This study is a quantitative evaluation of historic nesting levels of the Kemp's ridley sea turtle (Lepidochelys kempii) in 1947 based on (1) the Herrera film of a 1947 arribada, (2) Hildebrand's 1947 report regarding the 1947 arribada shown in the Herrera film, (3) historic documentation regarding the Herrera film, and (4) current nesting characteristics related to arribada size relative to total nests for a season. Using this information in a quantitative approach, we estimate a total of approximately 26 916 nests during the 1947 arribada recorded by Herrera. Based on current nesting trends, we also predict that this would equate to approximately 121 517 total nests for the 1947 season (range of 82 514–209 953), which would represent approximately 48 607 nesting females (range of 33 006–83 981). This suggests that during and prior to the 1947 nesting season a relatively robust population of Kemp's ridleys existed, which could support arribadas consisting of at least 26 916 females. The results of the current study indicate that from 1947 through 1985 (the lowest point in the decline of Kemp's ridley nesting) the Kemp's ridley population underwent a 99.4% decline (range of 99.2–99.7%) from an estimated 121 517 nests per season in 1947 to 702 nests per season in 1985. Although the Kemp's ridley population has been recovering since the 1985 season, it has deviated from its exponential recovery rate and has declined in recent years. The current levels of nesting (12 053 nests in 2014) are still relatively low at 9.9% (range of 5.7–14.6%) of the total estimated nests that occurred in 1947. It is currently not clear whether this population will recover to historic levels considering recent nesting trends and due to a variety of threats that may hinder its recovery.
The Japanese kelp Undaria pinnatifida was found on 7th September 2005 in Rı´a Deseado (Santa Cruz, Argentina). This invasive algae was registered from the lower intertidal to the upper levels of the subtidal zone. The sporophytes were fixed to slabs, gravel and rocks of variable sizes and were also present as epibionts of tunicates. The sporophytes total length ranged between 3 and 88 cm, with a mean of 28.75 cm in the intertidal and 38.3 cm in the subtidal. The density and biomass increased from the intertidal to the subtidal. The kelp population showed a higher number of small immature individuals in the intertidal than subtidal where the organisms were bigger and with more individual biomass. This first record of
The tope shark (Galeorhinus galeus Linnaeus, 1758) is a temperate, coastal hound shark found in the Atlantic and Indo-Pacific oceans. In this study, the population structure of Galeorhinus galeus was determined across the entire Southern Hemisphere, where the species is heavily targeted by commercial fisheries, as well as locally, along the South African coastline. Analysis was conducted on a total of 185 samples using 19 microsatellite markers and a 671 bp fragment of the NADH dehydrogenase subunit 2 (ND2) gene. Across the Southern Hemisphere, three geographically distinct clades were recovered, including one from South America (Argentina, Chile), one from Africa (all the South African collections) and an Australia-New Zealand clade. Nuclear data revealed significant population subdivisions (FST = 0.192 to 0.376, p<0.05) indicating limited gene flow for tope sharks across ocean basins. Marked population connectivity was however evident across the Indian Ocean based on Bayesian clustering analysis. More locally in South Africa, F-statistics and multivariate analysis supported moderate to high gene flow across the Atlantic/Indian Ocean boundary (FST = 0.035 to 0.044, p<0.05), with exception of samples from Struisbaai and Port Elizabeth which differed significantly from the rest. Discriminant and Bayesian clustering analysis indicated admixture in all sampling populations, decreasing from west to east, corroborating possible restriction to gene flow across regional oceanographic barriers. Mitochondrial sequence data recovered seven haplotypes (h = 0.216, π = 0.001) for South Africa, with one major haplotype shared by 87% of the individuals and at least one private haplotype for each sampling location except Port Elizabeth. As with many other coastal shark species with cosmopolitan distribution, this study confirms the lack of both historical dispersal and inter-oceanic gene flow while also implicating contemporary factors such as oceanic currents and thermal fronts to drive local genetic structure of G. galeus on a smaller spatial scale.
Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements.
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