The benthic communities of the soft seabed inside and outside the Cesano-Senigallia artificial reef (central Adriatic Sea) were investigated seasonally for 2 years (spring 1997 to winter 1999) to evaluate the effects of the reef on the surrounding bottom. The community living close to the reef is typical for the coastal area. Mean species richness and densities over the entire sampling period were comparable inside and outside the reef, while higher values were recorded at the control site. However, the ShannonWiener diversity index was higher close to the reef than at the control. Physical factors associated with the presence of the artificial structures appear to affect composition and abundance of the infauna community more than biological factors do (predation). The area inside the reef was characterized by fine mud favouring the settlement of deposit and suspension feeders, mainly polychaetes. Outside the reef, molluscs were numerically dominant, with an increasing proportion of sandy-bottom species with increasing distance from the structures. These differences were more marked in spring and autumn, while in the other seasons the reef effect appeared to be reduced to a narrow area close to the structures.
Understanding the role of ocean currents in the recruitment of commercially and ecologically important fish is an important step toward developing sustainable resource management guidelines. To this end, we attempt to elucidate the role of surface ocean transport in supplying recruits of European sardine (Sardina pilchardus) to the Gulf of Manfredonia, a known recruitment area in the Adriatic Sea. Sardine early life history stages (ELHSs) were collected during two cruises to provide observational estimates of their age-size relationship and their passive pelagic larval duration (PPLD). We combine these PPLDs with observations of surface ocean currents to test two hypotheses: (1) ELHSs are transported from remote spawning areas (SAs) by ocean currents to the Gulf of Manfredonia; (2) sardines spawn locally and ELHSs are retained by eddies. A historical surface drifter database is used to test hypothesis 1. Hypothesis 2 is tested by estimating residence times in the Gulf of Manfredonia using surface drifters and virtual particles trajectories that were computed from high-resolution observations of surface currents measured by a high-frequency (HF) radar net-work. Transport to the Gulf of Manfredonia from remote SAs seems more likely than local spawning and retention given a mismatch between observed PPLDs of 30-50 days and relatively short ( < 10-day) average residence times. The number and strength of connections between the gulf and remote SAs exhibit a strong dependence on PPLD. For PPLDs of 20 days or less, the gulf is connected to SAs on the western Adriatic coast through transport in the Western Adriatic Current (WAC). SAs on the east coast are more important at longer PPLDs. SAs in the northern and central Adriatic exhibit weak connections at all PPLD ranges considered. These results agree with otolith microstructure analysis, suggesting that the arrival of larvae in the gulf is characterized by repeated pulses from remote SAs. This is the first attempt to describe the processes related to Lagrangian connection to, and retention in, the Gulf of Manfredonia that will be complemented in the future using validated numerical ocean models and biophysical models.
Bianchetto [“white” late-larval and juvenile stages (‘fry’) mainly of sardine (Sardina pilchardus)] was fished traditionally along most of the Italian coast. The Gulf of Manfredonia (southwest Adriatic Sea) hosts a sardine nursery which was historically exploited by the bianchetto fishery using trawlnets; the fishery was banned in 2010. Here, we model this larval fishery under different assumptions of catch and natural mortality to assess its impact on the adult sardine stocks in the Adriatic Sea. The results show that the impact of the fishery is heavily dependent on the choice of early-stage natural mortality. The model proposed by Pepin (1991). Effect of temperature and size on development, mortality, and survival rates of the pelagic early life history stages of marine fish. Canadian Journal of Fisheries and Aquatic Sciences, 48: 503–518. was selected as the most plausible. Under this assumption, the direct effect of the bianchetto fishery in the Gulf of Manfredonia on the Adriatic adult sardine stock appears to be low, but not negligible, with impacts estimated as a 0.1–2% increase in the numbers of sardine at age 1 in the absence of a bianchetto fishery. Projections show that a 5% impact on age 1 sardine may be sufficient to bring the adult stock below safe levels. Therefore, given the uncertainties surrounding the impact assessment and the current status of the stock, if this fishery were to be resumed, catches should be kept at the lowest possible level until the underlying processes are better understood.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.