AAZPA 1984 ANNUAL PROCEEDINGS, PAGES 317-324

THE GREAT WHITE SHARK IN CAPTIVITY: A HISTORY AND PROGNOSIS

John C Hewitt, Aquatic Biologist, Steinhart Aquarium California Academy of Sciences, San Francisco, California

The history of the white shark, Carcharodon carcharias in captivity has not been a long or successful one. Of the approximately 30 individuals placed in captivity, the longevity record is only 16 days (Sea World, San Diego, August 1981), and no white shark has ever fed voluntarily while in captivity. In most cases it could be said that all these captive sharks were merely in the process of dying, with some taking longer than others.

CAPTURE AND TRANSPORT

The scenario seems to be quite similar in many instances. A small white shark is caught by a local commercial fisherman and, near death, transported to a nearby marina. In spite of careful attempts to keep the animal alive, this transport process further stresses the already debilitated shark. If still alive, an aquarium or oceanarium is called, and the animal is usually sold for a rather substantial sum of money. During the capture and sale process, a considerable amount of time passes before trained professional aquarists ever touch the animal. If stil1 gilling, the shark is then transported as rapidly as possible and placed in its ultimate destination. All too frequently either the transport techniques and equipment, or the targeted facility are inadequate in varying degrees in providing for the sharksÕ physiological needs. The result is that the shark labors at swimming for hours or days, frequently running into walls, glass, and other obstructions until it drifts to the bottom -- its final resting place. Further attempts at resuscitation or resurrection are futile, and the shark soon expires.

The reason for this lack of success are almost always related to the stresses associated with capture, transport and acclimation to the designated facility. A generalized failure to meet the stringent physiological requirements of this highly specialized animal is apparent. By inspecting the problems incurred in previous case histories of captive white sharks, and by providing for this animalÕs known and suspected requirements, we at Steinhart Aquarium feel that these obstacles can be overcome and successful maintenance and longevity achieved. 


Of the approximately 30 white sharks captured for display, most were caught in gill nets or trammel nets. A few were caught with purse seines, longlines, and infrequently by hook and line. On only three occasions has the institution attempting to keep a white shark actually mounted an expedition and captured the animal first-hand: Sea World of San Diego in 1971, the Sea World of Florida expedition to Sandy Hook, New Jersey in 1980, and the Steinhart Aquarium expedition to Ventura, California in 1983. On all other occasions the animal was caught incidental to fishing activities of other parties.

PHYSIOLOGICAL PROBLEMS

Due to the method in which gill nets function, the length of time the white sharks are held in the net, and the time elapsing prior to delivery of the shark to aquarium personnel, it is not surprising that these animals are frequently very near death upon arrival at a maintenance facility. Gill nets snare and entangle their prey holding them motionless, and in so doing create a mu1titude of physiological problems for the ordinarily free-swimming white shark.

White sharks, and other sharks which swim continuously from birth until death, are considered to be 'obligate ram ventilators'. This means that although some oral respiratory motion is present (J. E. McCosker, pers. comm.) they pass water over their gills primarily by opening their mouths while swimming. Inspection indicated that like tunas and skipjack, they probably lack the oral valves and pumping apparatus necessary to move sufficient volumes of water over their gills while stationary (Brown and Muir, 1970). Even in fish that do not rely on ram ventilation, forward motion may augment gill ventilation significantly (Hoar and Randall, 1978).

The result of being held stationary and therefore being unable-to breathe properly, coupled with the oxygen debt incurred during the inevitable struggling with the net, can cause acute respiratory distress and possible failure. When respiratory inadequacy occurs, muscle and blood chemistries are negatively affected as well. This, in turn, hinders the ability of the gills to take up oxygen from whatever water is being passed to the gill filaments. Muscle tissues are forced to function anaerobically, causing a pooling of this lactic acid ridden blood in the tissues since contractions of skeletal muscle probably create a force which drives blood back to the heart (Satchell, l965.) The veins entering the caudal vein in the postpelvic region have valves which prevent reflux of blood into the segmental vessels. The caudal vein is encased in cartilage, and the contracting muscles squeeze all the vessels in that region except the caudal vein, propelling blood from the arterial to the venous side of circulation (Hoar and Randall, 1970). The resulting lactic acid buildup immobilizes the ordinarily aerobically functioning red swimming muscle, and the white muscle as well, thus preventing swimming activity of any kind. The overall synergistic effects of these occurrences, if not alleviated, will rapidly cause death.

A further physiological complication which can occur, and which has both immediate and long—term effects is the depletion of energy reserves in the form of muscle glycogen. This depletion inevitably occurs as the animal attempts to free itself from a net, or during other vigorous activity related to its capture. Studies have shown that teleosts rapidly use muscle glycogen during vigorous muscular activity, and it frequently takes 24 to 48 hours, or longer for glycogen to return to resting—state levels even under ideal conditions (Black, et. al., 1962). Studies in progress at Steinhart Aquarium indicate that in white sharks and other elasmobranchs, the rates of muscle glycogen depletion and restoration are similar to that found in other fishes (Hewitt, in preparation). This is an important consideration when transporting and introducing the shark to the display. To expect a white shark to immediately swim continuously in a new environment, after thoroughly exhausting its energy reserves during the capture process, is unreasonable. In light of this, the previously popular practice of 'shark walking' used to revive a lethargic animal would probably be detrimental to the restoration of muscle glycogen levels. Walking a shark does assist the ram ventilation process, and possibly the return of venous blood to the heart, but the technique can hardly be considered ideal. Shark walking requires excessive handling and does not approximate actual swimming speed. It also may inhibit natural body movements, and result in additional stress. An alternative procedure will be discussed in a later section.

Recent findings concerning the warm-bodied nature of white sharksÕ red muscle tissue (Carey et al 1982) support the suggestion that the muscle physiology of these and other elasmobranchs is an even more important function to consider in the captive animal. It is a function which must be restored to a nearly normal state for long-term survival.

NEW STUDIES AND EXPERIMENTAL METHODS

At Steinhart Aquarium we have handled five small white sharks in the last few years, the latest being in August 1983. These experiences, and evaluations of other institutionsÕ attempts have enabled us to develop techniques which we feel will overcome the difficulties encountered previously. 


Restoring adequate respiratory function in the newly caught and subsequently stressed white shark is the most immediate concern. Super—oxygenated water helps create a high differential between partial pressures of oxygen in the shark blood and the water, and thus facilitates transport of gases across gill membranes. This, however, is not in itself sufficient. In order to allow ram ventilation to occur, we developed a specialized 'raceway' transport container in which we can create a three knot unidirectional current (Fig. 1). By tethering the shark with a specially designed harness (fitting around the body anterior to the first dorsal fin and posterior to the pectoral fins) and positioning it so that the current flows from head to tail, the animal can ram ventilate by merely opening its mouth. Tests conducted at Steinhart Aquarium (Hewitt, in prep.) showed that four to five times the water volume is passed over the gills per unit time in this manner than by letting the shark pump the water using buccal respiratory movements alone. A variety of methods have been used in several design forms in creating a raceway box, and refinements are still under way. The latest design resembles in concept the fish exercise chamber described by Beamish (1966), with some modification. Keep in mind however that the desired current effect is the important factor, regardless of the means by which it is achieved.

The maintenance of proper blood pH and chemistry has been stabilized by intravenously infusing the live animal with a combination of amino acids, B vitamins, electrolytes, and sodium bicarbonate in a 2.5% dextrose and saline solution. To insert the I.V. apparatus make a 1.5 cm long by 1.0 cm deep incision dorso—ventrally through the lateral line at least two thirds of the way back to the tail, severing the lateral cutaneous vein. The lateral cutaneous vein drains the lateral muscle segments of the body, and runs directly under the skin, parallel with and ventral to the lateral line groove. It extends from the middle region of the caudal fin forward, and joins the subscapular sinus. This in turn connects with the sinus venosus (Daniel, 1928). Using a ÔVenocath 16Õ (Abbot Laboratories, Chicago, IL) I.V. catheter (without the needle), and by depressing the posterior edge of the incision, the catheter can be inserted anteriorly by hand. Best results are obtained by inserting the catheter its full length, and securing it with one or two sutures to prevent withdrawal. This procedure becomes fairly routine with practice and although some superficial hemorrhaging will result with the initial incision, it quickly subsides.

The lateral cutaneous vein provides the ideal location for infusion of these substances since mixing with venous blood will occur in the sinus venosus prior to entry into the heart and gill arches. This facilitates oxygen uptake, lactic acid neutralization, and carbon dioxide discharge. A 2.5% dextrose and sodium chloride isotonic solution is the preferred medium over RingersÕ lactate since the dextrose will aid in muscle glycogen restoration, and since RingersÕ lactate is contra—indicated in the hyper—lactic acidotic conditions which frequently exist in the newly captured white shark. Blood gas studies conducted on small white sharks and mako sharks, Isurus oxyrinchus, during the summer of 1983, confirmed the effectiveness of this technique (Hewitt, in prep.).

The method of solving the problem of depleted energy reserves has already been described in part. As stated previously, muscle glycogen could take as long as 48 hours or more to return to resting—state levels. The infusion of dextrose should, however, continue until such levels are reached. We will accomplish this by keeping the shark in the transport container with the unidirectional current, super—oxygenated water, and I.V. infusion in place for as many days as necessary for recuperation. Periodic measurements of muscle glycogen, blood pH and dissolved gasses will be made to determine when these parameters are acceptable. 


Recently, some researchers have reported success using corticosteroid injections to revive and stimulate sharks during and after transport, however the long—term value of such treatment is questionable. By design, these steroids do briefly elevate serum glucose levels and liver glycogen levels, but do so at the expense of muscle glycogen, electrolyte balance, and calcium levels (Schering Corp. Kenilworth, NJ). Long—term effects could prove more detrimental than beneficial depending upon the condition of the shark. Certainly, if attempting to restore exhausted muscle glycogen, steroids would be of questionable value.

SUMMARY

It is encouraging to note that results from blood gas studies and muscle glycogen tests on three white sharks during the summer of 1983 tend to support the theories outlined here, although our sample size is limited. Previously the transport situation has been interpreted as detrimental and every attempt was made to get the animal to the targeted facility and out of the transport container as rapidly as possible. If, however, the animalÕs physiological needs are met in the transport situation, and recuperation is ongoing, it would be counter;productive to prematurely terminate the 'intensive care' environment.

Results obtained thus far suggest that Steinhart Aquarium has made significant advances in understanding the problems involved in white shark transport, and overcoming them. We will continue to refine and improve our techniques and we look forward to future opportunities to display these highly specialized and fascinating creatures.

Although it is difficult to establish a population estimate of the white shark, it is likely that their numbers will continue to expand with those of their main prey items, the elephant seal (Mirounga angustirostris), the harbor seal (Phoca vitulina), and the California sea lion (Zalophus californianus) (McCosker, 1984). As white shark numbers increase, the opportunities for study and display should increase as well. Similarly, as our knowledge and experience grows, the prognosis becomes brighter and more positive.

ADDENDUM

In June and July of 1984 the Steinhart Aquarium returned to Ventura California in an attempt to capture another small white shark. After sixteen days of fishing in that area, a small (1.5 meter) female specimen was obtained from a gill net fisherman. The animal had been captured approximately two miles off the beach in a monofilament halibut gill net, and was subsequently towed into Ventura harbor. Upon its arrival at the dock, it was tied by the tail, and hung in the water (head down) for approximately four hours until staff biologists arrived on the scene. Typically, the animal was very stressed, and exhibited many open lesions and abrasions from the capture net and transport. It was exhibiting respiratory movements, and swimming motion when stimulated, but was relatively weak and only moderately responsive.

The animal was loaded into the transport vehicle, and fitted into the specially designed harness mentioned previously in this paper. The unidirectional current with superoxygenated water was operational, and the animal was subsequently transported back to the Steinhart Aquarium. Due to mechanical breakdown of the transport vehicle, and the necessity for frequent stops to check on the condition of the fish (only one biologist was present) the total elapsed time from obtaining the shark, to arrival at the aquarium was sixteen hours.

Although the animals condition was much improved upon arrival at the aquarium, the transport was less than ideal for the following reasons; 1) Although the shark harness was fitted tightly, the fish was able to break free during episodes of violent swimming activity. 2) Continuous monitoring of the animals condition and behavior was not possible with only one biologist present. 
3) Scientific samples of blood and muscle tissues were not processed and analyzed since the transport occurred on a three day holiday weekend, and local laboratories were not functioning at full capacities.

The white sharks condition improved continually during the first 36 hours of confinement, but the following 40 hours produced a gradual decline in overall vitality, and the fish succumbed. Although not ultimately successful, this attempt provided additional valuable data and experience, and proved very enlightening. It appeared that the theories outlined previously do have merit, though the technical execution of these theories in this instance could have been improved. We are continuing to evaluate and modify our equipment and techniques, and are anxiously awaiting additional opportunities to work with this species. 


The Steinhart Aquarium is planning expeditions to the Farallon Islands in the fall of 1984, and to South Australia in early 1985 to conduct additional studies on pathological and physiological effects of stress during capture and transport in the white shark. In addition these studies are being expanded, and will include the electrophoretic analysis of the plasma proteins and hemoglobins of white sharks in different parts of the world in order to gain greater insight into the population biology of this fascinating animal.

LITERATURE CITED 


Beamish, F.W.H. 1966. Swimming endurance of some northwest Atlantic fishes. 3. Fish Res. Bd. Canada. 23(3):341-347.

Black, E.C., A.R. Connor, IC. Lau, and W. Chiu 1962. Changes in glycogen, pyruvate and lactate in rainbow trout (Salmo gairdneri) during and following muscular activity. J. Fish Res Bd. Canada. l9(3):409-436.

Brown, C.E. and Muir, B.S. 1970. Analysis of ram ventilation of fish gills with application to skipjack tuna (Katsuwonus pelamis).

Carey, F.G., C. Gabrielson, J.W. Kanwisher and 0. Brazier. 1982. The white shark Carcharodon carcharias, is warm-bodied. Copeia, 1982:254-260.

Daniel, J.F. 1928. The Elasmobranch Fishes. University of California Press, Berkeley, CA, 332pp.

Hoar, W.S. and RandallÕ, P.3. 1970. Fish Physiology, vol. 4, Academic Itess, NY, 532p.

--- Fish Physiology, vol. 7, Academic Press, NY, 576p.

McCosker, J.E. 1984. White shark attack behavior: predator and prey strategies. Bull. So. Calif. Acad. Sci., in press.

Satchell, C.H. 1965. Blood flow through the taudal vein of elasmobranch fish. Australian 3. Sci., 27:241-242.