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Fishery and Sea Resourcesgrowth [14, 15]. Many studies have beenconducted on the functional role of shallowwater environments, and correlationshave been found between abundance of juvenilesand environmental factors such astemperature, salinity, turbidity, availabilityof food, presence of predators and competitorsand the structural characteristics of thehabitat, especially plant coverage and substrate,i.e., type of sediment [11, 16, 17, 18,19]. The effects of these factors seem todiffer from species to species depending onthe case study. Species distribution is oftenthe result of a combination of several factors[20].Coastal lagoons and transitional water systemsin general are often strongly affectedby human activities (agriculture, urbanisation,industrialisation, fishing and aquaculture)and by their position between seaand continent. The artisanal and nonselectivefishing traditionally practised inlagoon systems affects the recruitment ofmigratory fish assemblages, as does pollution,to which lagoon ecosystems are particularlyvulnerable. The high residencetimes of both waters and sediments meanthat they tend to accumulate pollutants, oftencausing reduction (or degradation) ofessential habitats for fish species, such asnursery grounds. As a consequence, theconservation and management of lagoonfish populations now require continuousmonitoring of fishing and the designationand conservation of nursery grounds forcommercially important species [4]. However,proper management is hindered bythe lack of important information on theecology of each species (including the volumeof recruitment and the criteria adoptedby fish juveniles for habitat selection in thelagoon basin), information which needs tobe combined with data on the estimatedcatch [4].In this context, the objectives of this studywere 1) to verify the migration calendar ofeconomically important marine species enteringLesina Lagoon, 2) to assess the volumeof recruitment and 3) to describe thespatial distribution patterns of these speciesin the lagoon.2 Materials and Methods2.1 Study areaLesina Lagoon is situated on the Adriaticcoast of Southern Italy (15°45 ′ E, 41°88 ′N) (Figure 1). It has been declared a Siteof Community Importance and is includedin the Gargano National Park. The lagoonis oblong in shape, 22.4 km long and 2.4km wide on average. It has an area of 5136ha and a catchment basin of about 460 km 2[21]. The average depth is about 0.7 mand the maximum depth is about 1.5 m.It is separated from the sea by a sandbarabout 16 km long and 1-2 km wide. At apoint approximately 7 km from the westernend, the lagoon narrows, effectively creatingtwo sub-basins.The lagoon is connected to the sea by twotidal channels, Acquarotta and Schiapparo.The Acquarotta Channel, which links thewestern sub-basin of the lagoon with thesea, is about 3 km long, 6 to 10 m wideand from 0.8 to 2 m deep. At its seawardend there is an unauthorised landing stagefor fishing boats. The Schiapparo Channel,which joins the eastern part of the lagoonto the sea, is about 1 km long, about 25 mwide and between 2 and 4 m deep. Thetwo channels have sluices which serve toregulate exchanges between the lagoon andthe sea and complex fishing systems calledlavorieri, which trap adult fish moving tothe sea but allow juveniles and small-sized2100