Spawning migration movements of Mutton Snapper in Tortugas, Florida: Spatial dynamics within a marine reserve network

A marine reserve's effectiveness for sustaining transient spawning reef fish populations is dependent on inclusion of fish spawning aggregations and consideration of the natural spatial boundaries of the populations themselves. Seasonal migrations of Mutton Snapper Lutjanus analis between protected nearshore areas and spawning grounds on Riley's Hump in Dry Tortugas, Florida, were assessed from 2008 to 2012 by acoustic telemetry. Individual fish showed synchronized reproductive migrations (up to 5 trips fish−1 yr−1) from resident habitats to spawning grounds swimming at an estimated 63 ± 18 cm s−1 (mean ± SD) over minimum linear distances up to 35.2 km. Migrations occurred from April to August, corresponding with the lunar cycle and an increase in water temperature from 25 to 30 °C. Fish arrived on spawning grounds on the full moon and stayed for 7 ± 2 d (mean ± SD). Observations of multiple spawning events made one to five days after the full moon in the late afternoon confirm these movements as spawning migrations. Functional migration areas (109.59 ± 61.01 km2; mean ± SD), which included estimates of staging/courtship/spawning area (4.51 ± 1.84 km2 [mean ± SD]) and home site area (2.50 ± 1.31 km2 [mean ± SD]), were combined to estimate the minimum catchment area of the population studied (291.3 km2). Although this study focuses on movements and habitat use of a single fish species in the Tortugas, the results are relevant to the design of marine reserve networks intended to protect and manage fishes that undergo transient spawning migrations in other locations as well.