Movement patterns of juvenile lemon sharks Negaprion brevirostris within Atol das Rocas, Brazil: a nursery characterized by tidal extremes

Abstract

Movement patterns and habitat use of juvenile lemon sharks Negaprion brevirostris were monitored at Atol das Rocas, Brazil, an atypical nursery area for this species, characterized by extreme tides and a lack of seagrass flats and mangroves. Twenty-three sharks carrying transmitters were monitored using an array of bottom-fixed automated receivers during 3 trips over a total of 60 d. Transmitters were recorded on receivers over 13 000 times, and the majority of sharks were detected more than 100 times. Newborn sharks (60 to 80 cm total length, TL) showed restricted but repeated movements between small tide pools on reef flats at low tide and a small, shallow, nearby tidal creek at high tide. Larger sharks (up to 106 cm TL) sampled 6 and 20 mo after the study in March 2000 frequented the tidal creek and several other locations at high tide and a variety of larger pools at low tide, and in general exhibited more extensive movements within the atoll than did newborn sharks. Sharks approaching 2 yr of age were generally observed in specific pools or shallow water locations within the atoll during high and low tides, but also expanded their movements to include more of the atoll. Throughout the study, young lemon sharks appeared to concentrate movements within shallow-water low-tide refuges and separate high tidal areas. Movement patterns of sharks in Atol das Rocas differ from those at other well-studied lemon shark nursery locations, where individuals continuously occupy shallow flats and mangrove habitats. Nevertheless, lemon sharks in general restrict their movements to shallow-water habitats regardless of the specific nursery area occupied. This behavior is most likely related to predator avoidance. This study provides an example of the interaction between the physical environment and the biology of animals -in this case, the influence of the physical characteristics of a nursery area and the behavioral ecology of young lemon sharks. KEY WORDS: Shark nurseries · Tidal fluctuation · Refuging · Movement patterns · Predator avoidanceResale or republication not permitted without written consent of the publisher

Spatial and temporal movement patterns of a multi-species coastal reef shark aggregation

“…Our study presents long-term quantitative spatial and temporal information of a multi-species reef shark aggregation. Several hypotheses have been posed to explain reef shark aggregations, such as refuging (Klimley & Nelson 1984), predator avoidance (Wetherbee et al 2007), courtship, mating and pre-pupping (McKibben & Nelson 1986). Previous studies of daytime aggregations of reef-associated sharks suggested that aggregations were for behavioural thermoregulation to aid embryonic development or to avoid aggressive males (Economakis & Lobel 1998, Hight & Lowe 2007.…”

Complexities of coastal shark movements and their implications for management

“…Similar patterns have been observed for grey nurse (ragged tooth) sharks Carcharias tauras (Dicken et al 2007) and large juvenile white sharks, which range more widely than young-of-the-year in coastal adult habitats likely as a consequence of changing physiology (Weng et al 2007b) or resource exclusion. Lemon sharks also undergo an ontogenetic expansion of home ranges, with juveniles showing strong site fidelity and movement between tidal refuges, while adults range farther (Gruber et al 1988, Morrissey & Gruber 1993b, Wetherbee et al 2007, Chapman et al 2009). Similarly, juvenile blacktip sharks expand their home range over months due to changes in environmental conditions or ontogenetic changes in behaviour (Heupel & Hueter 2001, Heupel et al 2004, Heupel & Simpfendorfer 2005a).…”

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Sizing up the ecological role of sharks as predators

“…thresher shark). In general, the juvenile life stages of many coastal sharks tend to be found in shallow waters -possibly to minimise predation risk (Branstetter 1990, Heupel & Simpfendorfer 2005, Wetherbee et al 2007). Thus, the higher risk of predation upon small species and size classes of sharks would probably have an impact on their non-consumptive role through ecology of fear effects (e.g.…”