Habitat use and movement patterns of bull sharks Carcharhinus leucas determined using pop‐up satellite archival tags

Abstract

Habitat use, movement and residency of bull sharks Carcharhinus leucas were determined using satellite pop-up archival transmitting (PAT) tags throughout coastal areas in the U.S., Gulf of Mexico and waters off the south-east U.S. From 2005 to 2007, 18 fish (mean size = 164 cm fork length, L(F)) were tagged over all seasons. Fish retained tags for up to 85 days (median = 30 days). Based on geolocation data from initial tagging location to pop-off location, C. leucas generally travelled c. 5-6 km day(-1) and travelled an average of 143.6 km. Overall, mean proportions of time at depth revealed C. leucas spent the majority of their time in waters <20 m. They exhibited significant differences among depths but were not found at a particular depth regardless of diurnal period. Most fish occupied temperatures c. 32 degrees C with individuals found mostly between 26 and 33 degrees C. Geolocation data for C. leucas were generally poor and varied considerably but tracks for two individuals revealed long distance movements. One fish travelled from the south-east coast of the U.S. to coastal Texas near Galveston while another moved up the east coast of the U.S. to South Carolina. Data on C. leucas movements indicated that they are found primarily in shallower waters and tend to remain in the same location over long periods. While some individuals made large-scale movements over open ocean areas, the results emphasize the importance of the coastal zone for this species as potential essential habitat, particularly in areas of high freshwater inflow.

Conservation challenges of sharks with continental scale migrations

“…This result contrasts data from the Gulf of Mexico that documented mostly one way movements with an average distance of 140 km (Carlson et al, 2010). However, this previous research has been limited by the short-term nature of satellite-based telemetry in this species, and demonstrates the power of longer-term acoustic telemetry to detect seasonal and inter-annual migrations.…”

“…Movements and habitat use by juvenile bull sharks has been well-documented in several studies (Heupel and Simpfendorfer, 2008;Heithaus et al, 2009;Heupel et al, 2010;Curtis et al, 2013), but data on adult movements are limited (Daly et al, 2014). In one of the few explorations of adult movement satellite tagged C. leucas were tracked moving distances of 2-1506 km (mean 143.6 km) over periods up to 85 days in the Gulf of Mexico spending the majority of their time in warm, shallow coastal habitats (Carlson et al, 2010). Acoustic tracking in South Africa also recorded movements ranging from 433 to 709 km (mean 533 km) over periods of 10-22 months (Daly et al, 2014).…”

“…capable of long distance movements (Brunnschweiler et al, 2010;Carlson et al, 2010) based on limited satellite tagging. Recent research has indicated segregation by size may occur in C. leucas populations with smallest individuals using river habitats and largest individuals inhabiting marine regions (Simpfendorfer et al, 2005;Brunnschweiler and Barnett, 2013).…”

Diet of the bull shark, Carcharhinus leucas, and the tiger shark,Galeocerdo cuvier, in the eastern Pacific Ocean

“…It is one of the few shark species that is physiologically capable of spending time in fresh water (Pillans and Franklin, 2004) and has been reported in rivers and lakes (Thorson et al, 1973;Thomerson et al, 1977;Montoya and Thorson, 1982;Simpendorfer et al, 2005). The tolerance of bull sharks for low-salinity conditions allows them to frequent areas close to shore and near river mouths, where they may interact with other shark species (Carlson et al, 2010). The tiger shark reaches a larger size than the bull shark (over 550 cm) (Compagno, 1984), with a wide tolerance for different marine habitats at depths ranging from the surface to 140 m. This species is apparently nocturnal and shows a diel cycle of movement, moving inshore at night into shallow bays, estuaries, passes between islands, lagoons, and other shallow areas (e.g., Tricas et al, 1981;Alfonso and Hazin, 2015).…”

Bioaccumulation of organohalogenated compounds in sharks and rays from the southeastern USA

“…Shallow estuarine areas serve as nursery grounds for small juveniles, after which they move to coastal ocean waters as they begin to mature (Curtis et al, 2011). Adults have been found to migrate over fairly long distances (Carlson et al, 2010;Tillett et al, 2012). These sharks are opportunistic predators with a large variation in their diet spanning from teleost fishes to elasmobranchs, seabirds and marine mammals.…”