scholarly journals Peer Review #1 of "Satellite tagging highlights the importance of productive Mozambican coastal waters to the ecology and conservation of whale sharks (v0.1)"

2018 ◽  
Author(s):  
J Kiszka
Keyword(s):  
Peer Review ◽  
Coastal Waters ◽  
Whale Sharks ◽  
Satellite Tagging

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

2017 ◽  
Author(s):  
Christoph A Rohner ◽  
Anthony J Richardson ◽  
Fabrice R A Jaine ◽  
Michael B Bennett ◽  
Scarla J Weeks ◽  
...  
Keyword(s):  
Coastal Waters ◽  
Habitat Preferences ◽  
Movement Ecology ◽  
Whale Shark ◽  
Long Distance ◽  
Tropical Oceans ◽  
Whale Sharks ◽  
International Boundaries ◽  
Satellite Tagging ◽  
Analytical Approaches

Recent advances in tracking technologies and analytical approaches allow for deeper insights into the movement ecology of wide-ranging fishes. The whale shark Rhincodon typus is an endangered, highly migratory species with a wide, albeit patchy, distribution through tropical oceans. Aerial surveys along the southern Mozambican coast, conducted over a 5-year period, documented the highest densities of whale sharks to occur within a ~200 km long stretch of the Inhambane Province, with a pronounced hotspot adjacent to Praia do Tofo. We tagged 15 juvenile whale sharks with SPOT5 satellite tags off Praia do Tofo and tracked them for 1–87 days (mean = 26 days) as they dispersed from this area. Sharks travelled between 10 and 2,737 km (mean = 738 km) at a mean horizontal speed of 29 ± 30.7 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. 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. The increasing use of large-mesh gill nets in this coastal hotspot for whale sharks is a clear threat to regional populations of this iconic species.

Distribution of zooplankton inferred from hydroacoustic backscatter data in coastal waters off Ningaloo Reef, Western Australia

2002 ◽  
Vol 53 (6) ◽  
pp. 1005 ◽  
Author(s):  
Steven G. Wilson ◽  
Timothy Pauly ◽  
Mark G. Meekan
Keyword(s):  
Western Australia ◽  
Coastal Waters ◽  
Near Surface ◽  
Rhincodon Typus ◽  
Ningaloo Reef ◽  
The North ◽  
Whale Sharks ◽  
Bubble Layer ◽  
Surface Bubble

Hydroacoustic surveys were used to examine zooplankton distributions in coastal waters off Ningaloo Reef, Western Australia. Surveys were timed to coincide with the seasonal aggregation of whale sharks, Rhincodon typus, and other large zooplanktivores in these waters. The surveys examined scattering features of lagoon/shelf fronts, a series of cross-shelf transects and waters surrounding whale sharks swimming at the surface. These suggested that lagoon waters flow intrusively into shelf waters at reef passages in a layered exchange. Cross-shelf transects identified three vertical scattering layers: a surface bubble layer; a near-surface minimum layer; and a bottom maximum layer. Regions of intense mixing of lagoon and shelf waters were detected seaward and to the north of reef passages. Integrated acoustic mean volume backscatter of the bottom maximum layer increased with depth and distance offshore. Large subsurface aggregations of unidentified fauna were detected beneath whale sharks in the same area that manta rays and surface schools of euphausiids were also observed.

scholarly journals Oceanic adults, coastal juveniles: tracking the habitat use of whale sharks off the Pacific coast of Mexico

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3271 ◽  
Author(s):  
Dení Ramírez-Macías ◽  
Nuno Queiroz ◽  
Simon J. Pierce ◽  
Nicolas E. Humphries ◽  
David W. Sims ◽  
...  
Keyword(s):  
Coastal Waters ◽  
Gulf Of California ◽  
Pacific Coast ◽  
Early Morning ◽  
Eastern Pacific Ocean ◽  
Archival Tags ◽  
The Pacific ◽  
Habitat Differences ◽  
Frontal Zones ◽  
Whale Sharks

Eight whale sharks tagged with pop-up satellite archival tags off the Gulf of California, Mexico, were tracked for periods of 14–134 days. Five of these sharks were adults, with four females visually assessed to be pregnant. At least for the periods they were tracked, juveniles remained in the Gulf of California while adults moved offshore into the eastern Pacific Ocean. We propose that parturition occurs in these offshore waters. Excluding two juveniles that remained in the shallow tagging area for the duration of tracking, all sharks spent 65 ± 20.7% (SD) of their time near the surface, even over deep water, often in association with frontal zones characterized by cool-water upwelling. While these six sharks all made dives into the meso- or bathypelagic zones, with two sharks reaching the maximum depth recordable by the tags (1285.8 m), time spent at these depths represented a small proportion of the overall tracks. Most deep dives (72.7%) took place during the day, particularly during the early morning and late afternoon. Pronounced habitat differences by ontogenetic stage suggest that adult whale sharks are less likely to frequent coastal waters after the onset of maturity.

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