The Largetooth Sawfish, Pristis pristis, was for a long time considered extirpated from Peru. However, here we report the capture of 2 individuals from the north coast of Peru, indicating that this species is still extant in Peruvian waters. Both individuals were adult-sized and their encounters occurred during the austral summer, which could indicate a seasonal presence in those waters. Gillnets are still a major threat for the species as both specimens were incidentally captured with this gear. Our finding highlights the need for continuous research, awareness, and legal protection of this species.

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.

Background 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. Approach 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. Results 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. Conclusions 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.

The world’s largest extant fish, the whale shark Rhincodon typus, is one of the most-studied species of sharks globally. The discovery of predictable aggregation sites where these animals gather seasonally or are sighted year-round – most of which are coastal and juvenile-dominated – has allowed for a rapid expansion of research on this species. The most common method for studying whale sharks at these sites is photographic identification (photo-ID). This technique allows for long-term individual-based data to be collected which can, in turn, be used to evaluate population structure, build population models, identify long-distance movements, and assess philopatry and other population dynamics. Lagged identification rate (LIR) models have fewer underlying assumptions than more traditional capture mark recapture approaches, making them more broadly applicable to marine taxa, especially far-ranging megafauna species like whale sharks. However, the increased flexibility comes at a cost. Parameter estimations based on LIR can be difficult to interpret and may not be comparable between areas with different sampling regimes. Using a unique data-set from the Philippines with ~8 years of nearly continuous survey effort, we were able to derive a metric for converting LIR residency estimates into more intuitive days-per-year units. We applied this metric to 25 different sites allowing for the first quantitatively-meaningful comparison of sightings-derived residence among the world’s whale shark aggregations. We validated these results against the only three published acoustic residence metrics (falling within the ranges established by these earlier works in all cases). The results were then used to understand residency behaviours exhibited by the sharks at each site. The adjusted residency metric is an improvement to LIR-based population modelling, already one of the most widely used tools for describing whale shark aggregations. The standardised methods presented here can serve as a valuable tool for assessing residency patterns of whale sharks, which is crucial for tailored conservation action, and can cautiously be tested in other taxa.