Regional Studies in Marine Science 37 (2020) 101342 Contents lists available at ScienceDirect Regional Studies in Marine Science journal homepage: www.elsevier.com/locate/rsma ``Urbanite'' rays and sharks: Presence, habitat use and population structure in an urban semi-enclosed lagoon ∗ Fernando Tuya a, , Maite Asensio b, Alberto Navarro b a Grupo en Biodiversidad y Conservación, IU-ECOAQUA, Universidad de Las Palmas de Gran Canaria, Marine Scientific and Technological Park, Crta. Taliarte s/n, 35214 Telde, Spain b Snorkeling Experience, Av./ Mesa y López 57, 15A, 35010, Las Palmas de G.C., Spain article info a b s t r a c t Article history: There is a vital necessity to provide more biological data on rays and sharks to promote efficient Received 7 January 2020 conservation. In this study, we assembled a database of weekly sightings to describe temporal Received in revised form 12 June 2020 (seasonal) patterns in the presence of elasmobranchs within an urban, semi-enclosed, landscape (Las Accepted 20 June 2020 Canteras beach, Gran Canaria Island, eastern Atlantic). Data also provided insight into their habitat Available online 29 June 2020 use and population structure. From October 2015 to October 2018, eight species, either endangered Keywords: or ``data deficient'' according to the IUCN red list, were reported, including: the common eagle ray, Biodiversity Myliobatis aquila, the common stingray, Dasyatis pastinaca, the round stingray, Taeniurops grabatus, Chondrichthyans the spiny butterfly ray, Gymnura altavela, the bull ray, Aetomylaeus bovinus, the angel shark, Squatina Batoids squatina, the marbled electric ray, Torpedo marmorata and the hammerhead shark, Sphyrna zygaena. Conservation All species were predominantly observed at night. The species varied in their habitat use; D. pastinaca, Seasonality G. altavela and S. squatina dominated in sandy and mixed bottoms, while M. aquila and T. grabatus Atlantic ocean were mostly found in rocky and mixed bottoms. Both D. pastinaca and T. grabatus did not show any seasonal pattern, with consistent records all year around. In contrast, M. aquila, G. altavela and S. squatina showed some degree of seasonality. For five species, small-sized individuals were observed. If semi-enclosed embayments at oceanic islands, under intense human presence, are used by juveniles of endangered rays and sharks, proper management, e.g. limitation of putative human interactions, need to be considered to avoid disturbances. ' 2020 Elsevier B.V. All rights reserved. 1. Introduction describing patterns of distribution, foraging, reproduction, pup- ping and habitat use is a key factor to optimize management Elasmobranchs encompass a wide group of carnivorous and of these species (Le Port et al., 2012). Importantly, knowledge detritivorous fish distributed worldwide, from shallow waters to on the ecology of rays and sharks is relevant in areas of strong abyssal depths. About 25% of rays and sharks face extinction risk, interactions with humans, as is the case of urban environments, with recent declines in the abundance of certain species in the where a range of human actions (fishing, industrial activities, last few decades, mostly as a result of overfishing (Dulvy and For- tourism and leisure,) takes place (Gonçalves Silva and Vianna, rest, 2010; Dulvy et al., 2014; Lawson et al., 2019). Batoid species 2018). are particularly at risk of extinction, due to increasing anthro- Certain areas of the world are rich, not only in terms of pogenic threats, e.g. overfishing (Martins et al., 2018). In addition, the diversity of elasmobranchs, but also in the frequency of a large number of elasmobranchs are biologically and ecologically observations along nearshore waters. The Canary Islands is a unknown, e.g. abundance patterns and habitat uses, from most clear example; this Atlantic archipelago is the last worldwide of their distribution ranges. In this sense, a considerable number stronghold of the angel shark, Squatina squatina (Linnaeus, 1758) of rays and sharks are considered by the International Union for (Meyers et al., 2018; Lawson et al., 2019) and large aggregations the Conservation of Nature (IUCN) red list as ``data deficient''. of elasmobranchs are spotted near the shore (Assis et al., 2008; Clearly, there is a vital necessity to provide more biological data Narváez, 2013), even linked to human facilities, such as sea-cage on this fauna to promote conservation strategies (Dulvy et al., fish farms (Dempster et al., 2005; Tuya et al., 2006). The lack 2014; Martins et al., 2018; Lawson et al., 2019). For example, of bottom-trawling, as a result of a reduced continental shelf, is a key mechanism explaining the large abundance of rays and ∗ Corresponding author. sharks in this oceanic Archipelago (Brito et al., 2002). Coastal E-mail address: [email protected] (F. Tuya). landscapes of the Canary Islands typically include a mosaic of https://doi.org/10.1016/j.rsma.2020.101342 2352-4855/' 2020 Elsevier B.V. All rights reserved. 2 F. Tuya, M. Asensio and A. Navarro / Regional Studies in Marine Science 37 (2020) 101342 habitats, such as rocky reefs, seagrass meadows, unvegetated sed- iments (sandy bottoms), which offer suitable habitat for different life history stages of marine fish (Espino et al., 2015a), including elasmobranchs (Brito et al., 2002; Espino et al., 2015b). In this study, we assembled a database of species records (sightings) through weekly tours carried out by an ecotourism (snorkeling) enterprise to describe temporal (seasonal) patterns in the presence of elasmobranchs. More specifically, we used a 3 years-database (from October 2015 to October 2018) to assess whether seasonality affected the presence of elasmobranchs and to provide insight into their habitat use and population structure within a highly populated urban landscape (Las Canteras beach, Gran Canaria Island, northeastern Atlantic) that include several habitats (Tuya et al., 2019). This data may be relevant, for exam- ple, to infer potential movement of adults, as well to determine their reproductive, parturition, pupping seasons. From a manage- ment perspective, this biological data is valuable to help con- servation actions; for example, protection of juveniles at certain seasons, or restriction of certain human activities in the seasons of large aggregations of elasmobranchs (Heupel et al., 2007; Lawson et al., 2019). This is particularly pertinent in our case-study, as all analyzed species are either endangered or considered as ``data deficient'' by the IUCN red list. 2. Materials and methods 2.1. Study site This research was undertaken at Las Canteras beach, a nearshore semi-enclosed lagoon system located in the metropoli- tan area of Las Palmas de Gran Canaria, at the northern side of Gran Canaria Island (northeastern Atlantic Ocean) (Fig.1a). The city has approximately 400,000 inhabitants and the beach is a pivotal core for its social and economic progress, with more than 300,000 tourists, on average, visiting the beach every year (www.grancanaria.com/turismo/es). The beach is about 3 km long and is used by hundreds to thousands of people every day for sunbathing, swimming, snorkeling, diving, paddling or surfing. Sandy bottoms and rocky reefs are interconnected as irregular mosaics, typically between zero and three meters of depth (Fig. 1A, Tuya et al., 2019). An offshore sedimentary bar (ca. 2 km long) delimits the system's seaward extent (Fig.1b, Fig. 1A); the bar is Fig. 1. Location of (a) the study site (Las Canteras beach) at Gran Canaria Island fragmented at several places and ranges between 200 and 300 (eastern Atlantic), including (b) an aerial view of the semi-enclosed lagoon m offshore. At low tide, the bar is above the surface, providing (source: Google Earth). protection against swells. This semi-lagoon embayment has a maximum depth of 4 m; most of the study area is uniformly between 1 to 3 m depth. At high tide, however, the system is are carried out per week, always at low tide, during both day open to offshore waters. The study site is protected within the and night. Snorkeling guides collected data of occurring elas- framework of a ``Special Area of Conservation'' (code ES7010037, mobranchs on each tour, which typically took ca. 80–90 min, EU ``Natura 2000'' framework) (www.miteco.gob.es/es/costas/tem following the same routes (Fig. 1A). During this period, a total as/proteccion-medio-marino/biodiversidad-marina/espacios-mar of 671 tours (ca. 900 h of underwater observation) were carried inos-protegidos/red-natura-2000-ambito-marino/zec-es7010037. out. About 60% of this sampling effort was at daytime and 40% aspx). Commercial and recreational fishing is banned across the at nighttime. Seawater visibility typically ranged between 10 and entire beach. In addition, the beach holds the environmental qual- 25 m. Underwater torches were used at night. For each observa- ity certification UNE-EN ISO 14001 (AENOR). Seawater surface tion, the habitat around each elasmobranch was recorded. Three temperatures ranged between 18oC in winter (March–April) and habitat types were considered: sandy (interior of sandy bottoms 24.5oC in summer (September–October) through the study period located at least > 25 m from sandy–rocky transitions), mixed (Fig. 2A). (sandy–rocky transitions) and rocky bottoms (interior of rocky bottoms at > 25 m from sandy–rocky transitions) (Tuya et al., 2.2. Data compilation 2019). We also visually estimated the size of each elasmobranch (in intervals of 10 cm for adults and 5 cm for juveniles). Initially, Data on the presence of elasmobranchs (Fig. 3A) was pro- we validated length measurements by taking underwater pictures vided by tours (2–3 persons) carried out by the ecotourism en- with a marked (scale) of known length. For semi-rhomboidal terprise Snorkeling Experience (www.snorkelingexperience.com), rays: the common eagle ray, Myliobatis aquila (Linnaeus, 1758), from October 2015 to October 2018, including in all months the common stingray, Dasyatis pastinaca (Linnaeus, 1758), the through 3 successive years. Normally, 2 to 4 snorkeling tours spiny butterfly ray, Gymnura altavela (Linnaeus, 1758), and the F.