Whale shark (Rhincodon typus) seasonal presence, residence time and habitat use at darwin island, galapagos marine reserve

The life history of the whale shark (Rhincodon typus), including its reproductive ecology, still remains largely unknown. Here, we present results from the first whale shark population study around Darwin Island, Galapagos Marine Reserve. Following a diversified approach we characterized seasonal oc...

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Bibliographic Details
Published in:PloS one 2014-12, Vol.9 (12), p.e115946-e115946
Main Authors: Acuña-Marrero, David, Jiménez, Jesús, Smith, Franz, Doherty, Jr, Paul F, Hearn, Alex, Green, Jonathan R, Paredes-Jarrín, Jules, Salinas-de-León, Pelayo
Format: Article
Language:English
Subjects:
Acoustics
Analysis
Animal Migration - physiology
Animals
Aquatic mammals
Arches
Archives & records
Biology and Life Sciences
Biometrics
Cool season
Ecological effects
Ecology
Ecosystem
Ecuador
Feeding behavior
Female
Females
Fish populations
Habitat utilization
Islands
Life history
Male
Marine mammals
Migration
National parks
Nature reserves
Population Dynamics
Population structure
Population studies
Pregnancy
Pregnant women
Reproduction
Rhincodon typus
Rhincodontidae
Sea surface temperature
Seasons
Sharks
Sharks - physiology
Size distribution
Studies
Surface temperature
Temperature
Water temperature
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Summary:The life history of the whale shark (Rhincodon typus), including its reproductive ecology, still remains largely unknown. Here, we present results from the first whale shark population study around Darwin Island, Galapagos Marine Reserve. Following a diversified approach we characterized seasonal occurrence, population structure and size, and described habitat use of whale sharks based on fine scale movements around the island. Whale shark presence at Darwin Island was negatively correlated with Sea Surface Temperature (SST), with highest abundance corresponding to a cool season between July and December over six years of monitoring. From 2011 to 2013 we photo-identified 82 whale sharks ranging from 4 to 13.1 m Total Length (TL). Size distribution was bimodal, with a great majority (91.5%) of adult female individuals averaging 11.35 m±0.12 m (TL±SE), all but one showing signs of a potential pregnancy. Population dynamics models for apparently pregnant sharks estimated the presence of 3.76±0.90 (mean ± SE) sharks in the study area per day with an individual residence time of 2.09±0.51 (mean ± SE) days. Movement patterns analysis of four apparently pregnant individuals tracked with acoustic tags at Darwin Island revealed an intense use of Darwin's Arch, where no feeding or specific behavior has been recorded, together with periodic excursions around the island's vicinity. Sharks showed a preference for intermediate depths (20-30 m) with occasional dives mostly to mid-water, remaining the majority of their time at water temperatures between 24-25°C. All of our results point to Darwin Island as an important stopover in a migration, possibly with reproductive purposes, rather than an aggregation site. Current studies carried out in this area to investigate regional scale movement patterns may provide essential information about possible pupping grounds for this enigmatic species.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0115946