FASTING CONFINEMENT EFFECTS ON SHARKS 637 



selachians other than Squalus acanthias. Although the condition of the 

 animals, methods of maintenance, or time in captivity are rarely noted, these 

 may be necessary for evaluating experimental results. The changes described 

 in this study are great enough to significantly affect almost every aspect of 

 the animal's physiology. Alterations in kidney structure would affect any 

 study of kidney function. Rising sodium, potassium, and chloride levels and 

 changing urea levels would presumably affect transport rates of all excretory 

 sites. Alterations in enzyme activity, lipid relationships, and intermediary 

 metabolism would be expected in response to prolonged starvation. Changes 

 in total body water and compartmentalization of fluids are indicated. The 

 assessment of a shark's condition by "activity and color of the skin" 

 (Reznikoff and Reznikoff 1934) or by random selection from a population 

 of individuals of unknown history reduces the reliability of data collected. 

 The following recommendations are indicated. 



1. Attempts should be made to minimize the trauma of capture, and 

 animals should be brought aboard as quickly as possible. Prolonged 

 struggling on a line, in gill nets, or in trawls may affect serum parameters, 

 such as glucose levels, and blood loss may alter others, such as serum 

 proteins. 



2. As the population varies with regard to the nutritional state of 

 individuals, the "ideal" subject would be one with known history prior to 

 the start of an experimental procedure. Thus, adjustment to the conditions 

 of confinement may be a prerequisite for accurate physiological and 

 metabolic studies. Starvation appears to be a factor posing major problems, 

 and acceptance of food may be necessary criterion for "adjustment." Patent 

 (1970) reported an increase in liver glycogen following forced feeding, but 

 experiments conducted upon animals fed ad libitum would more closely 

 approximate the "normal" responses. It may be significant that Rail (1967) 

 described conditions under which Squalus acanthias may be induced to feed. 

 The key factors appear to be a large "volume of tank:size of animal" ratio, 

 and a small number of animals held in the pen. A circular tank may also have 

 been important, since animals swimming around the perimeter have an 

 unrestricted swimming space. 



Rail (1967) reported the water temperature as 13°-15°C. Some disagree- 

 ment exists regarding the temperature tolerance of Squalus acanthias. While 

 Simpson and Ogden (1932) state that "dogfish" die if held at greater than 

 18°C, references may be found describing Squalus held at 27° C (Rasmussen 

 1972) or 23°C (Sudak and Wilbur 1960). In a study of thermal tolerance in 

 marine animals, Huntsman and Sparks (1924) reported that lethal tempera- 

 tures for Squalus ranged from 28.5°C to 29.1°C (when exposed to a rate of 

 increase in temperature of l°/5 min). Many of the animals used in the 

 present study were caught on the surface when the water temperature was 

 17°C, and Lauter, Brown, and Trams (1968) obtained Squalus acanthias for 

 their studies by handline fishing when the water temperature was 17.5°C. It 

 is possible that elevated temperatures affect the animal's adjustment to 

 captivity by altering the metabolic rate and available oxygen. Environmental 



