The Socotra Archipelago, located in the eastern Gulf of Aden, has a unique marine environment which combines tropical and 'pseudo-temperate' elements. Studies on the fish biogeography of the archipelago, partially framed in regional studies, have substantially outpaced critical elementary research on the archipelago's fish diversity. The present study seeks to close this gap and identifies the Socotra Archipelago as a major hotspot of coastal fish diversity in the Indian Ocean. The archipelago supports unique coastal fish assemblages which are predominantly composed of coral-associated ("reef") species, in spite of the limited biogenic reef frameworks. A Preliminary Checklist comprises 682 species with confirmed records and a "Working List" includes an additional 51 records, totalling 733 faunal records in 108 families. The family Labridae is the most speciose, followed by Gobiidae, Pomacentridae, Serranidae and Chaetodontidae. The species richness of the archipelago is the highest when compared to adjacent Arabian ecoregions. The richness of the Acanthuridae, Chaetodontidae, Labridae, Pomacentridae and Pseudochromidae stand out as particularily high, and the richness of several families is as high as or higher than in the entire Red Sea. The total archipelagic richness is extrapolated at up to 875 species based on incidence-based richness models and expert opinion. Inshore fish inventories, covering 497 species, found between 14 and 132 species per site ((x) over bar = 66). Site diversity decreased across the archipelago from west to east and from north to south. Total fish diversity was highest around Socotra Island, followed by Abd al-Kuri & Kal Farun and Darsa & Samha. Occurrence frequencies were very unevenly distributed and dominated by Pornacentrus caeruleus and Thalassoma lunare, whilst many species were infrequent. The fish assemblages are dominated by species from the Indo-West Pacific and the north-western Indian Ocean. The assemblages are rich in rare species and hybrids, and include a low number of endemics (4-5), and a high number of species with far-reaching and Western Indian Ocean ranges.

During a survey of demersal fishes of the southern Red Sea coast of Saudi Arabia off Jizan, 98 species were collected by trawling. Five of these represent new records for the Red Sea: Saurida longimanus, Dactyloptena gilberti, Jaydia novaeguineae, Pomadasys maculatus and Parapercis maculata. Additionally a specimen of the rare moray Gymnothorax reticularis, previously known from only three specimens, was collected. Records of two species, Parastromateus niger and Pseudorhombus arsius, that formerly were considered questionable, are confirmed by collection of new voucher specimens. Validity of Laeops sinusarabici is confirmed. This study documents parts of the diversity of the demersal fish communities on sandy areas of the southern Red Sea, but also emphasizes that a large proportion of this area has not been explored.

Numerous photographs of live fishes posted by anglers and divers on social media and citizen science databases are important sources of information for ichthyological research. However, validating records that extend the known ecology and bathymetric or geographic distribution of species should rely on a rigorous identification process. The family Gobiidae, with their small size, superficial resemblance among species and high species richness are particularly difficult to identify. Therefore, the identification from photographs of live individuals of Mediterranean marine gobies from the continental shelf was studied. A dichotomous identification key is provided based on photographs of live individuals, allowing positive identification of 41 out of the 66 species reviewed in this publication. Then, for all 66 species we provide a brief description of important characters, which can be used for provisional identification for those species that could not be positively identified using the key. Pending further progress in identification of live individuals, we suggest that records extending the known geographic and ecological species distribution be taken into account only if they could be validated using the dichotomous identification key.

Thirty-eight species of moray eels (Muraenidae) from the Red Sea are reported in an updated review. A species account is provided for each species, along with a full synonymy of all nominal species described from the Red Sea. One species is new to science, G. pharaonis, and two species are new for the Red Sea, Gymnothorax phasmatodes (Smith) and Scuticaria tigrina (Lesson). Gymnothorax pharaonis n. sp. is a common species that has long been misidentified as G. undulatus (Lacepède), although it more closely resembles G. margaritophorus Bleeker, to which it is closely related phylogenetically. It is characterized by the following combination of characters: total vertebrae 123–128; body slender, depth at anus 17–28 in TL; maxillary teeth biserial, dentary and vomerine teeth in a single row; color brown with irregular dendritic pale markings, not interconnected or chain-like, with oblique, conspicuous, parallel streaks posteriorly in dorsal fin. The new record of the distinctive whitish G. phasmatodes is based on an underwater photograph taken at Jeddah, Saudi Arabia. The new record of Scuticaria tigrina is based on a specimen collected from Jeddah, Saudi Arabia, and underwater photographs taken from the northern part of the Red Sea. Based on an integrative taxonomical approach by a combination of morphological and phylogenetic analyses and re-examination of holotype specimens, Gymnothorax cinerascens (Rüppell) is resurrected as a valid species, and it is shown that previous records of G. hepaticus (Rüppell), with which it has previously been synonymized, should refer to G. cinerascens. The true G. hepaticus is redescribed based on examination of the holotype and additional specimens collected during the course of this study. The two species are distinguished by the color of the jaws, the position of the median intermaxillary teeth, and a slight difference in the preanal length. They are also clearly distinct genetically. The Red Sea record of Gymnothorax atolli (Pietschmann) is based on an error, possibly a misidentification of G. griseus (Lacepède). A key to the species of Red Sea moray eels and a phylogenetic tree of presently known lineages of Indo-Pacific moray eels are provided including recently collected Red Sea specimens.