Seasonal Variation in the Spatial Distribution of Basking Sharks (Cetorhinus maximus) in the Lower Bay of Fundy, Canada

Siders, Zachary A.; Westgate, Andrew J.; Johnston, David W.; Murison, Laurie D.; Koopman, Heather N.

doi:10.1371/journal.pone.0082074

Cited by 23 publications

(46 citation statements)

References 52 publications

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“…C. pacificus developmental stages (C) IV and V contain a large lipid droplet and are energetically dense. The CIV and CV stage of C. finmarchicus are targeted by basking sharks in the western North Atlantic (Baduini, 1995;Siders et al, 2013;Curtis et al, 2014). Off CA the CIV and CV stages occur year around but are most abundant in surface waters from April through October (Johnson and Checkley, 2004), although high concentrations of CV can also be found at depth during periods of diapause (see below).…”

Section: Geographic Movements and Essential Habitatmentioning

confidence: 99%

“…Unfortunately, which taxa they were targeting is not known. While copepods are thought to be the preferred prey (Baduini, 1995;Sims and Reid, 2002;Siders et al, 2013;Curtis et al, 2014), stomach contents from basking sharks foraging in deep waters in the Northwest Pacific Oceans included small crustaceans of up to 5.4 cm (Mutoh and Omori, 1978). One factor that suggests the basking shark was targeting copepods is the early ascent prior to dusk, which is unusual for pelagic fish that target the sound-scattering layer (Carey and Robison, 1981;Carey and Scharold, 1990;Musyl et al, 2004;Dewar et al, 2011).…”

Section: Vertical Movementsmentioning

confidence: 99%

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Basking Shark (Cetorhinus maximus) Movements in the Eastern North Pacific Determined Using Satellite Telemetry

et al. 2018

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To fill data gaps on movements, behaviors and habitat use, both near-and offshore, two programs were initiated to deploy satellite tags on basking sharks off the coast of California. Basking sharks are large filter-feeding sharks that are second in size only to whale sharks. Similar to many megafauna populations, available data suggest that populations are below historic levels. In the eastern North Pacific (ENP) Ocean, the limited information on basking sharks comes from nearshore habitats where they forage. From 2010 to 2011, four sharks were tagged with pop-off satellite archival tags with deployments ranging from 9 to 240 days. The tags provided both transmitted and archived data on habitat use and geographic movement patterns. Nearshore, sharks tended to move north in the summer and prefer shelf and slope habitat around San Diego, Point Conception and Monterey Bay. The two sharks with 180 and 240 days deployments left the coast in the summer and fall. Offshore their paths diverged and by January one shark had moved to near the tip of the Baja Peninsula, Mexico and the other to the waters near Hawaii, USA. Vertical habitat use was variable both within and among individuals and changed as sharks moved offshore. Nearshore, most time was spent in the mixed layer but sharks did spend hours in cold waters below the mixed layer. Offshore vertical movements depended on location. The shark that went to Hawaii had a distinct diel pattern, with days spent at ∼450-470 m and nights at ∼250-300 m and almost no time in surface waters, corresponding with the diel migration of a specific portion of the deep scattering layer. The shark that moved south along the Baja Peninsula spent progressively more time in deep water but came to the surface daily. Movement patterns and shifts in vertical habitat and use are likely linked to shifts in prey availability and oceanography. Data collected indicate the potential for large-scale movements and the need for international dialogue in any recovery efforts.

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Section: Geographic Movements and Essential Habitatmentioning

confidence: 99%

Section: Vertical Movementsmentioning

confidence: 99%

Basking Shark (Cetorhinus maximus) Movements in the Eastern North Pacific Determined Using Satellite Telemetry

et al. 2018

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“…1. The delineations of this area (10 570 km 2 ) were arbitrar- (Siders et al 2013) revealed that the highest densities of animals were predicted in August and September. Weather conditions on both survey days were similar (winds <15 km h −1 , 20+ km visibility).…”

Section: Surveysmentioning

confidence: 99%

“…In a recent basking shark habitat suitability model, Siders et al (2013) showed that suitable habitat was largely restricted to the deeper waters of the Bay of Fundy. The heterogeneous spatial distribution of our sightings (Fig.…”

Section: Availability Biasmentioning

confidence: 99%

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Population density and abundance of basking sharks Cetorhinus maximus in the lower Bay of Fundy, Canada

Westgate

Koopman²,

Siders³

et al. 2014

Endang. Species. Res.

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The conservation status of basking sharks Cetorhinus maximus in eastern Canadian waters is not clearly understood, in part because population densities and abundances have not been recently estimated. On September 11, 2009 and 2011, aerial surveys of basking sharks were conducted in the lower Bay of Fundy, Canada. Flyover tests of a wooden shark silhouette revealed that basking sharks were visible to a depth of 5 m. The proportion of time basking sharks were estimated between 0 and 5 m depth (availability bias) was 19% based on 1252 h of time-depth recorder data from 13 free-swimming sharks. During the 2 surveys, 26 sharks were sighted. Using the program Distance, availability bias corrected densities of 0.0513 sharks km −2 (2009, 95% CI = 0.0188 to 0.1402) and 0.0598 sharks km −2 (2011, 95% CI = 0.0358 to 0.1001) were reported. This corresponds to abundance estimates of 542 sharks (2009, 95% CI = 198 to 1482) and 632 sharks (2011, 95% CI = 377 to 1058) occupying a 10 570 km 2 area in the lower Bay of Fundy. Abundance was far lower than previously estimated using indirect methods and untested assumptions (Bay of Fundy = 4200 sharks). Previously published habitat suitability models for basking sharks in the Bay of Fundy predict heterogeneous habitat use, which would lower the overall abundance estimate. This lower population estimate for the Bay of Fundy, coupled with a very limited capacity to respond to significant levels of anthropogenic mortality, raises concerns about the conservation status of eastern Canadian basking sharks.

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Distribution of whale shark (Rhincodon typus) off northern Peru based on habitat suitability

González-Pestana

Maguiño

Mendoza

et al. 2020

Aquatic Conservation

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1. In the south-eastern Pacific Ocean, few studies of whale sharks (Rhincodon typus) exist. In Peru, the northern coast has been identified as the area with the highest presence of whale sharks, yet their ecology in this area is poorly defined.2. This study predicts the spatial distribution of whale sharks off coastal northern Peru (03 00 0 S-04 30 0 S) during La Niña and El Niño seasonal conditions, utilizing maximum entropy modelling. Between 2009 and 2018 (except for 2011), 347 whale sharks were geo-referenced in northern Peru with greatest data recordings in the austral summer and spring during La Niña events.3. Depth was the most important predictive variable for spatial distribution of whale sharks, followed by chlorophyll-a. Sharks were predicted in shallower coastal waters in which chlorophyll-a values are higher. 4. Habitat suitability was higher in the northern coastal part of the study area. Spring presents the most suitable environmental conditions for whale sharks, both during La Niña and El Niño conditions. The probability of whale shark presence in the north of Peru increases at higher chlorophyll-a and sea surface temperature values. Therefore, whale sharks appear to aggregate seasonally in northern Peru, potentially exploiting rich foraging grounds. 5. In these areas of high suitability, whale sharks are susceptible to fisheries, bycatch, ship collisions, unmanaged tourism, and pollution; thus, management actions should focus in these areas.6. This study represents a first step to understand the distribution and habitat suitability of whale shark in Peruvian waters. Further studies should identify suitable habitat for whale sharks in offshore areas. Also, these should focus on the connectivity of these aggregations with other localities in the south-eastern Pacific in order to contribute to regional strategies for the conservation of this iconic species in this particular region.

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Seasonal Variation in the Spatial Distribution of Basking Sharks (Cetorhinus maximus) in the Lower Bay of Fundy, Canada

Cited by 23 publications

References 52 publications

Basking Shark (Cetorhinus maximus) Movements in the Eastern North Pacific Determined Using Satellite Telemetry

Basking Shark (Cetorhinus maximus) Movements in the Eastern North Pacific Determined Using Satellite Telemetry

Population density and abundance of basking sharks Cetorhinus maximus in the lower Bay of Fundy, Canada

Distribution of whale shark (Rhincodon typus) off northern Peru based on habitat suitability

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