Using complementary visual approaches to investigate residency, site fidelity and movement patterns of the dusky grouper (Epinephelus marginatus) in a Mediterranean marine protected area

Abstract

Assessing individuals’ abundance, residency (presence at a site within a certain period) and site fidelity (tendency to return to the same site in subsequent seasons or years) is crucial for evaluating and improving the effectiveness of spatial conservation/management measures regarding ecologically and socio-economically valuable species. Using underwater visual census (UVC) and photo-identification (photo-ID) techniques, we estimated the abundance, residency and site fidelity of the dusky grouper, Epinephelus marginatus, at two protected sites within the Tavolara-Punta Coda Cavallo Marine Protected Area (Sardinia, Italy) in the summers of 2017–2018. The scope and spatio-temporal resolution of the study was extended by involving volunteer recreational divers in the photo collection. Grouper mean densities varied significantly across sampling dates, with a significant variability between the 2 years and the two investigated sites. At least 94 grouper visited the study sites in the summers of 2017–2018 based on the analysis of 968 high-quality photos using a semi-automated software to photo-identify individuals. Overall, the most frequently sighted grouper was recorded on 32 different days and 21 individuals (22%) identified in 2017 were re-sighted in 2018. The participation of volunteer recreational divers helped detect the inter-site (3.5–4 km apart) movements of a female and a male, supporting previous findings regarding the occurrence of reproduction-related movements. This study provides novel insights into the residency and site-fidelity patterns of the dusky grouper, and its small-scale movements probably related to reproduction. Specifically, we provide indications that effective protection from fishing should encompass the entire area used by grouper for reproductive movements.

Linking courtship calls and observed behaviours of Epinephelus marginatus in the wild offers new insights into its reproduction and conservation

“…Despite differences in sampling effort, potentially influencing the number and temporal distribution of the detected sounds, these findings suggest that the recording cycles used in this study effectively capture both short‐term (diel 14‐h periods) and long‐term (about 1 month) trends in dusky grouper acoustic activity. The most comprehensive acoustic activity pattern was recorded at MOL, despite recent evidence showing a lower dusky grouper abundance at MOL compared with SP, as determined through underwater visual census and photo‐identification during the same investigation period (Desiderà et al, 2021). This suggests that the findings at MOL are likely attributed to continuous recordings and minimal human‐made noise.…”

Movements of Hatchery-Reared Dusky Groupers Released in a Northeast Atlantic Coastal Marine Protected Area

“…Dusky groupers are known as highly sedentary species, showing strong site fidelity when adequate conditions are met, in particular, adequate habitat and prey availability [29][30][31][32][33][34]. According to previous studies on the habitat preferences of the dusky grouper [17,[60][61][62][63][64][65][66], both no-take areas on which the adult dusky groupers were released in the present study had favorable conditions for settlement, concerning habitat structure and complexity.…”

“…The persistent low number of dusky groupers in the region and the strong site fidelity when conditions are ideal (e.g., complex rocky habitat, between 15 to 40 m of depth) [29][30][31][32][33][34] can make restocking programs with hatchery-reared individuals a solution to local species recovery, though few studies have addressed this possibility [35,36]. The present work aimed to evaluate the feasibility of hatchery-reared young adult dusky grouper restocking in two small coastal no-take areas within SACVMP, specifically analyzing site attachment, activity patterns, and movements in the study areas using acoustic biotelemetry.…”

Grouping groupers in the Mediterranean: Ecological baselines revealed by ancient proteins

“…The IUCN lists Epinephelus aeneus as Near Threatened throughout its global distribution and Epinephelus marginatus as Vulnerable in the Mediterranean basin (Pollard et al, 2018). Mediterranean groupers are highly territorial fishes and often display spatial and temporal differences in spawning activities (Aronov & Goren, 2008;Desidera et al, 2019;Desiderà et al, 2021;Gökçe et al, 2003), making the likelihood of wild hybridisation between them low. ecological baselines for a key Mediterranean fishery which could be leveraged to define and assess conservation targets.…”

“…As upper trophic level fishes in Mediterranean rocky reef ecosystems, groupers are ecologically important for maintaining balanced and healthy food webs (Prato et al., 2013 ). Mediterranean groupers have different ecological niches with interspecific differences regarding habitats, trophic resources and spawning patterns (Aronov & Goren, 2008 ; Desidera et al., 2019 ; Desiderà et al., 2021 ; Gökçe et al., 2003 ). Epinephelus marginatus (dusky grouper) is generally beholden as the most abundant grouper species in the Mediterranean and is thus the most studied species (Condini et al., 2018 ).…”