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Octopus fisheries face heightened demand driven by depleted fish stocks and escalating economic value, leading to overextraction of octopus populations and magnifying threats to coastal ecosystems and the livelihoods of fishers who depend on them. Implementation of management strategies such as periodic fishing closures can offer sanctuary for octopus, providing the necessary space and time for the growth and reproduction of this rapidly proliferating species. Despite evidence of positive management outcomes, the role of periodic closures in the long-term sustainability of octopus populations remains uncertain. Here, we examine trends in octopus landings over time and the effects of periodic closures along the Mozambique Channel from Comoros to Madagascar (12°-25°S). Long-term trends in octopus landings varied across three regions: generally stable over a 6-year period in Comoros, increasing over a 4-year period in the Barren Isles and declining over a 17-year period in Atsimo Andrefana, Madagascar. We observed a significant increase in mean catch per unit effort (CPUE, kilograms/fisher-day), and mean total catch (kilograms/day) following periodic closures across villages extracting octopus from closure areas. When evaluating each region independently, we observed this positive effect across Comoros and Atsimo Andrefana, Madagascar while trends in the Barren Isles showed no effect of octopus closures. We applied generalized linear mixed models to examine the influence of 10 covariates on mean daily total catch and CPUE within 7 days and 30 days post-closure. Baseline conditions (quantified by the pre-closure CPUE and daily total catch), closure duration and start month of closure had positive, statistically significant correlations with post-closure CPUE and daily total catch. Additionally, closure duration from 13 to 16 weeks and closure size of approximately 70 hectares were qualitatively associated with net gains in CPUE. Although periodic closures yield positive outcomes for octopus fisheries, the effects may be short-lived, as observed in Atsimo Andrefana, Madagascar, where catch declined over the long-term despite temporary improvements. Our findings underscore a need for a diverse portfolio of management strategies to restore and sustain populations over the long-term. [ABSTRACT FROM AUTHOR]

Octopus fisheries face heightened demand driven by depleted fish stocks and escalating economic value, leading to overextraction of octopus populations and magnifying threats to coastal ecosystems and the livelihoods of fishers who depend on them. Implementation of management strategies such as periodic fishing closures can offer sanctuary for octopus, providing the necessary space and time for the growth and reproduction of this rapidly proliferating species. Despite evidence of positive management outcomes, the role of periodic closures in the long-term sustainability of octopus populations remains uncertain. Here, we examine trends in octopus landings over time and the effects of periodic closures along the Mozambique Channel from Comoros to Madagascar (12°-25°S). Long-term trends in octopus landings varied across three regions: generally stable over a 6-year period in Comoros, increasing over a 4-year period in the Barren Isles and declining over a 17-year period in Atsimo Andrefana, Madagascar. We observed a significant increase in mean catch per unit effort (CPUE, kilograms/fisher-day), and mean total catch (kilograms/day) following periodic closures across villages extracting octopus from closure areas. When evaluating each region independently, we observed this positive effect across Comoros and Atsimo Andrefana, Madagascar while trends in the Barren Isles showed no effect of octopus closures. We applied generalized linear mixed models to examine the influence of 10 covariates on mean daily total catch and CPUE within 7 days and 30 days post-closure. Baseline conditions (quantified by the pre-closure CPUE and daily total catch), closure duration and start month of closure had positive, statistically significant correlations with post-closure CPUE and daily total catch. Additionally, closure duration from 13 to 16 weeks and closure size of approximately 70 hectares were qualitatively associated with net gains in CPUE. Although periodic closures yield positive outcomes for octopus fisheries, the effects may be short-lived, as observed in Atsimo Andrefana, Madagascar, where catch declined over the long-term despite temporary improvements. Our findings underscore a need for a diverse portfolio of management strategies to restore and sustain populations over the long-term.

The study of geological sea-level proxies formed during previous interglacials is a common approach to assess how global sea level will evolve under warmer climate conditions. Over the last decades, technical advancements in both survey and geochronology have allowed improving our knowledge of past sea-level highstands. This is of prime importance to refine our understanding of processes contributing to sea-level changes, and ultimately to improve both local and global sea-level projections. Last Interglacial sea-level proxies in the Western Indian Ocean (and more specifically the island nation of Madagascar), have been less investigated than in other intertropical oceans over the last decades. As a result, paleo sea-level data in this region are less abundant and less precise than elsewhere. Here, we report the results of two field campaigns aimed at studying the site of Lembetabe, southwest Madagascar, where a fossil reef was first described by the researcher René Battistini more than 50 years ago. We estimate paleo relative sea level history in space and time from 15 new U-series ages from a fossil reef platform mapped with differential GNSS and drone photogrammetry. Our data suggest that, between 129 ka and 115 ka, paleo relative sea level at this location was about 3.4 ± 1.4 m above modern. Once corrected for glacial isostatic adjustment, we find that paleo global mean sea level did not exceed 3 m above modern. Only slight crustal subsidence would reconcile the peak Last Interglacial sea level measured at Lembetabe with the 5–10 m range reported in the literature. • Fossil reef dated to the Last Interglacial in southwest Madagascar. • Stable paleo relative sea level during the LIG at about 3.4 ± 1.4 m above modern. • Interplay between glacial isostatic adjustment and global mean sea level. [ABSTRACT FROM AUTHOR]

Background: There is increasing recognition of the concordance between marine biogeographic and phylogeographic boundaries. However, it is still unclear how population-level divergence translates into species-level divergence, and what are the principal factors that first initiate that divergence, and then maintain reproductive isolation. This study examines the likely forces driving population and lineage divergences in the broadly-distributed Indo-Pacific spiny lobster Panulirus homarus, which has peripheral divergent lineages in the west and east. The study focuses particularly on the West Indian Ocean, which is emerging as a region of unexpected diversity. Mitochondrial control region (mtCR) and COI sequences as well as genotypes of 9 microsatellite loci were examined in 410 individuals from 17 locations grouped into 7 regions from South Africa in the west, and eastward across to Taiwan and the Marquesas Islands. Phylogenetic and population-level analyses were used to test the significance and timing of divergences and describe the genetic relationships among populations. Results: Analyses of the mtCR revealed high levels of divergence among the seven regions (Ф = 0.594, P < 0.001). Microsatellite analyses also revealed significant divergence among regions, but at a much lower level (F = 0.066, P < 0.001). The results reveal different patterns of mtCR v. nDNA divergence between the two distinct peripheral lineages: a subspecies in South Africa and Madagascar, and a phylogeographically diverged population in the Marquesas. The results also expose a number of other more fine-scale population divergences, particularly in the Indian Ocean. Conclusions: The divergence of peripheral lineages in the west and east of the species' range appear to have been initiated and maintained by very different processes. The pattern of mitochondrial and nuclear divergence of the western lineage, implicates processes of parapatric isolation, secondary contact and introgression, and suggests possible maintenance through adaptation and behavioural reproductive isolation. In contrast, the eastern lineage appears to have diverged through a rare colonisation event, maintained through long-term isolation, and matches expectations of the core-periphery hypothesis. The process of active peripheral speciation may be a common force in the Indo-Pacific that helps drive some of the regions' recognized biogeographic boundaries. [ABSTRACT FROM AUTHOR]

Recent trends, variations and tele-connections between the two large regional sub-systems over the Asian domain, the South Asian and the East Asian monsoons are explored using data for the 1901-2014 period. Based on trend analysis a dipole-type configuration with north-drought and south-flood over South as well as East Asia is observed. Two regions over South Asia, one exhibiting a significant decreasing trend in summer monsoon rainfall over northeast India and the other significant increasing trend over the northern parts of the west coast of India are identified. Similarly two regions over East Asia, one over South Korea-southern parts of Japan and the other over South China are also identified both indicating a significant increasing trend in the summer monsoon rainfall. These trends are examined post 1970s. Possible factors associated with the recent trends are explored. Analysis of sea surface temperature (SST), mean sea level pressure and winds at lower troposphere indicates that the entire monsoon flow system appears to have shifted westwards, with the monsoon trough over South Asia indicating a westward shift by about 2-3° longitudes and the North Pacific Subtropical High over East Asia seems to have shifted by about 5-7° longitudes. These shifts are consistent with the recent rainfall trends. Furthermore, while the West Indian Ocean SSTs appear to be related with the summer monsoon rainfall over northern parts of India and over North China, the West Pacific SSTs appear to be related with the rainfall over southern parts of India and over South Korea- southern Japan sector. [ABSTRACT FROM AUTHOR]

The reef fauna connectivity of the West Indian Ocean ( WIO) is one of the least studied globally. Here we use genetic analyses of the grouper Epinephelus merra ( Bloch 1793) to determine patterns of connectivity and to identify barriers to dispersal in this WIO marine area. Phylogeographic and population-level analyses were conducted on cytochrome b sequences and microsatellites (13 loci) from 557 individuals sampled in 15 localities distributed across the West Indian Ocean. Additional samples from the Pacific Ocean were used to benchmark the WIO population structure. The high level of divergence revealed between Indian and Pacific localities (of about 4.5% in sequences) might be the signature of the major tectonic and climatic changes operating at the Plio- Pleistocene transition, congruently with numerous examples of Indo-Pacific speciation. In comparison, the E. merra sequences from the Indian Ocean constitute a monophyletic clade with a low average genetic distance (d < 0.5%). However both genetic markers indicated some structure within this ocean. The main structure revealed was the isolation of the Maldives from the WIO localities (a different group signature identified by clustering analysis, great values of differentiation). Both marker types reveal further significant structure within the WIO, mainly the isolation of the Mascarene Islands (significant AMOVA and isolation-by-distance patterns) and some patchy structure between the northernmost localities and within the Mozambique Channel. The WIO genetic structure of E. merra appeared congruent with main biogeographic boundaries and oceanographic currents. [ABSTRACT FROM AUTHOR]

The high financial costs and institutional constraints of adapting to climate change necessitate joint planning with other development and environmental priorities, especially in Small Island Developing States. In response, ecosystem-based adaptation (EbA) is gaining recognition as a cost-effective and synergistic approach for enhancing livelihoods through nature's services, building community resilience, and integrating marine spatial planning. Using Seychelles in the West Indian Ocean as a case study, we assess the readiness for climate change as a tool to implement and mainstream EbA across various spatial scales. Our assessment highlights certain governance mechanisms and policy processes that could contribute to joint adaptation and economic planning and in achieving multiple objectives. These include leadership, institutional mechanisms, science-policy nexus, decision-making structures, stakeholder involvement, and technological innovation. These readiness factors as well as knowledge gaps on future risks provide lessons for other SIDS in their climate change and integrated coastal management initiatives. As such, the needs to strengthen local governing capacity, secure sustainable funding, and promote adaptation research for long-term monitoring and cross-scale linkages are warranted. [ABSTRACT FROM AUTHOR]

Background: A rapid marine fish biodiversity assessment and subsequent surveys were conducted at D'Arros Island and St. Joseph Atoll, Amirantes, Republic of Seychelles. Results: Dive surveys recorded the first national occurrence of 16 reef associated fish species. Ten species had regionally cosmopolitan distributions in the West Indian Ocean and their occurrence in Seychelles was expected and confirmed. The occurrence of an additional six species represented range extensions of between approximately 2000 and 4300 km further than previously reported. Conclusions: The results of this assessment suggest that the current ichthyofaunal diversity of the Amirantes Island group in the Republic of Seychelles may be underestimated and future surveys are likely to reveal the presence of additional species. [ABSTRACT FROM AUTHOR]