Spotting the “small eyes”: using photo-ID methodology to study a wild population of smalleye stingrays (Megatrygon microps) in southern Mozambique

Background The smalleye stingray (Megatrygon microps) is a large and rare dasyatid ray, patchily distributed across the Indo-West Pacific. Free-swimming individuals have regularly been recorded in Southern Mozambican coastal waters utilizing different inshore environments. Distinctive features of the species include latitudinal rows of white spots on the dorsal surface of their pectoral disc. Methods This study aimed to determine if the natural spot patterns on M. microps are sufficiently unique and stable to use in photo-identification studies of wild populations. Research dive logs were combined with opportunistic photographs from local dive centers and recreational divers to create a photographic database from the Inhambane Province coastline. Results Seventy different individuals were identified over a 15-year period, all exhibiting uniquely identifiable patterns. Stingrays were easily identifiable over a period of six years with multiple re-sightings of the same individuals recorded. Analysis of encounters across the Inhambane coastline revealed that individual rays regularly use inshore reefs along a 350 km stretch of coastline. Fifteen stingrays were re-sighted during the study period, including one showing a 400 km return movement between Tofo Beach and the Bazaruto Archipelago, which is the longest distance traveled by a dasyatid ray on record. Several presumably pregnant females have also been recorded in the Bazaruto Archipelago National Park

Quantifying the distribution and site fidelity of a rare, non-commercial elasmobranch using local ecological knowledge

Fishery catch records offer limited data to assess the status of rare, non-commercial species, including some sharks. Despite marine megafauna creating an important source of revenue though tourism, basic spatial information required to create conservation strategies is not available for many of these species. A cost-effective approach to assess the distribution of rare, non-commercial species is required to manage resources and inform conservation strategies in data-deficient areas. This study provides new information on the distribution and abundance of the zebra shark in southern Africa and examines if local ecological knowledge can be used to identify spatial and temporal trends of rare, non-commercial elasmobranchs. Trends identified from fisher interviews at two locations were compared to those collected using structured dive surveys. Both fisher interviews and structured surveys identified similar hotspot areas and temporal changes in the zebra shark population. Photographs of zebra sharks taken by researchers, dive operators, and recreational scuba divers between Pomene and Sodwana Bay were used to identify and provide information on the size, sex and movement of individuals. A combination of geo-located data gathered from one hundred interviews conducted with fishers at four different locations within Mozambique and sightings information from scuba divers were used in a species distribution model to determine the relative importance of environmental predictors and identify further areas of suitable habitat. Sea surface temperature was the most important factor in the coldest months, with distance from shore most limiting habitat suitability at other times of year. This approach could be applied in data-deficient regions to highlight areas of interest, prioritise research activities and inform conservation actions for rare, non-commercial marine megafauna

Distribution of the reef manta ray <i>Mobula alfredi</i> and the oceanic manta ray <i>Mobula birostris</i> in the Philippines: a collaborative effort for conservation

From Crossref journal articles via Jisc Publications RouterHistory: epub 2022-12-19, issued 2022-12-19Article version: VoRPublication status: PublishedFunder: Rufford Foundation; FundRef: 10.13039/100007463Funder: Save Our Seas Foundation; FundRef: 10.13039/50110000766

Distribution of the reef manta ray <i>Mobula alfredi</i> and the oceanic manta ray <i>Mobula birostris</i> in the Philippines: A collaborative effort for conservation

From Crossref journal articles via Jisc Publications RouterHistory: epub 2022-11-30, issued 2022-11-30Article version: VoRPublication status: Publishe

Formulation and analysis of horizontal mergers among oligopolistic firms with insights into the merger paradox: a supply chain network perspective

Oligopolies, Supply chains, Horizontal mergers, Game theory, Nash equilibria, Network economics, Variational inequalities, Merger paradox,

Widespread diversity deficits of coral reef sharks and rays

A global survey of coral reefs reveals that overfishing is driving resident shark species toward extinction, causing diversity deficits in reef elasmobranch (shark and ray) assemblages. Our species-level analysis revealed global declines of 60 to 73% for five common resident reef shark species and that individual shark species were not detected at 34 to 47% of surveyed reefs. As reefs become more shark-depleted, rays begin to dominate assemblages. Shark-dominated assemblages persist in wealthy nations with strong governance and in highly protected areas, whereas poverty, weak governance, and a lack of shark management are associated with depauperate assemblages mainly composed of rays. Without action to address these diversity deficits, loss of ecological function and ecosystem services will increasingly affect human communities

Author Correction: Global status and conservation potential of reef sharks

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.</p

Global status and conservation potential of reef sharks

Decades of overexploitation have devastated shark populations, leaving considerable doubt as to their ecological status1,2. Yet much of what is known about sharks has been inferred from catch records in industrial fisheries, whereas far less information is available about sharks that live in coastal habitats3. Here we address this knowledge gap using data from more than 15,000 standardized baited remote underwater video stations that were deployed on 371 reefs in 58 nations to estimate the conservation status of reef sharks globally. Our results reveal the profound impact that fishing has had on reef shark populations: we observed no sharks on almost 20% of the surveyed reefs. Reef sharks were almost completely absent from reefs in several nations, and shark depletion was strongly related to socio-economic conditions such as the size and proximity of the nearest market, poor governance and the density of the human population. However, opportunities for the conservation of reef sharks remain: shark sanctuaries, closed areas, catch limits and an absence of gillnets and longlines were associated with a substantially higher relative abundance of reef sharks. These results reveal several policy pathways for the restoration and management of reef shark populations, from direct top-down management of fishing to indirect improvement of governance conditions. Reef shark populations will only have a high chance of recovery by engaging key socio-economic aspects of tropical fisheries