Quantification of Interactions Between Common Bottlenose Dolphins (Tursiops truncatus) and a Commercial Shrimp Trawler near Savannah, Georgia

Abstract

The common bottlenose dolphin (Tursiops truncatus) has been known to forage in association with shrimp trawlers by feeding on fish caught in or disturbed by nets and on discarded bycatch. In addition, common bottlenose dolphins in the estuarine waterways near Savannah, Georgia display a high rate of begging behavior, and it is hypothesized that interactions between bottlenose dolphins and the shrimp trawl fishery may be a contributing factor. The purpose of this study was to determine which activities of the shrimp trawl fishery resulted in associations between trawlers and bottlenose dolphins, and which activities resulted in bottlenose dolphins begging from the trawler. The presence of common bottlenose dolphins around a commercial shrimp trawler and the activity of the trawler were recorded for 129 h over 20 d Bottlenose dolphins associated with the shrimp trawler (i.e., within 150 m of the trawler) for 68 ± 33% of the day; and they associated with the vessel for the majority of the time spent in the net positions of haulback (90 ± 20%) and trawling (89 ± 17%). However, bottlenose dolphins approached the vessel (i.e., within 10 m) most often while the fishermen were manipulating and cleaning the nets (60 ± 23%) and least often during trawling (2 ± 5%). Begging was observed on 90% of days and occurred most often when the fishermen were cleaning the nets and bringing the trawl doors onboard the vessel (79% of days). Whether or not a bottlenose dolphin interacted with a trawler was dependent on several factors, including trawler activity, net position, and fisherman behavior. Furthermore, bottlenose dolphins that forage behind active trawlers may later engage in begging behavior as a result of direct interactions with fishermen, perpetuating the begging problem near Savannah.

Conflict analysis between commercial fisheries and common bottlenose dolphin (Tursiops truncatus) in the Dodecanese region, Greece

“…In front of the Meander River, East Kalymnos was found the area at highest risk of conflict, likely because of high fishing effort and the predominance of trawlers, the gear with the highest overlap with T. truncatus (Table 2). Frequent interactions between trawlers and T. truncatus also occur in Australia (Jaiteh et al, 2013) and the coast of the United States (Greenman, 2012; Kovacs & Cox, 2014). East Kalymnos also has high purse seiner fishing effort, which should reduce the likelihood of conflict with T. truncatus (Marçalo et al, 2015; Wise et al, 2007), although not enough to mitigate risk induced by the large number of trawlers and high total fishing effort.…”

A characterisation of common bottlenose dolphin (Tursiops truncatus) interactions with the commercial shrimp trawl fishery of South Carolina, USA

“…Using this SCGCS assessment (PBR = 64), the two known commercial dolphin takes that occurred in 1998 and 2002 are not enough to meet the NMFS criteria for classification as a Category II fishery (1% PBR <50% PBR). However, the SCGCS also includes the entire Georgia coast and a recent study found that dolphins frequently associated with shrimp trawlers near Savannah, GA (Kovacs and Cox, 2014). If dolphin takes in Georgia occur at a similar rate as in South Carolina, it may provide enough data to confirm its Category II designation.…”

Lords of the Rings: Mud ring feeding by bottlenose dolphins in a Caribbean estuary revealed from sea, air, and space

“…display a remarkably diverse array of individual and cooperative foraging tactics across their global distribution that typically reflect local adaptations to habitat conditions and prey types (Finn et al, 2009; Mann & Sargeant, 2003; Torres & Read, 2009). Specialized foraging methods documented to date include strand feeding (Hoese, 1971; Sargeant et al, 2005), kerplunking (Connor et al, 2000; Nowacek, 2002), cooperative foraging with fishermen (Pryor & Lindbergh, 1990), driver‐barrier feeding (Gazda et al, 2005), foraging in or around trawl nets (Kovacs & Cox, 2014), and using tools, particularly sponges (Krützen et al, 2014; Smolker et al, 1997) and shells (Allen et al, 2011; Wild et al, 2020).…”