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Lionfish (Pterois miles) were observed avoiding coral pinnacles inhabited by the moray eels Gymnothorax flavimarginatus and G. javanicus in the northern Red Sea, Egypt. Release of lionfish (Standard Length 93–104 mm) in such coral pinnacles in November 2016 resulted in almost immediate predation by large moray eels (Total Length > 1 m). Predation by moray eels may be the key control mechanism of population growth in the native biogeographical range of Pterois spp. and may indirectly explain the success of the invasive populations. This is the first video-documented record of moray eels feeding on the lionfish P. miles.

Individuals of the rabbitfish Siganus rivulatus (Siganidae) and surgeonfish Zebrasoma desjardinii (Acanthuridae) were observed feeding on ctenophores and scyphozoans in the northern Red Sea during late spring and early summer seasons between 2010 and 2015. Siganus rivulatus and Z. desjardinii, considered nominally herbivorous, preyed on relatively large ctenophores until disintegration, and on the moon jellyfish Aurelia aurita (Scyphozoa) until they sank to the bottom. Siganus rivulatus was the most dominant predatory fish feeding on gelatinous zooplankton (37 % of attacks on ctenophores and 51 % of attacks on A. aurita). Furthermore, prey individuals were usually approached by two or more fish simultaneously. Eleven additional fish species fed on gelatinous zooplankton, with Chaetodon fasciatus (Chaetodontidae) accounting for 27 and 12 % of the attacks on ctenophores and A. aurita, respectively, and Z. desjardinii for 17 and 24 % of the attacks. Other fishes attacked gelatinous zooplankton in ≤6 % of the observations. This study constitutes the first record of S. rivulatus and Z. desjardinii preying on ctenophores and also confirms preliminary observations of S. rivulatus feeding on scyphozoans. Although herbivorous fishes may accidentally ingest small invertebrates while feeding on algae, the deliberate feeding on gelatinous zooplankton observed for S. rivulatus and Z. desjardinii suggests that their trophic role should be reevaluated.

The introduction of lionfish into the western Atlantic and Caribbean Sea is widely recognized as the most successful marine fish invasion documented to date. In an effort to improve our understanding of the life history characters that facilitated this unprecedented invasion, we performed a mark–release–recapture study with 36 tagged individuals to document life history characteristics of the Red Sea lionfish, Pterois miles, in its native habitat. Monthly growth rates of juveniles ranged from 4.0 to 10.8 mm month−1 independent of water temperature. Highest juvenile growth rates (> 9.0 mm month−1) occurred between May and August when water temperature increased from 22.5 to 28.0 °C, while growth rates dropped sharply between August and September when water temperature was consistently high. Adult lionfish had relatively constant growth rates of 4–6 mm month−1. Despite high site fidelity of some individuals, recapture success gradually declined from 83 to 3% during the 15-month study period. Thus, the consistent population density of 95 fish ha−1 likely reflected a well-balanced exchange of individuals with adjacent reef habitats. To identify biotic constraints that may limit native lionfish populations, interactions with seven potential predatory and/or competitive grouper species were also investigated. Significantly, fewer lionfish were encountered in micro-habitats, where the Red Sea groupers Aethaloperca rogaa and Cephalopholis miniata resided. In addition, the presence of large groupers (> 250 mm TL) was significantly correlated with reduced numbers of lionfish, while small groupers (≤ 250 mm TL) appeared to have no impact. Our field observations suggest that the biotic interactions (e.g., habitat competition, and depredation) between grouper species and lionfish may play a role in lionfish distribution. This study provides new insights into the growth and ecology of lionfish in their native habitats to help illuminate links to their documented success in the invaded range.