FISHERY BULLETIN: VOL. 73, NO. 1 



small teeth approximately unilateral in the jaws 

 (Haedrich 1967). The larvae and juveniles occur 

 mainly in the surface layers of the ocean and are 

 frequently associated with animate or inanimate 

 floating objects. The adults, ranging in maximum 

 size from about 30 to 120 cm, form a diverse group 

 of temperate and tropical species which variously 

 occupy a wide range of depths in coastal and 

 oceanic waters (including mesopelagic and bathy- 

 pelagic levels). The Centrolophidae (six genera) 

 are either coastal or oceanic, the Stromateidae 

 (three genera) are coastal, the Amarsipidae (one 

 genus), Nomeidae (three genera), and Tet- 

 ragonuridae (one genus) are oceanic, and the 

 Ariommidae (one genus) are benthopelagic on the 

 continental shelf and slope. 



The purposes of the present paper are to 1) 

 describe the morphology and histology of the 

 stromateoid' swim bladder, 2) compare the 

 dimensions and capabilities of the stromateoid 

 swim bladder with that of other fishes of similar 

 and different habitats, and 3) discuss the 

 relationship of swim-bladder state and structure 

 to the behavior and mode of life of stromateoids 

 based upon the results of the present and other 

 studies. 



MATERIALS AND METHODS 



The majority of specimens examined (Table 1) 

 for swim-bladder structure and other morphologi- 

 cal detail were preserved although fresh or frozen 

 material of several species was studied. Observa- 

 tions on the behavior of certain species were made 

 and are briefly described in appropriate sections of 

 the paper. 



Specimens in addition to those personally col- 

 lected were obtained from the following institu- 

 tions: British Museum (Natural History), London; 

 Museum of Comparative Zoology, Harvard Uni- 

 versity, Cambridge, Mass.; Institute of Oceano- 

 graphic Sciences, Wormley, England; Natural 

 History Museum of Los Angeles County, Los 

 Angeles, Calif.; Scripps Institution of Oceanog- 

 raphy, La Jolla, Calif.; Southwest Fisheries 

 Center, National Marine Fisheries Service, 

 NOAA, La Jolla; Woods Hole Oceanographic 

 Institution, Woods Hole, Mass.; and Zoological 

 Museum, Copenhagen, Denmark. 



Swim-bladder dimensions were measured with 

 an ocular micrometer in either a dissecting or 

 compound microscope or, in large specimens, with 



96 



Table 1. — Stromateoid specimens examined for swim bladder 

 and other morphological characteristics. 



dial calipers. Swim-bladder and body volumes 

 were determined by displacement and/or, for the 

 former, calculated on the assumption that the 

 bladder was a prolate spheroid (u = 4/3TTab^, 

 where a and b are the major and minor semiaxes 

 (see Capen 1967)). Volume measurements were 

 made from swim bladders that were in most cases 

 well expanded. Ten percent was allowed for 

 shrinkage of preserved material. 



Transverse or longitudinal serial sections of the 

 swim bladder of 13 genera and species were cut at 

 S-jum thickness and stained with haemalum and 

 eosin. 



Buoyancy determinations were made by weigh- 

 ing each fish in air and in water of known temper- 

 ature and salinity. Results are expressed as the 

 percentage of the air weight that each fish 

 weighed in seawater. 



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