Satellite tagging highlights the importance of productive Mozambican coastal waters to the ecology and conservation of whale sharks

The whale shark Rhincodon typus is an endangered, highly migratory species with a wide, albeit patchy, distribution through tropical oceans. Ten aerial survey flights along the southern Mozambican coast, conducted between 2004–2008, documented a relatively high density of whale sharks along a 200 km stretch of the Inhambane Province, with a pronounced hotspot adjacent to Praia do Tofo. To examine the residency and movement of whale sharks in coastal areas around Praia do Tofo, where they may be more susceptible to gill net entanglement, we tagged 15 juveniles with SPOT5 satellite tags and tracked them for 2–88 days (mean = 27 days) as they dispersed from this area. Sharks travelled between 10 and 2,737 km (mean = 738 km) at a mean horizontal speed of 28 ± 17.1 SD km day−1. While several individuals left shelf waters and travelled across international boundaries, most sharks stayed in Mozambican coastal waters over the tracking period. We tested for whale shark habitat preferences, using sea surface temperature, chlorophyll-a concentration and water depth as variables, by computing 100 random model tracks for each real shark based on their empirical movement characteristics. Whale sharks spent significantly more time in cooler, shallower water with higher chlorophyll-a concentrations than model sharks, suggesting that feeding in productive coastal waters is an important driver of their movements. To investigate what this coastal habitat choice means for their conservation in Mozambique, we mapped gill nets during two dedicated aerial surveys along the Inhambane coast and counted gill nets in 1,323 boat-based surveys near Praia do Tofo. Our results show that, while whale sharks are capable of long-distance oceanic movements, they can spend a disproportionate amount of time in specific areas, such as along the southern Mozambique coast. The increasing use of drifting gill nets in this coastal hotspot for whale sharks is likely to be a threat to regional populations of this iconic species.

[1]  Zaven Arzoumanian,et al.  Undersea Constellations: The Global Biology of an Endangered Marine Megavertebrate Further Informed through Citizen Science , 2017 .

[2]  C. Rohner,et al.  Some like it hot: Repeat migration and residency of whale sharks within an extreme natural environment , 2017, PloS one.

[3]  A. Marshall,et al.  Steep declines in sightings of manta rays and devilrays (Mobulidae) in southern Mozambique , 2017 .

[4]  Nicolas E. Humphries,et al.  Oceanic adults, coastal juveniles: tracking the habitat use of whale sharks off the Pacific coast of Mexico , 2017, PeerJ.

[5]  R. Leeney.  Are sawfishes still present in Mozambique? A baseline ecological study , 2017, PeerJ.

[6]  M. Meekan,et al.  The ecological connectivity of whale shark aggregations in the Indian Ocean: a photo-identification approach , 2016, Royal Society Open Science.

[7]  A. Hearn,et al.  Adult female whale sharks make long-distance movements past Darwin Island (Galapagos, Ecuador) in the Eastern Tropical Pacific , 2016 .

[8]  J. Mair,et al.  Population Structure, Abundance and Movement of Whale Sharks in the Arabian Gulf and the Gulf of Oman , 2016, PloS one.

[9]  Kim Holland,et al.  Key Questions in Marine Megafauna Movement Ecology. , 2016, Trends in ecology & evolution.

[10]  R. Hueter,et al.  Vertical Movements and Patterns in Diving Behavior of Whale Sharks as Revealed by Pop-Up Satellite Tags in the Eastern Gulf of Mexico , 2015, PloS one.

[11]  Scarla J. Weeks,et al.  Laser photogrammetry improves size and demographic estimates for whale sharks , 2015, PeerJ.

[12]  E. F. Cagua,et al.  Acoustic telemetry reveals cryptic residency of whale sharks , 2015, Biology Letters.

[13]  A. Richardson,et al.  Whale sharks target dense prey patches of sergestid shrimp off Tanzania , 2015, Journal of plankton research.

[14]  A. Hearn,et al.  Whale Shark (Rhincodon typus) Seasonal Presence, Residence Time and Habitat Use at Darwin Island, Galapagos Marine Reserve , 2014, PloS one.

[15]  A. Marshall,et al.  Monitoring the effects of tourism on whale shark Rhincodon typus behaviour in Mozambique , 2014, Oryx.

[16]  M. Berumen,et al.  Movement Patterns of Juvenile Whale Sharks Tagged at an Aggregation Site in the Red Sea , 2014, PloS one.

[17]  L. Dubroca,et al.  Mortality of marine megafauna induced by fisheries: Insights from the whale shark, the world’s largest fish , 2014 .

[18]  F. Shillington,et al.  Cool, elevated chlorophyll-a waters off northern Mozambique , 2014 .

[19]  C. Mellin,et al.  Inter-ocean asynchrony in whale shark occurrence patterns , 2014 .

[20]  R Core Team,et al.  R: A language and environment for statistical computing. , 2014 .

[21]  A. Richardson,et al.  Diet of whale sharks Rhincodon typus inferred from stomach content and signature fatty acid analyses , 2013 .

[22]  Rafael Bravo de la Parra,et al.  Horizontal Movements, Migration Patterns, and Population Structure of Whale Sharks in the Gulf of Mexico and Northwestern Caribbean Sea , 2013, PloS one.

[23]  A. Hearn,et al.  Simple criteria to determine detachment point of towed satellite tags provide first evidence of return migrations of whale sharks (Rhincodon typus) at the Galapagos Islands, Ecuador , 2013, Animal Biotelemetry.

[24]  Michael B. Bennett,et al.  Trends in sightings and environmental influences on a coastal aggregation of manta rays and whale sharks , 2013 .

[25]  C. Mellin,et al.  Spatial and temporal predictions of inter-decadal trends in Indian Ocean whale sharks , 2013 .

[26]  David P. Robinson,et al.  Whale Sharks, Rhincodon typus, Aggregate around Offshore Platforms in Qatari Waters of the Arabian Gulf to Feed on Fish Spawn , 2013, PloS one.

[27]  Daniel P. Costa,et al.  New Insights into Pelagic Migrations: Implications for Ecology and Conservation , 2012 .

[28]  Scarla J. Weeks,et al.  When Giants Turn Up: Sighting Trends, Environmental Influences and Habitat Use of the Manta Ray Manta alfredi at a Coral Reef , 2012, PloS one.

[29]  Brendan J. Godley,et al.  Satellite Tracking of Manta Rays Highlights Challenges to Their Conservation , 2012, PloS one.

[30]  D. Rowat,et al.  A review of the biology, fisheries and conservation of the whale shark Rhincodon typus. , 2012, Journal of fish biology.

[31]  P. Valentine,et al.  Diving Tourism in Mozambique: An Opportunity at Risk? , 2011 .

[32]  D. Rowat,et al.  Long-term membership of whale sharks (Rhincodon typus) in coastal aggregations in Seychelles and Djibouti , 2011 .

[33]  K. M. Schaefer,et al.  Tracking apex marine predator movements in a dynamic ocean , 2011, Nature.

[34]  Scarla J. Weeks,et al.  How large is the world's largest fish? Measuring whale sharks Rhincodon typus with laser photogrammetry. , 2011, Journal of fish biology.

[35]  M. van den Berg,et al.  Circulation patterns in the Delagoa Bight, Mozambique, and the influence of deep ocean eddies , 2010 .

[36]  A. Monadjem,et al.  Developing a Code of Conduct for whale shark interactions in Mozambique , 2010 .

[37]  J. Ragle,et al.  IUCN Red List of Threatened Species , 2010 .

[38]  C. Bradshaw,et al.  To go or not to go with the flow: Environmental influences on whale shark movement patterns , 2010 .

[39]  D. W. Sims.  Tracking and Analysis Techniques for Understanding Free-Ranging Shark Movements and Behavior , 2010 .

[40]  Daniel P. Costa,et al.  Accuracy of ARGOS Locations of Pinnipeds at-Sea Estimated Using Fastloc GPS , 2010, PloS one.

[41]  S. Pierce,et al.  Seeing Spots: Photo-identification as a Regional Tool for Whale Shark Identification , 2010 .

[42]  J. Holmberg,et al.  Estimating population size, structure, and residency time for whale sharks Rhincodon typus through collaborative photo-identification , 2009 .

[43]  J. Brunnschweiler,et al.  Deep-diving behaviour of a whale shark Rhincodon typus during long-distance movement in the western Indian Ocean. , 2009, Journal of fish biology.

[44]  E. Revilla,et al.  A movement ecology paradigm for unifying organismal movement research , 2008, Proceedings of the National Academy of Sciences.

[45]  C. Bradshaw,et al.  Scarring patterns and relative mortality rates of Indian Ocean whale sharks , 2008 .

[46]  C. Bradshaw,et al.  Biophysical correlates of relative abundances of marine megafauna at Ningaloo Reef, Western Australia , 2007 .

[47]  Kwang-Ming Liu,et al.  Satellite tracking of juvenile whale sharks, Rhincodon typus, in the Northwestern Pacific , 2007 .

[48]  D. Rowat,et al.  Regional scale horizontal and local scale vertical movements of whale sharks in the Indian Ocean off Seychelles , 2007 .

[49]  G. Cliff,et al.  Aerial census of whale sharks (Rhincodon typus) on the northern KwaZulu-Natal coast, South Africa , 2007 .

[50]  S. Harding,et al.  Occurrence of whale sharks (Rhincodon typus) in Madagascar , 2007 .

[51]  Anthony J Richardson,et al.  Encounter success of free-ranging marine predator movements across a dynamic prey landscape , 2006, Proceedings of the Royal Society B: Biological Sciences.

[52]  Mark G. Meekan,et al.  Movements of whale sharks (Rhincodon typus) tagged at Ningaloo Reef, Western Australia , 2006 .

[53]  Zaven Arzoumanian,et al.  An astronomical pattern-matching algorithm for computer-aided identification of whale sharks Rhincodon typus , 2005 .

[54]  D. Ware,et al.  Bottom-Up Ecosystem Trophic Dynamics Determine Fish Production in the Northeast Pacific , 2005, Science.

[55]  João Antônio Lorenzzetti,et al.  Remote sensing data and longline catches of yellowfin tuna (Thunnus albacares) in the equatorial Atlantic , 2004 .

[56]  Anthony J. Richardson,et al.  Climate Impact on Plankton Ecosystems in the Northeast Atlantic , 2004, Science.

[57]  S. Eckert,et al.  Telemetry and Satellite Tracking of Whale Sharks, Rhincodon Typus, in the Sea of Cortez, Mexico, and the North Pacific Ocean , 2001, Environmental Biology of Fishes.

[58]  David W. Sims,et al.  Seasonal movements and behaviour of basking sharks from archival tagging: no evidence of winter hibernation , 2003 .

[59]  G. Kooyman,et al.  Movements of whale sharks (Rhincodon typus) in South‐east Asian waters as determined by satellite telemetry , 2002 .

[60]  B. Kjerfve,et al.  Whale sharks Rhincodon typus aggregate to feed on fish spawn in Belize , 2001 .

[61]  Timothy R. Parsons,et al.  Biological oceanography: an introduction. Second edition , 1997 .

[62]  Piotr Dawidowicz,et al.  Trade-offs in diel vertical migration by zooplankton: The costs of predator avoidance , 1994 .

[63]  Sharon L. Smith,et al.  The interaction of phytoplankton, zooplankton and currents from 15 months of continuous data in the Mid-Atlantic Bight , 1994 .

[64]  S. Plourde,et al.  Reproduction of the planktonic copepod Calanus finmarchicus in the Lower St. Lawrence Estuary: relation to the cycle of phytoplankton production and evidence for a Calanus pump , 1993 .

[65]  S. L. Ohlhorst.  Diel migration patterns of demersal reef zooplankton , 1982 .

[66]  A. Alldredge,et al.  Distribution, abundance, and substrate preferences of demersal reef zooplankton at Lizard Island Lagoon, Great Barrier Reef , 1977 .

[67]  G. E. Hutchinson,et al.  A treatise on limnology. , 1957 .