ONR Report ACR-208

SHARK RESEARCH

Present Status and Future Direction

Oceanic Biology Program

April 1975

OFFICE OF NAVAL RESEARCH

DEPARTMENT OF THE NAVY

Arlington, Virginia

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REPORT DOCUMENTATION PAGE

I. REPORT NUMBER

ACR 208

2. GOVT ACCESSION NO.

4. TITLE (and Subtitle)

Shark Research: Present Status and Future
Direction

7. authors;
Multiple Authors - Workshop Participants
Editor: Bernard J. Zahuranec

9. PERFORMING ORGANIZATION NAME AND ADDRESS

U. S. Navy, Office of Naval Research,
Oceanic Biology Program (Code H8U)
Arlington, VA 22217

II. CONTROLLING OFFICE NAME AND AODRESS

Office of Naval Research (Code U8H)
Arlington, VA 22217

14 MONITORING AGENCY NAME 4 ADDRESSf// different from Controlling Otllce)

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3. RECIPIENTS CATALOG NUMBER

5. TYPE OF REPORT & PERIOD COVERED

Workshop Proceedings ,
30, 31 July, 1 Aug 1971*

6. PERFORMING ORG. REPORT NUMBER

6. CONTRACT OR GRANT NUMBERS

10. PROGRAM ELEMENT, PROJECT. TASK
AREA o WORK UNIT NUMBERS

12. REPORT DATE

April 1975

13. NUMBER OF PAGES

58

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16. DISTRIBUTION STATEMENT (ol thla Report)

Approved for public release; distribution unlimited

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18. SUPPLEMENTARY NOTES

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19. KEY WORDS (Conilnu. on raverae aide It necaaaary and Identify by block number)

Sharks, Shark Research, Elasmobranch Biology, Marine Biology

20. ABSTRACT (Continue on ravaraa tide It nacaaeary and Identity by block number)

In the summer of 197*+ a three day workshop was convened by the Office of
Naval Research. Purpose of the workshop was to access the present status of
shark research and to discuss areas of potential future research. The
results of these discussions constitute the main portion of this report and
include the following recommendations :

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20. Abstract (Continued)

1. A proposed "Guide to the Sharks of the World" to be produced by a
multiplicity of authors in a loose leaf format in order to insure wide
dissemination of accurate and up-to-date information about the identification
and biology of sharks.

2. A proposed "Systematic Catalogue of Sharks and Rays of the World"
intended as a companion to the guide listed above but containing more technical,
information for specialists .

3. A proposed Shark Data Bank where potentially useful ecological data oi.
sharks may be gathered and collated as contributed, perhaps much of it
collected incidental to other marine research.

h. Concentrated ecological and behavioral studies on a variety of
representative and preferably ubiquitous species of sharks such as the great
white shark, tiger shark, bull shark, or oceanic whitetip.

5. Expansion of research using the most advanced ethological tech-
niques for investigating social, rhythmic and feeding behavior, especially
toward a quantification of the results.

6. Continuation of research: behavioral, physiological and anatomical;
on shark sensory systems: acoustic, chemical, visual and electric; as well as
on a number of other systems : central nervous system, orientation mechanisms
and the osmoregulatory system.

7. The establishment and maintenance of an effective reporting system
for shark incidents, perhaps within the framework of a re-established
Shark Attack File with its attendant function of analysis and reporting.

8. Improved dissemination of information about sharks in relation

to man including medical treatment for shark attack injuries and the reassess-
ment of accurate and current information in training programs .

9. Discontinuance of the purchase of Shark Chaser by the Department
of Defense along with the objective assessment of all proposed deterrents
especially in light of technical and operational requirements.

10. An accurate assessment and further investigation of the problem
of sharks attacking and biting mooring lines and equipment, especially
through the establishment of a central clearing house for the collection and
study of fishbite incident reports.

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CONTENTS

I . Preface iv

II . Introduction 1

III . Recommendations 2

Part A. Whole Organism Studies 2

1. Systematics and Distribution of Sharks 2

2 . Ecology of Sharks 4

3 . Behavior of Sharks 7

Part B. Studies of Systems and Organs 11

1. Visual System 11

2 . The Chemical Senses 14

3. Acousticolateralis System 16

4 . Other Systems 20

Part C. Studies of Sharks in Relation to Man 28

1. Nature and Significance of Hazard to Man 28

2. Nature and Significance of Hazard to Moored Systems.. 34

IV. Closing Statement 37

V. References Cited 39

VI. Workshop Participants 52

ill

PREFACE

In the summer of 1974, during the three day period 30 July through
1 August, a conference on shark research was held at the Naval Postgraduate
School in Monterey, California. Convened by the Oceanic Biology Program
(Code 484) of the Office of Naval Research, the conference brought together
a number of people concerned with sharks and shark research including
scientists and representatives of the Air Force, Army, Coast Guard and a
variety of Navy commands. The purpose of the conference was to assess the
present status of shark research and to discuss areas of potential future
research. The results of these discussions constitute the main portion of
this report and appear as Section III.

The report itself was produced in rough form by the attendees during
the conference. The attendees were divided into three working groups
each with its own chairman: Whole Organism Studies, Dr. Richard H. Rosen-
blatt, Scripps Institution of Oceanography; Studies of Systems and Organs,
Dr. Thomas B. Thorson, University of Nebraska; Studies of Sharks in Rela-
tion to Man, Mr. F. G. Wood, Jr., Naval Undersea Center, San Diego. Dr.
Rosenblatt also acted as overall chairman of the conference. Each working
group produced its own section of the final report. These sections were
combined and comments were solicited from all attendees which were then
incorporated into the final report.

It is obvious that without the intensive and conscientious efforts of
all participants, this report could not have been completed in as short a
time. Sincere thanks are due to all of them and especially to the chairmen
who gave so willingly of their time. Thanks are also due to the faculty
and staff of the Naval Postgraduate School in Monterey, particularly LCDR
Calvin Dunlap who handled the local arrangements. The facilities and
setting of the school were most conducive to the deliberations and success-
ful attainment of the goals of the conference. The help with logistics
provided by Ms. Mary Frances Thompson of the American Institute of Biolo-
gical Sciences is also appreciated.

Finally, during the time that this report was in preparation, the
participants were saddened to hear of the unexpected passing away of one of
their members. Dr. Albert Tester of the University of Hawaii, who contri-
buted unstintingly of his time, knowledge of, and experience with sharks,
will be missed by his colleagues. His memory and the many contributions
he made to our knowledge of sharks will live on.

Bernard J. Zahuranec
Editor and Workshop Convener
Washington, D.C.
April 1975

IV

INTRODUCTION

Since the Second World War, the United States Navy has supported
basic and applied research on elasmobranchs. This has resulted in a great
advance in our knowledge of sharks, their capabilities and recently, their
behavior, including the publication of numerous scientific papers and two
major volumes about sharks: Sharks and Survival, edited by P.W. Gilbert
(1963) and Sharks, Skates and Rays, edited by P.W. Gilbert, R.F. Mathewson
and D.P. Rail (1967). Research on sharks has given us some appreciation of
the remarkable abilities of these animals which are so primitive, yet are
so well adapted for the role they play in the environment. Undoubtedly,
future research efforts will enable us to know them still better.

The sharks are part of the major group of non-bony fishes known as
elasmobranchs which include the skates and rays. The sharks are primarily
carnivores and many of the larger species apparently are the top predators
in their environment. This role is not widely appreciated and not well
understood. In fact, the exact position and role of most of the species of
sharks in the marine ecosystem is poorly known despite the large size and
spectacularity of most kinds of sharks.

The main areas of shark research discussed at the Monterey Conference
included those which, in the past, had been judged to be of most interest
to the U.S. Navy. These research areas have a more direct bearing on the
capabilities of sharks to act as predators on humans. Intentionally, no
attempt was made to cover all aspects of elasmobranch research since these
can be as diverse as the entire discipline of biology. In fact, it was
suggested that a second workshop be. held in the future, concentrating on
those aspects of elasmobranch biology such as immunobiology, cellular
metabolism, pathology, etc., wherein the elasmobranch is essentially
utilized simply as another kind of experimental animal of convenience or
choice. In addition, because the conference was in the nature of a work-
shop discussing areas of potential future research, this resulting report
cannot be considered a review of the entire field of elasmobranch research,
even in those topics specifically covered and represented by the partici-
pants.

BJZ

RECOMMENDATIONS

PART A. WHOLE ORGANISM STUDIES

1 . Systematics and Distribution of Sharks

a. Present Status and General Recommendations

Since the publications of Bigelow and Schroeder's monumental works in
1948, much knowledge has been accumulated about the biology and identifi-
cation of the over 300 species of sharks.

Many problems relating to the classification of sharks have been
resolved in the past decade, in many cases as a result of ONR support.
Whereas, in the 1950' s far example, identification of many species of
dangerous sharks was hampered by the chaotic state of taxonomy, it is now
possible, at least for specialists, to identify these species with a high
degree of certainty.

However, dissemination of this improved knowledge to the greatly
increased number of people interested in sharks has been slow and in-
efficient. Implementation of the recommendations in this report would
facilitate the widest distribution of this information to the greatest
possible audience.

We recognize that users of this information fall into two large groups,
the interests of which may overlap. Accurate identification is essential,
for example, by those persons in shark- infested areas in order to assess
the degree of danger to which they may be exposed. A diver working in an
area where there may be many individuals of a harmless species may be
greatly aided by this knowledge. Conversely, the accurate identification
of dangerous species and some general knowledge of their habits will
suggest appropriate caution for protection of personnel and in the planning
of operations. In the event of attack, accurate identification of the
shark involved is essential in any report of the incident; incorrect ident-
ification will lead to future misunderstandings.

Accurate identification is also essential to those studying the
physiology, behavior, medical, and bionic aspects of sharks. For example,
a behavioral scientist who documents a lack of territorial aggression in
a misidentif ied species may dangerously mislead personnel who encounter
a similar species that is territorially aggressive.

Trustworthy identification of dangerous sharks in both the laboratory
and in the field will insure efficient use of research and mission funds.
Research experiments or field encounters involving misidentif ication may
lead to the waste of resources and the endangering of personnel.

We recommend assembly of two manuals which would disseminate present
and future knowledge to all groups associated with shark biology. The
first, "A Guide to Sharks of the World," would allow ease of identification,
and provide general information on distribution and pertinent habits.
The second, "A Systematic Catalogue of Sharks and Rays of the World,"
would provide a universal reference list allowing increased stability of

species names and better communications among observers of sharks
throughout the world.

b. Proposed "Guide to Sharks of the World"

This book should be produced in a loose-leaf three-hole notebook
format similar to some Naval Oceanographic Office publications. This
would allow future revision, the participation of a number of appropriate
specialists as authors, addition of new observations, and immediate pro-
duction of sections on well-known sharks, with the eventual addition of
information on species which are presently under study. This concept is
being successfully used by the United Nations Food and Agriculture Organ-
ization in its production of species identification sheets for fishery
workers and fishermen in the Mediterranean and Black Seas (Fischer, 1973).

A short introductory chapter including diagrams and a glossary would
instruct the reader in the use of the book. A second chapter similar to
that of Gilbert (1963a) and Baldridge (1974) , should be devoted to advice
for persons in the water who may encounter sharks. A simple, brief index
would direct the user to the appropriate subsection of species accounts.
Each species account would follow a uniform format consisting of 1-2 pages,
and include the author and date of issue.

A typical account would include the following information:

1) English common names (if one exists) .

2) Proper scientific name (further information can be sought in
the companion catalogue; see below).

3) Accurate line drawings of a side view of the whole shark,
vertical view of head, representative teeth or tooth sets,
and any other significant characteristics.

4) Diagnostic external characters.

5) Statement of dental formula and significant vertebral counts.

6) General distribution map.

7) Natural history notes including size range, size at maturity,
food habits, depth range, and whether oceanic, inshore, or
deep-water.

8) Significant behavioral information including possible
agonistic display, territoriality, and implication in human
attack. (If a species is known to be relatively harmless,
this can be stated in such a manner that caution is still
preserved) .

9) Any important economic significance.

10) Short list of references for wider information.

An appendix would advise the reader on a uniform procedure by which to
record written and photographic information in the event that the guide
does not allow positive identification of a possible rare species, or in
the event that a significant behavioral or ecological observation is made.
Sample forms to be sent to the Shark Data Bank (described in Ecology
section below) should be included.

A second appendix would include a list of dangerous shark species
likely to be found in a specific area, e.g., the open ocean tropical
Pacific, the coast of Asia, etc.

c. Proposed "Systematic Catalogue of Sharks and Rays of the World"

This manual is intended as a more specialized companion to the
"Guide" and would be of greatest use to researchers in interpreting the
work and observations of others. In the past, a number of scientific
names have been used for a single species, usually resulting in confusion.
This catalog would indicate the correct name and list other names that
have been incorrectly used in the past. It would also include a signifi-
cant bibliographic references and technical information such as type
localities and an index of names.

d. Production and Coordination

Much of the necessary information has already been accumulated and
merely needs to be collated and edited. In several cases, however, studies
must be undertaken to fill gaps in our knowledge. Primary examples are
the taxonomy of the lemon shark genus Negaprion and the stingray family
Dasyatidae.

It is anticipated that the existing editorial staff of an organization
such as the American Institute of Biological Sciences could effectively
conduct the necessary editing and coordination under contract arrangement.
Under AIBS aegis it might also be possible to partially underwrite pro-
duction costs by subscription sales of the manuals.

2. Ecology of Sharks

a. Present Status and General Recommendations

Ecological studies of sharks are of interest in a purely scientific
sense because sharks are among the top carnivores in most marine eco-
systems. More pertinent to the present purposes, basic ecological data
(particularly on population dynamics) are needed to predict abundance and
size composition of shark populations at a given place or season, to
evaluate the effectiveness of shark control programs, and to reliably
extrapolate results of laboratory studies to the field situation.

Intensive ecological studies have been made on very few species of
sharks, notably the spiny dogfish (Ford, 1921; Hickling, 1930; Templeraan,
1944; Holland, 1957), soupfin shark (Ripley, 1946), school shark (Olsen,
1954), scalloped hammerhead (Clarke, 1971), and sand bar shark (Springer,
1960). In most of these cases, knowledge of the species' ecology is still
incomplete, and no intensive studies have been conducted on really signifi-
cantly dangerous species. It is clear that more ecological data, (e.g.,
seasonal and spatial changes in abundance, age and growth, reproductive
potential, food habits) are needed, particularly for dangerous species.

The paucity of reliable ecological data on sharks is, in a large part,
due to the difficulty and expense involved in collecting and handling
sufficient numbers of specimens. It is no accident that most studies

have involved data collected by either shark fisheries or control programs.
While such sources are useful, they are limited in number and most have
already been tapped. Furthermore, for obtaining ecological information,
sampling programs operated for such purposes as fisheries or control
efforts are less effective than sampling programs designed by an ecologist.

Thus, it is unrealistic to expect thorough studies of all species of
sharks or even all dangerous ones. Consequently, we recommend two main
thrusts in ecological studies of single species: 1) Establishment of a
uniform reporting and storage system for ecological data on all species,
and 2) Concentrated studies on a few representative and preferably ubi-
quitous species.

b. Proposed Shark Data Bank

Obviously, there are in existence, potentially useful ecological data
on sharks, much of them collected incidental to other marine research.
Such data are unlikely to ever be published. Furthermore, it is likely
that, with encouragement, even more useful ecological data could be
collected by marine scientists in the future.

To make such data more widely available, we recommend production and
distribution of a standard, computer-compatible data reporting format,
centralized storage of these data, and their availability to interested
scientists. The format should include species, size, sex, reproductive
condition, stomach contents, wounds, parasites, etc. of the specimen, and
collection data such as location, time, depth, temperature, bottom type,
and gear. We suggest that instructions and data sheets be included in the
synoptic "Guide to the Sharks of the World" mentioned above and that the
National Oceanographic Data Center (NODC) is the likely service agency for
deposition and dissemination of the data.

Such a data bank would be useful in several respects. First, by
central collection of data from widely scattered sources it seems likely
that a more coherent picture of the ecology of even rarely studied species
(e.g., the great white shark) will emerge. In addition, given that the
data may not be sufficient or reliable enough for publication, it could
at least serve as a preliminary base for intensive studies and could help
to indicate to what extent data from an extensive study of one species
can be extrapolated to others. Finally, the existence and distribution of
a standardized data format would stimulate taking and recording of eco-
logically pertinent data by non-specialists who might ordinarily make no
or limited notes on sharks taken incidentally.

c. Proposed Single Species Investigations

It is further recommended that intensive ecological studies be carried
out for the few species which constitute the principal hazard to man in
the sea. Though positive identification of the sharks which have attacked
humans is rarely obtained, enough such information is available to implicate
the great white shark, Carcharodon carcharias, and the tiger shark,
Galeocerdo cuvier , as clearly the most dangerous to man.

The white shark is a large circumglobal pelagic species, more often

encountered in temperate waters than tropical, but nowhere abundant
(Bigelow and Schroeder, 1948; Lirabaugh, 1963; Lineaweaver and Backus,
1970). Remarkably little is known about this shark; for example, there
are still no reliable data on the number of young that may be found in a
single female. Much effort would have to be expended to gather information
on this species, but we feel that some attempt should be made to advance
our knowledge of this most-feared species. Tracking of single individuals
to which sonic tags have been affixed, for example, would be of great
interest.

No excuse exists for the paucity of data on the tiger shark which is
one of the most abundant and widespread species of tropic seas. A broad-
based detailed study of this species could profitably be undertaken,
utilizing methods which would allow comparisons with life history data
gathered for other pelagic species.

Because of their great abundance and the threat they pose to survivors
of air and sea disasters well off-shore (Suda, 1953; Strasburg, 1958;
Limbaugh, 1963; Nelson, 1969; Lineaweaver and Backus, 1970; Myrberg, et al,
1972), the oceanic white tip shark, Carcharhinus longimanus ( = C. maou) ,
the silky shark, C. falciformis, and the blue shark, Prionace glauca,
should be investigated. For these three species, unpublished data are
available from tuna longline fishing, particularly from Japanese fishery
research vessels.

Studies should also be carried out on at least one of the ubiquitous
near-shore species of Carcharhinus or Negaprion. Emphasis may well be
given to the proven dangerous species of Carcharhinus (Davies, 1964;
Johnson and Nelson, 1973) such as the bull shark, C. leucas, grey reef
shark, C. amblyrhynchos ( = C. menisorrah) , or to the lemon shark,
Negaprion sp. (Springer, 1950; Banner, 1968). However, it should be noted
that studies of a smaller, less dangerous, but more feasibly investigated
species, such as the blacknose shark, C. acronotus, or the reef blacktip
shark, C^. melanopterus are not necessarily worthless from the practical
standpoint. Some of the basic biological information obtained for one
species of a genus may be extrapolated to other members of the genus.
Such comparative data are also needed to determine the roles that these
common species play in the ecosystem.

d. Inter-Specific Relationships

The most pertinent aspect of inter-specific relationships of sharks
involves their feeding habits. Although scattered data exist on food items
of sharks, much more work is needed on stomach content analyses, particu-
larly with regard to species of prey. The available data suggest that
most sharks are opportunistic feeders without clear preferences; this
view may have resulted simply from lack of information or poor identifica-
tion of prey. Limited studies have been carried out on natural predator-
prey relationships, i.e., preference, availability and abundance of prey,
habits of prey species, and their relationship to the shark's ability to
detect or capture them (see Banner, 1972).

Interspecific shark predation is of particular importance. It is
known, for example, that the young of sandbar sharks, Carcharhinus
milberti, and "puppy" sharks, C_. porosus, are important food items for the

dangerous bull shark C. leucas. Thus, predation by the bull shark may be

a natural control on the populations of other shark species. Conversely,

the availability and abundance of the prey shark species may affect the
distribution and abundance of the predator.

Information is also lacking on competition. In many localities quite
similar species with apparently identical food habits seem to occupy
the same habitat. A good example is the relationship between the silver-
tip and Galapagos sharks, which are often found together at offshore
islands (Limbaugh, 1963).

3 . Behavior of Sharks

a. Introduction

Early investigations of shark behavior centered on the study of captive
animals with experiments demonstrating responsiveness under various
stimulus situations. While profitable research still continues along
these lines (e.g., Banner, 1967; Davies e_t a_l . , 1963; Gruber, 1967;
Hodgson and Mathewson, 1971; Graeber et_ al_. , 1973; Kleerekoper, 1967;
Kuchnow and Gilbert, 1967; Tester and Kato, 1966), technical developments
have recently permitted significant strides in studying these animals
under natural conditions (Banner, 1972; Hodgson, 1971; Myrberg et al . , 1969a,
1969b, 1972b) . Continued developments along these and other avenues will
aid dramatically in answering questions unresolved by previous research.

b. Social Behavior

Existing knowledge of social behavior in sharks is based largely on
fishery catch statistics and anectodal accounts. As discussed above,
recent technical developments and refinement of analysis, as used by
workers in various behavioral disciplines, will surely provide the
opportunity for obtaining a greater understanding of the social activities
carried out by these animals. Examples of such technical developments
include the use of underwater habitats, closed-circuit television, tele-
metry and photography (see Herrnkind, 1974) . Examples of the refinement
of analyses alluded to above include the use of information and communica-
tion theory; sequential, pattern interval, and time series analysis; the
ethogram; and various types of level-adequate motivation and situation
analyses (see Hinde, 1970; Marler and Hamilton, 1966; Myrberg, 1972a).
It is essential that innovative programs continue to incorporate quanti-
tative, as well as qualitative, information in their methodology.

Various statements have appeared in the literature, regarding the
social organization and group structure of sharks (e.g., Springer, 1967);
yet, quantitative information exists presently for only two species: the
smooth dogfish, Mustelus canis, (Allee and Dickinson, 1954) and the bonnet-
head shark, Sphyrna tiburo, (Myrberg and Gruber, 1974). Virtually nothing
is known about shark behavior in the following broad areas: territoriality,
species recognition and interactions, reproductive behavior, agonistic
behavior and other sequentially related activities. Such knowledge is
critical in understanding, predicting and controlling any interaction
between sharks and man, including that of shark attack. For example, a

recent study has indicated that some attacks are motivated by social
factors rather than feeding (Baldridge and Williams, 1969). Understanding
the causal factors which underlie behavior will require experimental
manipulation and comparative behavioral analysis among a variety of
representative species. An important aid in this regard will be to obtain
and standardize dossiers of behavior patterns (i.e., ethograms) such as
those initiated by Myrberg and Gruber (1974) for the bonnethead shark and
by Johnson and Nelson (1973) for the gray reef shark. These will not only
provide the opportunity for comparative analysis, but they will also be
vital in planning, analyzing and interpreting future observations from
both the field and laboratory.

c. Rhythmic Behavior

The universality of rhythms in biological systems is now established,
and recent studies indicate that sharks are not exceptions (Hobson, 1968;
Myrberg and Gruber, 1974; Nelson and Johnson, 1970; Randall, 1967;
Springer, 1963; Graeber, 1974). For example, diel rhythms, regulated by
the daily light cycle, are known to determine the activities of tropical
reef fishes (Hobson, 1965, 1968, 1972; Collette and Talbot, 1972). Thetr
influence on the behavior of sharks, however, is less well known. Quanti-
tative information exists on only a few species (horn, swell, angel and
blue sharks), all of which are basically nocturnal (Nelson and Johnson,
1970; Standora e_t a_l. , 1972). We are not aware of any information on
rhythms related to moon phase and only little that is related to tidal
cycles. Seasonal or other long term rhythms are only slightly better
known. For example, migrations have been studied by various tagging pro-
grams (Davies and Joubert, 1967; Kato and Carvallo, 1967; Olsen, 1953, 1954;
Springer, 1960; Tester, 1969), but they still remain pootly understood.
Since long-term tagging programs generally yield low return for the effort
expended, we recommend their support only where a well established fishery
permits adequate recovery.

Controlled studies, demonstrating endogeneity, have been conducted
for only two species - certain circadian rhythms of the horn and swell
sharks (Nelson and Johnson, 1970). The effects of exogenous factors on
rhythms, other than those involving the daily light cycle, are virtually
unknown .

The most profitable line for future research would seem to center
around the daily routines of sharks under natural or semi-natural conditions.
Recent advances in ultrasonic telemetry and direct observations offer much
promise in this area (Herrnkind, 1974; Myrberg, 1973; Standora et al. ,
1972). Knowledge of daily movements, levels of responsiveness and habitat
preference will aid in predicting and perhaps controlling those activities
of sharks that conflict with the interests of man.

d. Feeding Behavior

We know of only one significant experimental study of feeding behavior
in free-ranging sharks (Gray reef, blacktip reef and reef whitetip sharks -
Hobson, 1963); yet, since the experimental design demanded that food be
presented to the sharks, natural feeding was not involved. There are
scattered, anecdotal accounts of natural feeding (e.g., Bullis, 1961;
Eibl - Eibesfeldt and Haas, 1959), but quantitative observations have not

8

been attempted. Some information on food preference is available from
fishery catch statistics and the food habits of a few species are known
from studies of gut contents (e.g., the lemon shark - Banner, 1972; Clark
and von Schmidt!, 1965; Randall, 1967).

Obviously, feeding is essential behavior for sharks and in the case
of interactions with man - perhaps their major activity. Thus, although
studies of natural feeding are difficult to accomplish, programs of
research incorporating innovative techniques for the field deserve high
priority. Some attacks on man may well be motivated by social factors,
as noted above but undoubtedly feeding motivates others. Certainly^ the
danger from shark attack is acute during certain types of group feeding,
such as those culminating in the "feeding frenzy."

e. Responses of Sharks to Specific Stimuli

Numerous studies have been conducted on the responsiveness of sharks,
both captive and free-ranging, to specific stimulus situations, often
somewhat artificial in nature due to a desire to control certain con-
founding variables. The aim of such studies has often been to determine
not only the gross stimuli "perceived" by the subjects, but to provide
insight into more specific factors which are associated with a given
sensory modality, such as sensitivity, masking, adaptation, activation of
response by selective factors, etc. It is hoped that future efforts along
such lines will continue to contribute to a better understanding of how
free-ranging sharks detect and locate objects of interest within their
sphere of influence.

When interest is directed at determining the range and sensitivity of
sensory modalities, programs often incorporate conditioning paradigms
(behavioral or physiological) or electrophysiological techniques. These
subjects will be covered in a later portion of this report.

1) Acoustic Stimuli

It had long been suspected by fishermen and divers that many sharks
were highly responsive to water-borne sounds (Eibl-Eibesf eldt and Haas,
1959; Hobson, 1963; Wright, 1948). That suspicion has now been elevated
to conclusive fact, our knowledge being greatly augmented since the initial
demonstration of shark attraction by low frequency sounds (Nelson and
Gruber, 1963). The phenomenon of acoustic attraction appears widespread
among the active, predatory species; to date, such attraction has been
experimentally shown by members of at least 20 species, covering five
families (Banner, 1968, 1972; Limbaugh, 1963; Myrberg, 1969, 1972b;
Myrberg et al. , 1969a & b, 1972; Nelson and Johnson, 1970, 1972; Nelson
e_t al . , 1969; Richard, 1968). In general, the most effective sounds for
attracting sharks are low frequency (800 Hz or below - with attractiveness
apparently increasing with decreasing frequency to, at least, 10 Hz) and of
a pulsed nature, i.e., apparently simulating hydrodynamic or other sounds
produced by wounded (struggling) or actively feeding, or otherwise milling,
fishes. These conditions are believed to represent feeding opportunities
for large predacious fishes - sharks included. Erratic or intermittant
pulsed presentations appear more effective than those having pulses of a
constant repetition rate. Yet, within the latter group, the more rapid
the rate, the more attractive the sound, at least up to 20 pulses/sec.

Differential attraction does not seem related to either a temporal
summation of acoustic energy within a given band or, with reason, to
the pulse duration. Continuous signals, sounds having a single pulse, or
those having relatively long interval are rarely attractive.

One study addressed the difficult problem of determining the biologi-
cal significance of acoustic stimuli in the predatory behavior of the lemon
shark (Banner, 1972). Similar field studies are encouraged for other
species, where possible. Efforts have also centered on determining those
variables within the acoustic stimulus itself, that sharks attend to, i.e.,
particle displacement or associated functions (Banner, 1967), the frequency
spectrum (Myrberg et al . , 1969b and 1972) and pulse character and inter-
mittancy (Myrberg e_t a_l. , 1972; Nelson and Johnson, 1972). Such research
provides not only information on the acoustical modalities of sharks, but
also a method whereby free-ranging sharks can be brought to a specific
location for experimental purposes (e.g. Evans and Gilbert, 1971), as well
as for monitoring shark-shark and shark-diver interactions (e.g., Myrberg
et al., 1972). Recent findings have also suggested the possibility of
repulsion of certain species of sharks by acoustic means under specific
circumstances (Banner, 1972; Myrberg, 1974); this line of research should
be explored further.

2) Chemical Stimuli

Detection of and orientation to various chemical stimuli by sharks
have also been important subjects of study during the past decade (Bald-
ridge, 1966, 1969 a & b, 1971; Hobson, 1963; Hodgson, Mathewson and
Gilbert, 1967; Katsuki et al. , 1969; Kleerekoper, 1967; Tester, 1963). The
effectiveness of these stimuli in attracting sharks from a considerable
distance is directly related to water currents. As above, attractive
stimuli have been those which apparently represent wounded or distressed
prey. There has been little success in using chemical stimuli as repellents
as discussed in a later section of this report. Such repellents appear
generally ineffective in driving sharks from their prey, with one possible,
recently discovered, exception (Clark, 1974). Another recent study has
also shown two distinct ways in which sharks use olfaction to locate odor
sources (Hodgson and Mathewson, 1971). Yet, much remains to be learned.
Innovative studies of the chemical modalities of sharks deserve continued
support .

3) Visual Stimuli

Laboratory studies of vision in sharks have brought forth much informa-
tion about the capabilities of the modality (see next section), but field
work, to determine the role of vision in behavior of these animals is
virtually unknown (a few exceptions include studies by Johnson and McFadden,
1971 and Tester e_t a_l. , 1968). Yet, observed interactions among sharks,
such as threat and mutual interaction displays (Church, 1961; Johnson and
Nelson, 1973; Myrberg and Gruber, 1974) clearly indicate that vision is an
important modality in the lives of these animals. In feeding, for example,
vision is thought to direct the final approach of many sharks to prey
(Gilbert, 1966). Research directed at the functional significance of the
modality is badly needed, perhaps with focus on the use of models, reflected
images and other controlled stimuli.

4) Electric Stimuli

The ampullae of Lorenzini have been identified in the shark,

10

Scyliorhinus canicula, and the ray, Raja clavata, as sensitive electrical
receptors, used to detect minute electric fields as discussed in greater
detail in the next section. Orientation to such fields produced by prey
has been demonstrated in the laboratory (Dijkgraaf and Kalmijn, 1962,
1963; Kalmijn, 1966, 1971, 1972) and though the distance over which this
modality operates is apparently quite limited, its extreme sensitivity
(0.01 uv/cm) strongly indicates a critical role in prey detection.
Speculation has also brought forth the possibility that such sensitivity
could aid in navigation or obstacle avoidance in turbid water based on
the awareness of changes in the earth's magnetic field (Kalmijn, 1972,
1973, 1974). Although these findings certainly do not rule out the
possibility of a multi-functional role for the ampullae of Lorenzini in
elasmobranch fishes, it is obvious that this modality should be examined
in additional species and the phenomenon of electroreception be examined
by extensive field investigations, when methodology permits.

PART B. STUDIES OF SYSTEMS AND ORGANS

A quick tally of physiological papers in the last several symposia on
shark research reveals especially heavy representation of studies in the
areas of neurobiology and of osmoregulation. Thus, our emphasis here
upon those same areas may reflect the continuing major thrusts of physio-
logical research on sharks. The perspectives which follow are organized
around the various functions involved, with suggestions of promising areas
of future research in each section.

1. Visual System

This report covers that modality whose adequate stimulus is photic
energy and whose function is to detect and transform spatial-temporal
photic information to a frequency modulated neural signal which eventually
informs the organism about its external environment. The elasmobranchs
possess such a system which fits the general vertebrate plan. This system,
however, has become uniquely adapted to the individual behavioral, physio-
logical and environmental requirements of the animal it serves. These
visual adaptations are so sophisticated that one gets the impression that
vision must play an important role in the lives of some, if not all,
sharks.

Tinbergen (1952)has correctly pointed out that the first task in
investigating the behavior of an animal is a careful study of its sensory
capacities. Such studies, typically involving psychophysics and neuro-
physiology not only provide data on the physiological mechanisms subserving
a particular modality, but give some understanding of properties of the
organism's physical world. Clearly, each animal has its own "Merkwelt"
or perceptual world which frequently is very different from our own. Thus,
in observing an animal it must be clearly understood that certain stimuli
can influence, indeed, release behavior and, equally important, other
stimuli can never affect the animal's activities. It is for these reasons
that the sensory systems of sharks are being studied in both laboratory
and field.

11

In the most recent review of vision in sharks, Gilbert (1963b) -nade
no mention of photochemistry, neurophysiology or psychophysics, reflecting
the limited information available at that time. Lately, knowledge of the
visual system has rapidly increased as a result of research in diverse
biological disciplines. Typically, experimental studies center on
questions such as: what is the structure of the visual system; how do the
component parts work; and what is the biological function or importance of
the system. The significance of these questions relates to elucidation of
physiological mechanisms of vision and their behavioral correlates.

a. Anatomy

Recent advances have been made in the areas of: 1) retinal history,
both at the light and electron microscope level (Hamasaki and Gruber, 1965;
Gruber, Gulley and Brandon, in press; Stell, 1973); 2) retino-tectal pro-
jections and the central visual pathway (Ebbesson, 1972; Graeber, Ebbesson
and Jane, 1973 - see page 21) ; 3) pineal apparatus (Rudeberg, 1969;
Hamasaki and Streck, 1971; Gruber et a_l . , 1975); and 4) tapetum and iris
(Denton and Nichol, 1964; Kuchnow and Gilbert, 1967; Wang, 1969). Thus,
the structure of the visual system, already reasonably well known, con-
tinues to be profitably investigated. Two areas of future study on the
structure of the visual system could produce useful data:

1) An ultrastructural investigation of receptor cytoarchitecture
and the synaptic relations within the retina with emphasis

on the outer plexiform layer. Such a study would aid in
interpretation of neurophysiological results and visual data
in general.

2) The function of the eye as an optical system including
refraction, cardinal planes, nodal points, accommodation,
preretinal absorption and spectral reflection from the tapetum.
These data could be utilized in producing a schematic or
model eye. Thus, levels of photic stimuli impinging on the
cornea could be specified at the receptor level. In addition,
the physical limitations of the dioptric parts of the eye
would be known.

b. Physiology

Areas encompassed within visual physiology include: 1) vegetative
physiology of the eye such as nutrition of the lens, cornea, iris and
retina; 2) photobiology, including identification of visual pigments,
kinetics of bleaching and photoproducts; 3) neurophysiology, including
electroretinograms (ERG's), intercellular records such as S-potential,
intracellular or single unit records and resultant data on frequency
codes, receptive fields, and visual mechanisms; 4) psychophysics, in-
cluding conditioned responses and natural orientations providing informa-
tion about visual capabilities, stimulus limits and visual mechansisms
involved with behavioral functions.

While more is known about the neurophysiology of vision in elasmo-
branchs than many other organisms, these studies are still in their
initial stages. Several electroretinographic studies have been accom-
plished (Dowling and Ripps, 1970; Green and Sigal, 1973; Gruber, 1973;

12

Hamasaki and Bridges, 1965; and Kobayashi, 1962), and S-potentials have
been reported on (Dowling and Ripps, 1971; Tamura and Niwa, 1967).
Receptive field mapping by single unit technique (Naka and Witkovsky, 1972)
and tectal studies have also been accomplished. Although much data on
visual mechanisms has been derived from ERG studies, single unit analyses
are lacking, especially in the higher visual centers (see page 21).

Little is known of the vegetative physiology of the eye. Visual
pigments from several elasmobranchs have been extracted and characterized
(Denton and Shaw; 1963; Bridges, unpublished). The more revealing
techniques of microspectrodensitometry have not been attempted on shark
retinas.

c. Behavioral Aspects

Few psychophysical studies on vision have been reported though train-
ing experiments have yielded reliable data on dark-adaptation, brightness
discrimination, critical frequency of flicker-fusion, visual sensitivity,
colior discrimination and pattern discrimination (Aronson e_t al . , 1967;
Cla'rk, 1959; Graeber et_ al. , 1973; Gruber, 1975). These data have tended
to confirm the results of physiological studies and have strengthened the
view that sharks have an extremely functional visual system. Any
discussion of visual capability must account for both visual acuity and
light sensitivity. Thus, when one asks if an animal has "good vision" the
inquiry may concern either spatial resolution (acuity) or how well an
animal can see in dim light (sensitivity) . We can state that sharks have
extremely good vision regarding sensitivity factors. Their sensitivity
to light spans the visible spectrum, from blue to deep red and they are
ten times more sensitive than man under similar test conditions. Nothing
at all is known of spatial resolution in these creatures. Some estimates
have been made, based on packing density of photoreceptors (Franz, 1931)
but these are largely speculative. The temporal resolution of sharks is
similar to man's and is the type associated with a duplex retina. Thus,
under high illumination a shark can detect, as flashing, light which is
intermittently blocked 40 times per second. This has theoretical impli-
cations with regard to function of cone photoreceptors and practical
implications on how fast a shark can swim without its visual world
blurring.

The large gap here is in visual acuity. This factor is amenable to
analysis by physiological and behavioral techniques and should be under-
taken. By determining parameters such as the spatial modulation transfer
function, practical knowledge can be gained on the ability of sharks to
distinguish two contours as separate. Additionally, theoretical data
on size tuned channels in the sharks visual system could be derived.

Another area of importance concerns qualitative aspects of vision:
for example, do sharks possess trichromatic color vision? Again, for
both theoretical and practical reasons the nature and importance of color
vision must be revealed.

Finally, as mentioned in the previous section, the role of vision in
the field behavior of sharks is virtually unknown. Not only does little
useful information exist on the behavior of sharks in general, but it is
also conceptually difficult to establish criteria for determining the

13

relative importance of visual stimuli in the field or the effects of
visual stimuli on motivation. This is an area which can bridge the gap
between field and laboratory studies and strong consideration should be
given to any promising studies of this kind. The main difficulty with
this type of investigation involves adequate and reliable methodology.
Until this is properly developed, we will still be guessing!

In summary, knowledge of visual structure and function has rapidly
advanced during the past decade: several investigators are applying
methods from various disciplines to the study of vision in elasmobranchs.
It is now possible to make definitive statements on visual capability in
these animals and the picture which emerges is quite different from
classical descriptions. Still, as in other phases of elasmobranch biology
tangible progress in understanding the visual system in sharks is just
beginning.

2 . The Chemical Senses

The senses of smell and taste are closely involved with the feeding
and attack behavior patterns of sharks. As a consequence, research on
these senses of sharks has had a long history. When G.H. Parker published
his classic summary of "Smell, Taste, and Allied Senses in the Vertebrates"
(1922) there were already many descriptions of the gross morphology of
chemical sense organs of sharks. Some of Parker's colleagues had also
studied the effects of plugging one nostril in a shark (resulting in
circular movements), and attempts were being made to determine the groupings
of chemicals which stimulated olfactory, gustatory, and skin chemore-
ceptors of sharks. However, the latter studies, on modalities of effective
stimuli, were completely inconclusive.

During most of the intervening half century, research on the chemical
senses of sharks has been essentially a refinement of behavioral studies
and anatomical investigations which could have been appreciated by Parker
and others early in this century. Screening programs for repellents,
tests of the attractiveness of various potential food substances, and
comparative anatomical studies have dominated the field. A few field
studies on feeding behavior of pelagic sharks under natural conditions
were made, but mainly on a catch-as-catch-can basis, often in conjunction
with natural history expeditions primarily concerned with other objectives.
Tester (1963) has given a valuable summary of that phase of the studies on
chemical senses of sharks. He noted that there was a need for:

1) Electrophysical studies of receptor function, already in
widespread use on other sensory systems of other animals.

2) Electro-dissection or other precise techniques of neurosurgery
to localize functions within the CNS concerned with the
chemical senses.

3) Tests with pure single chemicals which trigger important
patterns of behavior in sharks.

4) Determination of chemically-mediated patterns of behavior
in sharks of other kinds and in other circumstances, beyond
the few species and laboratory situations most studied.

14

The call for some shift of focus was in no way a repudiation of the
value of anatomical and behavioral studies. Certainly the ultimate test
of insights is in their applicability to understanding the behavior of
intact animals in their normal environments. However, the major shift
indicated at this time was toward more molecular and cellular levels of
investigation.

During the 1960's and 1970' s, modern electrophysiological methods have
been applied to analyzing the chemical senses of various elasmobranchs.
The first breakthrough came with the recordings of electrical activities
of masses of cells in various parts of the shark's brain — the electro-
encephalograph (EEG) — which provided a picture of the functions of
various surface areas of the brain (Gilbert, Hodgson, and Mathewson, 1964).
It was found that variations in EEG patterns could be correlated with
chemical stimulation and with behavior patterns of lemon sharks (Negaprion) ,
nurse sharks (Ginglymo stoma) and bonnet sharks (Sphyrna tiburo) . In some
of these studies chronically implanted brian electrodes were used, and
responses of sharks to pure chemicals were tested in a hydrodynamic tunnel
(Hodgson, Mathewson and Gilbert, 1967).

Very recently, electrophysiological recordings have been made from
the olfactory tracts of hammerhead sharks exposed to chemical stimuli.
This was done by a student at the University of Hawaii (A. L. Tester,
personal communication) .

Amino acids, short-chain tertiary amines, and purified hemoglobin
(human and bovine) have been found especially effective in altering EEG
patterns, and in eliciting typical orientation behavior — either klino-
taxis or rheotaxis — in lemon and nurse sharks (Hodgson and Mathewson,
1971) . Results similar to those obtained under controlled laboratory
conditions have been observed with open-sea tests using these purified
chemicals, making observations by a remotely-controlled underwater tele-
vision camera, (R.F. Mathewson and E.S. Hodgson, personal communication).

The linking of electrophysiological analysis with field studies of
behavior, and the limitation of stimulation to single pure chemical stimuli,
bring the study of shark chemical senses to a new level of sophistication
and usefulness. Laboratory EEG analysis has good predictive value for
behavior of sharks in open sea. Furthermore, the use of single pure chem-
icals gives access to future studies on exact chemical mechanisms of
stimulation. We can now ask a whole series of new questions about olfaction
and taste in sharks:

1) What is the mechanism of interaction between a chemical
stimulant and the receptor cell membrane?

2) Once more is known about that, it would be possible to
investigate specific blocking agents of anti-metabolites
which might interfere with these specific processes. In
other words, how might the specific mechanism of stimulation
be modified, and possibly controlled?

3) How can we get single cell, or few-fiber experimental prepar-
ations, to reveal the action potentials which must certainly
be involved in stimulation by chemicals? Additional studies
of the ultrastructnre of olfactory nerves, and taste

15

receptors, may indicate the best ways of solving this
problem.

4) How are the immediate effects of chemoreceptor stimulation
coded into patterns of afferent impulses which enable sharks
to discriminate various chemical stimuli? And how many
types of chemical structure or modalities of stimuli, are in
fact detected?

Probably the most powerful tools to study mechanisms of chemical
stimulation include both electrophysiological methods, to detect receptor
responses, and radio-isotope techniques, to label and follow the distri-
bution of chemical stimuli. The first tests with labeled stimuli have
recently been completed and suggest that neural mechanisms of behavior
are somehow automatic, once initiated, and play out a sequency of re-
sponses that is independent of the initial stimulus (E.S. Hodgson,
R.F. Mathewson and A. Karsten, personal communication). This opens up
additional new perspectives in the study of innate, more or less auto-
matic responses "wired into" the CNS of the shark; it is possible that
many feeding and attack behavioral patterns fall into this category, and
consequently they deserve further study.

Many physiological studies of the chemical senses are handicapped by
lack of knowledge of the fine structure of the tissues involved. To
our knowledge, no electron microscope studies have been made on the ultra-
structure of either olfactory or gustatory sensory cells in elasmobranchs.
It would be worthwhile to determine more precisely how an olfactory cell
differs from a gustatory cell, whether cilia or villi are present on the
exposed surface, the nature of organelles, the nature of innervation,
etc. The barbels of bottom feeders, such as Ginglymostoma , should be
studied for the presence of external taste buds and how they compare in
structure with those of teleosts.

A further limitation has been that most physiological studies on the
chemical senses have been done with four or five species in the genera
most readily maintained in captivity: Mustelus, Squalus, Negaprion,
Ginglymostoma , and (very recently) Sphyrna. It is obvious that with some
250-300 species of sharks, each specially adapted to its own environment,
it sometimes involves unwise extrapolations to attempt predictions about
the physiology and behavior of other species, or even of these better-
studied species in other areas of the world. Careful physiological
studies require adequate laboratory facilities and with the development
of new marine laboratories there may be opportunities for highly desirable
comparative studies on additional species of sharks.

3. Ac oustico lateralis System

This is a complex sensory system which is deeply involved in shark
predation and defense. It is comprised of the sensory canals of body and
head, the pit organs, the ampullae of Lorenzini and the ear. Basically,
the sensory organ is the neuromast and the actual receptor of the organ
is the hair cell (Dijkgraaf, 1963).

a. Sensory Canals

The gross morphology and histology of the sensory canals, their

16

tubules and their neuromasts are reasonably well known for sharks and
rays from the works of older authors, augmented by more recent studies,
e.g., Tester and Kendall (1969) for Carcharhinus. The orientation of
the tubules and tapering caudad bore of the canal provide for a slow
tailward flow of seawater through the canal. The rate of flow should be
determined for several species. The function of peculiar vesiculated
cells adjacent to the neuromast in the canal epithelium, greatly elaborated
in the anterior head canals, should be investigated. The recent study of
Liddicoat and Roberts (1972), showing the canal fluid of dogfish to have
the same ionic content as seawater, should be repeated for other species.
These latter studies would contribute to our knowledge of ionic regulation
of body fluid, and the part played in establishing a sodium-potassium ratio
optimal for electrogenesis in the hair cells.

The fine structure and orientation of hair cells of the canal organ
has been studied extensively in teleosts but not in sharks. Roberts and
Ryan (1971) have made Electron Microscope (EM) studies in Scyliorhinus.
Similar studies should also be undertaken in other common sharks, including
both bottom-dwelling and pelagic species in order to contribute to our
knowledge of how a hair cell functions as a receptor of displacement waves.
Items of interest are (1) the orientation of hair cells along the canal
with respect to the position of the kinocilium (movement in one direction
produces excitation and in the oposite direction, inhibition); (2) the
presence of different types of hair cells; (3) the nature of organelles;
and (4) the presence of both afferent and efferent synapses.

Roberts and Russell (1970) and Roberts (1972) , again working with
Scyliorhinus, have made the only study in sharks of the source of efferent
activity that modulates the afferent firing of the hair cells in the canal
organ. Since the results are not clear cut, the work should be repeated
and expanded, preferably with other species. This work is essential to a
complete understanding of how the canal organ functions as a receptor of
displacement waves.

Given that the ordinary lateral-line organs are displacement receptors,
the following questions arise (cf. Dijkgraaf's lateral-line review, 1963):
(1) What are the displacements that sharks detect in their daily life?
Here we should distinguish between (a) displacements imposed upon the
animals from external sources, in which case the receptor system operates
in a passive mode, and (b) displacements resulting from the animal's own
activity relative to the environment with the receptor system operating in
active mode. (2) What may be the biological significance of the various
displacements (e.g. detection of other animals by the displacements re-
sulting from their swimming or ventilation movements, detection of objects
by the distortions they cause in the sharks' own* "underwater bow waves")?
(3) How do sharks mechanically relate to their environment? How do they
integrate the information from their spread-out lateral-line organs, and
how do they analyze the spatial and temporal aspects of natural displace-
ment fields? To answer these questions, the physics of the pertinent
displacement fields should be studied more rigorously, the biological
relevance should be determined in well-planned behavioral tests, and the
central processing of the total receptor input should be investigated by
recording the electrophysiological responses of peripheral nerves and
central nuclei.

17

b. Pit Organs

The gross morphology, histology and innervation of these organs have
been described in several species of sharks by Budker (1938), Tester and
Nelson (1967) and Tester and Kendall (1967). They resemble the canal
organs and, in fact, have been called free neuromasts by some authors.
However, there is doubt as to whether they actually have a cupula or
whether the sensory surface is merely coated with an undefined mucus layer.
There is still some question as to whether they have cilia: only a brush-
like fringe can be seen under the light microscope. The only EM work to
date is referred to by Katsuki, Hashimoto and Kendall (1971) who state
"Hama and Yamada (in preparation) confirmed electron-microscopically the
ciliary structure of the hairlike process in these sensory cells." There
is need for further EM studies of the pit organs of sharks to further
elucidate the fine structure of the sensory cell and to compare it with
that of the lateral line hair cell. Suitable preparations are difficult
to make because of protective modified scales.

The function of the pit organ is still uncertain. Onada and Katsuki
(1972) imply that it has the dual function of mechanoreception and chemo-
reception. In earlier papers, Katsuki and his co-workers have implied,
from electrophysiological experiments, that it is primarily a salinity
detector. How its true function or functions (from the shark's point of
view) can be determined is problematical. Since it apparently does have
mechanoreceptive functions it may contribute to the sharks ability to
orient and home in on a near field sound source, or it may serve to detect
changes in flow pattern. Further electrophysiological experiments,
augmented by behavioral experiments, should be undertaken to clarify its
alleged mechanoreceptive and/or chemoreceptive function. For behavioral
experiments, some method will have to be devised to occlude or otherwise
nullify either the sensory canals or the pit organs, both of which are
serviced by the same nerve, in order to investigate their functions
separately. It may also be necessary to occlude the ampullae of Lorenzini
and the ear when studying the response to displacement waves.

c. Ampullae of Lorenzini

These unique organs, located on the dorsal, ventral, and lateral
surfaces of the shark's head, have been subject to many morphological,
electrophysiological, and behavioral studies over the years. The organ is
a flask-like tube with an opening on the head and is filled with a mucoid
jelly. Its blind end has a central plate and several out-pouchings lined
with sensory epithelia. EM studies by Waltman (1966) show that the pear-
shaped sensory cells have a cilium or hair with a supporting structure that
differs from that of the "ordinary" lateral-line haircell. Despite this
and other differences, the ampullae are still considered to be "specialized"
lateral-line organs.

Excised ampullae of Lorenzini have been shown by many authors (see
Murray, 1974) to respond to a variety of stimuli: thermal, mechanical,
chemical, and electrical. Nerve recordings from free-swimming sharks
(Scyliorhinus) revealed, however, that in situ ampullae, though still very
sensitive to weak electric fields, do not appreciably respond to mechanical
perturbations nor to thermal gradients in the water (Kalmijn, 1972, 1974).
These results accord with the location of the sensory epithelia deeply

18

buried under the skin. Obara and Bennett (1972) recently presented a
novel theory and preliminary experimental evidence regarding the receptor
mechanism of the ampullae of Lorenzini in an effort to explain their high
electrical sensitivity and the anomalous polarity of response.

It seems now generally agreed that the ampullae of Lorenzini function
as electroreceptors. It has been shown by Dijkgraaf and Kalmijn (1962,
1963) that sharks and rays respond to very weak electric fields of the
order of 0.1 uV/cm, and that their high electrical sensitivity is due to
the ampullae of Lorenzini. Subsequent studies (Kalmijn, 1966) lowered this
threshold to 0.01 uV/cm, representing the greatest electrical sensitivity
known in the animal kingdom. Further behavioral experiments by Kalmijn
(1971) showed that both Scyliorhinus and Raja are able to detect flatfish
buried in the sand by virtue of the bioelectric potentials that the prey
produce. The predators cued in on the flatfish's bioelectric fields
from distances up to 10-15 cm. Because of the biological significance of
this response, Kalmijn concluded that sharks and rays are endowed with an
acute electric sense and that the ampullae of Lorenzini are true electro-
receptors.

The high electrical sensitivity of sharks and rays allows for some
interesting speculations. If the animals are capable of interpreting the
large-scale electric fields induced by open-ocean streams flowing through
the earth's magnetic field, they may sense upstream and downstream
directions, e.g. for compensating unwanted drift or for gaining passive
transport. If the animals are capable of appreciating the electric fields
that they produce when swimming through the earth's magnetic field, they
may even sense the actual compass directions. The feasibility of orienting
with respect to uniform electric fields has recently been demonstrated in
successful training experiments on catfish and weakly electric fish. More-
over the shark Triakis was found to respond in a frightened manner to local,
experimentally induced non-uniformities in the earth's magnetic field
(Kalmijn, 1973, 1974). Since understanding the principles of shark navi-
gation and open-ocean orientation in general is of utmost importance, these
advanced studies should be pursued tenaciously despite their inherent bio-
logical, physical, and technological difficulties.

Although there is good evidence that the ampullae of Lorenzini serve
an electroreceptive function, this does not necessarily rule out multi-
functional performance, e.g. the ampullae may serve as mechanoreceptors to
enable sharks to distinguish between the texture of objects in "head
bumping", though the ordinary lateral-line organs and the free nerve
endings could be involved as well. The responses of the ampullae of
Lorenzini to stimuli of various modalities should be critically examined in
other sharks and rays, particularly the pelagic species, using both electro-
physiological and behavioral techniques. A fruitful approach in the invest-
igation of the ampullae of Lorenzini may be through the use of recently
developed locomotory monitoring techniques under controlled conditions
(Kleerekoper, 1969).

d. The Ear

The gross morphology and histology of the elasmobranch ear has been
known since the classical work of Retzius in 1881, and has been updated for
Squalus acanthias by Quiring (1930), for Raja clavata by Lowenstein,

19

Osborne and Wersall (1964) and for Carcharhinus by Tester, Kendall and
Milisen (1972) . The fine structure of the sensory epithelia of the ear
of Raja, including the orientation of the hair cells, has been determined
by Lowenstein, Osborne and Wersall (1964). Rauchbach and Arenberg (1972,
1973) have demonstrated the use of the scanning EM (SEM) to show the
structure of hair cells of the ear of Negraprion and have diagrammed their
orientation. J. Corwin (U. of Hawaii graduate student) is presently
using both transmission EM (TEM) and SEM to study hair cell orientation
in Carcharhinus, particularly with respect to the little known organ, the
macula neglecta. EM work should be continued and extended to other genera
to provide a firm basis for the interpretation of electrophysiological
experiments designed to illucidate how the ear functions in hearing.
Other functions of the ear — equilibrium and muscle tonus maintenance —
have been worked out for the ray by Lowenstein and Sand (1940a and b) and
by Lowenstein and Roberts (1950) . This work should be extended to other
sharks .

There have been many papers in recent years on hearing in sharks,
including both tank experiments and studies with free-swimming animals
in their natural environment. Although it has been shown that the re-
sponse varies with the nature of the sound (continuous, pulsed, train,
etc.) and that the response is directional, it has not yet been established
whether the stimulus is received through the lateral line, the ear, or
both.

There is need for determining if ahd how the ear participates in
hearing. Much can be learned from electrophysiological studies of micro-
phonics in various parts of the ear of an immobilized submerged shark,
utilizing an underwater sound source as stimulus. There are indications
that the macula neglecta may be a main organ of hearing in rays (Lowenstein
and Roberts, 1951) and in sharks (Faye, Kendall, Popper and Tester, 1974).
Further electrophysiological experiments, with particular attention to this
organ, should be undertaken.

It might be possible to perform diagnostic behavioral experiments to
clarify the role of the ear in hearing, subjecting sharks in tanks or in
cages in the open environment to underwater sound sources. However it
would be difficult to ablate the ear without causing problems in equilib-
rium and it would be difficult to ablate the lateralis system because
of its complexity. The possibility exists of correlating behavioral and
electrophysiological observations by inserting electrodes into the macula
neglecta of both ears and telemetering the responses. However, it is
difficult to implant electrodes without damaging other parts of the ear
and it is difficult to firmly anchor the electrode assembly to the skin.
It should be possible to overcome those technological problems in the
future.

4. Other Systems

a. Central Nervous System

In sharks, as in any organism, the understanding of an integrated
behavior pattern should involve the study of various relevant components
of the central nervous system. During the past few decades, such attempts
to understand the nature of shark attacks have centered primarily on

20

investigating sensory systems at the peripheral level. Typical has been
the emphasis on olfaction and vision and their roles in guiding behavior.

Although these latter studies have led to some interesting and
worthwhile findings, it is our belief that in order to understand and
predict shark behavior, it will first be necessary to correct the lack of
emphasis which has been placed on studying the shark central nervous
system. It is here where the necessary integration of various sensory
inputs occurs and where the animal's motivational state and past experi-
ences exert their influence on behavior. By having dwelled on studies
of isolated physiological systems, shark research is at a point where we
now know a fair amount about both the effective stimulus modalities and
mechanisms of shark sensory physiology but almost nothing about how such
sensory information gets translated into actual response patterns. As a
result, the stage is set for a new, more molar type of research into the
psychobiology of shark behavior. The scope of this research program
should eventually encompass such topics as central cross-modal sensory
interaction, sensori-motor integration, and neural arousal mechanisms
with an emphasis on the behavioral implications of these central neural
processes. Hopefully, the following brief description of some such work
already begun in sharks and other fishes will help clarify the type of
research program we believe could be profitably pursued.

1) Central Sensorimotor Integration

As Ebbesson (1970, 1972) has pointed out, several of the revolutionary
developments in neuroantomical technology have recently been applied to
study elasmobranchs. Use of these methods, e.g., Nauta and Fink-Heimer
degeneration techniques, electron microscopical analysis, etc., has led to
a marked change in our understanding of the structure of the shark brain
and, in many instances, a complete reversal of traditional beliefs
(Ebbesson & Heimer, 1970; Ebbesson & Ramsey, 1968; Ebbesson & Schroeder,
1971; Graeber & Ebbesson, 1972). For instance, work on the olfactory
inputs to the brain has shown that only a relatively small portion of the
shark forebrain (formerly called the "smell brain") received any infor-
mation regarding olfactory stimuli (Ebbesson, 1972; Ebbesson & Heimer,
1970). However, due to the rather limited attention given to central
nervous system investigations in elasmobranchs, there is still a large
void to be filled concerning how the brain processes olfactory as well as
other sensory information.

In this regard, there has been practically no work done since the
turn of the century on relating brain anatomy and physiology to actual
behavior. Nevertheless, a recent series of studies has demonstrated the
fruitfulness of this approach (Graeber & Ebbesson, 1972; Graeber, Ebbesson
& Jane, 1973; Graeber, e_t al, 1972). Here relatively standard methods of
behavioral analysis were used to study the contributions of various central
nervous system structures to visually guided behavior in the nurse shark,
Ginglymostoma cirratum. Contrary to traditional belief it was found that
the processing of visual information into action involved much more than
the midbrain optic tectum. Instead, by depending heavily on both thalamic
and telencephalic nuclei, the central processing of visual cues in sharks
may more closely resemble that in mammals and reptiles.

These findings obviously suggest that the neural basis of visually
guided shark attack is more complicated that previously imagined. They

21

also indicate an increased capability for multi-modal sensori-motor
integration. Hence, it is not surprising to the neurobiologist that
shark behavior is apparently less stereotyped than often conceived on tht
basis of the shark's traditionally primitive simple brain. The naivete
of this old notion is further pointed out by recent field studies
(Johnson & Nelson, 1973) and Baldridge's (1974) analyses which have
demonstrated the variability and unpredictability of shark attacks on
humans.

Similar studies on the central neural mechanisms integrating vibratory
tactile, electrical, and olfactory cues into response patterns are sorely
needed and now appear feasible. Some such work has been initiated by
Roberts, who has investigated the motor end of the stimulus response
chain in dogfish. (Roberts, 1969a, 1969b; Roberts & Russell, 1972).

Another intriguing and promising approach to brain-behavior studies
in sharks has been suggested by Okado and his colleagues (1969). Their
delineation of the substantial morphological differences among the brains
of different species strongly argues for a comparative strategy to answer
some of the questions about the relationships between brain structure and
behavior. This has yet to be tried amidst a laboratory setting.

As might be expected from the newly discovered complexity of the shark
forebrain, shark behavior has recently been shown to be more flexible than
previously thought. A number of learning experiments have demonstrated
that both lemon and nurse sharks can be trained as easily as many mammals
and can retain learned tasks for a considerable period of time (Aronson,
1963; Aronson et al, 1967; Clark, 1959; Graeber, 1972; Graeber & Ebbesson,
1972). The importance of such learning studies should not go unrecognized.
Much of the progress which has been made in relating brain structure and
physiology to behavior in mammals has resulted from experiments employing
learned tasks to assess the effects of experimentally varying central
neural states. It is now possible to apply similar behavioral technology
to learning more about shark brain function. Moreover, the learning data
underscore the important contribution of past experience in determining
the momentary response tendencies of these animals. Consequently, it can
be expected that experiential factors will influence the effectiveness of
any technologies intended to thwart or predict shark behavior, especially
in a given locale.

The hypothalamus and related areas of the brain have been shown to be
the focal point for arousal or motivational systems related to feeding
and attack in fishes as well as other vertebrates. For this reason a
separate section dealing with this important topic in sharks and bony
fishes is included below.

2) Neural Mechanisms of Feeding and Aggression

Feeding patterns have been described for many sharks maintained in
captivity and in the wild (Clark, 1963; Gilbert, 1970; Graeber, 1974;
Hodson et al . , 1967; Kalmijn, 1971; Randall, 1963; Springer, 1967; Tester,
1963) . The presence of chemical stimuli such as are released from freshly
killed animals can cause considerable attraction of sharks and may result
in a so-called "feeding frenzy" in which sharks are known to bite at any-
thing that moves. Some of the sharks themselves may be eaten during this

22

activity. The description of this "feeding frenzy" is suggestive of
some of the responses that have been evoked by electrical stimulation
of the hypothalamus (inferior lobe) and midbrain in teleosts (Demski
and Knigge, 1971; Demski, unpublished observation), in which the stimulated
animals swarm around rapidly attacking many different objects which inclu-
ded food, gravel, debris, other fish and other inanimate objects. It
should be noted that in some stimulations arousal seemed to be less intense
and the fish either attacked only another fish or snapped at food objects
or gravel. Similar arousal and feeding activity in fishes has been evoked
by stimulation of the olfactory tracts (Grimm, 1960), anterior commissure
(Fiedler, 1964), and the area near the medial forebrain bundle (Demski,
1973). These observations, along with the results of studies that indicate
that olfactory cues alone can trigger similar activity in several teleosts
(Grimm, 1960; Demski, 1973), suggest that the arousal and snapping activity
evoked from the fish hypothalamus may be related to activation of normal
forebrain olfactory input to the hypothalamus that runs in the medial
forebrain bundle (Demski, 1973). It also seems reasonable to suggest that
an analogous situation may exist in sharks which have a similar forebrain
bundle input into the periventricular portion of the hypothalamic inferior
lobes (Demski, 1974; Ebbesson, 1972), and which are also greatly aroused
by olfactory cues. Consistent with this idea are reports of increased
electrical activity in the forebrain of nurse, lemon and bonnet head
sharks in response to perfusion of the nasal openings with extracts of
normal food substances (Gilbert e_t a_l . , 1964). Thus it would be interesting
to know if stimulation of the hypothalamus and forebrain olfactory pathways
in this group would evoke similar responses to those observed in teleosts.

In addition to olfactory information, the hypothalamus in various
teleosts is reported to receive visual, gustatory and possibly acoustic
inputs (see Ariens Kappers e_t al. , 1936; Aronson, 1963; Schnitzlein, 1964;
Tuge e_t a_l . , 1968). Thus the hypothalamus may be one of the major sensory
integrative centers in the fish brain. Its main output pathways run to the
cerebellum, brain stem motor nuclei and possibly spinal cord as well (see
above references) ; this suggests that it is likely to strongly influence
motor systems. The above anatomical considerations led Herrick (1905) to
postulate that the teleost hypothalamus is a sensorimotor correlation
center which is involved in feeding activity. As mentioned above, the
results of electrical stimulation experiments are consistent with this
idea. Internal stimuli such as blood glucose levels may also be important
in determining the hypothalamic activity in fishes in a similar manner as
proposed for mammalian species (see De Groot, 1967). Thus the study of
teleost and shark hypothalamus may give valuable insight into the role of
many sensory factors in the determination of predatory behavior of sharks.

Many shark attacks may be agonistic in nature rather than related
primarily to feeding (Baldridge and Williams, 1969; Johnson and Nelson,
1973). If this is the case, it is likely that hypothalamic mechanisms
similar to those described for feeding are also involved since, in teleosts,
electrical stimulation of the hypothalamus frequently evokes both prey
catching as well as intraspecif ic aggression (Demski and Knigge, 1971;
Demski, 1973).

Considerable information on the neural mechanisms of feeding and
aggression in sharks may be derived by repetition of experiments carried
out in teleosts and other vertebrate groups since there are at least

23

general similarities in the hypothalamic mechanisms for these responses
in many species. The following types of studies should lead to valuable
contributions in this field: electrical stimulation of the hypothalamus
in free-swimming sharks; study of the effect of lesions of the hypothalamus
and related areas on feeding and attack; and analysis of the detailed
anatomy, electrophysiology and pharmacology of the shark hypothalamus and
its related areas.

b. Orientation Mechanisms

In all animals, the capability to perform movements whose direction
is related to environmental cues is of paramount significance and will be
referred to as "orientation" in this statement (Schone, 1973) . In fishes,
its survival value is obvious in many critical biological functions: the
localization of prey or predator, mate and spawning site, advantageous or
noxious physical and/or chemical conditions. In all these circumstances,
locomotion must be directed or oriented in relation to environmental stim-
uli, singly or in combinations, perceived through sensory mechanisms, and
evaluated by the central nervous system. In spite of the impressive
array of functions which directly depends on the capability of orientation,
the mechanisms by which physical and chemical cues are used in directing
locomotion are insufficiently known at best in the higher fishes and
almost entirely speculative in the elasmobranchs.

The available information regarding sharks refers almost exclusively
to the localization of food sources and the role of chemical and acoustic
cues in orientation (Parker, 1910; Sheldon, 1911; Parker and Sheldon, 1913;
Aronov, 1959; Teichmann and Teichmann, 1959; Pavlov, 1962; Tester, 1963;
Hobson, 1963; Kleerekoper, 1963; Myrberg et al. , 1969 and 1972; Nelson and
Johnson, 1972) . The effectiveness of orientation through chemoreception
in the absence of other directional cues has been a topic of much specu-
lation and some descriptive and quantitative experimentation (Kleerekoper,
1962, 1965, 1967 a and b, 1969; Mathewson and Hodgson, 1972). These
investigations have indicated that accurate localization of a chemical cue
by elasmobranchs is affected by and dependant on water flow. A recent
laboratory study, employing electronic techniques and time series analyses
of various locomotor variables, monitored during many hours, quantified
the relationship between chemical cue and water flow in the orientation of
Ginglymostoma cirratum (Kleerekoper e_t a_l. , 1975) . It was established
that accurate localization of a chemical cue was dependent on flow of the
medium. In the absence of such flow, localization became generalized.

Elegant experiments on electrical orientation have been performed in
both sharks (Scyliorhinus, Triakis) and rays (Raja, Platyrhinoidis) . Well-
aimed feeding responses were evoked and directed by the bioelectric fields
that prey (e.g. the flatfish Pleuronectes) produce (Kalmijn, 1966, 1971,
1972). At short range (a few inches), electrical cues appeared to dominate
chemical cues. The acute electric sense of sharks and rays may well play
an important part in the animal's daily life (Kalmijn, 1974).

Orientation in sharks by acoustical cues has been studied in recent
years by various workers (Nelson and Gruber, 1963; Banner, 1968, 1972;
Myrberg, 1969; Myrberg et al. , 1969, 1972; Nelson and Johnson, 1970, 1972)
who have provided evidence for the possible role of low frequency sounds
in the localization of prey by these animals. Attempts to demonstrate

24

orientation through sound in teleosts have been inconclusive and the
physical basis for an orientation mechanism using acoustical cues seems
difficult to formulate.

A physical theory of electrical orientation with respect to open-ocean
streams and to the earth's magnetic field has recently been developed
(Kalmijn, 1973, 1974). Now that we know the high electrical sensitivity
of the animals and the strengths of the pertinent stimulus fields, it
seems quite feasible that electro-orientation aids short- and long-range
navigation in sharks and rays.

The possible significance of other sensory cues for orientation in
sharks has hardly been considered experimentally. Although the lateralis
system has been studied to a considerable extent in these animals, its
role in orientation is unknown. Orientation through temperature perception
and vision has not been investigated. Particularly, the possibility of
perception of and oriented response to polarized light deserves early
investigation in view of recently demonstrated capabilities of some
teleosts in response to the e-vector of a polarized laboratory "sky"
(Kleerekoper e_t al_. , 1973) and in field experiments (Waterman, 1973) , In par-
ticular, the interaction of two or more cues in locomotor orientation in
sharks merits urgent attention. Apart from the recent experiments on
flow-chemical and electrical-chemical cue interaction, no work has been
done in this area. Many of these fields of research will have to be
attacked initially in the laboratory so that quantitative approaches can
be used. Recent monitoring and statistical techniques would enhance the
chances of success. New telemetric techniques now offer possibilities in
the field for the coarser tracking of movements of sharks and for the
design of meaningful experimentation. Whether in the laboratory or in the
field, it should be emphasized that short term experiments on locomotor
orientation do not inspire confidence in view of the great variability in
this behavior over time. This variability can be statistically accounted
for in stochastic models of locomotor behavior extending in time.

c. Osmoregulation

The biology of the shark's nervous system, both motor and sensory, is
of obvious importance to its efficiency as a predator and its threat to
man. Perhaps less apparent, yet a most important aspect of the shark's
physiology, is the way it maintains water and solute balance under con-
ditions which tend to disrupt it, i.e., its osmoregulatory mechanisms.

Earlier work on elasmobranch osmoregulation has been reviewed, and
much of the recent work reported, in two symposium volumes: Gilbert,
Mathewson, and Ralls (1967); and Goldstein (1972).

In broad outline the major features of the osmoregulation of marine
elasmobranchs have been fairly well worked out. Instead of regulating
the solute content of the body fluids well below that of the sea water,
with the expenditures of much energy, as is done by marine teleosts,
elasmobranchs accumulate large quantities of organic substances, especially
urea, and to a lesser extent trimethylamine oxide. These are retained in
quantities sufficient to make the body fluids hyperosmotic to sea water
and thus provide water for a limited quantity of urine, relatively con-
centrated, but still hypotonic to the serum. Excess salt is excreted by

25

way of the rectal gland.

In freshwater teleosts, the osmotic imbalance between body fluids
and environment is reversed, since the salt content is regulated at only
a very slightly lower level than in the marine teleosts. But when
euryhaline elasmobranchs such as the bull shark Carcharhinus leucas and
the sawfish Pristis perotteti move from the sea to fresh water the imbalance
is not reversed but simply increased. The osmotic influx of water therefore
increases and the quantity of urine increases accordingly and its concen-
tration is reduced, both by a factor of 15 to 20. The urea content of the
body fluids decreases to about 30 to 50 percent of the marine level, and
presumably the rectal gland stops excreting salt. When the elasmobranchs
return once more to the sea, they revert to the marine osmoregulatory
pattern.

The completely freshwater stingrays of South American rivers (family
Potamotrygonidae) have abondoned the accumulation of urea as an osmoregu-
latory agent and are unable to retain urea even in response to transfer
into saline water. Essentially they deal with their osmotic problems as
freshwater teleosts. In contrast to these rays, freshwater stingrays of
the Benue River of Nigeria (family Dasyatidae) deal with their osmotic
problems essentially as the euryhaline shark and sawfish, retaining urea,
but at a reduced level.

In recent years, more studies have been conducted in the general area
of osmoregulation than in any other area of elasmobranch physiology except
perhaps neurobiology. Many facets of the overall problem have been at
least touched on, for instance, the biosynthesis of urea and trimethylamine
oxide and the influence of various experimental regimens on that synthesis
and the enzymes involved; the influence of various substances, procedures
and environmental salinities on urea levels; membrane transport of urea
and various inorganic ions; ietention of urea by tubular reabsorption and
gill membrane impermeability; various aspects of rectal gland function;
and the influence of endocrine secretions on osmoregulation.

Nevertheless, much remains to be learned before we have a reasonably
complete understanding of how elasmobranchs deal with their osmoregulatory
problems, especially as they move between areas of differing environmental
salinities.

No aspect of osmoregulation is fully understood and any of the areas
mentioned above would profit by study in greater depth and particularly
by comparison of a greater variety of species. Perhaps most enlightening
would be the application of already used techniques and experimental pro-
cedures to the truly euryhaline species. In this way the rates and
directions of the processes that make up the total osmoregulatory function
can be watched under controlled manipulations in species that are able to
make the requisite changes to accommodate to both sea water and fresh
water.

In the past, many attempts have been made to observe changes when a
shark is transferred from sea water to fresh water, but almost invariably
the wrong species have been selected — species that are not truly
euryhaline and therefore are not fully able to make the necessary physio-
logical adjustments. Therefore, when placed, for instance, in 50 percent
sea water for several hours, they retain excessive water, are unable to

26

retain their normal salt concentration, their hematocrit falls, and they
soon die unless returned to their accustomed habitat. On the contrary,
Carcharhinus leucas and Pristis perotteti in fresh water are able to
maintain their water and salt balance and normal hematocrit values
indefinitely. The problem has been to obtain and maintain in captivity the
small specimens most desirable for such studies. Given the necessary
holding facilities and a dependable supply of experimental animals, these
species are potentially a most valuable source of information, until now
largely out of reach.

5. Closing Statement

By virtue of expertise represented or lacking on the committee, this
portion of the report deals primarily with certain topics and neglects
others. Lack, of treatment of an area does not imply that the area is un-
important or is not an appropriate subject for research. Various aspects
of reproductive physiology, immunobiology, pharmacology, and cell biology
and metabolism have been studied in recent years by a number of investi-
gators whose publications suggest fruitful lines of future research. The
digestive process, muscle physiology, endocrinology, and parasitology have
received less attention but they also offer ample opportunity for investi-
gation in elasmobranchs. These and other areas may also be of primary in-
terest and be expected to produce important results.

It is gratifying to note the progress that has been made in the neuro-
biology, sensory physiology, and osmoregulation of elasmobranchs during
the last decade. Several promising, areas of research have been indicated
in this report. If implemented, these should provide additional funda-
mental information to explain the behavior of sharks and how they respond
to environmental stimuli.

Various techniques and methods are common to diverse experimental
studies on sharks and other elasmobranchs. At present, there are no
readily available sources to which a researcher can refer in designing and
carrying out studies on sharks. In addition, many important parameters
related to the handling and maintenance of sharks are presently not known.
For these reasons, it is important that workers in the fields of experi-
mental physiology and behavior of elasmobranchs be brought together to
exchange information and collate and publish the available data on experi-
mental techniques. Included in such a symposium should be the following
topics:

1. Electrode implantation techniques.

2. Stressful effects of captivity and handling.

3. Effects of pharmacological agents normally used as
anesthetics, etc.

4. Pathobiology and nutrition.

5. Maintenance techniques including the use and composition
of physiological solutions.

27

PART C. STUDIES OF SHARKS IN RELATION TO MAN

1. Nature and Significance of Hazard to Man

a. Introduction

Although statistically infrequent, shark attack remains a significant
physical and psychological problem for naval personnel. The circumstances
under which sharks constitute a threat are primarily the following:

(a) Survival situations (air and sea disasters)

(b) Swimmer/diver operations

(c) Recreational swimming and diving

An indirect personnel hazard could result from shark- inflicted damage
on deep-sea navigational buoy moorings or surveillance equipment (see
Part C, Section 2) .

Assessment of the problems requires collection and analysis — on a
continuing basis — of accurate data. The effectiveness of. such as assess-
ment is largely dependent on the availability of objective reports.

In the past the Navy supported, through ONR, the establishment and
maintenance of such reporting procedures by means of the Shark Attack File.
In 1967 support for this program was terminated, and no systematic collec-
tion of incidents has been possible since that time. The final report from
this project (Baldridge 1973, 1974) resulted in the most complete analysis
of shark attacks yet produced.

Emerging from the purposes of the Shark Attack File was Bureau of
Medicine Instruction 6400. 2A which required a world-wide reporting of shark
attacks on naval personnel and civilians under naval jurisdiction. No
reports of attacks on naval personnel have resulted, although independent
documentation has indicated that personnel covered by that instruction
have indeed been victims of shark attack. An effective reporting procedure
is seen as mandatory (a) because of the need to identify possible causative
and predictive factors of attack on man, (b) to provide an enlightened
basis for development of anti-shark measures, (c) to identify changing
trends in location and pattern of attacks, and (d) to provide information of
such nature and accuracy as to allay unnecessary fears about shark attack.

b. Hazards

1) Physical Hazard

Shark injuries are often massive and usually characterized by shock,
trauma, and loss of blood, not unlike combat injuries. The treatment pro-
cedures are virtually identical in both situations. It is only in recent
years that the importance of immediate on-site preliminary treatment for
this type of injury has been recognized. The work by Davies and Campbell
(1962) has dramatically demonstrated the value of having plasma available
for immediate use on the beach before transporting the victim to a facility
for more intensive care.

28

Pathogenic organisms such as haemolytic streptococci (ibid.) from
the shark's mouth may constitute an additional serious complication.

Current medical practices, both military and civilian, do not reflect
these findings.

2) Psychological Hazard

There is understandably a widespread apprehension of sharks and the
possibility of shark attack, despite the relatively low incidence of
attacks. Abundant evidence indicates that apprehension, even in the
absence of a shark sighting, has an adverse effect on performance, whether
in a survival situation or in the execution of an operational task. Appre-
hension lessens the individual's chances for survival or diminishes the
operator's ability to accomplish his mission.

A message (272349Z Aug 74) from the Commander, Amphibious Forces
Pacific, to the Naval Scientific Advisory Program requesting test and
evaluation of a wet suit incorporating shark-bite resistant material
(KEVLAR ; see Physical Deterrents) was prefaced with the following statement:

The shark hazard to Navy Divers has been a
continual threat over the years, both in the
sense of producing actual casualties and in
the psychological effect of degrading effect-
iveness of divers who must work in waters in
which sharks have recently made an attack.

Official concern with possible hazards is also reflected in the basic
UDT/SEAL training lesson plan having to do with dangerous marine life. This
states: "The appearance of a shark as large as the diver or two or more
sharks in the diving area should be sufficient reason for the diver to
terminate his diving activities and leave the water."

Examples of operator apprehension and official concern leading to
mission interference can be cited:

In a night-recovery training exercise prior to
the splashdown of Apollo 15, the practice capsule
was in the water and the UDT personnel were in the
process of attaching the flotation collar. Three
helicopters containing the primary recovery team
and two reserve teams were overhead shining spot-
lights on the capsule.* At this point, the officer-
in-charge, also overhead in a backup helicopter,
noticed that at least six sharks were circling the
capsule. The training operation was immediately
aborted. With realization of the disastrous
implications the shark hazard presented, recovery
personnel were subsequently equipped with CO darts
(see Physical Deterrents) .

*ln operational or survivor recovery operations utilizing helicopters, there
exists the possibility, still unconfirmed, that the beat of the rotors on
the water sends out low frequency vibrations similar to those that are
known to attract sharks (see page 9 ) .

29

On 21 April 1963, a naval officer assigned to
Underwater Demolition Team TWENTY TWO, LTJG J.W.
Gibson, was attacked and fatally wounded by a shark
at the head of Magens Bay, St. Thomas, Virgin
Islands. The shark was caught on the following day
and positively identified as the perpetrator of the
attack by the undigested remains of the victim found
in its stomach.

Personnel of UDT-22, which had been deployed to
the Virgin Islands for advanced training, recall
that apprehensions about the possibility of shark
attack rose sharply after the death of LTJG Gibson.
The rationale for the attack most frequently ex-
pressed by UDT personnel on scene was that the shark
was "sick" and its attack was therefore extremely
unusual.

A training exercise conducted a few days after
LTJG Gibson's death, involving diver lock-out from
a submarine, was cancelled after two pairs of divers
locked-out and reported seeing sharks that appeared
aggressive. Operations were not resumed that day,
and the submarine returned to port. On the following
day the operation was successfully completed, with
no sharks sighted.

During the Fall of 1969, a classified underwater
construction project was carried out by divers of •
Underwater Demolition Team ELEVEN. In one stage of
the project, use of underwater explosives was required
on a daily basis. Diving operations were frequently
hampered by aggressive behavior of the numerous sharks
that unfailingly appeared in the work area after the
detonation of the explosives. The sharks congregated
in such large numbers after each detonation, and their
behavior was so menacing, that resumption of work was
delayed up to two hours on several occasions.

When work was resumed it was necessary to put two
pairs of divers into the water; one pair to work and
one pair to watch for and ward off sharks that
approached too closely. Work dives were often terminated
when persistently aggressive sharks forced divers to
leave the water. The of f icer-in-charge requested
permission to arm his divers with powerheads, but
authorization was not granted because of the potential
danger to personnel posed by the powerhead itself
and concern that the thrashing and bleeding of a
wounded shark would serve to attract more sharks.

c. Countermeasures

Advisable behavioral countermeasures which should be incorporated into
training materials have been set forth in detailed fashion in an ONR
report (Baldridge, 1973).

30

1) Personnel Training

Because shark attacks are rare, very little aircrew and UDT/SEAL
training is devoted to shark hazard. UDT/SEAL training for example,
includes only a two-hour lecture on dangerous marine life. Ordinarily,
this minimal information regarding sharks is not a matter of concern.
However, when an individual is in a survival situation, or sharks are
encountered in swimmer /diver operations, a knowledge of shark behavior and
proper response to shark activity may become crucial. The extent of
coverage of training information should range from simple and accurate
basics for aircrewmen to more detailed information for UDT and SEAL
personnel whose normal sphere of operations is underwater. Examples of the
kind of information that swimmer/diver personnel could use are: distin-
guishing features of dangerous species of sharks, recognition of distinctive
threat postures which may precede attack, and knowledge of characteristic
activity patterns, such as the movement of blue sharks from open sea to
shallow coastal waters at dusk, with return to deeper waters at dawn.

This behavioral information, only recently acquired by ONR contractors,
illustrates the desirability of frequently updating training manuals and
films. Training materials currently in use contain a great deal of out-
of-date and inaccurate information. The U.S. Navy Diving Manual, for
example, emphasizes the danger of killer whales, even though there has
never been a documented record of an attack on a human. The Air Force
film entitled Shark Defense (TF-5589-B) also contains inaccurate information
("it is difficult for sharks to make sharp turns"), and advocates a number
of courses of action which are either ineffective (for example, tearing up
bits of paper and scattering them on the water) or inadvisable (rubbing
bare fingers on the rubber life raft, to make a sound which, in actuality,
might attract sharks). While this film is 10 years old, it is still being
shown.

Proper training not only saves lives but also facilitates the success-
ful and expeditious accomplishment of tasks and missions.

2) Chemical Deterrents

Although a number of devices for deterring sharks have been proposed,
(Gilbert and Gilbert, 1973), the standard deterrent issued to military
personnel since World War II is a cake of water soluble wax containing 80%
nigrosine dye and 20% copper acetate, called "Shark Chaser." In early
tests it was reportedly effective in repelling several species of sharks.
However, a mounting body of evidence has now conclusively demonstrated
that Shark Chaser has no significant deterrent value against most dangerous
sharks. Even such psychological benefits as it may have provided have
diminished with the growing awareness that it does not afford effective
protection. But the inefficacy of Shark Chaser has not been clearly demon-
strated in operational use (a shark exposed to Shark Chaser may have had no
intention of attacking in the first place), and no practical, effective
substitute has become available. Moreover, it is only recently that the
growing body of evidence from observations and controlled experiments (Kato,
1962) has conclusively established the lack of value of this chemical
deterrent.

For the above reasons Shark Chaser is still issued to military per-
sonnel. In the period from November 1969 through February 1974, the

31

Department of Defense purchased 84,450 packets at a cost of approximately
$345,000. In addition, each packet comes boxed in a cardboard container
that bears a two-year expiration date, which probably accounts for the
continuing purchase of 15,000 to 20,000 packets per year. (This information
obtained from Naval Air Systems Command Code 531 as supplied by Defense
General Supply Center, Richmond, Va.)

Although an effective substitute for Shark Chaser is clearly needed,
it is questionable whether any chemical deterrent which diffuses to form a
cloud around the user is practical. The quantity of material required to
maintain an effective concentration for the desired period of time and
the problem of insuring complete envelopment are among the reasons why such
chemical deterrents appear to offer little promise (Baldridge, 1969a and b) .

However, the recent discovery of a biological substance that has a
unique deterring effect of sharks requires further investigation. A flat-
fish, Pardachirus, which occurs in the Red Sea and Indian Ocean, secretes
a milky substance that at certain levels of dilution, is highly toxic to
a number of forms of life and extremely aversive to sharks. It has been
demonstrated that a shark will not close its jaws on the living fish and
that under experimental conditions the substance affords protection to
other kinds of fish that the shark would otherwise eat. The substance
acts with remarkable rapidity; even fish enveloped by a shark's open jaws
have later shown no scratch or mark (Clark and Chao, 1972; Clark, 1974).

3) Physical Deterrents

Protective devices may be either active or passive. Of passive devices
for individual protection in a sea survival situation, one promising device,
the Shark Screen, appears to be an inexpensive, practical, and highly
effective means of preventing shark bite (Johnson, 1968). Shark Screen is
a bag of thin, tough plastic with a collar consisting of three inflatable
rings. The user partially inflates one of the rings by mouth and gets into
the bag. He then fills it with water by dipping the edge so that it be-
comes turgid, presenting to any shark a large, solid-looking black object.
The rings can be fully inflated at leisure. The bag retains any fluids
or wastes which might attract and arouse a shark. It also effectively
attenuates the bioelectric and galvanic fields produced by the person and his
gear, which otherwise might elicit attack through the shark's acute electric
sense (Kalmijn, 1971). It is believed that minor packaging and material
problems can be solved so that the final product will occupy no more space
than that now required for a packet of Shark Chaser.

A new material called "KEVLAR" developed by Dupont is being used for
bullet-proof vests and jackets. Preliminary tests indicate that it offers
promise as a sharkbite resistant material which could be incorporated into
wet suits.

A variety of devices for actively deterring sharks have been developed
or proposed, most of them for use by a diver (as opposed to devices for area
protection). In assessing these a number of factors must be taken into
consideration, including practicality, cost, reliability, effectiveness,
and safety for the user. A device practical for sport divers might be
prohibitively burdensome for UDT/SEAL personnel. Cost, within reasonable
limits, must be balanced against portability, effectiveness, and reliability.

32

Simplest and cheapest of devices in use is a short club, the "shark
billy," which is rated moderately effective. At the other extreme are
electrical or electronic shield devices which are expensive and complex.
So far these have not proven to be effective and in some instances have
constituted a hazard for the user (Gilbert, 1968).

Conventional power heads or "bang sticks" are relatively inexpensive
and have some effectiveness, but are not readily reloaded. The recently
developed "Sea-Way" power head is highly effective and easily reloaded,
but, like bang sticks, would be of limited utility to military divers who
are often burdened with other gear and sometimes required to operate
clandestinely.

The electronic dart, which is designed to electronarcotize a shark,
and the C0„ dart, which injects carbon dioxide into the shark under high
pressure (Langguth, 1972), are moderately effective but relatively
expensive, and unless equipped with extension poles (which reduce their
portability) require that the user be in very close contact with a shark.

One novel device, the drogue dart, is a barb with a small parachute
attached. When the barb, mounted at the end of a pole, is implanted in a
shark it breaks away and the parachute provides an off-balance impediment
to the shark's swimming. This device, while cheap and effective with
small sharks, has not been tested with large sharks.

Recent accounts of acoustic devices that repel sharks warrant investi-
gation (see Banner, 1972; Myrberg, 1974), although they raise questions of
cost and practicality. The great advantage of an acoustic device, assuming
that there is a sonic stimulus which will repel sharks, is that it would
operate at a distance. A disadvantage is that it could not be used in
clandestine swimmer/diver operations.

In summary, no existing device satisfactorily meets the specifications
for military swimmer/diver use, although some have utility in special
circumstances.

4) Area Protection

Area protection may at times be desirable at an underwater construction
site or a recreational bathing area. Again, no wholly satisfactory device
or system is known, each being deficient in one respect or another. A net
enclosure is effective but expensive and usually impractical. Gill-netting
and fishing for sharks have proved effective in Australian beaches but
are expensive, long-term measures. An electrical device called "Shark
Shield" has seen some use by shrimp fishermen to keep sharks out of their
nets, but it is expensive and of limited practicality for area protection
(Gilbert and Gilbert, 1973). The possibility of attracting sharks away from
the area of concern by means of acoustic techniques developed in the course
of ONR-sponsored research might prove moderately effective but has obvious
drawbacks.

The fact that porpoises have on occasion been known to attack and kill
sharks has led to the suggestion that they be specially trained to provide
protection for swimmers and divers. In an ONR-sponsored project conducted
at the Mote Marine Laboratory a bottlenose dolphin was indeed trained to
harass a large sandbar shark and drive it out of the pool, but when a bull

33

shark, one of the species known to be dangerous to man (and, probably,
porpoises) was introduced, the porpoise exhibited flight behavior and
refused to respond to any commands (Irvine, et al., 1973). While not
conclusive and providing little optimism for development of a porpoise
anti-shark system the experiment raised the intriguing question of what
sensory cues were used by the porpoise in distinguishing two rather similar
species of carcharhinid shark.

d. Principal Recommendations

1) The establishment and maintenance of an effective reporting system
for shark incidents.

2) Re-establishment of the Shark Attack File with its attendant
function of analysis and reporting.

3) Dissemination of information regarding need for treatment at
the recovery site of shock and trauma of shark-attack injury.

4) Incorporation of current and accurate information in training
programs and training aids.

5) Discontinuance of purchase of Shark Chaser by DoD.

6) Objective assessment of proposed deterrents with consideration to
R&D and operational requirements.

2. Nature and Significance of Hazard to Moored Systems*

a. Introduction

Deployment of moored systems for the collection of oceanographic,
meteorological, or surveillance data over extended periods of time has
prompted an investigation of factors responsible for equipment loss within
the rated life of moorings, which could not be attributed to hydrodynamic
forces or encounter with surface craft or submersibles.

b. Discussion

Evidence accumulated from a comprehensive review of the limited
literature reveals that sharks, including the oceanic whitetip Carcharhinus
longimanus, mako shark Isurus oxyrinchus and blue shark Prionace glauca
are incriminated in the biting and slashing of deep-sea moorings (Starkey,
1974; Stimson and Prindle, 1967). This has been verified by dental im-
pressions and recovery of tooth fragments from various types of plastic
cable armor to depths of approximately 1500 feet. Histograms of biting
recorded on experimental moorings in Atlantic waters near Bermuda indicated
that bites occurred with greatest frequency near the permanent thermocline
(Turner and Prindle, 1967). Apparently, "fishbite" on mooring lines and
cables is less of a problem in the Pacific, although detailed evidence is
lacking.

*This material was prepared by Roland J. Starkey, Jr., Environmental and
Ocean Science Laboratory, General Electric Company, who was unable to attend
the workshop.

34

For the most part, trials with baited samples of armored cable in
tensile frames have been unsuccessful, although in one case Prionace glauca
punctured samples of polyethylene and polycarbonate in trials conducted
off the southeast coast of Massachusetts (Stimson and Prindle, 1967).
Studies of this kind cannot be considered realistic since they fail to
stimulate the stratification of the moorings' physio-chemical and biological
environment.

It has been theorized that sharks usually do not exert maximum biting
strength on cables because they are attracted to foreign objects on or in
the immediate vicinity of the cables, rather than to the cables themselves.
Walden and Panicker (1973) ascribe the "dental floss effect" to a slashing
phenomenon. This may occur when the shark is casually searching for food,
and the cable is rapidly drawn across the tip of one or more teeth as a
result of whip-lash motion mediated by fluctuating currents or by movement
of surface or sub-surface buoys. From an operational standpoint, slashing
at any depth may expose one or more conductors, interrupting data collection,
decreasing tensile strength, and contributing to the premature loss of an
entire system. For these reasons various studies are being conducted to
develop armor for multiple-conductor cables so that they will be resistant
to attack by sharks and other fishes but still possess the tensile strength
and characteristics (including diameter, weight, flexibility, etc.) necessary
for deep-sea deployment of navigational buoys as well as instrument packages
(Hartman, 1972; Preston, et al., 1973).

Concurrent interest has developed in investigating factors attracting
sharks, and countermeasures suitable for use in shallow and deep-water
applications. One factor under consideration is low-frequency sound
generated by cable movement, generally referred to as "strumming", which
may be similar to the low frequency vibrations that are known to attract
sharks (Myrberg et al. , 1969 a & b, 1972b; Nelson and Gruber, 1963; Nelson
and Johnson, 1972; Nelson et al. , 1969). Various types of ant i- strumming
devices are currently in use or undergoing evaluation to determine their
effectiveness. The simplest involves the application of polyethylene ribbons
at regular intervals along the length of the cable. Quantitative data are
not available to confirm the efficacy of this method.

Based on examination of recovered deep-sea moorings it has also been
hypothesized that sharks may be attracted to cables by visual clues elicited
by an assortment of bioluminescent organisms accumulating on the cables'
surface (Turner, 1965). Flashes of light would be triggered by mechanical
stimuli as the cable strums, possibly evoking a positive phototropic
response.

The high frequency of biting reported near the permanent thermocline
suggests that a higher concentration of food organisms may exist there.
This could increase the incidence of random encounters and expression of
the "dental floss" effect.

Olfactory clues from chemical messengers cannot be discounted, since
recovered moorings are often covered with a variety of unidentifiable decayir
biological materials. This is generally referred to as "Sea Snot" and is
frequently seen in the Bermuda area (Gifford, 1973). Garbage is also found
on deep-sea mooring cables, and similarly could be expected to attract
sharks and smaller fishes as aromatic degradation products are continuously

35

leached into the water.

Other possible attractants include current meter rotors (Walden and
Panicker, 1963), hydrophones, or any equipment which could contribute to
sound propagation, owing either to moving parts or to in-line sensor
housings larger in diameter than the cable.

It has been speculated that shark attack on scuba divers could be
provoked by galvanic currents generated by dissimilar metals of the regu-
lator, tank, and backpack strap (Klimley, 1974). Similar currents may be
produced in cables when care isn't taken to maximize cathodic protection
of instrument cases or achieve electrical isolation of aluminum and
stainless steel hardware (Morey, 1973). The importance of this requires
further clarification. However, as discussed previously, those elasmo-
branchs investigated have demonstrated great sensitivity to weak electric
fields.

c. Conclusions and Recommendations

1) Moored systems for the collection of oceanographic, meteorological,
and surveillance data are susceptible to damage or loss owing to
biting or slashing by fishes, including sharks.

2) The extent and seriousness of the problem cannot be determined from
presently available evidence, although "fishbite" incidents are
apparently more common in tropical Atlantic waters.

3) A central office (probably in the Naval Oceanographic Office)
should be established for collection and study of reports of
fishbite incidents, and users of moored systems should be informed
of the existence of such an office. Information provided to such
an office would permit determination of the identity of the
perpetrators of such "attacks" as well as the geographical and
seasonal occurrence of fishbite incidents.

4) Further investigations are needed to understand the reasons for
the apparent attraction of sharks and other fishes to mooring
lines and cables.

5) Information derived as a result of the above recommendations

can be used to help develope more effective and practical mooring
lines and cables.

36

CLOSING STATEMENT

In summary then, this workshop has attempted to review some of the
main areas of shark research and to suggest those areas where efforts
expended may give the most profitable results in the future. It is hoped
that this report will prove useful not only for scientists but for planners,
research managers, Navy personnel, and laymen interested in sharks and
shark research.

In abbreviated form, these recommendations can be summarized as
follows:

1. A proposed "Guide to the Sharks of the World" to be produced
by a multiplicity of authors in a loose leaf format in order
to insure wide dissemination of accurate and up-to-date
information about the identification and biology of sharks.

2. A proposed "Systematic Catalogue of Sharks and Rays of
the World" intended as a companion to the guide listed
above but containing more technical information for
specialists.

3. A proposed Shark Data Bank where potentially useful
ecological data on sharks may be gathered and collated
as contributed, perhaps much of it collected incidental
to other marine research.

4. Concentrated ecological and behavioral studies on a
variety of representative and preferably ubiquitous
species of sharks such as the great white shark, tiger
shark, bull shark, or oceanic whitetip.

5. Expansion of research using the most advanced ethological
techniques for investigating social, rhythmic and feeding
behavior, especially toward a quantification of the results.

6. Continuation of research: behavioral, physiological and
anatomical; on shark sensory systems: acoustic, chemical,
visual and electric; as well as on a number of other systems:
central nervous system, orientation mechanisms and the
osmoregulatory system.

7. The establishment and maintenance of an effective reporting
system for shark incidents, perhaps within the framework of

a re-established Shark Attack File with its attendant function
of analysis and reporting.

8. Improved dissemination of information about sharks in relation
to man including medical treatment for shark attack injuries
and the reassessment of accurate and current information in
training programs.

9. Discontinuance of the purchase of Shark Chaser by the Department
of Defense along with the objective assessment of all proposed

37

deterrents especially in light of technical and operational
requirements.

10. An accurate assessment and further investigation of the
problem of sharks attacking and biting mooring lines and
equipment, especially through the establishment of a central
clearing house for the collection and study of fishbite
incident reports.

BJZ

38

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49

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51

WORKSHOP PARTICIPANTS

Dr. SHELDON APPLEGATE

Los Angeles County Museum of

Natural History
Exposition Park
Los Angeles, California

Dr. ARTHUR J. BACHRACH
Naval Medical Research Institute
National Naval Medical Center
Bethesda, Maryland

Dr. H. DAVID BALDRIDGE
Senior Research Associate
Mote Marine Laboratory
9501 Blind Pass Road
Sarasota, Florida 33581

Mr. LEONARD CAMPAGNO
Department of Biological Science
Stanford University
Stanford, California 94305

Dr. EUGENIE CLARK
Department of Zoology
University of Maryland
College Park, Maryland

Dr. THOMAS A. CLARKE

Associate Professor of Oceanography

Hawaii Institute of Marine Biology

University of Hawaii

Coconut Island, P.O. Box 1346

Kaneohe, Hawaii 96744

Dr. LEO S. DEMSKI

Department of Anatomy

L.S.U. Medical Center

1542 Tulane Avenue

New Orleans, Louisiana 70112

LCDR CALVIN DUNLAP
Department of Oceanography
Naval Postgraduate School
Monterey, California 93940

Dr. JAMES F. FISH

Oceanographer

Naval Undersea Center Code 405

San Diego, California 92110

Mrs. CLAIRE GILBERT
Mote Marine Laboratory
9501 Blind Pass Road
Sarasota, Florida 33581

Dr. PERRY W. GILBERT

Director

Mote Marine Laboratory

9501 Blind Pass Road

Sarasota, Florida 33581

Captain R. CURTIS GRAEBER
Research Psychologist
Pioneering Research Laboratory
U.S. Army Natick Laboratories
Natick, Massachusetts 07160

Dr. SAMUEL H. GRUBER

Assistant Professor of Marine Science

University of Miami

Dorothy H. and Lewis Rosenstiel

School of Marine & Atmospheric

Science
10 Rickenbacker Causeway
Miami, Florida 33149

Dr. EDMOND HOBSON
Marine Science Center
P.O. Box 398
Avalon, California 90704

Dr. EDWARD S. HODGSON
Chairman, Department of Biology
Tufts University
Medford, Massachusetts 02155

Dr. SUSUMU KATO

Fishery Biologist, Research

National Marine Fisheries Service

Southwestern Center Tiburon Lab.

P.O. Box 98

Tiburon, California 94920

Dr. HERMAN KLEEREKOPER
Professor of Biology
Department of Biology
Texas A&M University
College Station, Texas 77843

52

LCDR IRVE C. LEMOYNE
Assistant for Special Units
NAVSHIPS Code 00C-3
Naval Ship Systems Command
Washington, D.C. 20362

Captain PAUL G. LINAWEAVER
Senior Medical Officer
Submarine Development Group One
Fleet Station Post Office CSDG-1
San Diego, California 92132

Dr. ARTHUR A. MYRBERG, Jr.
Professor of Marine Science
Rosentiel School of Marine &

Atmospheric Science
University of Miami
4600 Rickenbacker Causeway
Miami, Florida 33149

Dr. DONALD NELSON
Associate Professor of Biology
California State University
Long Beach, California 90840

Ms. SHAREE J. PEPPER

Research Biologist

Environmental Information Division

Air Training Command 3636 CCTWg

Maxwell AFB, Alabama 36112

Dr. JOHN E. RANDALL

Ichthyologist

Bernice P. Bishop Museum

P.O. Box 6037

Honolulu, Hawaii 96818

Dr. RICHARD ROSENBLATT
Professor of Marine Biology
Department of Oceanography
Scripps Institution of Oceanography
University of California, San Dieog
La Jolla, California 92037

LT. RAYMOND SMITH

RDT&E Officer, Naval Inshore Warfare/

Amphibious Group Eastern Pacific

Command
U.S. Pacific Fleet

U.S. Naval Amphibious Base, Coronado
San Diego, California 92155

Mr. STEWART SPRINGER
Senior Research Associate
Mote Marine Laboratory
9501 Blind Pass Road
Sarasota, Florida 33581

Mr. JAMES STEWART

Diving Officer

Scripps Institution of Oceanography

University of California, San Diego

La Jolla, California 92037

Dr. LEIGHTON TAYLOR, Jr.
Hawaii Cooperative Fishery Unit
U.S. Fish & Wildlife Service
Department of Zoology
University of Hawaii
Honolulu, Hawaii 96822

Dr. ALBERT L. TESTER
Senior Professor of Zoology
Edmondson Hall, 2538 The Mali
University of Hawaii at Manoa
Honolulu, Hawaii 96822

Ms. MARY-FRANCES THOMPSON
American Institute of Biological

Science
1401 Wilson Boulevard
Arlington, Virginia 22209

Dr. THOMAS B. THORSON
Professor of Zoology
School of Life Sciences
University of Nebraska - Lincoln
Lincoln, Nebraska 68508

LCDR JOSEPH A. UNDERWOOD USCG
Naval Aviation School Command
Naval Air Station
Pensacola, Florida 32508

Mr. LIONEL WEINSTOCK

Materials Engineer

Life Support, Survival & Rescue

Branch
Crew System Division
Naval Airsystems Command
Washington, DC 20361

53

Mr. F. G. WOOD, Jr.

Marine Bioscience Program Office

Biosystems Research Dept. (4003)

Naval Undersea Center

San Diego, California 92132

Mr. BERNARD J. ZAHURANEC
Assistant Program Director
Oceanic Biology Program
Code 484

Office of Naval Research
Arlington, Virginia 22217

In addition, several people who were invited to participate, were unable
to attend, but did contribute to the final written report:

Dr. SIDNEY R. GALLER

Deputy Assistant Secretary for

Environmental Affairs
Room 3425

Office of Environmental Affairs
Department of Commerce
Washington, DC 20230

Dr. ADRIANUS J. KALMIJN
Associate Scientist
Woods Hole Oceanographic

Institution
Woods Hole, Massachusetts 02543

Dr. ROBERT F. MATHEWSON

Director

Tice Biological Research Laboratory

P.O. Box 387

Tice, Florida 33905

Mr. ROLAND STARKEY

Code M 1320

General Electric Co.

Valley Forge Technology Center

P.O. Box 8555

Philadelphia, Pennsylvania 19101

54