Angel sharks are among the most threatened fish worldwide, facing regional and global extinction. In Europe, populations of the three Critically Endangered angel sharks (Squatina aculeata, Squatina oculata and Squatina squatina) have been severely depleted. Taking advantage of the last global ‘hotspot’ of the angelshark, Squatina squatina, this study gathered data through a citizen science programme to describe the occurrence of this shark in the coastal waters of the Canary Islands. Specifically, this study described (1) the population structure, and (2) habitat use of this species, which was used in a Species Distribution Model to (3) examine realized and potential distribution patterns, and to (4) determine the relative importance of environmental predictors on the occurrence of S. squatina. Over the 12 months sampling period (April 2014 – March 2015), 678 sightings were reported. Individuals ranged from 20 to 200 cm (total length). Larger sightings of both females and neonates occurred mostly in April to July, i.e. during the pupping season. Males were significantly more frequent in November to January, i.e. during the mating season. Angelsharks were encountered at depths from <1 m to a maximum of 45 m. Small‐sized individuals (i.e. neonates) exclusively occurred in shallow water (0–25 m). Most sharks occurred on sandy bottoms adjacent to reefs. Even though sightings were recorded at all seven islands in the archipelago, there were fewer encounters in the western than the eastern islands. The Species Distribution Model indicated that the probability of occurrence mainly correlated with sea surface temperature, chlorophyll, salinity and depth. Areas with the greatest habitat suitability were in shallow water. The angelshark displayed spatial (vertical and horizontal) and temporal segregation by size and sex. This information is vital to inform conservation of this Critically Endangered shark in its last stronghold.

Understanding the details of local and regional extinctions allows for more efficient allocation of conservation activities and resources. This involves identifying where populations persist, where populations may still be present, and where populations may be locally extinct. Three threatened angel sharks occur in the Eastern Atlantic and Mediterranean Sea: Sawback Angelshark (Squatina aculeata), Smoothback Angelshark (Squatina oculata), and Angelshark (Squatina squatina). Population sizes and geographic ranges of these species have been reduced due to overfishing and habitat loss, placing them among the world s most threatened chondrichthyans. We revise distribution maps, review global status, and present a Conservation Strategy to protect and restore these angel shark populations by minimizing fishing mortality, protecting critical habitat, and mitigating human disturbance. Updated distributions reveal that a halving of the geographic extent may have occurred for all three species, with potential declines of 51% for Sawback Angelshark, 48% for Smoothback Angelshark, and 58% for Angelshark. While 20 national and international management measures are now in place for Angelshark, only half of these include the other two species. We encourage further conservation action to adopt and develop this Conservation Strategy to restore angel shark populations to robust levels and safeguard them throughout their range.

As an increasingly important resource in ecological research, citizen scientists have proven dynamic and cost‐effective in the supply of data for use within habitat suitability models. With predictions critical to the provision of effective conservation measures in cryptic marine species, this study delivers baseline ecological data for the Critically Endangered angelshark (Squatina squatina), exploring: (i) seasonal, sex‐differentiated distributions; (ii) environmental distribution predictors; and (iii) examining bias‐corrected, imperfect citizen science data for use in coastal habitat suitability models with cryptic species. Citizen science presence data, comprising over 60,000 hours of sampling effort, were used alongside carefully selected open‐source predictor variables, with maxent generating seasonal male and female habitat suitability models for angelsharks in the Canary Islands. A biased prior method was used, alongside two model validation measures to ensure reliability. Citizen science data used within maxent suggest that angelshark habitat suitability is low in coastal areas during warmer months, with fewer occurrences despite a negligible change in sampling effort. The prime importance of bathymetry may indicate the importance of depth for reproductive activity and possible diel vertical migration, whereas aspect may act as a proxy for sheltered habitats away from open ocean. Substrate as a predictor of female habitats in spring and summer could imply that soft sediment is sought for birthing areas, assisting in the identification of areas critical to reproductive activity and thus locations that may benefit from spatial protections. Model outputs to inform recovery plan development and ecotourism are identified as plausible safeguards of population recovery, whereas the comparison of biased and bias‐corrected models highlights some variance between methodologies, with bias‐corrected models producing greater areas of habitat suitability. Accordingly, an adaptive framework is provided for the implementation of citizen science data within the modelling of cryptic coastal species distribution.

1. The identification and effective protection of nursery areas is critical for elasmobranch conservation. Research on the angelshark (Squatina squatina) is in its infancy, and is particularly challenging during the early life stages, in part because of their rarity, but also because of their camouflage and cryptic behaviour. 2. Focused research on the identification and protection of juvenile angelshark habitat in their stronghold of the Canary Islands has been identified as a priority action to help safeguard the future of this species. 3. This study combines citizen-science data, satellite imagery, and focused snorkel surveys to complete a first evaluation of juvenile angelshark habitat in the region, upon which further research can be built. 4. One confirmed nursery area, 13 potential nursery areas, and 21 beaches needing further study were identified in this study, based on the existing nursery area criteria. 5. The results were used to develop eight key recommendations on how local and national governments can better protect juvenile angelsharks in the Canary Islands. 6. Further research is urgently needed to confirm whether other beaches in the archipelago meet the nursery area criteria.

In this study, we used a historical collection of photographs taken by recreational fishers from 1940 to 2014, at the island of Gran Canaria, to show both a significant decrease in the mean total length of Epinephelus marginatus and a concurrent change in the composition of captures. Before 1980, the mean total length of fish caught and photographed was c. 100 cm, while after 2009 this was typically < 40 cm. Before 1980, the predominant captured species was E. marginatus (an apex predator), but currently the majority of catches are of omnivorous species, in particular the parrotfish, Sparisoma cretense and seabreams Diplodus spp. Overall, integration of these results indicates a qualitative and quantitative variation in captures of recreational fishers, probably as a sign of change in ecological balances and the overfished status of many target species.