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 



