Alex Hearn

Alex Hearn
Universidad San Francisco de Quito (USFQ) · Department of Biology

PhD

About

117
Publications
44,605
Reads
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1,651
Citations
Citations since 2016
61 Research Items
1285 Citations
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
Additional affiliations
August 2015 - February 2017
Universidad San Francisco de Quito (USFQ)
Position
  • Lecturer
October 2008 - March 2013
University of California, Davis
Position
  • Project Scientist

Publications

Publications (117)
Article
Full-text available
Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first globa...
Article
Full-text available
Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first globa...
Article
Full-text available
Variability and climate change due to anthropic influence have brought about alterations to marine ecosystems, that, in turn, have affected the physiology and metabolism of ectotherm species, such as the common hammerhead shark (Sphyrna lewini). However, the impact that climate variability may have on this species’ distribution, particularly in the...
Article
Full-text available
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. Th...
Article
Full-text available
Significance Global vessel traffic is increasing alongside world economic growth. The potential for rising lethal ship strikes on endangered species of marine megafauna, such as the plankton-feeding whale shark, remains poorly understood since areas of highest overlap are seldom determined across an entire species range. Here we show how satellite...
Article
Full-text available
Sphyrna lewini is a viviparous shark that pups in shallow coastal waters. Given dramatic declines in the S. lewini Eastern Pacific population, it is essential to identify nursery grounds that could potentially increase the resilience of adult populations. Here, we provide evidence of a putative nursery ground for S. lewini at an oceanic island in t...
Article
Full-text available
We present a compilation of published telemetric results, complemented by the addition of new results where necessary, to justify the expansion of the marine protected areas in the Eastern Pacific. In addition, we furnish evidence that fishing effort by commercial vessels, carrying position-monitoring, satellite-communicating radio beacons, has dim...
Article
Full-text available
Understanding the link between seamounts and large pelagic species (LPS) may provide important insights for the conservation of these species in open water ecosystems. The seamounts along the Cocos Ridge in the Eastern Tropical Pacific (ETP) ocean are thought to be ecologically important aggregation sites for LPS when moving between Cocos Island (C...
Article
No-take marine protected areas (MPAs) can provide spatial refuge for species throughout all or part of their life-cycles. Cabo Pulmo National Park (CPNP) is a no-take MPA located on the south-east coast of the Baja California Peninsula, Mexico, where there has been an increase in the abundance and diversity of elasmobranch species since its closure...
Article
Full-text available
Shark fishing, driven by the fin trade, is the primary cause of global shark population declines. Here, we present a case study that exemplifies how industrial fisheries are likely depleting shark populations in the Eastern Tropical Pacific Ocean. In August 2017, the vessel Fu Yuan Yu Leng 999, of Chinese flag, was detained while crossing through t...
Article
Full-text available
106,107 ✉ replying to A. V. Harry & J. M. Braccini Nature https://doi.org/10.1038/s41586-021-03463-w (2021) Our global analysis 1 estimated the overlap and fishing exposure risk (FEI) using the space use of satellite-tracked sharks and longline fishing effort monitored by the automatic identification system (AIS). In the accompanying Comment, Harry...
Article
This article is a response to Murua et al.'s Matters Arising article in Nature, "Shark mortality cannot be assessed by fishery overlap alone," which arose from arising from N. Queiroz et al. Nature https://doi.org/10.1038/s41586-019-1444-4 (2019).
Article
Cabo Pulmo National Park was established in 1995 and has since seen a large increase in fish biomass. An unoccupied aerial vehicle (UAV) was used to survey shallow coastal habitat in which lemon sharks (Negaprion brevirostris), bull sharks (Carcharhinus leucas) and Pacific nurse sharks (Ginglymostoma unami) were recorded. Sharks were more common in...
Chapter
In this paper, we propose a new automated method based on deep convolutional neural networks to detect and track critically endangered hammerhead sharks in video sequences. The proposed method improved the standard YOLOv3 deep architecture by adding 18 more layers (16 convolutional and 2 Yolo layers), which increased the model performance in detect...
Preprint
Full-text available
Understanding the link between seamounts and large pelagic species (LPS) is critical for guiding management and conservation efforts in open water ecosystems. The seamounts along the Cocos Ridge in the Eastern Tropical Pacific (ETP) are thought to play a critical role for LPS moving between Cocos Island (Costa Rica) and Galapagos Islands (Ecuador)....
Preprint
Full-text available
Spatial management through the implementation of marine protected areas is one strategy to limit the extraction of sensitive marine species. Understanding the area used by marine life is thus a key step towards the evaluation of the management framework and efficacy of a protected area. To provide information of the protective coverage of the Galap...
Article
Effective ocean management and the conservation of highly migratory species depend on resolving the overlap between animal movements and distributions, and fishing effort. However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fle...
Article
Full-text available
There is a great need to understand how resource interactions alter the functioning of ecosystems, where the selective elimination of pelagic fishes can lead to changes in food web structure. This work analyzes the trophic niches of three species of commercial importance in the Galapagos Marine Reserve, yellowfin tuna, Thunnus albacares (TA), skipj...
Chapter
Marine animal tracking has become one of the major tools used to understand the behavior and ecology of a multitude of species in the ocean, thus there is an increasing body of knowledge about this subject worldwide, particularly for sharks. Nevertheless, little was known of the movement patterns of shark in the Mexican Pacific (MXP) and Gulf of Ca...
Article
Full-text available
A series of habitat suitability models were created based upon 2-dimensional tracking of Green Sturgeon and hydraulic simulations. This is an effort to better understand the relationship between the population decline, habitat suitability, and knowledge of the remaining post-dam era habitat available to Green Sturgeon. Records of the movements of G...
Article
Full-text available
ABSTRACT. Association of sharks with Las Gemelas Seamount and first evidence of connectivity with Cocos Island, Pacific of Costa Rica. Introduction: Seamounts and oceanic islands are known as hotspots of pelagic biodiversity, which highly migratory species use as natural biological corridors. Although marine protected areas have been established in...
Article
Full-text available
Sporadic aggregations of decapod crustaceans can occur for various reasons and in some cases their drivers are poorly understood. Objective: Here, we present our observations of an apparently rare massive aggregation of pelagic swimming crabs, Euphylax dovi. Methods: During a research cruise at Cocos Island (5°32’34” N, 87°05’06” W), we encountered...
Preprint
Full-text available
Long-distance movements of sharks within and between islands pose substantial challenges for resource managers working with highly migratory species. When no-take zones do not cover the critical areas that sharks use as part of their lifecycle, exposure to fishing activities can be significant. Shark movements between the Marine Protected Areas (MP...
Article
This is the first description of the residency and diel movements of Sphyrna lewini at the Revillagigedo National Park, Mexico. A total of 11 adults scalloped hammerheads ranging from 200‐300 cm TL were monitored using acoustic telemetry during 2013‐2015 at four sites at San Benedicto Island. Diel and residency patterns were described based upon 58...
Article
Full-text available
Effective ocean management and conservation of highly migratory species depends on resolving overlap between animal movements and distributions and fishing effort. Yet, this information is lacking at a global scale. Here we show, using a big-data approach combining satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of...
Article
Full-text available
Many species of sharks form aggregations around oceanic islands, yet their levels of residency and their site specificity around these islands may vary. In some cases, the waters around oceanic islands have been designated as marine protected areas, yet the conservation value for threatened shark species will depend greatly on how much time they sp...
Article
Full-text available
We used acoustic telemetry to determine the spatial and temporal overlap between adult Green Sturgeon movements and areas affected by dredging within the San Francisco Estuary. Autonomous receivers were deployed for 3 years within the lower Estuary at priority locations to assess the potential for adverse effects on Green Sturgeon. Green Sturgeon w...
Article
Full-text available
Abstract Whale sharks (Rinchodon typus) are found in shallow coastal and deep waters of tropical and warm temperate seas. Population genetic studies indicate high connectivity among populations, and an Indo-Pacific meta-population has been suggested with potential migrations among some ocean basins. Here, we present the satellite track of a trans-P...
Article
Full-text available
The whale shark is an ideal flagship species for citizen science projects because of its charismatic nature, its size, and the associated ecotourism ventures focusing on the species at numerous coastal aggregation sites. An online database of whale shark encounters, identifying individuals on the basis of their unique skin patterning, captured almo...
Article
The conservation benefits of the Galapagos Marine Reserve (GMR), created in March 1998, have been consistently proved for endemic species and populations with limited movements. Yet, to date, no study has explored its effects on highly-migratory pelagic species, such as tuna. To this end, the impact of the GMR on the behavior and productivity of tu...
Article
Full-text available
In this commentary, we describe how geomagnetic intensity can be used to estimate latitude, discuss its strengths and weaknesses, and argue for its potential use along with irradiance measurements for estimating the latitude of a migratory fish carrying an archival tag. We conclude this commentary by suggesting that researchers and tag manu-facture...
Article
Full-text available
Satellite tracking of 27 whale sharks in the eastern tropical Pacific, examined in relation to environmental data, indicates preferential occupancy of thermo-biological frontal systems. In these systems, thermal gradients are caused by wind-forced circulation and mixing, and biological gradients are caused by associated nutrient enrichment and enha...
Article
Full-text available
The potential effectiveness of marine protected areas (MPAs) as a conservation tool for large sharks has been questioned due to the limited spatial extent of most MPAs in contrast to the complex life history and high mobility of many sharks. Here we evaluated the movement dynamics of a highly migratory apex predatory shark (tiger shark Galeocerdo c...
Data
Map showing the study sites of (a) Bachas-Salinas, and (b) Isabela-South and Cerro-Ballena. White sea turtle icons indicate the most important nesting beaches for green sea turtles in the area, according to Zárate and Dutton [40] and Zárate et al. [34]. Black crosses show the locations of SBRUV deployments, and black rectangles show the locations o...
Data
Frequency distribution of the time interval (in days) between subsequent detections of satellite locations obtained for tagged sharks. (PDF)
Data
Chronology of acoustic detections for each of the acoustic-tagged sharks (TS1-TS20) by site (colour coded). (PDF)
Data
Total number of sharks recorded in the study. Sharks observed in each season, of each size class, and of each sex, at each location (the numbers observed by stereo-BRUVs and by capture are given in parentheses, respectively). Sampling effort was not quantified for captures. For stereo-BRUVs, effort varied among locations but was equal between seaso...
Data
Acoustic detections of the sharks tagged with acoustic devices in the four VR2W receivers deployed at the study locations. (CSV)
Data
Satellite positions of the sharks tagged with satellite devices. (CSV)
Data
Stereo-BRUVs data for the study locations. (CSV)
Article
Full-text available
Vast sections of the Sacramento River have been listed as critical habitat by the National Marine Fisheries Service for green sturgeon spawning (Acipenser medirostris), yet spawning is known to occur at only a few specific locations. This study reveals the range of physical habitat variables selected by adult green sturgeon during their spawning pe...
Article
Full-text available
Ocean sunfishes, with their peculiar morphology, large size, and surface habits, are valuable assets in ecotourism destinations worldwide. This study investigates site fidelity and long-range movements of short ocean sunfish, Mola ramsayi (Giglioli 1883), at Punta Vicente Roca (PVR) off Isabela Island in the Galapagos Islands. Five individuals were...
Chapter
Full-text available
The Eastern Tropical Pacific is rich with ocean predators such as large schools of scalloped hammerhead sharks. This ocean region, which stretches down the Pacific Coast from the Gulf of California to Ecuador, is known as a treasure trove of wonders by divers, wildlife enthusiasts, and eco-adventurers. It is home to a host of endemic, native and mi...
Article
Full-text available
Most previous studies on whale shark movements have been on immature sharks. Here, we present tracking data for large females that we tagged at the Galapagos Islands, where they occur seasonally. We conducted fieldwork at Darwin Island (1.67, 92.0°W) from July to October in 2011 and in 2012. We often saw individual sharks several times on a particu...
Conference Paper
Full-text available
Background Gathering data on the life of enigmatic animals remains a challenge, despite its important role in biodiversity conservation and management. For many species, biogeographic investigations are largely the result of information that is generated from multiple sources, often over long time-scales, because measuring biogeographic and biologi...
Conference Paper
Full-text available
Background The Galapagos Whale Shark Project is a multi-institutional effort initiated in 2011 with the aim to characterize the presence, population structure and movement patterns of whale sharks within and around the Galapagos Marine Reserve. This specific study aimed to understand their occurrence, residency and habitat use around Darwin Island,...
Conference Paper
Background The Galapagos Whale Shark Project is a multi-institutional effort initiated in 2011 with the aim to characterize the presence, population structure and movement patterns of whale sharks within and around the Galapagos Marine Reserve. This specific study aimed to understand their occurrence, residency and habitat use around Darwin Island,...