Spawning Migrations of the Atlantic Goliath Grouper along the Florida Atlantic Coast (original) (raw)
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Marine Ecology Progress Series, 2020
Characterizing the behavior of coral reef fishes at home reef sites can provide insight into the mechanisms of spatial ecology and provide a framework for spatial resource management. In the Caribbean, populations of Nassau grouper Epinephelus striatus have declined due to fishing impacts on spawning aggregations. Despite local and regional efforts by fisheries managers to implement regulations protecting spawning aggregations, few Nassau grouper populations appear to be recovering. In order to improve management strategies for this critically endangered species, it is necessary to understand the spatial ecology of the species across seasons and years. In the Cayman Islands, we used a multi-year, presence/absence, depth-coded acoustic tagging dataset of Nassau grouper to characterize patterns in the species’ behavior and vertical habitat use at home reef sites. Twenty acoustically tagged individuals (56-84 cm, 70.01 ± 7.40 cm; total length, mean ± SD) maintained consistent home reef...
Website: http://www. …, 2006
The Cayman Islands Department of Environment needs to assess the effectiveness of Nassau grouper (Epinephelus striatus) spawning aggregation site closures by gaining a better understanding of how local grouper populations use the aggregation sites. During the January 2005 spawning season thirty Nassau grouper were acoustically tagged off the Little Cayman west end aggregation site and during the summer of 2005 an additional twenty Nassau groupers were tagged around Little Cayman. By tagging fish on the aggregation we have been able to determine where fish go after they leave the spawning aggregation. By tagging fish around Little Cayman prior to the 2006 spawning season we will be able to determine the proportion of fish from around the Island that attend the west end spawning aggregation. Also, the frequency of aggregation attendance by individual fishes as a function of demography will be assessed. Initial results show that 60% of the groupers tagged during the January, 2005 aggregation returned to aggregate during the February full moon. Furthermore, these 18 returning fish were amongst the largest of the 30 tagged. Ultimately, this information will allow us to assess the current and future impacts of protections afforded Cayman's spawning aggregations. Moreover, the study will define an aggregation's "sphere of influence" both geographically and demographically and will thus aid in the management of local Nassau grouper populations.
Activity patterns of three juvenile goliath grouper, Epinephelus itajara, in a mangrove nursery
The goliath grouper (jewfish) , Epinephelus itajara, is found in tropical and subtropical waters of eastern and western Altantic ocean. The species—listed as critically endangered by the World Conservation Union has been protected through a total fishing ban in U.S. federal and state waters since 1990 and in puerto Rico and U.S. virgin Islands waters since 2004. As one of the few grouper species that shows a high affinity for mangrove-dominated areas, E. itajara typically spends its first 5–8 yrs in that nearshore habitat before migrating to adult habitats (i.e., coral reefs, rock ledges, isolated patch reefs, and artificial structures) . To date, knowledge of the movement of goliath grouper juveniles within their mangrove nursery areas is based mainly on conventional tagging studies, which provide limited insight into the fine-scale activity patterns. In the present study, we used electronic acoustic tags and stationary hydrophone receiver stations to examine the activity patterns of three tagged juveniles inhabiting the fringing red mangrove shorelines of Ten Thousand Islands, southwest Florida, U.S.A. Our primary objective was to examine the extent to which juvenile activity was associated with time of day and tidal stage. To test our ability to detect movement at fine timescales over periods of weeks to months, as well as cues for fish movement, we examined the relationship between fish presence- absence, tidal cycle, and time of day in juvenile goliath grouper. Our results provide insight into multiple habitat use by this species and are important to consider when designing and implementing population abundance surveys.
Using Dual-Frequency Sonar to Survey Juvenile Goliath Grouper, Epinephelus itajara
2008
The goliath grouper, Epinephelus itajara, is the largest grouper in the Atlantic Ocean, exceeding 2 m in total length and 400 kg. Juveniles (< 1 m TL) inhabit fringing red mangrove (Rhizophora mangle) shorelines, whereas adults inhabit coral reefs, patch reefs, reef ledges, and artificial reefs. After reaching commercial extinction in the late 1980s, the species has been protected in U.S. state and federal waters since 1990. Underwater visual census to study distribution and abundance of juveniles are critical to evaluate population recovery and essential fish habitat but are often limited due to low visibility in mangrove shorelines. Here we present a new type of juvenile goliath grouper surveys using high-resolution dual-frequency sonar (DIDSON). DIDSON technology uses multiple narrow hydroacoustic beams (96 at 1.8 MHz and 48 at 1.0 MHz) to produce high-resolution, near-field image streams similar to that of a black-and-white video camera. It can record the shape and size of ta...
Spatial dynamics of the Nassau grouper Epinephelus striatus in a Caribbean atoll
Marine Ecology Progress Series, 2007
Worldwide, chronic overfishing has depleted populations of large predatory reef fishes and caused unexpected, top-down changes in coral reef ecosystems. Groupers are especially susceptible to overexploitation, because they aggregate to reproduce at specific locations and times. An understanding of the spatial dynamics of these fishes is critical for fisheries management and conservation. However, movements and migration dynamics of endangered reef fishes are poorly known. We show, using acoustic telemetry, that Nassau groupers Epinephelus striatus exhibit highly synchronised migration to spawning sites, despite their otherwise solitary habits. Reproductive adults leave their individual territories in shallow waters near the winter full moons, and migrate to the same spawning site up to 4 times yr-1. At the spawning site, a remarkable population-wide depth change occurs within an hour as individuals dive to a maximum depth of 255 m. Our results greatly expand the previously known migration frequency and depth range of this species, and reveal an unexpected yet predictable complexity of adult fish migration between habitats. Effective conservation of this threatened species requires that deeper reefs and the timing of migration events be incorporated into fisheries management plans.
Marine Ecology Progress Series
Marine fish movement plays a critical role in ecosystem functioning and is increasingly studied with acoustic telemetry. Traditionally, this research has focused on single species and small spatial scales. However, integrated tracking networks, such as the Integrated Tracking of Aquatic Animals in the Gulf of Mexico (iTAG) network, are building the capacity to monitor multiple species over larger spatial scales. We conducted a synthesis of passive acoustic monitoring data for 29 species (889 transmitters), ranging from large top predators to small consumers, monitored along the west coast of Florida, USA, over 3 yr (2016-2018). Space use was highly variable, with some groups using all monitored areas and others using only the area where they were tagged. The most extensive space use was found for Atlantic tarpon Megalops atlanticus and bull sharks Carcharhinus leucas. Individual detection patterns clustered into 4 groups, ranging from occasionally detected long-distance movers to fr...
Goliath grouper Epinephelus itajara sound production and movement patterns on aggregation sites
Endangered Species Research, 2009
Sound production by goliath grouper Epinephelus itajara was characterized on 2 aggregation sites in the Gulf of Mexico off the southwest coast of Florida, which are likely to be spawning sites, based on the presence of fish with ripe gonads. Goliath grouper produced predominately lowfrequency single-pulse sounds with dominant frequencies around 60 Hz. Long-term acoustic recordings documented that sounds were most frequently produced between 01:00 and 03:00 h. Sound production had a lunar periodicity, with reduced levels occurring for several days around the full moon. A single goliath grouper was implanted with an acoustic telemetry transmitter that indicated the depth of the fish. This fish remained on the aggregation site for all but 1 d of the 2 mo record and was located near the bottom (46 m) for the majority of the time. Several forays to shallower depths were detected, most of which occurred near midnight and 03:00 h. These short-duration shallow-water forays could possibly indicate spawning ascents. The combination of passive acoustics and active acoustic telemetry indicates that efforts to document spawning should be concentrated around midnight. The prolific sound production of goliath grouper will allow large spatial and temporal scale mapping and monitoring of aggregation sites.
Although the spawning migration of summer flounder Paralichthys dentatus from estuarine and coastal waters to the shelf break is well described, relatively little is known about the distribution and movements of summer flounder in inshore waters. According to recent results from the Virginia Game Fish Tagging Program, small fish (<16.5 inches or 419 mm total length [TL]) appear to exhibit some degree of site fidelity during the period of estuarine use (Lucy and Bain 2006). We postulated that size may be an important factor contributing to variation in summer flounder movements and distributions within Chesapeake Bay. In this study, we used acoustic tags to study habitat associations and localized movements of small and large summer flounder at three sites in lower Chesapeake Bay: Gloucester Point, York Spit light, and Back River reef. We also investigated the effects of tides, light levels, temperature, and barometric pressure on small-scale movements (on the order of 200-400 m) of individual fish because previous work indicated that environmental factors may affect movements of summer flounder. Summer flounder exhibited differences in site fidelity which was most pronounced during the summer; fish were retained at Back River reef for longer periods of time than at the other two sites. We also documented movement of fish between our study sites, but this movement was generally unidirectional, with more fish exhibiting movements to Back River reef than to any other site. None of the fish tagged and released at Back River reef were detected at either of the other two sites. Together, these observations indicate that Back River reef may be preferentially used by summer flounder. Dispersal from Back River reef was gradual throughout the summer and fall, similar to the pattern of dispersal observed on the continental shelf off the coast of New Jersey (Fabrizio et al. 2005). The time of dispersal from the continental shelf was similar to those observed in Chesapeake Bay, with 50% of fish dispersing by 5 September 2003 on the shelf and by 26 August 2006 in the Bay. This implies that there may be similarities in the duration of summer flounder habitat use in Chesapeake Bay and on the continental shelf. We found no statistically significant difference in dispersal of large and small fish from Back River reef. Fish were continuously detected until early December 2006 at Back River reef, but no summer flounder were detected between 5 February 2007 and late March 2007, indicating that tagged fish had dispersed from the York River and Chesapeake Bay (possibly moving to offshore spawning sites). Summer flounder returned to our Chesapeake Bay sites at the end of March 2007. Time of day, tidal stage, temperature, and barometric pressure affected summer flounder movements over scales of 200-400 m at Back River reef. We detected and documented significant variation in activity levels among individual fish, but overall, fish were more active during night than during the day, and more active at slack tide than during either ebb or flood tides. Fish size was not a significant factor in accounting for variability in mean activity levels. In addition, fish at Back River reef appeared to partition site use on the basis of size. In summary, activity levels are highly variable among individual fish, and summer flounder movements on the order of 200-400 m are affected by environmental characteristics such as temperature and tides. We also observed large-scale (>1 km) movements of fish, including the movement of fish from Gloucester Point and York Spit light to Back River reef. The appearance of Gloucester Point-tagged fish in the mainstem of Chesapeake Bay during the fall was suggestive of directed movements, such as those associated with migration to offshore spawning sites.