Settlement and RECruitment processes in fish species of interest for RECreational fishing

In fish, the processes that regulate the shift from pelagic to benthic life (settlement, as part of the recruitment process) are key to population dynamics. These regulatory processes are complex in nature and hardly known in temperate areas. In the Mediterranean, littoral species are subjected to high human pressure. Recreational fishing is an emerging pressure which is difficult to manage. Marine Protected areas (AMPs) are important tools used for managing coastal fisheries. However, the effects of AMPs on early live history of fish are poorly understood. REC2 has the general aim of obtaining quantitative information on settlement processes of littoral fish that are exploited by receational fishing. We also hope to contribute to the knowledge of AMPs effects on reproduction and settlement.

The specific questions we want to contribute to are i) Connectivity: does dispersal by marine currents on its own explain the origin of the settled individuals? ii) Reproductive potential: Is the egg production dependent only on the stock biomass? Does the explotation rate affect the adults reproductive potential?

In REC2 we will use a wide combination of hypotheses and methodologies to tackle these questions. The project will be developed in the Bay of Palma, with high anthropogenic impact, and at the Cabrera Archipelago National Park (PNMTAC), with low anthropogenic impact. The scientific team, belonging to 3 institutions, has worked together in the past and has proven knowledge and experience to successfully conduct the proposed objectives.

Objective 1 will set up hypotheses on the connectivity among specific areas, based on the reanalysis of samples and data obtained from previously funded projects of the scientific team. On the other hand, the effects of human pressure on the adults will be initially evaluated within this objective.

Objective 2 is the most innovative. The optimal sampling methods are unknown, so a first task will be devoted to the comparison of multiple sampling methods for pre and post-settlers. We will select the best combination of methods in order to analyse the temporal variability of settlement and the connectivity at small scale. Locations to conduct these analyses will be carefully selected according to the patterns of larval concentrations defined from Objective 1. Within the novel techniques, we will analyse stereoscopic images obtained through underwater video, and we will try to infer the ontogenetic movement from the micro chemical composition in otoliths (in relation to the already identified environmental gradients).

Objective 3 will analyse the effect of the habitat type and quality (selected according to the degree of fishing pressure) on the adult’s reproductive potential. A total egg production model for the selected species will be built.

In Objective 4, a theoretical exercise (computer simulations) of the influence of PNMTAC on the possible settlement both within and outside the Park will be performed using the egg production model as an initial state. The generated knowledge will be synthesised in conceptual models that improve our understanding of the life cycle of the selected species, and the knowledge will be transferred into management schemes.

Leave a Reply