Structural differences alter residency and depth activity of red snapper (Lutjanus campechanus) at two artificial reefs

[Display omitted] •Red snapper were tracked at a shallow nearshore reef and a deeper offshore reef.•Fish were of similar size at both reefs but had less site fidelity at the deep reef.•The deep reef had 20-m vertical relief, and fish swam among structure at depth.•The shallow reef had little (≤ 4 m) vertical relief, and fish swam above structure.•At both reefs, fish were shallower at night and changed depth use in colder months. Artificial reefs are being deployed in increasing numbers in the northern Gulf of Mexico to provide hard structure habitat, mainly for red snapper (Lutjanus campechanus). To improve artificial reef design, further research is necessary to elucidate reef fidelity and structural use of red snapper on artificial reefs that vary in vertical relief and distance from shore. In the current study, 30 red snapper were tagged with acoustic transmitters to compare depth and site fidelity for just over one year between two reefs: a nearshore shallow reef made up of many small structures with a vertical relief of 1−4 m and an offshore deeper reef consisting of a single ship with a vertical relief of 5−20 m. Lower site fidelity and residency were observed at the deeper reef and no movement between reefs was observed. Fish at both reefs were shallower and more active at night, suggesting a change in foraging behavior. Fish depth followed a lunar periodicity but was not consistent with spawning period. Long residencies of some fish at each reef suggests that fish stayed throughout the spawning season. However, the nearshore reef had a larger proportion of resident fish. Reef structural differences, such as material dispersion between both reefs, may explain residency. Future reef deployments would benefit from identifying key reef designs that provide improved habitat for increased residency.