Investigations on the diversity of cryptobenthic reef fishes resulted in observation of seven new geographic records for Lakshadweep waters, India: halfbarred goby Amblygobius semicinctus, target shrimpgoby Cryptocentrus strigilliceps, thread shrimpgoby Ctenogobiops mitodes, eye-bar goby Gnatholepis anjerensis, Miki's dwarfgoby Eviota mikiae, Erythrops goby Bryaninops erythrops, and Enneapterygius sp. Ctenogobiops mitodes is a new record to Indian waters. The genera Cryptocentrus and Bryaninops are reported from Lakshadweep for the first time. The observations were conducted in the lagoon and reef slope of Kavaratti Island, one of the 12 atolls of the Lakshadweep archipelago, from January–March 2021. The cryptobenthic reef fishes were observed and recorded through underwater photography and videography.

The implementation of consistent and continuous biodiversity survey efforts over a long period of time is imperative to the examination of temporal diversity patterns and the evaluation of existing conservation measures' effectiveness. In Hong Kong, a marine biodiversity hotspot in the South China Sea, reef fish diversity has been poorly documented due to inconsistent and sparse biodiversity surveys, posing considerable challenges to long-term monitoring of biodiversity dynamics. To fill in the data gap, regular scuba underwater visual surveys were conducted across 55 dive sites in Hong Kong during the wet seasons from 2018–2021. After ~3171 hours of underwater survey, 31 reef fish species from 14 families that are new to Hong Kong have been recorded, including species from Acanthuridae, Chaetodontidae, Diodontidae, Gobiidae, Labridae, Mullidae, Nemipteridae, Pinguipedidae, Pomacanthidae, Pomacentridae, Ptereleotridae, Solenostomidae, Tetraodontidae and Tetrarogidae. As Hong Kong sits within the natural distribution range of the newly recorded species, the possibility of artificial release was eliminated after careful consideration. These species were all found outside the currently established Marine Protected Areas (MPAs) in Hong Kong, indicating the need for comprehensive research to identify potential marine reef fish hotspots in areas that are unprotected thus far. Our findings demonstrate the need to establish a long-term monitoring programme that can fill in data gaps of local marine biodiversity to enable the establishment of effective MPAs, and to lay down a baseline for future research and monitoring, so as to safeguard Hong Kong's marine biodiversity in the long term.

Understanding the role played by sunken vessels in Mediterranean marine ecosystems is acquiring increasing importance. The aim of this research was to study the fish communities associated with four shipwrecks, by means of underwater visual censuses performed by a remotely operated vehicle, and to test the differences in composition of fish assemblages between these shipwrecks and the adjacent soft bottoms, considered as control sites. Multivariate analysis on the total fish assemblage showed significant differences between wrecks and controls. Results also showed higher levels of species richness and abundance near all wrecks than at a short distance from them on soft bottoms, thus indicating that these sunken vessels, thanks to their higher habitat complexity, act as artificial reefs, attracting aggregations of fish species and leading to a greater diversification of the local fish assemblage. Nevertheless, shipwrecks, which are an ideal target for recreational fishermen, could contribute to the over-exploitation of some high-value fish species, such as Mycteroperca rubra, Dentex dentex and Diplodus spp., attracted by the artificial hard substrate of the vessel-reefs. The recent European directives suggest an urgent need for a better understanding of the crucial role played by these potential sources of pollutants on marine environments and ecosystems. An ecosystem approach to study and monitor these pollutant sources is, therefore, mandatory for appropriate remediation and/or mitigation of the potential negative effects on a productive and healthy ocean.

The rising impact of invasive species and climate change on Mediterranean fish biodiversity highlight the urgency to evaluate the current status of natural assemblages. Here we investigated the rocky-reef fish of Malta and Lampedusa (Strait of Sicily, Mediterranean Sea), two islands of high biogeographical importance subjected to a different level of protection and anthropic pressure. By using underwater visual census, a total of 192 counts were performed in May–June and September–October 2007 using a hierarchical spatial design and four depth layers. Overall, 23 families and 61 different taxa were recorded. Out of them, two highly invasive species were censused (i.e. Siganus luridus and Fistularia commersonii) with relatively low abundances. Native Labridae and Sparidae shape the assemblage structure of both islands, and thermophilic species such as Sparisoma cretense and Thalassoma pavo occur with high densities. The fish assemblages of Malta and Lampedusa were relatively similar in species composition, richness and total abundance. Nevertheless, multivariate analysis depicted significant differences between these two islands, mainly attributable to the unevenness of Labridae. Significant differences in the size distribution of the most abundant species were detected between islands, with parallel variation across time. The pattern of spatio-temporal variability of the whole assemblage structure strongly resembled that of nekto-benthic fish, hence pointing out the relevance of this guild as an indicator species group in future monitoring activity. This study will serve as a current baseline against which future changes in the central Mediterranean fish assemblages can be assessed.

The sea cucumber fishery has been providing an important means of livelihood to the coastal fishing communities in Sri Lanka for centuries. Stock status, level of exploitation and mortality parameters of eleven commercial sea cucumber species were studied off the north-west and the east coasts of Sri Lanka using data collected from an underwater visual census and fishery-dependent surveys carried out in 2008 and 2009. The total abundance of sea cucumbers was higher in the north-west than the east (P < 0.01). However, the total abundance of all the species declined between 2008 and 2009. The commercial fishery predominantly relies on two nocturnal species: Holothuria spinifera and Thelenota anax. Holothuria spinifera had the highest contribution (73.2%) to the total landings in the north-west while this was provided by T. anax (93%) in the east. Both catch per unit effort and total landings declined in 2009 compared to 2008 having three exceptions (H. spinifera, Holothuria atra and Stichopus chloronotus) in the north-west. Further, the collection of immature individuals, reduced landings of high-value species and temporal shifting of fishing activities were observed in both areas. Two approaches (simple linear regression and random effects models) were used to estimate the natural mortality of sea cucumbers and the estimated values were 0.50 yr−1 and 0.45 yr−1, respectively. Apart from the management of local sea cucumber resources, this information is important to update the regional and global sea cucumber statistics as well as for launching regional management programmes.