Survival during settlement is a limiting variable for recruitment and is believed to be strongly determined by biological interactions and sea conditions.
This study examined the settlement patterns of the white seabream (Diplodus sargus) related to relevant biotic and abiotic factors. The demography of juveniles was studied in six coves in Menorca Island (Balearic Islands, W Mediterranean), located in wind exposed and sheltered coasts.
The obtained results showed that the settlement period extended from early May to late June and maximum juvenile densities varied between 5 and 11 ind. m-1, with maximum values observed in late May simultaneously occurring in both types of coasts.
The analysis of juvenile survival revealed different stages in the size-mortality relationships: an initial density-dependent stage for smaller juveniles (<20mm total length), followed by a density-independent stage in which other factors (environmental effects) dominated survival for bigger size classes (>20 mm total length). The authors state that because of these variations, the number of juveniles present at the end of the period was unrelated to their initial density and average survival varied among locations. In summary, recruitment was primarily limited by denso-dependent procedures at the settlement stage, and by sea conditions at post-settlement, where extreme wave conditions depleted juveniles.
The obtained results and their interpretation allowed the authors to suggest that the similar strength in larval supply between zones, in addition to the similar mean phenology for settlers, points out to the fact that all fish may come from the same parental reproductive pool.
It is concluded that these biotic and abiotic factors should be taken into account when assessing relationships between settlers, recruits and adults of white seabream.
Cuadros A, Basterretxea G, Cardona L, Cheminée A, Hidalgo M, Moranta J (2018) Settlement and post-settlement survival rates of the white seabream (Diplodus sargus) in the western Mediterranean Sea. PLoS ONE 13(1):e019027