Temporal and ontogenetic changes in the trophic signature of an invasive marine predator

Many successful invasive species have generalist diets, but the extent to which they can track changing resources has seldom been documented. Stable isotope analysis was used to measure dietary shifts with ontogeny and over time in relation to changes in prey availability for Indo-Pacific lionfish (Pterois sp.). These are invasive predators that are well established throughout the western North Atlantic and Caribbean where they have caused significant decreases in native reef fish populations in some areas. Samples and observations were made off New Providence Island, Bahamas during the summers of 2008 and 2010. Lionfish delta N-15 and delta C-13 values increased only weakly with body length, suggesting that processes other than growth also contribute to stable isotope variability. The trophic niche of lionfish changed significantly between years, concomitant with large changes in native fish prey abundance and community structure. The trophic niche of large lionfish expanded, increasing in trophic diversity at the population level and showing lower individual trophic similarity, while that of small lionfish remained similar in size but shifted towards more N-15-enriched and C-13-depleted prey sources. The ability of lionfish to modify their diet over time may have facilitated their expansion and persistence at high densities in some areas despite local prey depletion.