Long-Term Horizontal and Vertical Movement Patterns of Yellow Snapper (Lutjanus argentiventris) and Leopard Grouper (Mycteroperca rosacea) At a Spawning Aggregation Site and No-Take Marine Reserve, Los Islotes, Gulf of California

Long-term horizontal and vertical movement patterns of yellow snapper (Lutjanus argentiventris) at a spawning aggregation site and no-take marine reserve, Los Islotes, Gulf of California.

Some of the most targeted fish species in Gulf of California commercial fisheries are those known to form seasonal spawning aggregations.  The exploitation of spawning aggregations is thought to have lasting negative effects for populations, and marine reserves have been proposed as a tool to mitigate losses resulting from this practice.  However, it is difficult to properly design or implement effective reserves without information about the site fidelity, space use, and movement patterns of target species.  We implanted 25 yellow snapper (Lutjanus argentiventris) and 3 leopard grouper (Mycteroperca rosacea) with coded acoustic transmitters, a portion of which were pressure-sensing and provided instantaneous depth data.  Movements of tagged fish were monitored within an array of underwater acoustic receivers at the Los Islotes no-take reserve, a spawning site for both species in the southwestern Gulf of California.  As of February 2011, 80% percent of snappers and all groupers tagged in September 2010 were detected regularly by the array.  Both species showed high overall site fidelity to the reserve, calculated as the proportion of days present since release (snapper, 0.71 ± 0.29; grouper, 0.98 ± 0.02).  Snappers (8.2 ± 1.6 m) exhibited shallower and less variable mean depth distributions than did groupers (12.6 ± 6.4 m).  The majority of fish from both species showed diel shifts in horizontal and vertical distribution within the reserve.  Little similarity was observed among individuals in their patterns of movement or fidelity to specific areas of the array.  Continued monitoring of Los Islotes will allow us to quantify annual fidelity, identify changes occurring during spawning periods and evaluate the role of this reserve in the management of these species.