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Stephen Kajiura, Ph.D. - Florida Atlantic University. Boca Raton, FL, US

Stephen Kajiura, Ph.D. Stephen Kajiura, Ph.D.

Professor | Florida Atlantic University

Boca Raton, FL, UNITED STATES

Stephen Kajiura researches the integration of sensory biology and behavior with functional morphology.

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Biography

Stephen Kajiura's lab is primarily interested in the integration of sensory biology and behavior with functional morphology. He employs behavioral assays, field observations, and comparative morphology to test hypotheses about the evolution of biological structures. He has concentrated primarily on the elasmobranch fishes, which provide an opportunity to investigate various sensory modalities among closely related but morphologically dissimilar species. Also, he maintains an active research program studying the annual blacktip shark migration. This work incorporates aerial surveys, transmitter instrumentation, and field observations.

Areas of Expertise (4)

Shark Behavior

Sensory Biology

Elasmobranchs

Comparative Morphology

Education (1)

University of Hawaii: Ph.D. 2011

Selected Media Appearances (10)

Manta Ray Nursery Discovered Off Palm Beach County Coast

CBS Miami  

2020-10-03

“Think of a shark under a steam roller and flattened out and then you have a ray,” said Stephen Kajiura, director of FAU’s Elasmobranch Laboratory.

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Oil Spills May Ruin Electric Sensing Abilities of Stingrays

Inside Science  

2020-09-30

"It’s kind of out of sight, out of mind," said Stephen Kajiura, a biologist at Florida Atlantic University in Boca Raton and one of the two co-authors of a new study published recently in the journal Zoology that looks at how oil affects the ability of stingrays to hunt.

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What are stingrays?

Live Science  

2020-09-01

Most stingrays live in coastal saltwater environments rather than the open ocean, said Stephen Kajiura, professor of biology at Florida Atlantic University. However, there is one species of stingray that lives in open ocean waters, called the pelagic stingray (Pteroplatytrygon violacea), he said.

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Overfishing erased sharks from many of the world's reefs, researchers say

UPI  

2020-08-27

"A lot of these sharks are highly migratory species, and the problem is we might enact protections in the U.S. but that only works while they're here," Kajiura said. "So it's important to have these protections become global as possible."

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Shark vs. Surfer Clip: How You Can Be Mistaken For Food [EXCLUSIVE]

Screen Rant  

2020-07-31

Screen Rant's exclusive Shark vs. Surfer clip brings viewers to Marjorie's Sunset Surf where Professor Stephen Kajiura explains just how sharp shark jaws really are and how a sunset surf provides the perfect setting for a shark to confuse a human for something else on the surface.

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See how blacktip sharks evade hungry hammerheads in these tense drone videos

CNET  

2020-05-14

The videos were captured close to the shore of Palm Beach County and they're as heart-pounding as any scene from an action movie. "The chasing events showed the hammerhead struggling as it experienced difficulty following the blacktips into the shallow waters," said FAU biologist Stephen Kajiura, co-author of the study.

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Blacktip sharks begin annual migration to Florida's south Atlantic coast

Tampa Bay Times  online

2019-02-28

Dr. Stephen Kajiura, a researcher at Florida Atlantic University, has been tracking the migration patterns of these apex predators by air and sea. Now Kajiura's latest tool is providing thorough details about their every move.

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Thousands of sharks make annual migration off Florida coast

Orlando Sentinel  online

2019-02-27

"We welcome blacktip sharks back to South Florida because they are critically important to our ecosystem," said Stephen Kajiura, a professor of biological sciences at FAU in a report on the FAU website. "They sweep through the waters and ‘spring clean’ as they weed out weak and sick fish, helping to preserve coral reefs and sea grasses."

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FAU shark researcher weighs in on shark bite data

WFLX  

2019-01-30

Dr. Stephen Kajiura, a shark researcher at Florida Atlantic University, weighed in on the data. "People might be better educated, people might pay attention," said Dr. Kajiura...

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Number of shark bites dropped last year, both in Florida and worldwide

Tampa Bay Times  

2019-01-28

The blacktips migrate back and forth along the Atlantic coast, from Virginia and the Carolinas to Florida each year. Stephen M. Kajiura, a scientist at Florida Atlantic University, has spent the past decade keeping tabs on that migration when it reaches Florida...

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Selected Articles (5)

Effect of Deepwater Horizon Crude Oil Water Accommodated Fraction on Olfactory Function in the Atlantic Stingray, Hypanus sabinus Scientific ReportsF

EJ Cave, SM Kajiura

2018 The Deepwater Horizon oil spill was the largest accidental marine oil spill in history, releasing nearly 5 million barrels of crude oil. Crude oil causes both lethal and sublethal effects on marine organisms, and sensory systems have the potential to be strongly affected. Marine fishes rely upon the effective functioning of their sensory systems for detection of prey, mates, and predators. However, despite the obvious importance of sensory systems, the impact of crude oil exposure upon sensory function remains largely unexplored. Here we show that olfactory organ responses to amino acids are significantly depressed in oil exposed stingrays. We found that the response magnitude of the electro-olfactogram (EOG) to 1 mM amino acids decreased by an average of 45.8% after 48 h of exposure to an oil concentration replicating that measured in coastal areas. Additionally, in oil exposed individuals, the EOG response onset was significantly slower, and the clearing time was protracted. This study is the first to employ an electrophysiological assay to demonstrate crude oil impairment of the olfactory system in a marine fish. We show that stingrays inhabiting an area impacted by an oil spill experience reduced olfactory function, which would detrimentally impact fitness, could lead to premature death, and could cause additional cascading effects through lower trophic levels.

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Magnetic field discrimination, learning, and memory in the yellow stingray (Urobatis jamaicensis) Animal CognitionF

KC Newton, SM Kajiura

2017 Elasmobranch fishes (sharks, skates, and rays) have been hypothesized to use the geomagnetic field as a cue for orienting and navigating across a wide range of spatial scales. Magnetoreception has been demonstrated in many invertebrate and vertebrate taxa, including elasmobranchs, but this sensory modality and the cognitive abilities of cartilaginous fishes are poorly studied. Wild caught yellow stingrays, Urobatis jamaicensis (N = 8), underwent conditioning to associate a magnetic stimulus with a food reward in order to elicit foraging behaviors. Behavioral conditioning consisted of burying magnets and non-magnetic controls at random locations within a test arena and feeding stingrays as they passed over the hidden magnets. The location of the magnets and controls was changed for each trial, and all confounding sensory cues were eliminated. The stingrays learned to discriminate the magnetic stimuli within a mean of 12.6 ± 0.7 SE training sessions of four trials per session. Memory probes were conducted at intervals between 90 and 180 days post-learning criterion, and six of eight stingrays completed the probes with a ≥75% success rate and minimum latency to complete the task. These results show the fastest rate of learning and longest memory window for any batoid (skate or ray) to date. This study demonstrates that yellow stingrays, and possibly other elasmobranchs, can use a magnetic stimulus as a geographic marker for the location of resources and is an important step toward understanding whether these fishes use geomagnetic cues during spatial navigation tasks in the natural environment.

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Etmopterus lailae sp. nov., a new lanternshark (Squaliformes: Etmopteridae) from the Northwestern Hawaiian Islands ZootaxaF

DA Ebert, YP Papastamatiou, SM Kajiura, BM Wetherbee

2017 A new species of lanternshark, Etmopterus lailae (Squaliformes: Etmopteridae), is described from the Northwestern Hawaiian Islands, in the central North Pacific Ocean. The new species resembles other members of the “Etmopterus lucifer” clade in having linear rows of dermal denticles, and most closely resembles E. lucifer from Japan. The new species occurs along insular slopes around seamounts at depths between 314–384 m. It can be distinguished from other members of the E. lucifer clade by a combination of characteristics, including a longer anterior flank marking branch, arrangement of dermal denticles on the ventral snout surface and body, flank and caudal markings, and meristic counts including number of spiral valve turns, and precaudal vertebrate. A key to species of the Etmopterus lucifer-clade is included.

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Pulse trawling: Evaluating its impact on prey detection by small-spotted catshark (Scyliorhinus canicula) Journal of Experimental Marine Biology and EcologyF

Stephen Kajiura et al

2017 Pulse fishing may pose a promising alternative for diminishing the ecosystem effects of beam trawling. However, concerns about the impact on both target and non-target species still remain, amongst others the possible damage to the electro-receptor organs, the Ampullae of Lorenzini, of elasmobranchs. The current study aimed to examine the role of pulsed direct current (PDC) used in pulse trawls on the electro-detection ability of the small-spotted catshark, Scyliorhinus canicula. The electroresponse of the sharks to an artificially created prey-simulating electrical field was tested before and after exposure to the pulsed electrical field used to catch flatfish and shrimp. No statistically significant differences were noted between control and exposed animals, both in terms of the number of sharks exhibiting an electroresponse prior to and following exposure as well as regarding the timing between onset of searching …

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Quantification of Massive Seasonal Aggregations of Blacktip Sharks (Carcharhinus limbatus) in Southeast Florida PloS OneF

Stephen M Kajiura, Shari L Tellman

2016 Southeast Florida witnesses an enormous seasonal influx of upper trophic level marine predators each year as massive aggregations of migrating blacktip sharks (Carcharhinus limbatus) overwinter in nearshore waters. The narrow shelf and close proximity of the Gulf Stream current to the Palm Beach County shoreline drive tens of thousands of sharks to the shallow, coastal environment. This natural bottleneck provides a unique opportunity to estimate relative abundance. Over a four year period from 2011–2014, an aerial survey was flown approximately biweekly along the length of Palm Beach County. A high definition video camera and digital still camera mounted out of the airplane window provided a continuous record of the belt transect which extended 200 m seaward from the shoreline between Boca Raton Inlet and Jupiter Inlet. The number of sharks within the survey transect was directly counted from the video. Shark abundance peaked in the winter (January-March) with a maximum in 2011 of 12,128 individuals counted within the 75.6 km-2 belt transect. This resulted in a maximum density of 803.2 sharks km-2. By the late spring (April-May), shark abundance had sharply declined to 1.1% of its peak, where it remained until spiking again in January of the following year. Shark abundance was inversely correlated with water temperature and large numbers of sharks were found only when water temperatures were less than 25°C. Shark abundance was also correlated with day of the year but not with barometric pressure.

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