Progression of invasive lionfish in seagrass, mangrove and reef habitats

Abstract

The invasion of the Indo-Pacific lionfish Pterois volitans into the western Atlantic, Caribbean Sea, and Gulf of Mexico is the fastest ever documented for a marine fish. Few studies have addressed the establishment of lionfish populations within a location, and habitats other than reefs have been largely overlooked. The present study reconstructed the invasion around South Caicos, Turks and Caicos Islands (TCI), from multiple sources of data. Densities and size frequen- cies of lionfish were compared in deep reefs (10 to 30 m) and shallow habitats (seagrass, man- grove, sheltered reef, and exposed reef <5 m deep) over a 4 yr period (2007 to 2010). By the end of 2010, lionfish had been observed in all 5 habitats. There was a lag of almost 7 mo between the first sightings in shallow habitats (December 2007) and in deep reefs. After 2 to 3 yr, the density of lionfish in deep reefs surpassed those in shallow habitats. In November 2010, mean density was over 10× higher on deep reefs (9.51 lionfish seen observer �1 h �1 ± 5.37 SD) than in seagrass (0.87 ± 0.41; p < 0.05), which was significantly higher than in other shallow habitats (sheltered reef: 0.52 ± 0.47; exposed reef: 0.12 ± 0.13; and mangrove: 0.06 ± 0.10; p < 0.05). Lionfish on deep reefs (TL = 22.7 ± 7.5 cm) had significantly larger total lengths (TL; mean ± SD) than those in seagrass (TL = 15.0 ± 4.3 cm; p < 0.05) or sheltered reefs (TL = 14.6 ± 6.8 cm; p < 0.05). Assuming one population with ontogenetic movement between habitats, density and age estimates suggest that lionfish may have moved to deep reefs from other habitats. The results suggest that lionfish may settle preferentially, but not exclusively, in shallow habitats before moving to deep reefs.