Reproductive behaviours of groupers (Epinephelidae) in the Tavolara-Punta Coda Cavallo Marine Protected Area (NW Mediterranean Sea)

Reproductive behaviours, alongside peculiar biological traits (e.g., large size, late sexual maturity, hermaphroditism), make some species particularly susceptible to overfishing. Groupers (Epinephelidae), ecologically and economically valuable species, are among the most vulnerable of all teleost fish worldwide. Due to their life-history traits, particularly reproductive ones, and their high commercial value, many grouper populations have undergone serious declines due to overexploitation and some species are even at great risk of extinction. Effectively enforced Marine Protected Areas (MPAs) have proven crucial for reversing this trend and promoting the recovery of depleted grouper populations by prohibiting fishing activities. Groupers are regarded as flagship species since more large-sized individuals can be found within fully protected areas compared to unprotected areas. Therefore, besides being commercially important as fishing resources and ecologically relevant as high-level predators, groupers are increasingly considered as important attractions for diving ecotourism in many effective MPAs. While multiple studies have demonstrated MPAs’ effectiveness in recovering depleted fish populations, little is known about the extent to which MPAs protect the integrity of fish reproductive behaviours. In this thesis, the reproductive biology of the most iconic grouper species in the Mediterranean Sea - the dusky grouper, Epinephelus marginatus - was investigated. The goal of this project was to evaluate the effectiveness of protection measures on the reproductive behavioural traits of this species. For this research, a combination of multiple, complementary and non-invasive study approaches was employed within a North-Western Mediterranean MPA, the Tavolara-Punta Coda Cavallo MPA (TPCC MPA). More specifically, to locate potential spawning aggregation sites both inside and outside the TPCC MPA, the local ecological knowledge of spear-fishers about past and present occurrences of the dusky grouper was surveyed. Then, to assess whether the selected protected and unprotected sites could be likely to host spawning aggregations, Underwater Visual Census (UVC) surveys were conducted to collect size and abundance data of E. marginatus both inside and outside the TPCC MPA. Results indicate that very few and small-sized individuals were recorded at unprotected sites, as opposed to protected ones, making the occurrence of spawning aggregations less likely outside the TPCC MPA. Therefore, by focusing only on protected sites, data about the abundance, sex, residency patterns and inter-site movements of individuals were collected by combining UVC and photo-identification approaches. Besides having intentionally collected photos while carrying out research fieldwork, local recreational photographers-divers were engaged in a correlated citizen science initiative and significantly contributed to broaden this research both in time and space. Finally, dusky grouper reproductive behaviours were observed during in situ diver surveys and the associated sound production was recorded through passive acoustic monitoring (PAM). Audio-recordings analyses helped not only to validate the courtship calls of the dusky grouper for the first time in the wild, but also to determine the temporal patterns of its courtship activity. Altogether, these results provide further evidence that effective protection measures (fully protected areas) are crucial in ensuring the occurrence of the study species aggregation and reproduction, and, ultimately, the long-term viability of its populations. This research also provides support for using PAM as a useful tool for monitoring dusky grouper reproduction and supporting decision makers in setting effective conservation and management measures. Finally, this thesis provides new insights into the reproductive behaviours of two other grouper species that were documented at the same reproductive sites of the dusky grouper.