Mismatch in early life traits between settlers and recruits in a Mediterranean fish: Clue of the relevance of the settlement tail?

Abstract

Background. Life stage transitions (e.g., settlement and recruitment), characterized by high mortality rates, act as selective bottlenecks for fishes with a bipartite life cycle. Mortality at these stages is usually selective and potentially affected by larval history. This process is reflected in an inconsistency in larval traits’ distribution between subsequent life stages (e.g., settlers and recruits) originating from the same reproductive season. Despite the importance of this issue only very scarce information is available about this aspect of Mediterranean fishes life histories. Materials and methods. Here we described settlement and investigated the match/mismatch of larval traits between settlers and recruits coming from the same reproductive season, using the white seabream, Diplodus sargus sargus (Linnaeus, 1758), as a model species along ~ 200 km of the Apulian Adriatic coast (south-western Adriatic Sea, Italy). Both microstructure and chemistry analyses were carried out on otoliths of settlers (n = 140) and recruits (n = 113). Results. We highlighted a mismatch in two life traits, i.e., PLD (pelagic larval duration) and natal origin, between settlers and recruits. Recruits showed PLD longer than the maximum recorded for settlers, and a higher number of natal sources compared to settlers. Mismatch in PLD could suggest selective juvenile mortality related to PLD, and recruits with higher PLD potentially originated from the settlement tail (i.e., settled after the settlement peak). Conclusion. Our findings can support hypotheses suggesting that 1) a fraction of juveniles are selectively eliminated; 2) settlement tail could play a relevant role in replenishing local populations of white seabream.

Keywords

• coastal fish
• white seabream
• Diplodus sargus sarg