Individuals oi Achatina fiilica (Bowdich, 1822) were observed preying on veronicellid slugs at two sites on the island of Oahu, Hawaii. As such, the presence of A. fulica may pose a greater threat to terrestrial mollusc conservation than previously imagined. It is our hope that this note provides some impetus for other researchers to explore the possible predation impacts of introduced populations ot A. fulica and to consider the possibility that other introduced snails and slugs may be having as yet unforeseen or unnoticed impacts.

In 1956, the shallow-water grouper Cephalopholis argus was introduced from Moorea (French Polynesia), where grouper diversity (14 species) is high, to the Main Hawaiian Islands (MHI), where only 2 rare native deep-water groupers occur. In this non-native environment, the species has flourished and has become the dominant apex predator on many reefs. In the present study, a comparison of non-native populations of C. argus in the MHI with native populations in Moorea showed that mean total length (32.0 vs. 26.9 cm), mass (722 vs. 326 g), growth, and body condition were each significantly elevated in the MHI. In addition, while an ontogenetic shift towards larger prey occurred in both locations, it was faster and more consistent in Moorea than in the MHI. As a result, while small C. argus of comparable size in the 2 locations consumed similar-sized prey, large C. argus in Moorea consumed significantly longer and deeper-bodied prey than their counterparts in the MHI. This pattern was unrelated to the size distributions of available prey and may thus reflect stronger intra-and interspecific competition for small prey in Moorea. Although ecological release in a broader sense (i.e. a combination of predator release, parasite release, and competitive release) may play a role, the most direct explanation for the observed differences between C. argus in native habitats in Moorea (with many competing grouper species) and non-native habitats in the MHI (few competitors) would be competitive release (here used in the sense of benefits resulting from the reduction of interspecific competition). KEY WORDS: Competitive release · Ecological release · Interspecific competition · Niche shift · Invasive species · Peacock hind · Main Hawaiian Islands · Moorea (French Polynesia)Resale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 439: 203-212, 2011 204 Due to their geographic and hydrographic isolation, the Main Hawaiian Islands (MHI hereafter) have a unique assemblage of coral reef and shore fish species, with one of the highest rates of endemism (~25%) in the world (Randall 2007). Compared to most tropical Pacific locations, several fish families are underrepresented or completely absent from the shallow inshore reefs of the MHI. Among these is the family Serranidae, specifically the subfamily Epinephelinae, or groupers (Randall 1987). In 1956, the grouper species peacock hind, Cephalopholis argus, was introduced into this environment from Moorea, French Polynesia (where it is known as 'roi') (see Fig. 1) in an attempt to create a grouper fishery (Oda & Parrish 1981, Randall 1987. Initially introduced to the islands of Oahu and Hawaii, it has since spread to all of the MHI, and has become the domi nant apex predator on many reefs ). Concern about potential negative effects of this -in evolutionary terms -new predation source on native Hawaiian reef fish assemblages, which have evolved without shallow water groupers, have resulted in recent investigations of the feeding ecolo...

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