610 ECOLOGY AND BEHAVIOR 



The elasmobranchs are interesting in that they appear more susceptible 

 to stress than routine laboratory research animals such as rats, mice, 

 cats, monkeys, and man. Why sharks and rays, an evolutionarily suc- 

 cessful group of animals, should be so susceptible to so many forms of 

 stress, many of which are considered to be so slight as to still render 

 them experimentally normal, is not answered. 



Rasmussen and Rasmussen (1967) 



Selachians that survive the rigors of capture often fail to adapt to pro- 

 longed confinement. Representatives of only 6 of the 17 families of sela- 

 chians have been consistently maintained in captivity for periods longer than 

 a year (Clark 1963). These may be characterized as generalized carnivores 

 found in coastal waters; they represent the more primitive of extant families 

 (White 1937). 



The more specialized members of both the galeoid and the squaloid line- 

 ages fail to adapt to confinement. Those that survive capture cease normal 

 feeding, at least temporarily (Essapian 1962), and most experimental studies 

 have been conducted on animals recently subjected to the traumas both of 

 capture and subsequent starvation. Several authors have stated or implied 

 that the captive population differs from the wild (Rasmussen and Rasmussen 

 1967; Dawson 1933; Esapian 1962; Murdaugh and Robin 1967), but no 

 attempt has been made to determine the significance of the differences. 



This study attempts to assess the effects of confinement and starvation on 

 the spiny dogfish, Squalus acanthias. Captive Squalus are popular research 

 animals and have contributed significantly to our understanding of selachian 

 physiology. The conditions of confinement were chosen to approximate 

 those at a typical marine research facility. 



This report considers the behavioral, histological, and physiological 

 changes that accompanied confinement. These are integrated to provide 

 guidelines for evaluating Squalus as an experimental animal. Understanding 

 the changes brought about by confinement and starvation is vital to evalua- 

 tion of data collected from animals held under these conditions. 



MATERIALS AND METHODS 



Field research was conducted in the Isle of Shoals, off Portsmouth, New 

 Hampshire. A substantial population of Squalus appears here in mid-June, 

 when surface temperatures approach 14° C. 



A variety of capture methods were employed, including gill netting, long- 

 lining, and trawling. Animals obtained through trawling were too severely 

 injured to survive for more than a few hours. Autopsies indicated severe 

 internal injuries and hemorrhaging. 



Animals were held in floating pens, moored in 15-20 feet of water. Median 

 partitions divided the pens into 10 ft X 5 ft X 6 ft (3.0 m X 1.5 m X 1.8 m) 

 compartments. During 1971, animals were identified by notches made in 

 their fins; in 1973, small plastic tags were affixed by metal wires inserted 

 through the first dorsal fin or the caudal peduncle. Tag shape designated the 



