Short and long-term movement and site fidelity of juvenile Haemulidae in back-reef habitats of a Caribbean embayment

Abstract

Studies showing that tagged reef fish connect different habitat types are crucial for effective ecosystem management on a seascape-level, but are rare. Therefore we analysed movement of juvenile Haemulon flavolineatum and Haemulon sciurus among seagrass beds, mangroves and fossilised eroded coral shoreline. Fishes were tagged individually with external, short-term bead-tags (both species) or with internal, long-term coded wire tags (H. flavolineatum only). We also tested the hypothesis that in spatially continuous habitat types with many seemingly suitable resting sites, these fishes show high fidelity to only a small number of sites. The linear distribution range of daytime sites was 4–171 m for H. flavolineatum and 4–152 m for H. sciurus, but in agreement with our hypothesis, externally tagged fishes showed high fidelity to small spatial areas within this range: the percentage of resightings within a 10 m radius of the core area of presence (i.e. the site used most intensively) was 69% for bead-tagged H. flavolineatum, and 62% for H. sciurus during the 47-day study-period. Site fidelity was also present over a longer time span: of the 1114 coded wire tagged H. flavolineatum 51 were recaptured and 49 of them were still present at the tagging location after 163–425 days at liberty. Median linear movement within a day was small (5 m for H. flavolineatum and 8 m for H. sciurus), nonetheless, part of the bead-tagged Haemulidae moved from shoreline shelter habitats (mangroves and rocky shoreline) to adjacent seagrass beds (mean ± SD distance moved 23 ± 10 m) in the afternoon, likely to start feeding there during daylight. When comparing the habitat type occupied during the late afternoon (15:30–17:30 h) and morning (8:00–10:30 h) on two subsequent days, most movement occurred from seagrass beds back to shoreline habitats (mean distance moved 23 ± 10 m), indicating that in the morning these fishes had returned to shelter sites at the shoreline. The current study thus shows existence of connectivity between back-reef habitats through fish movement on a relatively small spatial scale.