Seasonal fish abundance and seagrass cover data, Zanzibar, Tanzania 2014-2015

We conducted a field survey in four sites around Unguja Island (Zanzibar, Tanzania): two no-take MPAs (Chumbe and Mnemba Islands) and two unprotected, fished sites (Changuu island and Mnemba reef).The study was conducted during three seasons in 2014-2015: November-December 2014, April-May 2015 and July-August 2015. Sampling was carried out in sub-tidal seagrass beds dominated by <i>Thalassodendron ciliatum.</i>At each site, fish and seagrass sampling was conducted in 10 replicate transects (except in one of the MPAs, where only 7 transects could be sampled due to the limited size of the protected seagrass bed), which were randomly placed &gt; 5 m apart and parallel to the shore. The surveys were carried out during high neap tide (± 3 h) through underwater visual census by snorkelling along 25×4 m belt transects. A snorkeler swam the transects twice during approx. 10 min. All fish observed within or crossing the transect were counted, identified to the lowest taxonomic level possible (usually species), and their body length was visually estimated to the nearest 5 cm. Based on the estimated sizes, all individual fish were then grouped into three age classes (juveniles, subadults and adults). The bottom per cent cover of seagrass was visually estimated within 0.25 m² quadrates placed at 5 m intervals along each transect (resulting in six subsamples per transect).