First estimates of population size and home range of Caribbean reef and nurse sharks using photo-identification and BRUVS

The assessment of parameters population size and individual home range is important for effective conservation management of sharks. This study uses the novel application of photo identification (photo-ID) to BRUVS footage as a non-invasive alternative to tagging in order to generate individual capture histories. These were used in mark-recapture models to estimate effective population sizes and to determine home ranges. In the Cayman Islands a total of 499 shark sightings of six coastal shark species were recorded on BRUVS from 2015 - 2018, but re-sighting rates were only sufficient for the determination of population parameters for two species - Caribbean reef shark (Carcharhinus perezi) and nurse shark (Ginglymostoma cirratum). The calculated super-population sizes for Caribbean reef shark (180 ± 37 SE) and nurse shark (336 ± 61 SE) were greater than the estimates for each species based on a closed-population model (Caribbean reef shark: 128 ± 40 SE, nurse shark: 249 ± 48 SE), though both measures indicated that there were about twice as many nurse sharks (1.3 - 1.8 sharks/km2) as Caribbean reef sharks (0.7 – 1 shark/km2) within the study area. The demographic compositions included numerous immature individuals, indicating that breeding of both species takes place within the study area of 188 km2. Most recognizable individuals of both species showed linear home ranges of <20 km, but a few individuals were observed to have moved longer distances (Caribbean reef shark: 125.37 km, nurse shark: 156.07 km). The data indicate that the home ranges and long-distance movements of individual sharks observed within the islands’ marine protected areas (MPAs) often extend to areas beyond the MPA’s boundary, potentially exposing them to fishing activities. This study provides the first estimates of population size for Caribbean reef and nurse sharks in the Cayman Islands and the first estimate of a Caribbean reef shark population globally

A test in a high altitude lake of a multi-parametric rapid methodology for assessing life in liquid environments on planetary bodies: A potential new freshwater polychaete Tubeworm community

On our planet, aqueous environments such as deep sea or high-altitude aphotic lakes, subject to present or past volcanic activity and active deglaciation, may provide analogs to the aqueous environments found on such planetary bodies as Europa, Titan or Enceladus. We report here on the methodologies and technologies tested in Laguna Negra, a high altitude lake in the Central Andes, Chile, for exploring and assessing the presence of life within planetary lakes or interior oceans. We adopted a multi-parametric Rapid Ecological Assessment (REA) approach centered around collecting video imagery (by an Underwater Imaging System) and sampling benthic sediments (for sedimentological, biological and geochemical analysis) to depths of 272 m, to complement physico-chemical sampling of the water column and collection of shallow sediments for microbiological analysis (reported in separate publications). This enabled us to classify and assess the apparent status of benthic habitats, based on substrata and environmental characteristics, together with floral and faunal community characteristics and bioturbation artifacts. Video imagery showed that the lower water column was characterized by a variably intense sestonic flux of particles and debris, among which were planktonic organisms such as ostracods, copepods, and possibly cladocerans. Sediment analysis revealed at all depths abundant diatom frustules, mainly of an acidophile pennade diatom Pinnularia acidicola, amid vegetal debris likely originating from littoral macrophytes. Video imagery showed that the lakebed was partly covered by microbial mats and depositional matter and harbored an unexpectedly rich assortment of macrofauna, including sponges, tubificid worms, flatworms, bivalves and crustaceans. Various forms of bioturbation were also encountered, some with the animals in the tracks. Most notably, at the deepest site, a previously undescribed faunal feature was evident, apparently formed by a mat-like community of several layers of what appeared to be polychaete tubeworms, possibly of the family Siboglinidae. It is hypothesized that the hydrothermal activity observed in the region may supply the compounds able to support the deep-water microrganisms from which such tubeworms typically gain sustenance. Such processes could be present on other deep and aphotic liquid-water-bearing planetary bodies

Red sea coral reefs

173 p.: ill. ;26 c

The Benthic Megafaunal Assemblages of the CCZ (Eastern Pacific) and an Approach to their Management in the Face of Threatened Anthropogenic Impacts

We present here the results of a UNESCO/IOC baseline study of the megafaunal assemblages of the polymetallic nodule ecosystem of 5 areas within the Clarion Clipperton Zone (CCZ) of the eastern Pacific Ocean. The work was undertaken with a view to investigating the structure of the epifaunal populations associated with the benthic biotopes being targeted for nodule mining and developing an appropriate set of management tools and options. The general characteristics of nodule ecosystem and assemblages and their sensitivity to deep-sea mining are discussed in relation to water masses, surface to seabed water circulation, the nepheloid layer and processes taking place at the sediment interface. Management tools considered include species diversity and vulnerability indexes, GIS systems, zoning, and 3D rapid environmental assessment (REA). These strategies are proposed for trial during pilot mining operations within the CCZ

Individual residency behaviours and seasonal long-distance movements in acoustically tagged Caribbean reef sharks in the Cayman Islands

Understanding how reef-associated sharks use coastal waters through their ontogeny is important for their effective conservation and management. This study used the horizontal movements of acoustically tagged Caribbean reef sharks (Carcharhinus perezi) to examine their use of coastal space around the Cayman Islands between 2009 and 2019. A total of 39 (59.1%) tagged sharks (male = 22, female = 17, immature = 18, mature = 21) were detected on the islands wide network of acoustic receivers. The detection data were used to calculate values of Residency Index (RI), Site-Fidelity Index (SFI) and minimum linear displacement (MLD), as well as for network analysis of individual shark movements to test for differences between demographics, seasons, and diel periods. Sharks were detected for up to 1,598 days post-tagging and some individuals showed resident behaviour but the majority of tagged individuals appear to have been one-off or only occasional transient visitors to the area. Generally, individuals showed strong site-fidelity to different areas displaying linear home ranges of &lt; 20 km. The evidence indicates that there was no pattern of diel behaviour. Tagged sharks generally showed increased movements within and between islands during the summer (April-September), which may be related to breeding activity. Some individuals even made occasional excursions across 110 km of open water &gt; 2,000 m deep between Grand Cayman and Little Cayman. One mature female shark showed a displacement of 148.21 km, the greatest distance reported for this species. The data shows that the distances over which some sharks moved, greatly exceeded the extent of any one of the islands' marine protected areas indicating that this species may be more mobile and dispersive than previously thought. This study provides support for the blanket protection to all sharks throughout Cayman waters, which was incorporated within the National Conservation Act in 2015.</p

Corrigendum: The Benthic Megafaunal Assemblages of the CCZ (Eastern Pacific) and an Approach to their Management in the Face of Threatened Anthropogenic Impacts

We present here the results of a UNESCO/IOC baseline study of the megafaunal assemblages of the polymetallic nodule ecosystem of 5 areas within the Clarion Clipperton Zone (CCZ) of the eastern Pacific Ocean. The work was undertaken with a view to investigating the structure of the epifaunal populations associated with the benthic biotopes being targeted for nodule mining and developing an appropriate set of management tools and options. The general characteristics of nodule ecosystem and assemblages and their sensitivity to deep-sea mining are discussed in relation to water masses, surface to seabed water circulation, the nepheloid layer and processes taking place at the sediment interface. Management tools considered include species diversity and vulnerability indexes, GIS systems, zoning, and 3D rapid environmental assessment (REA). These strategies are proposed for trial during pilot mining operations within the CCZ