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Although transboundary conservation areas (TCAs) are critical tools for protecting ecosystems and ecological processes that transcend national jurisdictions, they are challenging to create due to the differences in governance contexts and capacity and power dynamics among countries. Marine TCAs are also more difficult to enforce relative to terrestrial TCAs because most nations still treat oceans as open access. Current guidelines for TCA development and implementation also focus mostly on terrestrial TCAs, which are not practical for marine TCAs. Hence, we reviewed the challenges associated with the design and management of marine TCAs and devised analytical and practical approaches to support the application of spatial planning frameworks and adaptive governance mechanisms. We used the lessons from the review to examine the decisions made for the proposed marine TCA in the Kenya-Tanzania border region and created options and considerations to promote effective design and management processes. We found the obstacles to marine TCAs in general are related to issues of fit, particularly differences in environmental research capacity, socioeconomic contexts, and internal institutional arrangements. These included differences in knowledge and capacity for marine ecological research and conservation; ability to adjust and update data; differences in values, interests, and resource uses; conservation costs; jurisdictional differences; engagement of multiple levels of organization; and differences in legal bases and policy development processes. Understanding and reconciling these challenges during the TCA development process can help enhance meaningful discussions in the design of the TCA and cultivate the enabling conditions for collaborative governance across countries and within different levels of organization from national to local actors.

Consideraciones en el diseño y gestión del área marina de conservación transfronteriza en Kenia y Tanzania Resumen Aunque las áreas de conservación transfronterizas (ACT) son herramientas importantes para proteger los ecosistemas y los procesos ecológicos que trascienden la jurisdicción nacional, crearlas es un reto debido a la diferencia en los contextos de gobierno y la capacidad y las dinámicas de poder entre los países. Las ACT marinas también son más difíciles de ejecutar en relación a las terrestres porque la mayoría de los países todavía tratan al océano como de libre acceso. Los lineamientos actuales para el desarrollo e implementación de las ACT también se enfocan principalmente en las ACT terrestres, lo cual no es práctico para las ACT marinas. Por lo tanto, revisamos los retos asociados con el diseño y gestión de las ACT marinas y concebimos estrategias analíticas y prácticas para apoyar con la aplicación de los marcos de planeación espacial y los mecanismos de gobierno adaptativo. Usamos lo aprendido con la revisión para analizar las decisiones tomadas para la ACT marina propuesta en la región fronteriza de Kenia y Tanzania y creamos opciones y consideraciones para promover el diseño y procesos de manejo efectivos. Encontramos que los obstáculos para las ACT marinas en general se relacionan con temas de ajuste, en particular las diferencias en la capacidad de investigación ambiental, los contextos socioeconómicos y los acuerdos institucionales internos. Estos obstáculos incluyeron diferencias en el conocimiento y capacidad para la investigación ecológica marina; la habilidad para ajustar y actualizar datos; las diferencias en los valores, intereses y usos de los recursos; los costos de conservación; las diferencias jurídicas; la participación de varios niveles de organización; y las diferencias en las bases legales y los procesos de desarrollo de políticas. El entendimiento y reconciliación de estos retos durante el proceso de desarrollo de una ACT puede ayudar a mejorar las discusiones significativas en el diseño de la ACT y a cultivar las condiciones que permitan la gestión colaborativa entre los países y entre los diferentes niveles de organización, desde el nacional hasta los actores locales.

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The coastline of Sub-Saharan Africa hosts highly diverse fish communities of great conservation value, which are also key resources for local livelihoods. However, many costal ecosystems are threatened by overexploitation and their conservation state is frequently unknown due to their vast spatial extent and limited monitoring budgets. Here, we evaluated the potential of citizen science-based eDNA surveys to alleviate such chronic data deficiencies and assessed fish communities in Mozambique using two 12S metabarcoding primer sets. Samples were either collected by scientific personnel or trained community members and results from the two metabarcoding primers were combined using a new data merging approach. Irrespective of the background of sampling personnel, a high average fish species richness was recorded (38 ± 20 OTUs per sample). Individual sections of the coastline largely differed in the occurrence of threatened and commercially important species, highlighting the need for regionally differentiated management strategies. A detailed comparison of the two applied primer sets revealed an important trade-off in primer choice with MiFish primers amplifying a higher number of species but Riaz primers performing better in the detection of threatened fish species. This trade-off could be partly resolved by applying our new data-merging approach, which was especially designed to increase the robustness of multiprimer assessments in regions with poor reference libraries. Overall, our study provides encouraging results but also highlights that eDNA-based monitoring will require further improvements of, for example, reference databases and local analytical infrastructure to facilitate routine applications in Sub-Saharan Africa.

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Invasive species disrupt relations between endemics and their ecosystem and are an increasing biodiversity conservation problem. The Hemidactylus genus comprises the most successful invasive reptile species, including the worldwide-distributed Hemidactylus mabouia. In this study, we used 12S and ND2 sequences to taxonomically identify and tentatively determine the diversity and origin of these invaders in Cabo Verde while also clarifying this for several Western Indian Ocean (WIO) populations. By comparing our sequences to recently published ones, we showed, for the first time, that Cabo Verde individuals belong to the H. mabouia sensu stricto lineage and that both of its sublineages (a and b) occur there. Both haplotypes are also in Madeira, which indicates a connection between these archipelagos, possibly related to the past Portuguese trading routes. Across the WIO, results clarified the identity of many island and coastal populations, showing that this likely invasive H. mabouia lineage is widespread in the region, including northern Madagascar, with important conservation implications. Colonisation origins were difficult to access due to the wide geographical spread of these haplotypes; thus, several possible scenarios were outlined. The introduction of this species throughout western and eastern Africa may threaten endemic taxa and needs to be closely monitored.

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Tropical deep reefs (>30 m) are biologically and ecologically unique ecosystems with a higher geographic reach to shallow (<30 m) reefs. Yet they are poorly understood and rarely considered in conservation practices. Here, we characterise benthic and fish communities across a depth gradient (10-350 m) in remote coral atolls in Seychelles, Western Indian Ocean. Using taxonomic and trait-based approaches we present the taxonomic and functional composition of shallow and deep reef communities, with distinct communities and traits dominating different depths. Depth-related changes in community metrics (taxa richness, abundance and biomass) and functional diversity metrics (richness, dispersion, and evenness) indicate complex relationships across different biological components (fish, benthos) that differ between shallow and deep reefs. These in turn translate into different patterns of reef resilience against disturbance or species invasions with depth. Notably, deep reefs host on average fewer and less abundant taxa but with higher functional contribution and originality scores, some of which are of conservation concern. Overall, the results highlight the unique nature of deep reefs that requires their explicit consideration in conservation and management activities.

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Zooplankton plays an essential role in marine ecosystems as the link between primary producers (phytoplankton) and higher trophic levels in food webs, and as a dynamic pool of recruits for invertebrates and fish. Zooplankton communities are diverse with a patchy distribution at different spatial scales, influenced by oceanographic processes. The continental shelf of eastern South Africa is narrow and exposed to the western-boundary Agulhas Current, with some shelter against strong directional flow provided by the broader KwaZulu-Natal Bight, a coastal offset adjacent to an estuary. We compared zooplankton species richness, diversity and relative abundance of key taxa among sheltered and exposed shelf areas using metabarcoding and community analysis, to explore the ecological role of the bight in a highly dynamic ocean region. Metabarcoding recovered higher richness and diversity at a finer resolution than could previously be achieved with traditional microscopy. Of 271 operational taxonomic units (OTUs) recovered through metabarcoding, 63% could be matched with >95% sequence similarity to reference barcodes. OTUs were dominated by malacostracan crustaceans (161 spp.), ray-finned fishes (45 spp.) and copepods (28 spp.). Species richness, diversity and the relative abundance of key taxa differed between sheltered and exposed shelf areas. Lower species richness in the bight was partly attributed to structurally homogeneous benthic habitats, and an associated reduction of meroplanktonic species originating from local benthic-pelagic exchange. High relative abundance of a ray-finned fish in the bight, as observed based on fish eggs and read counts, confirmed that the bight is an important fish spawning area. Overall, zooplankton metabarcoding outputs were congruent with findings of previous ecological research using more traditional methods of observation.

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Seagrass meadows are considered crucial natural carbon stocks. However, in Tanzania, few species have been assessed for their potential carbon stocks and variability in percentage organic carbon (%Corg) stocks. The study reports the contributions of seagrasses Halodule uninervis and Syringodium isoetifolium in carbon storage in WIO region. Findings revealed a significantly higher %Corg in seagrass meadows compared to unvegetated, confirming that seagrass heightens organic carbon storage. The seagrass carbon storage varied significantly among sites ranging from 4.05 ± 0.7% in Kaole to 0.62 ± 0.05% in Kunduchi. Syringodium isoetifolium meadows had higher organic carbon (p = 0.002) than H. uninervis. The partial least square analysis showed that below- and aboveground biomass and canopy height were positively correlated to %Corg. Sediment density and porosity were the vital predictor but negatively correlated with %Corg. The study showed a higher %Corg in the marine protected area, which could be linked to seagrass structural complexities and sediment porosity.

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Invertebrate gleaning is a small-scale fishery that commonly occurs in the intertidal zone across the tropical Indo-Pacific. In this study, we investigated and analyzed several components of this fishery on the island of Unguja, Zanzibar by employing the social-ecological systems framework from Ostrom 2009. In doing so, we conducted ecological surveys, catch assessments, interviews with gleaners, household surveys, focus group interviews and analyzed the governance structure. This social-ecological systems analysis showed that gleaning is important for food security, local culture and livelihood. Yet, the multiple approaches in our study revealed that the local intertidal zone is degrading and that the gleaned catch is changing. Local narratives indicate that economically important bivalves (Modiolus spp.) and gastropods (Strombus spp.) are in decline, which was paralleled with low abundances of both genera within the ecological survey of the intertidal and catch landing assessment. We recommend that invertebrate gleaning, a fishery mainly comprised of women should be included in fisheries management.

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A new species of Eniochobothrium Shipley and Hornell, 1906 was recovered from the Oman cownose ray (Rhinoptera jayakari Boulenger) from the body of water off the south-eastern coastline of the KwaZulu-Natal Province, South Africa. Eniochobothrium acostae n. sp. is described on morphological and molecular grounds. The new species is placed within Eniochobothrium (viz., Eniochobothrium gracile Shipley and Hornell, 1906, Eniochobothrium qatarense Al Kawari, Saoud and Wanas, 1994, Eniochobothrium euaxos Jensen, 2005) by possessing key generic characteristics such as the absence of a vagina, expansion of the anterior region of the strobila forming a trough and presence of a thick-walled cirrus sac. Molecular phylogenetic analyses of the partial 28S rRNA and mtCOI genes confirm the generic characterisation as the newly proposed species groups together with other members of the genus. Eniochobothrium acostae n. sp. currently represents the largest described species of the genus; it possesses slightly fewer testes compared to most congeners, given that this feature has been provided in the original description (e.g., E. euaxos and E. qatarense). The new species of Eniochobothrium is the fourth valid species described to date and the first species record from South African waters.

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BACKGROUND AND AIMS: The tribe Danaideae (Rubiaceae) is almost exclusively endemic to the Western Indian Ocean Region (WIOR), and encompasses the genera Danais, Payera and Schismatoclada that occur in humid, sub-humid and mountain and mountain bio climate zones. Much of the species diversity is endemic to restricted, remote and/or mountainous areas of Madagascar and recent field work on the island indicates substantial unknown diversity of the Danaideae. Furthermore, the monophyly of the Malagasy genera Payera and Schismatoclada has been questioned in previous work, species delimitations and phylogenetic relationships within the genera are poorly understood, and the distribution and evolution of gross morphological features have not been assessed. METHODS: We conducted morphological investigations, and produced robust phylogenies of Danaideae based on nuclear and plastid sequence data from 193 terminals. Ample plant material has been newly collected in the WIOR for the purpose of the present study, including potentially new species unknown to science. We performed Bayesian non-clock and relaxed-clock analyses employing three alternative clock models of a dataset with a dense sample of taxa from the entire geographical ranges of Danaideae. Based on the results, we discuss species diversity and distribution, relationships, and morphology in Danaideae. KEY RESULTS: Our results demonstrate the monophyly of Danaideae, its three genera and 42 species. Nine species are resolved as non-monophyletic. Many geographically distinct but morphologically heterogeneous lineages were identified, and morphological features traditionally considered diagnostic of subgroups of the genera, used for example in species identification keys, are not clade-specific. CONCLUSIONS: Our results demonstrate that Madagascar contains ample previously undocumented morphological and species diversity of Danaideae. Our novel approach to molecular phylogenetic analyses as a precursor to taxonomic revisions provides numerous benefits for the latter. There are tentative indications of parallel northward diversification in Payera and Schismatoclada on Madagascar, and of geographical phylogenetic clustering despite the anemochorous condition of Danaideae.

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Marine symbioses are integral to the persistence of ecosystem functioning in coral reefs. Solitary corals of the species Heteropsammia cochlea and Heterocyathus aequicostatus have been observed to live in symbiosis with the sipunculan worm Aspidosiphon muelleri muelleri, which inhabits a cavity within the coral, in Zanzibar (Tanzania). The symbiosis of these photosymbiotic corals enables the coral holobiont to move, in fine to coarse unconsolidated substrata, a process termed as "walking." This allows the coral to escape sediment cover in turbid conditions which is crucial for these light-dependent species. An additional commensalistic symbiosis of this coral-worm holobiont is found between the Aspidosiphon worm and the cryptoendolithic bivalve Jousseaumiella sp., which resides within the cavity of the coral skeleton. To understand the morphological alterations caused by these symbioses, interspecific relationships, with respect to the carbonate structures between these three organisms, are documented using high-resolution imaging techniques (scanning electron microscopy and µCT scanning). Documenting multi-layered symbioses can shed light on how morphological plasticity interacts with environmental conditions to contribute to species persistence.

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Tunas are among the most traded and valued fish species, and good traceability of tuna products in the world market is needed to protect both consumers and tuna stocks. To that purpose, high-resolution proton nuclear magnetic resonance (1H NMR) spectroscopy combined with multivariate data analysis was used to investigate the molecular components of the aqueous extract of white and red muscles in three species of wild tropical tuna species, namely yellowfin tuna (Thunnus albacares), skipjack tuna (Katsuwonus pelamis) and bigeye tuna (T. obesus). Principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) applied to the processed 1H NMR spectra showed significant separation according to the species and size category (i.e., small tunas < 80 cm fork length vs large tunas > 80 cm fork length), the storage conditions on-board the purse-seine vessels (i.e., brine- vs deep-freezing), and the geographical origin (i.e., where the tuna was caught: Mozambique Channel vs western-central Indian Ocean). The major groups of metabolites responsible for differentiation in PLS-DA score plots were the dipeptides (anserine, carnosine) and organic acids (lactate, creatine/phosphocreatine) in the white muscle, and the free amino acids, essential nutrients (choline and its derivatives, phosphatidylethanolamine), dipeptides and organic acids in the red muscle. Our results showed that NMR-based metabolomics is a powerful tool to efficiently discriminate specific profiles among wild tuna species, raw muscle tissues, fish storage conditions and tuna geographical origin.

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Oysters are important resources for the daily diet, a source of economic income for many coastal communities and a delicacy for the tourism industry. In this study, the oysters (Pinctada capensis and Saccostrea cucullata) were investigated with the aim to assess the catch per unit effort, density and size composition. The study was conducted over a three-year period on Inhaca Island, Southern Mozambique. For both species, perception of fishery trends from collectors was carried out through habitat censuses and interviews. Transects, quadrats and daily fisheries catches approaches were used. Results show that P. capensis is the most exploited on the island. A total of 72.1% of respondents pointed that the oyster P. capensis is decreasing, due to excessive catching (75.4%) followed by natural death (24.6%), while 20.9% affirmed that the resource is stable and 7.0% are unaware about the resource trend. Oyster densities, sizes and catches per unit effort were higher in less accessible areas only for P. capensis. The present study provides valuable baseline information to recommend best practices to improve the exploitation, and access the need for introduction of aquaculture, towards the sustainable management and conservation of oysters, and ultimately to ameliorate people's livelihoods.

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The poorly known majid genus Majella Ortmann, 1893, is revised. The genus was previously known only from one species, M. brevipes Ortmann, 1893, described from Japan and reported from east Africa. Majella brevipes is redescribed and figured in detail from the type and material from the type locality, Sagami Bay in Japan. This species is now restricted to Japan. Specimens from east Africa are herein described as two new species: M. skolopion n. sp. and M. pristis n. sp.; they differ markedly from M. brevipes (now restricted to Japan) in the arrangement of spines on the carapace and pereopods, third maxillipeds, male pleon and gonopods.

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Generating genomic data for 19 tropical reef fish species of the Western Indian Ocean, we investigate how species ecology influences genetic diversity patterns from local to regional scales. We distinguish between the α, ß and γ components of genetic diversity, which we subsequently link to six ecological traits. We find that the α and γ components of genetic diversity are strongly correlated so that species with a high total regional genetic diversity display systematically high local diversity. The α and γ diversity components are negatively associated with species abundance recorded using underwater visual surveys and positively associated with body size. Pelagic larval duration is found to be negatively related to genetic ß diversity supporting its role as a dispersal trait in marine fishes. Deviation from the neutral theory of molecular evolution motivates further effort to understand the processes shaping genetic diversity and ultimately the diversification of the exceptional diversity of tropical reef fishes.

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The species of the cosmopolitan sponge genus Mycale occurring in the tropical Indo-West Pacific region and adjacent subtropical waters are reviewed taxonomically. Specimens incorporated in the collections of the Naturalis Biodiversity Center form the basis of this comprehensive study, supplemented by (type) specimens borrowed from or examined in other institutions. Specimens available numbered 351, belonging to 44 species, including 14 species new to science, Mycale (Aegogropila) prognatha sp.nov., Mycale (Carmia) amiri sp.nov., Mycale (Carmia) fungiaphila sp.nov., Mycale (Carmia) monomicrosclera sp.nov., Mycale (Carmia) tenuichela sp.nov., Mycale (Carmia) tubiporicola sp.nov., Mycale (Carmia) tydemani sp.nov., Mycale (Mycale) asigmata sp.nov., Mycale (Mycale) grandoides sp.nov., Mycale (Mycale) sundaminorensis sp.nov., Mycale (Naviculina) mascarenensis sp.nov., Mycale (Paresperella) sceptroides sp.nov., Mycale (Paresperella) seychellensis sp.nov., Mycale (Zygomycale) sibogae sp.nov. Three species, indicated by the designation 'aff.', were not definitely assigned to known or new species due to uncertainty of their identity. The genus Kerasemna, previously considered a junior synonym of Mycale, was revived as an additional subgenus Mycale (Kerasemna). One species, previously assigned to the genus Desmacella as D. lampra De Laubenfels is here reassigned to Mycale, subgenus at present undecided. Additionally, species previously reported from the region but not represented in our collections are briefly characterized and discussed. We propose new names Mycale (Mycale) mauricei nom.nov. for Mycale macrochela Burton (junior primary homonym of Mycale fistulata var. macrochela Hentschel) and Mycale (Mycale) bouryesnaultae nom.nov. for Mycale (Mycale) fibrosa Boury-Esnault Van Beveren (junior primary homonym of Mycale (Aegogropila) adhaerens subsp. fibrosa Koltun). Keys to the species of each subgenus occurring in the region are provided. The opportunity of having studied this comprehensive set of species and specimens from the tropical Indo-West Pacific is taken to review and discuss the morphological and biogeographical data gathered so far on the genus Mycale. The genus currently comprises approximately 255 accepted species, with highest diversity focused in tropical Atlantic and Indo-West Pacific regions as well as in warm-temperate Mediterranean-Atlantic regions.

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An annotated checklist of chondrichthyan fishes (sharks, batoids, and chimaeras) occurring in South African waters is presented. The checklist is the result of decades of research and on-going systematic revisions of the regional fauna. The chondrichthyan fauna of South Africa is one of the richest in the world with 191 species, comprising 50 families and 103 genera. It consists of 30 families, 64 genera, and 111 species of sharks; 17 families, 36 genera, and 72 species of batoids; and, 3 families, 5 genera, and 8 species of chimaeras. The most species-rich shark families are the whaler sharks Carcharhinidae with 20 species followed by the deepwater catsharks Pentanchidae with 13 species. The most species-rich batoid families are the hardnose stakes Rajidae with at least 21 species followed by the stingrays Dasyatidae with 13 species. This monograph represents the first detailed annotated checklist of chondrichthyans from South Africa in over 30 years.

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Persistent halogenated compounds (PHC) are of concern for human and environmental health. Persistent Organic Pollutants (POPs) are regulated by international treaties, but alternative compounds such as novel brominated flame retardants (NBFRs) and Dechlorane Plus (DP) are not-yet they are increasingly used. There are no data on PHCs in coral reef biota from tropical islands in the western Indian Ocean (WIO). For this assessment, three hard coral genera, two soft coral genera, and ember parrotfish (Scarus rubroviolaceus) were collected from the remote Rodrigues, Agalega, and St. Brandon's Atoll (Republic of Mauritius) in the Mascarene Basin of the WIO. Five compounds - Pentabromotoluene (PBT), γ-HCH, p,p'-DDE, HCB, and BDE-47- were quantifiable in all samples. Hard coral consistently contained the lowest concentrations of PHCs, except for NBFRs. The presence of BDE-47 suggests long-range aerial transport. We quantified DP, currently a candidate POP, in coral reef biota. PBT was measured in all samples also suggests long-range transport. Because the hard coral, soft coral, and fish had differing concentrations and patterns of PHCs, future surveys should stratify sampling accordingly. Agalega and St. Brandon's Atoll can be considered as locations to monitor changes in background concentrations of pollutants due to their remoteness.

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Mercury, omega-3 (docosahexaenoic acid, DHA and eicosapentaenoic acid, EPA) and macronutrients (fat and proteins) were quantified on a wet weight (ww) basis in 20 species of fish taken as bycatch in tropical tuna fisheries. Based on a hazard quotient taking into account mercury and omega-3 contents, a benefit-risk assessment for the consumption of these pelagic species was conducted for three people categories: young children, children and adults. All fish bycatch were found to be an excellent source of proteins (min‒max = 14.4-25.2 g/100 g fillet), had low omega-6/omega-3 ratios (<1, except for silky shark), and had mercury content below the safety limits defined by sanitary agencies. Silky shark and Istiophoridae had the highest mercury contents (min‒max = 0.029-0.317 ppm ww). Omega-3 contents were the lowest in silky shark (0.2 ± 0.2 mg/100 g fillet) and the highest in striped marlin (3.6 ± 3.2 g/100 g fillet). Billfishes (Istiophoridae, including striped marlin), minor tunas (Scombridae), and Carangidae had the highest omega-3 contents (min‒max = 0.68-7.28 g/100 g fillet). The highest hazard quotient values obtained for silky shark and great barracuda reflected a lower nutritional benefit (i.e., low omega-3 source) than risk (i.e., mercury exposure), making them not advisable for consumption. Eight species had low hazard quotients, and among them cottonmouth jack and flat needlefish were found of high health interest (high protein, moderate fat contents, and low omega-6/omega-3 ratio). A daily serving portion of 85-200 g (according to people category) can be recommended for these species. Batfish, and to a lower extent pompano dolphinfish and brassy chub, can also be consumed safely and would provide greater health benefits than risks. These results advocate for a better access of these species to local populations.

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A new stingray, Hemitrygon yemenensis sp. nov., is described from old preserved material collected on the Arabian Sea coast of eastern Yemen. Consistent with other members of the genus, H. yemenensis sp. nov. is a small dasyatid (males mature at ~22 cm disc width), but it is the only Hemitrygon known to occur outside the western Pacific and eastern Indian Oceans. Hemitrygon yemenensis sp. nov. most closely resembles H. bennetti, but H. yemenensis is separable based on several characters including a longer and more narrowly pointed snout, shorter tail, and a longer disc and head. Hemitrygon yemenensis is unknown to science beyond the two type specimens collected nearly 120 years ago.

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Little is known about the prevalence of microplastics (MPs) in East Africa. In the present study, sediments were sampled at 18 sites along the Tanzanian coast that exhibit different levels of anthropogenic activity and were extracted using floatation methodology. Cockles (Anadara antiquata) were collected only from eight sites and MPs were extracted following NaOH digestion. MPs were most abundant at Mtoni Kijichi Creek (MKC, 2972 ± 238 particles kg-1 dry sediment), an industrial port in Dar es Salaam, and significantly higher than all other sites where the abundance range was 15-214 particles kg-1 dry sediment (p < 0.05, one-way ANOVA). Fragments and fibers were found at all sites. Polypropylene and polyethylene were identified polymers. MPs were found in cockles from all sampled sites with both frequencies of occurrence and MPs per individual subject to site-specific variation. This study provides a baseline of MP data in a previously uninvestigated area.

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