important in the management of the Ningaloo Marine Park; the northern and southern sections of the Marine Park may need to be managed differently. Surveying biological groups over the whole Marine Park is difficult and time consuming; further sampling in more locations and at different times of year are required to build on the findings of our study. There are clear seasonal differences in primary productivity in the lagoons, which likely drive significant community-wide changes throughout the year. These seasonal variations will also affect the validity of the habitat maps, which were based on imagery collected at only one time of year. Seasonal sampling will improve the reliability of the habitat maps and also give a better understanding of how the Ningaloo system operates.