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Abstract

Whale sharks usually form aggregations by gender and age in many nearshore waters, but they can be as well solitary wanderers. In the Eastern Pacific, there are regular sightings of whale sharks in the Gulf of California and the Galapagos Islands. Tracking studies indicated movement of individuals from Galapagos to the edge of the continental shelf off northern Peru. Although the presence of whale sharks off the Peruvian coast has been reported since 1955, no proper research has been conducted so far. Therefore, there is a critical information gap on their biology, ecology and population status, fundamental information to plan local and international conservation actions. In Peru, no direct fishing occurs, but incidental captures had been reported and many individuals retained. In spite of being a member of international conventions, Peru does not have any local or national protection laws for whale sharks. We started a program; the first one conducted in Peru, to generate knowledge about whale sharks in the region. Our monitoring program includes two components: interviews and boat surveys. Interviews were conducted with fishermen, on-board observers, captains and diving companies in fishing ports located in northern Peru. Interviews included questions about whale shark presence, their behavior, body metrics, dates, times and areas of sightings, as well as an explanation with images for the correct identification of species. Boat surveys for whale shark sightings were planned based on the interview information. During each survey, we recorded whale shark biological data like size, gender, behavior, scars, geo-position, date, time, besides water temperature. Pictures taken were compared with the database from Mexico and submitted to the Wildbook of Whale Sharks. We conducted 185 interviews that provided information on 272 whale shark observations. Interviews suggest that there are two marked seasons for whale shark aggregations in Peru, one in the austral summer and one in the spring, with the highest densities observed in the summer. The whale sharks were seen mostly as solitary animals, and within 50 miles off the coast. The individual size was estimated between 10 and 49 feet. The juveniles showed a mode of 16 feet and most of them were observed while feeding. Adults (>29 feet) were usually seen in the open ocean with a size mode of 32 feet. From October 2014 to March 2015 we conducted 17 boat surveys. Four more were conducted in the summer 2015–2016. Surveys resulted in twelve whale shark encounters, ten of which were observed while feeding, half as solitary animals and the rest in groups. The size of these sharks was estimated between 13 and 17 feet, which classifies them as juvenile sharks. The twelve observations resulted in ten unique individuals without a match in any of the photoID databases. From this, we were only able to determine the gender of eight of them resulting in 100% males. Interviews and boat surveys indicate a prevalent presence of whale sharks in Peru, which is influenced by seasons. Individuals are more common during the austral spring and summer. There seems to be spatial segregation with larger whale sharks, likely adults, seen in the open ocean, while juveniles are seen closer to the coast. The northern coast of Peru seems to be used by juvenile males during the summer for feeding purposes in shallow waters. Our study has photo-identified ten new individual whale sharks for the Eastern Pacific. This represents a unique opportunity to conduct more research in the region to elucidate connectivity with other areas and to involve stakeholders in future whale shark management and conservation.

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/content/papers/10.5339/qproc.2016.iwsc4.32
2016-05-15
2019-11-12
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