Grouper Tales: Use of Acoustic Telemetry to Evaluate Grouper Movements at Western Dry Rocks in the Florida Keys

Abstract

The Western Dry Rocks (WDR) area off Key West, Florida, is an open fishing area that contains a multispecies fish spawning aggregation site, but grouper spawning there has yet to be confirmed. The movements of 18 adult and subadult grouper at WDR were tracked using acoustic telemetry to determine how this area is used by grouper species and whether it contains a grouper spawning aggregation site. Tagged fish consisted of 10 Black Grouper Mycteroperca bonaci, 5 Nassau Grouper Epinephelus striatus, 2 Gag M. microlepis, and 1 Yellowfin Grouper M. venenosa. Overall, tagged grouper were more likely to be present in the WDR array during winter spawning months, with species-specific seasonal differences. Our results indicated that grouper presence increased during spawning months, although some adults and subadults were present year-round. Grouper made more movements per day during nonspawning months compared to spawning months, although the north side of WDR was the most heavily used area, regardless of the time of year. Additionally, spatial graphs of grouper movement suggested that different grouper species utilized different areas of WDR. Increased presence of grouper during spawning months suggests that the WDR area may contain a grouper spawning aggregation site, which would mean that fish species aggregate to spawn at this location year-round. The success of the Florida Keys fisheries critically depends on the protection of multispecies spawning aggregations like that potentially contained at WDR.

Under pressure: Comparing in situ and boat tagging methods using time-to-event analyses

“…Receiver location depths ranged from 3 -43 m. Receivers depicted on this map were deployed during different times from 2008 -2018, depending on the study. Details regarding receiver timing can be found in Feeley et al 2018, Herbig et al 2019, and Keller et al 2020. Bathymetry data is a part of the Florida Keys National Marine Sanctuary Digital Atlas (Taylor et al 2018).…”

“…Fish caught in underwater traps (times between checking and rebaiting traps were approximately 1-12 hours) had their tags inserted in situ by a team of divers. A detailed description of boat and in situ tagging and acoustic array designs can be found in Feeley et al (2018), Herbig et al (2019), and Keller et al (2020).…”

Networked Animal Telemetry in the Northwest Atlantic and Caribbean Waters

“…Many grouper species aggregate in reef habitats, particularly spawning locations, and can be extremely vulnerable to overfishing if these areas are heavily targeted (Robinson et al 2015). Keller et al (2020, this themed issue) employed acoustic telemetry to assess the use of a potential aggregation site for multiple grouper species in the Florida Keys. Such sites are frequently considered as locations for MPAs, but the effectiveness of MPAs in protecting species may depend on the extent of movement outside of their boundaries (Pittman et al 2014).…”

Under pressure: comparing in situ and boat tagging methods using time-to-event analyses

“…Data collected from acoustically tagged fish can be used to investigate a wide variety of biological and ecological questions. For example, acoustic telemetry data have provided answers to broad ecological questions, such as revealing previously unknown migration patterns for certain species [12,28] and have also been used to answer more localized questions, such as patterns of habitat use in a specific location [15,18]. Although acoustic telemetry studies have been rapidly increasing in number over the past 20 years [6], there are far fewer studies that examine the influence of tagging methodology on acoustic telemetry results [9].…”

“…Lindholm et al [22] used saturation diving from the Aquarius underwater laboratory in the Florida Keys to internally tag fish, and Tuohy et al [43] used closed circuit rebreathers. Recently, Feeley et al [12], McCallister et al [26], Bryan et al [4], and Keller et al [18] all describe internally tagging reef fish in situ.…”