scientific article | Proc Gulf Caribb Fish Inst | open access
Biggs CR, Nemeth RS
Spawning aggregations are a common reproductive strategy for large, reef fish. Although they are predictable in time and space, they remain difficult to quantify. The majority of studies on spawning aggregations have not gone beyond describing behavior or reporting the time of visual observation. Acoustic telemetry provides the opportunity to expand the extent and detail of information collected regarding the timing and movement of fish at an aggregation site. This study describes the size, duration and monthly variation of an aggregation of dog snapper (Lutjanus jocu) and Cubera snapper (Lutjanus cyanopterus) at the Grammanik Bank, U.S. Virgin Islands using acoustic telemetry and 12 years of visual surveys. Twenty-two Cubera and 29 dog snapper were implanted with acoustic tags and tracked between June and September 2014. Residence events were calculated when two or more detections were recorded at one receiver within 0.5 hour. Abundance data was collected opportunistically with visual surveys from 2002 - 2014 and lengths were measured with laser calipers mounted on a video camera in 2014. Dog and Cubera snapper begin aggregating in February, with peaks in March and May, respectively. Cubera were resident in pulses during the first two weeks after the full moon June-September, but were not resident the third week after the full moon in several months. Individual Cubera were resident for just over a week on average. The most residence events for dog snapper were recorded in the first two weeks after the full moon. Fish tended to remain within the receiver array throughout the following weeks, but individuals were resident for an average of only five days. These results provide information that is critical to the effective design and implementation of protected or closure areas around spawning sites. This study also illustrates a method for collecting spawning timing data that is much less labor intensive than visual surveys, which has been used in the past.
SCUBA (open-circuit or unspecified)