Linking sardine recruitment in coastal areas to ocean currents using surface drifters and HF radar: a case study in the Gulf of Manfredonia, Adriatic Sea

Abstract

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.

Toward a European Coastal Observing Network to Provide Better Answers to Science and to Societal Challenges; The JERICO Research Infrastructure

“…JERICO-RI currently provides a network of multiplatform coastal observations (Charria et al, 2016;Berta et al, 2018;Heslop et al, 2019), which are being integrated into a System of Systems. Basic elements of the System are nationally funded observing platforms, e.g., FerryBoxes, fixed platforms e.g., moorings, pilings (Kbaier Ben Ismail et al, 2016), underwater gliders (Cotroneo et al, 2019), HF radars (Rubio et al, 2011(Rubio et al, , 2017Sciascia et al, 2018), profilers and vessels of opportunitye.g., fishing-boats (Aydogdu et al, 2016). Common scientifically sound best practices are adopted, as far as possible, including technologies used, deployment, maintenance, quality control and assessment of data, and delivery to European databases.…”

Eddy Detection in HF Radar-Derived Surface Currents in the Gulf of Naples

“…The product consists of a two-dimensional velocity field with a spatial resolution of 1 km over an area of approximately 20-30 km alongshore by 15-20 km offshore, and with an hourly frequency. The specifics of the radar network operating in the GoN can be found in [30]; see [20] for a review on HF radar theory and its applications to coastal current observations; [34] for a recent utilization of HF radar-detected transport to fisheries. Specific applications to the GoN in terms of description of the dynamics, data validation, as well as their use in conjunction with numerical models, can be found in [24,25,33,[35][36][37][38].…”

Molecular and Morphological Identification and Seasonal Distribution of Eggs of Four Decapterus Fish Species in the Northern South China Sea: A Key to Conservation of Spawning Ground

“…The northern SCS continental shelf is an important spawning and nursery ground for various commercial fishes, such as jack mackerel, sardines, and Japanese scad (Zhang et al, 1985). Recent progress in understanding the biology and ecology of early life history stages and recruitment processes of these pelagic species has been made (Xie and Watanabe, 2007;Kasai et al, 2008;Nishiyama et al, 2014;Sciascia et al, 2018). However, due to difficulties identifying fish eggs and larvae, information on the early life stages of these species, especially their spawning grounds based on ichthyoplankton surveys in the SCS, is limited (Zhang et al, 1985;Zhou et al, 2011;Li et al, 2014;Chen et al, 2018).…”