MASTERS OF THE WATER-BONY FISHES 



291 



Fig. 168. Shore eelpont. 



Fig. 169. Northern slippery dick. 



Fig. 170. Pearlfish. 



NORTHERN SLIPPERY DICK: Rissola viaroinata 



Size: Up to 6 inches. 



Distribution: New York to the Gulf of Mexico. 



Identification: Same as for the family. 



Habits: This fish is a burrower in shallow sandy shores. It probably eats 

 invertebrates. 



Similar Species: Several Atlantic species are found in the West Indies and 

 north in warm temperate waters. On the West Coast several species range north 

 to southern California. Herald (1953) reports that a spotted cusk eel, Oto- 

 phidiiim taylori, adapted to captivity quickly. He says that this fish adopts a 

 position standing on its tail on the tank bottom and customarily enters hiding 

 places tail first as does the pearlfish. 



PEARLFISHES: Family Fierasferidae 



These are among the most specialized and interesting of fishes because of their 

 habit of living nonparasitically in the mantle cavities of oysters, where they are 

 sometimes trapped and covered with mother of pearl by their host, or, more 

 often, in the cloaca of a sea cucumber, especially the beche-de-mer. These are 

 small fishes with large heads and a body that tapers off to a point behind. There 

 are several species of the single genus in tropical seas. They are pearly in color 

 and semitransparent. 



pearlfish: Fierasfer affinis 



Size: Up to 5 inches. Usuallv smaller. 



Distribution: Florida to the West Indies. 



Identification: Same as for the family. 



Habits: This fish lives symbiotically in the cloaca of sea cucumbers, or in the 

 shells of molluscs. It is not a parasite, but merely uses these retreats as a home, 

 as a blenny might use a tin can or rock crevice. At night, thev wander from these 

 homes to search out their invertebrate food. They may be captured bv collecting 

 large sea cucumbers and examining them with a probe or cutting them open. 

 Linton (1907) placed a pearlfish in a dish with a large, living sea cucumber and 

 observed that the fish hunted around the dish aimlessly until contact with the 

 sea cucumber was rriade, then forced its way, tail-first, into the cloaca, a feat 

 taking about thirty seconds. 



