Early-life stages play a key role in the spatio-temporal dynamics of marine populations due to their highly dispersive properties, their sensitivities to environmental factors and their influences on juveniles’ replenishment. However, these stages are difficult to monitor, so that in-situ observations are scarce and disparate, preventing a good understanding of the control they exert on population dynamics.

The Mediterranean coastlines have been highly surveyed during the last decades in different sub-regions; yet no effort was made to assemble observations originating from different research projects and countries. Moreover, this sea has been exploited for centuries and is now recognized as a climate-change hotspot, so that it represents an ideal laboratory to address the role of anthropogenic pressures on marine populations. To advance our knowledge, we build an exhaustive compilation of historical data collected over the past decades up to present. From spawning to settlement, it evaluates both egg and larval stages of coastal fishes characterized by bipartite life cycles.

This compilation gathers 44 datasets from North-Western Mediterranean countries (including coastlines of Spain, France, Italy, Croatia and Montenegro) over the last three decades (1993-2021) originating from 48 data providers. We consider direct and indirect observations of early-life stages such as otoliths’ data, datasets of settlers and juveniles sampled by underwater visual census, shore seine, hand-nets or light-traps, as well as fish eggs and larvae sampled with plankton nets.

All those types of data are harmonized into a uniform dataset that informs on the periods and locations of spawning and settlement. While some sampling techniques directly provide the variables of interests, other methods require a-posteriori estimations based on growth models from the Dynamic Energy Budget (DEB) theory, using taxon-dependent parameters available in the online Add-my-Pet database. Finally, the complete database consists in several taxon, each of them being associated with dates of both spawning and settlement, as well as other information such as the pelagic larval duration, measures of uncertainties and sampling characteristics (location, depth, etc).

Statistical analyses of the consolidated database describe the overall coverage of sampling and evaluate the sampling gaps over space and time in order to guide future sampling efforts. In fact, sampling mainly occurs around marine reserves and from May to October. The general coverage of spawning and settlement is then assessed, looking at the differences between observed data (same distribution as sampling) and back-calculated data (nearly uniformly distributed over the year).  Moreover, the overall taxa distribution is described, mainly represented by Sparidae. Thus, this database informs early-life traits and their variability for different coastal fish taxa in the North-Western Mediterranean in order to document their evolution in a changing world. Indeed, this database will be publicly available to help undertake future connectivity and climatic studies.