Shark Repellent Research Articles

The great white bite: A critique of the Western Australian government’s shark hazard mitigation drum line program

The fatal shark bite of a scuba diver off the coast of Esperance in Western Australia in January 2020, followed in recent months by a further four fatalities in New South Wales and Queensland, has once again sparked debate about government policies to protect humans from potentially dangerous marine life. This debate is not new; during 2010–13 Western Australia experienced an unusually high level of human fatalities from shark bites. These events precipitated the introduction of the Western Australian Shark Hazard Mitigation Drum Line Program, a controversial and costly pre-emptive state government initiative that cost approximately $13.6 million for shark repellent responses, and the implementation of a Shark Response Unit. This research utilises official documents obtained under the Freedom of Information Act 1989 (Cth), together with interviews with relevant stakeholders, media reports, and public submissions to critically examine the political antecedents of a costly and flawed shark hazard mitigation program. It also provides lessons for how governments construct problems and manage marine environments and protected species. It concludes, utilising the theory of claims-making, that shark bite increases in Western Australia was a media constructed social problem, used to convince the government that a catch-and-kill policy of an internationally protected species was necessary to avert a perceived economic downturn in tourism revenue and to appease an invented public outcry.

Decay as a defense against sharks and venom evolution in Australian snakes

Scaring sharks with chemistry By day, Eric Stroud was a research chemist for Pfizer and, later, a pharmaceutical industry consultant. But at night, he would hunker down in his New Jersey basement around children’s plastic swimming pools filled with small sharks, pursuing his real passion: chemical shark repellents. Pharma “paid the bills while I indulged in this hobby, which became a small, part-time business. Then it became a full-time business,” remembers Stroud, cofounder of shark repellent developer SharkDefense. His obsession started in 2001 on a cruise, when Stroud’s wife innocently asked him why there wasn’t a repellent for sharks. That led him down a rabbit hole of research into the long, unsuccessful history of chemical shark repellents. Stroud was especially interested in the idea that there is a chemical signal from dead sharks that repels live ones. In reports that date as far back as the 1700s, fishermen have hung

Sharks senses and shark repellents.

Despite over 70 years of research on shark repellents, few practical and reliable solutions to prevent shark attacks on humans or reduce shark bycatch and depredation in commercial fisheries have been developed. In large part, this deficiency stems from a lack of fundamental knowledge of the sensory cues that drive predatory behavior in sharks. However, the widespread use of shark repellents is also hampered by the physical constraints and technical or logistical difficulties of deploying substances or devices in an open-water marine environment to prevent an unpredictable interaction with a complex animal. Here, we summarize the key attributes of the various sensory systems of sharks and highlight residual knowledge gaps that are relevant to the development of effective shark repellents. We also review the most recent advances in shark repellent technology within the broader historical context of research on shark repellents and shark sensory systems. We conclude with suggestions for future research that may enhance the efficacy of shark repellent devices, in particular, the continued need for basic research on shark sensory biology and the use of a multi-sensory approach when developing or deploying shark repellent technology.

Chemical shark repellent: Myth or fact? The effect of a shark necromone on shark feeding behavior

Since 1942, the search for an effective chemical shark repellent has been ongoing research concern in the United States. A long-standing anecdote that sharks avoid areas containing decomposing shark tissue has initiated new interest in identifying trace chemical alarm signals produced during decomposition (necromones). A commercially-sourced shark necromone produced from putrefied shark tissue was evaluated over a five-year period in South Bimini, Bahamas. Competitively-feeding populations of Caribbean reef sharks (Carcharhinus perezi) and blacknose sharks (Carcharhinus acronotus) were exposed to necromones using pressurized aerosol canisters at the surface. Shark density estimations were made at the initial, 1 min and 5 min intervals after preliminary exposure along with continuous exposure of feeding stimulus. In both species, an unambiguous halt in feeding behavior was observed within 1 min after exposure of the necromone. For aerosol delivery, a 150 mL dose of the necromone from a single aerosol canister is able to halt all feeding activity in a combined population of C. perezi and C. acronotus. Shark necromones induced a spectacular alarm response in interacting sharks resulting in a temporary evacuation of an area containing feeding stimuli. Additionally, sharks were not deterred by alternative treatment presentations of 10% weight percent (w/w) aqueous urea, 10% w/w oleic acid in ethanol, or water buffered to pH 8.5. Habituation to the necromone was not observed for repeated tests at the same location. In all experiments, the presence of a shark necromone did not produce a similar aversion response for teleosts as observed in C. perezi or C. acronotus; however, anecdotal observations demonstrate that teleosts increased their feeding rate in the presence of the necromone. Experimental controls using denatured ethanol or water confirmed that feeding sharks were not deterred by bubbles, sound, or the solvents used to extract the necromones. Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry indicates that the necromone is a complex solution rich in amino acids and putrefaction products. Experiments demonstrate that the key chemical component responsible for the alarm response is within these amino acids and/or putrefaction products, but further experimentation is needed to more accurately identify the active ingredient. Shark necromones hold particular promise for use in shark bycatch reduction and conservation. The existence of a putative chemical shark repellent has been confirmed.

The emerging field of electrosensory and semiochemical shark repellents: Mechanisms of detection, overview of past studies, and future directions

Since the sinking of the USS Indianapolis (CA-35) and associated shark attacks in 1945, the quest to find an effective shark repellent has been endless. Early efforts were focused on finding a shark repellent which would minimize the probability of a shark attack. However, studies illustrate that shark populations are drastically declining which has led to calls for effective management policies and practices to reduce both directed catch and bycatch of various shark species. With increased need for shark conservation, the focus has shifted to protecting sharks from harmful anthropogenic pressures, such as fishing gear and beach nets. Current shark repellent technologies which aim to minimize elasmobranch mortality in fishing gears include: permanent magnets, electropositive metal (EPM) alloys, and semiochemicals. This paper will review present electrosensory and semiochemical shark repellents, the mechanisms of elasmobranch (e.g. shark, skate and ray) detection and repellency, species-specificity in elasmobranch response to the stimuli, and environmental and biological conditions which may influence repellent success. Future research to enhance our knowledge on electrosensory repellents and to improve the success of repellent implementation and application will be discussed.

Synthesis of the Aglycone of the Shark Repellent Pavoninin-4 Using Remote Functionalization

[reaction: see text] The aglycone of shark repellent pavoninin-4, (25R)-5alpha-cholestan-3alpha,15alpha,26-triol 26-acetate 1a, was synthesized from (25R)-cholest-5-en-3beta,26-diol 4 (26-hydroxycholesterol) in eight steps in 18% overall yield. Breslow's remote functionalization strategy was used as a key step to introduce the C-15alpha alcohol on a steroid D ring. An efficient synthesis of the 26-hydroxycholesterol from the 16beta hydroxyl steroid, (25R)-cholest-5-ene-3beta,16beta,26-triol (3a), is also reported.

Synthesis of the Shark Repellent Pavoninin-4

[reaction: see text] The first synthesis of the shark repellent pavoninin-4, 3, was achieved in 12 steps with 21% overall yield from diosgenin, 8. Key reactions involve an efficient synthesis of the C-15alpha hydroxyl steroid from a C-16beta hydroxyl steroid by an unexpected 1,2-transposition strategy, a stereospecific glycosylation of a hindered C-15alpha alcohol using glycosyl fluoride as a glycosyl donor and a highly chemoselective acetylation of the C-26 primary alcohol by catalytic transesterification.

Managers, Workers, and Corporate Control

ABSTRACTIf management has high private benefits and a small equity stake, managers and workers are natural allies against takeover threats. Two forces are at play. First, managers can transform employees into a “shark repellent” through long‐term labor contracts and thereby reduce the firm's attractiveness to raiders. Second, employees can act as “white squires” for the incumbent managers. To protect their high wages, they resist hostile takeovers by refusing to sell their shares to the raider or by lobbying against the takeover. The model predicts that wages are inversely correlated with the managerial equity stake, and decline after takeovers.

Studies toward the synthesis of the shark repellent pavoninin-5.

Sharks are the most dangerous predators of people in the sea, resulting in people being mauled and killed each year. A shark repellent could help to diminish this danger. The aglycone of the shark repellent pavoninin-5, (25R)-cholest-5-en-3beta,15alpha,26-triol (5a), was synthesized from diosgenin (9). Removing mercury from the Clemmensen reduction of 9 gave a higher yield of (25R)-cholest-5-en-3beta,16beta,26-triol, 10a, and was also more environmentally friendly. Attempted methods for the transposition of the C-16beta hydroxyl to the 15alpha position are described. A successful method for this transposition via the 15alpha-hydroxy-16-ketone, 8a, using the Barton deoxygenation reaction on the 16-alcohol 14b, is reported.

Boards of Directors and Shark Repellents:Assessing the Value of an Agency Theory Perspective

Because shark repellents decrease the vulnerability of firms (and their incumbent managers) to the market for corporate control, the decision to adopt these devices represents an excellent test of agency theory. In this empirical study, we examined the relationships between the adoption of shark repellents and several mechanisms that, according to agency theory, should align the interests of corporate board members and shareholders and/or make directors more effective monitors of management behaviour. Of the variables included, only board stock ownership (especially by employee directors) was linked to a reduced propensity to adopt shark repellents in the predicted manner. Two variables not immediately as‐ sociated with agency theory — the proportion of inside directors appointed by the incumbent chief executive officer (CEO) and a lower ratio of CEO compensation to the compensation of other top executives — were linked to higher rates of shark repellent adoption. Given that agency theory explains relatively little of the variance in shark repellent adoption, we advocate serious consideration of other theoretical formulations for corporate governance, including two approaches — stewardship theory and agent morality — that take the moral (‘other regarding’) obligations of directors seriously.

Synthesis of pavoninin-1, a shark repellent substance, and its structural analogues toward mechanistic studies on their membrane perturbation

Pavoninin-1 ( 1), which was isolated from a defense secretion of the sole Pardachirus spp. as an ichthyotoxic and a shark repellent principle, and its structural analogue 2 were synthesized, where glycosylation using an 2-azidoglycosyl sulfoxide ( 10) afforded the corresponding β-glycoside exclusively in high yield. Introduction of the α,β-unsaturated ketone system in the ring A of 1 was achieved by phenylselenenylation of dihydropavoninin-1 ( 3) and subsequent oxidative elimination without protection of the hydroxyl groups in the sugar portion. The mode of action of these glycosides was evaluated for their perturbation on phosphatidylcholine liposomal membrane, using the fluorescent dye leakage method. The results revealed that membrane affinity does not parallel membrane perturbation but rather compensates it, and the spatial arrangement of hydrophobic and hydrophilic regions within a molecule is likely to reflect on the difference in potency of action among them.

Solution conformations of peptides representing the sequence of the toxin pardaxin and analogues in trifluoroethanol-water mixtures: Analysis of CD spectra

The cytolytic activities and conformational properties of pardaxin (GFFALIPKIISSPLFKTLLSAVGSALSSSGEQE), a 33-residue linear peptide that exhibits unusual shark repellent and cytolytic activities, and its analogues have been examined in aqueous environment and trifluoroethanol (TFE) using CD spectroscopy. A peptide corresponding to the 1-26 segment and an analogue where P7 has been changed to A show greater hemolytic activity than pardaxin. While the peptide corresponding to the N-terminal 18-residue segment does not exhibit hemolytic activity, its analogue where P7 is replaced by A is hemolytic. The secondary structural propensities of the peptides were inferred by deconvolution of the experimental spectra into pure components. Pardaxin, its variant where proline at position 7 was replaced by alanine, and shorter peptides corresponding to N-terminal segments exist in multiple conformations in aqueous medium that are comprised of beta-turn, beta-sheet, and distorted helical structures. With increasing proportions of TFE, while helical conformation predominates in all the peptides, both distorted and the regular alpha-helices appear to be populated. Analysis of CD spectra by deconvolution methods appears to be a powerful tool for delineating multiple conformations in peptides, especially membrane-active peptides that encounter media of different polarity ranging from aqueous environment to one of low dielectric constant in the hydrophobic interior of membranes. Our study provides further insights into the structural requirements for the biological activity of pardaxin and related peptides.

Solution structure of pardaxin P-2

Pardaxin is a mucosal secretion of the Pacific sole Pardachirus pavoninus that exhibits unusual shark repellent and surfactant properties [Thompson, S. A., Tachibana, K., Nakanishi, K., & Kubota, I. (1986) Science 233, 341-343]. This 33 amino acid polypeptide folds into ordered structures in trifluoroethanol-water solution and in micelles but adopts a random-coiled structure in water solution. The complete proton NMR spectrum of pardaxin P-2 has been assigned in CF3CD2OD/H2O (1:1) solution, and the three-dimensional structure has been elucidated with distance restrained molecular dynamics calculations. It is demonstrated that peptide segments within the 7-11 and 14-26 residue stretches are helical while residues at the C- and N-terminus exist predominantly in extended conformations in solution. The dipeptide 12-13 segment connecting the two helices exists as a bend or a hinge allowing the two helices to be oriented in a L-shaped configuration. These studies establish that pardaxin P-2 adopts a novel amphiphilic helix (7-11)-bend (12-13)-helix (14-26) motif with Pro-13 forming the focal point of the turn or bend between the two helices.

The effectiveness of sodium lauryl sulphate as a shark repellent in a laboratory test situation

Swim‐through chemical repellency tests, using sodium lauryl sulphate (SLS), cupric acetate, and rotenone, were conducted in a specially‐designed roundabout tank on horn sharks, Heterodontus francisci, swell sharks, Cephaloscylliun ventriosum, and leopard sharks, Triakis semifasciata. Effective concentration thresholds (EC50s) were calculated for two levels of response: (1) minimum noticeable and (2) strong. The SLS EC50s were: horn shark 43.6 and 174.5 ppm; swell shark 95.1 and 160.0 ppm; and leopard shark inconclusive and 113.1 ppm. No response was discernible from cupric acetate. Rotenone evoked a weak response with an EC50 of 5.7 ppm, but no strong response.The ratio of the minimum noticeable EC50: 24‐hour lethal concentration (LC50) indicated the relative repellency (compared to toxicity) of the chemicals. The ratio for SLS was 19:1 and for rotenone 57:1. SLS did not provoke a repellency response at a low enough concentration to function effectively as a classical, surrounding‐cloud type, repellent. The range of potency of SLS, however, does allow it to be used as a directional repellent.

Channel formation properties of synthetic pardaxin and analogues

Six analogues of teh 33-residue shark repellent neurotoxin pardaxin were synthesized by the solid phase method: [Ala13]pardaxin, [Gly14,Gly15]pardaxin, des[1----9]pardaxin, [N1-succinamido]pardaxin, C33-dihydroxyethylamido]pardaxin, and C33-[diaminoethylamido]pardaxin. The spectroscopic and functional characterizations of the analogues are described. The peptides were characterized spectroscopically by circular dichroism (CD) before and after binding to soybean vesicles. They were characterized functionally by measuring their potential to evoke the dissipation of diffusion potential and calcein release from sonicated unilamellar soybean liposomes, by determining their ability to create single channels in planar bilayers, and by measuring their cytolytic activity on human erythrocytes. The behavior of the analogues modified at the C terminus is similar to that of pardaxin. [N'-succinamido]Pardaxin, however, reveals an increase in alpha-helicity both alone and in the presence of liposomes. It has the same potency as pardaxin to dissipate diffusion potential, to evoke calcein release and to produce single channels in lipid bilayers, but at a slower rate than that of pardaxin. It has more than 70-fold less cytolytic activity than pardaxin. [Ala13] Pardaxin has twice the alpha-helical content than pardaxin, both alone and in the presence of vesicles, yet it has less effect on the diffusion potential and calcein release, and it does not have cytolytic activity on human erythrocytes. Both [Gly14,Gly15]pardaxin and des[1----9]pardaxin are much less potent than pardaxin in all effects. However des[1----9]pardaxin exhibits a slight change in alpha-helicity upon binding to vesicles, whereas [Gly14,Gly15]pardaxin does not. The results support a model in which pardaxin is composed of two putative alpha-helices separated by proline. The N-terminal alpha-helix is important for the insertion of the peptide to the lipid bilayer, and the C-terminal amphiphilic alpha-helix is the ion channel lining segment of pardaxin.

Shark Repellent: Not Yet, Maybe Never

An effective life jacket shark repellent packet remains an officially stated, unsatisfied requirement of the sea and air military services. Shark Chaser of World War II, a useful psychological crutch for the times, has been deemed inefficacious, and its procurement has been cancelled. Systems analyses clearly indicate inherent, irreconcilable incompatability between stringent military packet specifications and limited capabilities of known candidate chemicals to evoke rapid diminution of aggressive shark behavior. Guidelines for realistic estimates of minimum acceptable potencies are prescribed for future research on shark repellents. Prospective use of semiochemicals is considered, and corresponding changes in current research directions are suggested.

ChemInform Abstract: Synthesis of Mosesin‐4, a Naturally Occurring Steroid Saponin with Shark Repellent Activity and Its Analogue 7‐β‐Galactosyl Ethyl Cholate.

ChemInformVolume 21, Issue 2 Natural Products ChemInform Abstract: Synthesis of Mosesin-4, a Naturally Occurring Steroid Saponin with Shark Repellent Activity and Its Analogue 7-β-Galactosyl Ethyl Cholate. D. GARGIULO, D. GARGIULO Dep. Chem., Columbia Univ., New York, NY 10027, USASearch for more papers by this authorT. A. BLIZZARD, T. A. BLIZZARD Dep. Chem., Columbia Univ., New York, NY 10027, USASearch for more papers by this authorK. NAKANISHI, K. NAKANISHI Dep. Chem., Columbia Univ., New York, NY 10027, USASearch for more papers by this author D. GARGIULO, D. GARGIULO Dep. Chem., Columbia Univ., New York, NY 10027, USASearch for more papers by this authorT. A. BLIZZARD, T. A. BLIZZARD Dep. Chem., Columbia Univ., New York, NY 10027, USASearch for more papers by this authorK. NAKANISHI, K. NAKANISHI Dep. Chem., Columbia Univ., New York, NY 10027, USASearch for more papers by this author First published: January 9, 1990 https://doi.org/10.1002/chin.199002297Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume21, Issue2January 9, 1990 RelatedInformation

Synthesis of mosesin-4, a naturally occurring steroid saponin with shark repellent activity, and its analog 7-β-galactosyl ethyl cholate

The first synthesis of mosesin-4 ( 13), a naturally occurring steroid saponin with shark repellent activity, and its analog 19, isdescribed. They both possess a free galactose residue attached axially at the 7α position of the steroidal aglycon. Methyl cholate 3-cathylate (2) was used as a model for exploring various several methods to glycosidate the severely hindered 7α-position. Best results were obtained with β-galactose pentacetate ( 3a), using trimethylsilyl triflate as a promoter, in 1,2-dichloroethane, at −20°C, for 14 hours.

Shark Repellent Anti-Takeover Measures for the Hospitality Industry

The 1980s have become the decade of the corporate takeover—often under unfriendly circumstances. When hospitality turns into hostility, these practical strategies may help prevent your hotel or restaurant company from becoming shark bait

Shark repellent lipophilic constituents in the defense secretion of the Moses sole ( Pardachirus marmoratus)

The defense secretion of Moses sole ( Pardachirus marmoratus), the fish known to repel sharks, contains lipophilic ichthyotoxins in addition to pardaxin, a peptidic ichthyotoxin. Pardaxin has previously been regarded as the only factor responsible for the shark repellency of the secretion. On the basis of the shark repellent activity observed with the lipophile, it is considered to participate in the repellency of the secretion. Further separation of the toxic lipophile yielded five steroid monoglycosides, named mosesins. Their structures have been elucidated by nuclear magnetic resonance spectroscopy and corroborated by correlating them spectroscopically or chemically to cholic acid or to pavoninins, the related glycosides isolated from the secretion of the congeneric peacock sole, P. pavoninus.