Predation by the invasive Indo-Pacific lionfish impacts native fish populations within the Caribbean region and threatens to expand further into Brazil and the Mediterranean. Identifying the range-restricted native fish species with high predation vulnerability in these areas ahead of the invasion front combined with the knowledge of the time a lionfish population typically takes to reach dangerously high densities could help conservation planners attain positive outcomes and reduce biodiversity loss. This study estimated the vulnerability of all Caribbean and endemic Brazilian shorefishes to lionfish predation based on seven ecological and biological traits (e.g. body size, habitat preference, etc.). To facilitate the traits analysis, REEF interns compiled data on the body shape of 1,500 Caribbean fishes. Results from that analysis identified 77 Caribbean and 29 Brazilian species with high vulnerability (i.e. small and narrow-bodied reef fishes) and restricted ranges. The REEF Volunteer Fish Survey Project dataset from the Tropical Western Atlantic was then used to test whether this vulnerability score could explain the species' presence in the lionfish diet by using REEF survey data on the average abundance of fish species documented in published lionfish diet field studies conducted in six Caribbean regions. The same REEF dataset was also used to estimate the rate of relative lionfish abundance increase from initial lionfish sighting to peak local density. Those results showed that an average of five years (and a median of nearly 2 years) elapses from first sighting to maximum observed lionfish densities. These findings support that control measures implemented at the invasion front (in places like Brazil) ahead of the ~two-year lag to peak lionfish density may avert species’ extirpation. This finding is especially critical for places like Brazil, where 12 range-restricted reef fishes occur only in oceanic islands, and management intervention could have a large impact. In addition to Brazil, spatial richness analyses revealed hotspots of vulnerable species in The Bahamas, Belize and Curaçao.