FISHERY BULLETIN: VOL. 74, NO. 4 



another except for the abundance of Scrge^tes 

 aflaiiticKs and Sergio grand is (Sund 1920) in 

 Bermuda relative to Fuerteventura (the Fuerte- 

 ventura material all came from a single cruise and 

 may have lacked some of the less-abundant 

 species). More surprising, the Atlantic sergestids 

 were very similar to the Hawaiian species, par- 

 ticularly the half-red types. "Sergestex cornicidum 

 Kr^iyer 1855"' replaced its close relative, S. erectits 

 in the Atlantic, and two rare Bermuda species, S. 

 edirardsii Kr6yer 1855 and Sergia talismaui 

 (Barnard 1947), had close relatives, Sergesfes 

 c())isohri H IIS and Sergia fidgens, in Hawaiian 

 waters; otherwise, all the half-red species in the 

 two Atlantic studies also occurred in the present 

 study. There were some differences in abundance 

 and vertical distribution, partly real and partly 

 due to differences in sampling. Sergestes vigilax 

 was more abundant than 5. armotiis in the Atlan- 

 tic studies, and S. sargassi was more abundant 

 than 5. pecfiuotiis; the opposite was true in 

 Hawaiian waters. S. atlaiificus was more abun- 

 dant near Bermuda and less abundant near Fuerte- 

 ventura than near Hawaii. Sergestes coniiciiliou 

 was more broadly distributed at night than its 

 Hawaiian counterpart, S. ereetus. The biggest 

 differences were the rarity or absence in the 

 Atlantic collections of the S. oriental is types and 

 the half-red Sergia species, both of which were 

 abundant in Hawaiian waters. Still, the similar- 

 ities between the subtropical Atlantic and Pacific 

 were considerable: one or more large species with 

 short third maxillipeds and with fairly deep 

 nighttime distributions, one or two smaller species 

 with short maxillipeds and living shallower at 

 night (in Bermuda), and a variety of species with 

 long maxillipeds occurring in closely related 

 groups of large and small species. 



The all-red sergestids also showed similarities 

 between the subtropical Atlantic and Pacific, 

 although the parallelism was not as striking as in 

 the half-red types. Sergia ten u irem is was found in 

 all three areas. The role of S. gardineri was filled 

 in the Atlantic by the closely related S. splendens 

 (Sund 1920). It was somewhat larger than 5. 

 gardineri, exceeding 11 mm CL, but had no po- 



■'Crosnier and Forest (1973) have reviewed the systematics of 

 Atlantic species of Yaldwin's "Sergestex coniiciiliini" species 

 group. They replaced S. coniiciiliini Kreiyer with S. heu^eni 

 (Ortmann 1893) and three new species-S. parasi'miiiiidux, S. 

 pediformiff, and S. curratux. Donaldson's figure of 5. coniiciiltnu 

 corresponded to S. curratuf:. Foxton gave no drawings of S. 

 corniculinii, but a later study in the same area, Foxton and Roe 

 (1974) found S. Iienseni and S. ciirvatiig. 



tential competition in the 10- to 15-mm CL size 

 range like the Hawaiian S. higemmea. The nearest 

 Atlantic equivalents of S. ineqiialis and S. bisul- 

 eata, respectively S. robusta (Smith 1882) and S. 

 grandis, lived much deeper at night, in the 400- to 

 600-m zone, which was nearly devoid of sergestids 

 around Hawaii. Sergia filicta (Burkenroad 1940) 

 may be the Atlantic counterpart of S. laminata, 

 but very little is known about either species. 

 Sergia japoniea (Bate 1881) had no Hawaiian 

 equivalent, and S. maxima had no Atlantic 

 equivalent. Neither Atlantic study mentioned 

 Petalidium, so it is unclear whether there is an 

 Atlantic counterpart to the Hawaiian Petalidium 

 siispiriosum {P.faliaceiim Bate 1881 occurs in the 

 South Atlantic (Kensley 1971) ). Both oceans thus 

 contain an all-red assemblage consisting of one or 

 more nonmigrators, a small, abundant species 

 with a shallow nighttime range, and several larger 

 species living deeper at night. In general, the 

 Hawaiian area appears to have more half-red and 

 fewer all-red sergestid species than the sub- 

 tropical Atlantic. 



While the parameters of Table 8 indicate that 

 Hawaiian sergestids have partitioned the mid- 

 water environment, this study has left unclear the 

 ecological significance of most of the parameters. 

 Differences in size, length of third maxilliped, and 

 nighttime vertical range are presumably related 

 to diet, but the data on feeding show little dietary 

 specialization other than the ability of some 

 species to eat submillimeter-sized zooplankton. A 

 more elaborate study may reveal more subtle 

 variations in diet, perhaps related to vertical 

 distribution of prey or differences in hunting 

 strategies. Daytime vertical distribution and color 

 pattern seem most likely related to predation. 

 Virtually nothing is known about predation on 

 Hawaiian sergestids. The division of half-red 

 sergestids into species with organs of Pesta and 

 species with lensed cuticular photophores has an 

 unknown ecological significance. Cuticular photo- 

 phores are fixed in position, but I have observed 

 sergestids with organs of Pesta rotating them 

 through nearly 180°, maintaining a vertical orien- 

 tation of the photophores regardless of the atti- 

 tude of the animal (see also Omori 1974). Studies of 

 live sergestids may reveal differences in behavior 

 between the two groups related to the need for 

 ventral countershading. Hawaiian sergestids ap- 

 pear to occupy distinct niches, but the niches 

 cannot be defined yet in an ecologically meaning- 

 ful way. 



834 



