Productivity in natural and artificial habitats in brackish water systems: an example from Aphanius fasciatus populations

1 - Venice Lagoon is characterized by many different shallow-water habitats, where salt marshes represent important habitats for many nektonic species. On the other side, small lagoon islands show a typical landscape dominated by agricultural gardens and orchards, that still host small ditches once used in traditional fishery activities but now abandoned. 2 - Aims of this study is to determine the productivity of these habitats for the nektonic community, referring to the small teleost Aphanius fasciatus (Valenciennes, 1821), listed in Annex II of ‘Habitat’ Directive 92/43/CEE. 3 - One year monthly samplings were performed in four sites: two natural salt marshes and two systems of artificial ditches. All collected fish were photographed and then released. Only a sub-sample was preserved for laboratory analysis. 4 - Data show that artificial habitats host higher biomass of A. fasciatus, yielding higher secondary production respect to natural salt marshes, while P:B ratios vary in accordance to different environmental features and the related life history strategies adopted by the four populations. 5 - Results of this study highlight the relevance of these artificial habitats in the conservation of an important resident fish species