The rare and sporadic live capture of 

 stromateoids prevents the development of appro- 

 priate procedures for long-term maintenance. To 

 date, maintenance trials indicate (pers. obs.; R. L. 

 Haedrich pers. commun.) that the fishes will grow 

 rapidly for short periods but then lose interest in 

 feeding and gradually decline in health, especially 

 as the adult stage is reached when pelagic 

 stromateoids generally change their mode of life 

 and occupy greater depths. The initial growth and 

 high conversion efficiency followed by the reduced 

 growth and lowered efficiency of/, lockingtoni are 

 consistent with these observations. 



The apparent adaptive strategy for pelagic exis- 

 tence of juvenile/, lockingtoni involving locomotor 

 behavior, buoyancy, and lipid content parallels 

 that described (Bone and Brook 1973) for juvenile 

 (85-200 mm SL) Schedophilus medusophagus 

 from the North Atlantic. There is no swim bladder 

 in either species in this size range, the lipid con- 

 tent of both is low and both species are slightly 

 negatively buoyant (weight in water 0.35-0.53% of 

 weight in air for S. medusophagus). In each case, 

 the pectoral fins are important in generating both 

 thrust and lift. 



The two species also appear to undergo similar 

 changes in mode of life as the adult stage (about 

 >200 mm SL) is reached and the fishes become 

 independent of floating objects and occupy greater 

 depths in the water column. Data, particularly on 

 adultS. medusophagus, indicate that certain den- 

 sity reducing mechanisms (increase in lipid and 

 water content, decrease in dense tissues, i.e., mus- 

 cle and bone) are more prominent than in the 

 juvenile stage. Horn (1975) found that a large (285 

 mm SL) specimen of S. medusophagus was neut- 

 rally buoyant, swam in a slow, near-anguilliform 

 manner and had relatively small pectoral fins of 

 minor importance in generating thrust and lift. 

 Lipid content in the same specimen was relatively 

 high, especially in the bones (spine 23% and skull 

 21% lipid by dry wt) (Lee et al. 1975). 



Data are yet insufficient on adult/, lockingtoni 

 to fully demonstrate parallel strategies in the two 

 species. The relative length of the paired fins of 

 Icichthys, however, decrease with age (Haedrich 

 1966) at a rate and magnitude similar to that in S. 

 medusophagus. In addition, the muscles of large 

 (270 mm SL) Icichthys are soft and loosely packed 

 as in Schedophilus. Data on buoyancy and lipid 

 content of adult /. lockingtoni are needed to test 

 the hypothesis. 



Acknowledgments 



Special recognition is due Wayne S. White who 

 dexterously captured the/, lockingtoni and helped 

 identify the medusa with which the fish was as- 

 sociated. I thank Charles F. Phleger for determin- 

 ing the lipid content and the captain and crew of 

 the RV Nautilus for facilitating a safe open-water 

 diving operation. 



Literature Cited 

 Bone, Q., and C. E. R. brook. 



1973. On Schedophilus medusophagus (Pisces: 

 Stromateoidei). J. Mar. Biol. Assoc. U.K. 53:753-761. 

 FITCH, J. E. 



1949. Some unusual occurrences of fish on the Pacific 

 Coast. Calif. Fish Game 35:41-49. 

 FITCH, J. E., AND R. J. LAVENBERG. 



1968. Deep-water teleostean fishes of California. Univ. 

 Calif. Press, Berkeley, 155 p. 

 HAEDRICH, R. L. 



1966. The stromateoid fish genus Icichthys: notes and a 

 new species. Vidensk. Medd. Dan. Naturhist. Foren. 

 129:199-213. 



1967. The stromateoid fishes: systematics and a classifica- 

 tion. Bull. Mus. Comp. Zool. Harv. Univ. 135:31-139. 



Hastings, W. H., and l. M. Dickie. 



1972. Feed formulation and evaluation. In J. E. Halver 

 (editor), Fish nutrition, p. 327-374. Academic Press, NY. 



Horn, m. h. 



1975. Swim-bladder state and structure in relation to be- 

 havior and mode of life in stromateoid fishes. Fish. Bull., 

 U.S. 73:95-109. 



Lee, R. F., C. f. phleger, and M. H. Horn. 



1975. Composition of oil in fish bones: possible function in 

 neutral buoyancy. Comp. Biochem. Physiol. 50B:13-16. 

 MANSUETI, R. 



1963. Symbiotic behavior between small fishes and jel- 

 lyfishes, with new data on that between the stromateid, 

 Peprilus alepidotus, and the scyphomedusa, Chrysaora 

 quinquecirrha. Copeia 1963:40-80. 



MAUL, G. E. 



1964. Observations on young live Mupus maculatus 

 (Gunther) and Mupus ovalis (Valenciennes). Copeia 

 1964:93-97. 



Phillips, A. M., Jr. 



1972. Calorie and energy requirement. In J. E. Halver 

 (editor), Fish nutrition, p. 1-28. Academic Press, N.Y. 

 TIEMEIER, O. W., C. W. DEYOE, A. D. DAYTON, AND J. B. SHRA- 

 BLE. 



1969. Rations containing four protein sources compared at 

 two protein levels and two feeding rates with fingerling 

 channel catfish. Prog. Fish Cult. 31:79-89. 



MICHAEL H. HORN 



Department of Biology 

 California State University 

 Fullerton, CA 92634 



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