Dataset Information

Temperature and the vertical movements of oceanic whitetip sharks, Carcharhinus longimanus.

ABSTRACT: Large-bodied pelagic ectotherms such as sharks need to maintain internal temperatures within a favourable range in order to maximise performance and be cost-efficient foragers. This implies that behavioural thermoregulation should be a key feature of the movements of these animals, although field evidence is limited. We used depth and temperature archives from pop-up satellite tags to investigate the role of temperature in driving vertical movements of 16 oceanic whitetip sharks, Carcharhinus longimanus, (OWTs). Spectral analysis, linear mixed modelling, segmented regression and multivariate techniques were used to examine the effect of mean sea surface temperature (SST) and mixed layer depth on vertical movements. OWTs continually oscillated throughout the upper 200?m of the water column. In summer when the water column was stratified with high SSTs, oscillations increased in amplitude and cycle length and sharks reduced the time spent in the upper 50?m. In winter when the water column was cooler and well-mixed, oscillations decreased in amplitude and cycle length and sharks frequently occupied the upper 50?m. SSTs of 28?oC marked a distinct change in vertical movements and the onset of thermoregulation strategies. Our results have implications for the ecology of these animals in a warming ocean.

SUBMITTER: Andrzejaczek S

PROVIDER: S-EPMC5974137 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Temperature and the vertical movements of oceanic whitetip sharks, Carcharhinus longimanus.

Andrzejaczek Samantha S Gleiss Adrian C AC Jordan Lance K B LKB Pattiaratchi Charitha B CB Howey Lucy A LA Brooks Edward J EJ Meekan Mark G MG

Scientific reports 20180529 1

Large-bodied pelagic ectotherms such as sharks need to maintain internal temperatures within a favourable range in order to maximise performance and be cost-efficient foragers. This implies that behavioural thermoregulation should be a key feature of the movements of these animals, although field evidence is limited. We used depth and temperature archives from pop-up satellite tags to investigate the role of temperature in driving vertical movements of 16 oceanic whitetip sharks, Carcharhinus lo ...[more]

PMID: 29844605

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Project description:Southeast Florida witnesses an enormous seasonal influx of upper trophic level marine predators each year as massive aggregations of migrating blacktip sharks (Carcharhinus limbatus) overwinter in nearshore waters. The narrow shelf and close proximity of the Gulf Stream current to the Palm Beach County shoreline drive tens of thousands of sharks to the shallow, coastal environment. This natural bottleneck provides a unique opportunity to estimate relative abundance. Over a four year period from 2011-2014, an aerial survey was flown approximately biweekly along the length of Palm Beach County. A high definition video camera and digital still camera mounted out of the airplane window provided a continuous record of the belt transect which extended 200 m seaward from the shoreline between Boca Raton Inlet and Jupiter Inlet. The number of sharks within the survey transect was directly counted from the video. Shark abundance peaked in the winter (January-March) with a maximum in 2011 of 12,128 individuals counted within the 75.6 km(-2) belt transect. This resulted in a maximum density of 803.2 sharks km(-2). By the late spring (April-May), shark abundance had sharply declined to 1.1% of its peak, where it remained until spiking again in January of the following year. Shark abundance was inversely correlated with water temperature and large numbers of sharks were found only when water temperatures were less than 25 °C. Shark abundance was also correlated with day of the year but not with barometric pressure. Although shark abundance was not correlated with photoperiod, the departure of the sharks from southeast Florida occurred around the vernal equinox. The shark migration along the United States eastern seaboard corresponds spatially and temporally with the spawning aggregations of various baitfish species. These baseline abundance data can be compared to future studies to determine if shark population size is changing and if sharks are restricting their southward migration as global water temperatures increase.

Dataset Information

Temperature and the vertical movements of oceanic whitetip sharks, Carcharhinus longimanus.

Publications

Temperature and the vertical movements of oceanic whitetip sharks, Carcharhinus longimanus.

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