JOSEPH T. EASTMAN, Department of Biological Sciences, Ohio University, Athens, Ohio 45701
The fish fauna of the antarctic shelf is unique among marine habitats. The fauna is dominated by a single group of perciform fishes known as notothenioids. In the absence of competition from other fish groups, notothenioids underwent a depth-related diversification involving the alteration of density. Although lacking swim bladders, notothenioids occupy most water column and benthic niches and constitute 90-95 percent of the fish biomass on the antarctic shelf (Eastman 1993). The six families and 95 antarctic species of this endemic suborder may be the marine equivalent of a lacustrine adaptive radiation and the only known species flock of marine fishes (Eastman and Clarke in press). The notothenioid antifreeze glycopeptides, originating from trypsinogen, are a uniquely derived key innovation that may have allowed notothenioid diversification in subzero waters (Chen, DeVries, and Cheng 1997). Thus, the antarctic shelf is an insular evolutionary site, with an endemic fish fauna equally as interesting, but less well known, as those in Lake Baikal in Siberia or the African Great Lakes.
Although fishes were first collected in the southern Ross Sea nearly 100 years ago, the fauna is still incompletely characterized. This was demonstrated during cruise 96-6 (18 December 1996 to 8 January 1997) of the R/V Nathaniel B. Palmer when this vessel was first employed for fishing in the Ross Sea. Although time for fishing was limited, a small but important collection was obtained, including one new species. The effectiveness of the Palmer in towing relatively large commercial bottom trawls was also established. The fishes will be utilized in a continuing study of the evolution and adaptation of the antarctic fish fauna (Eastman 1993).
Fishing was conducted at 12 stations, with additional surface collecting in a tide crack at station 108 (table 1). A variety of gear was used, but a 10-meter-long Marinovich Gulf Coast style flat trawl, a type of otter trawl, was most effective in obtaining maximum familial and species diversity. A summary of the catch is presented in table 2. Taxonomic nomenclature for fishes is that used by Gon and Heemstra (1990), with the exception that the nominal species Cryodraco atkinsoni was recognized as distinct from Cryodraco antarcticus . To ensure accuracy, experts were enlisted to verify identifications of some groups. Artedidraconids were identified by R.R. Eakin, University of New England-Westbrook College Campus, Portland, Maine; zoarcids by M.E. Anderson, J.L.B. Smith Institute of Ichthyology, Grahamstown, South Africa; and rajids by J.D. McEachran, Texas A&M University, College Station, Texas. Voucher specimens were deposited in the museums associated with these institutions (table 2).
The catch yielded 326 specimens representing 8 families and 32 species (table 2). Among the specimens were one new species, seven rare species, two new locality records for the Ross Sea, three records for most southerly occurrences in the southern ocean, and eight new depth records. Notothenioids dominated the catch in terms of number of specimens (76.1 percent) and species richness (84.4 percent). Notothenioids accounted for 77.3 percent of fish biomass at station 93 (75°S) and 91.2 percent at station 119 (77°S).
The new species, a large (250 millimeters standard length) and distinctive artedidraconid of the genus Pogonophryne , will be formally described by R.R. Eakin and J.T. Eastman. It has been deposited in the Smithsonian Institution, National Museum of Natural History, Washington, D.C., under the catalog number USNM 345594.
The notothenioid families Bathydraconidae and Channichthyidae were especially well represented in terms of taxonomic coverage. Ten of 16 bathydraconid species occur in East Antarctica, and nine of these were captured during cruise 96-6. Similarly 10 of 16 channichthyids are found in East Antarctica, and seven of these were obtained.
The catches made with the flat bottom trawl at stations 93 and 119 were noteworthy in that 148 of 326 specimens, 45 percent of the total catch during cruise 96-6, were obtained at these two stations. The 30-minute trawl at station 93 may have been one of the most productive in the history of antarctic ichthyology. Twenty species were collected—44 percent of the 45 fish species known from the entire Ross Sea (Anonymous 1967). In addition to the new species of Pogonophryne , the 19 other species from this station included one rajid, one muraenolepid, two zoarcids, three nototheniids, five bathydraconids, five channichthyids, and two other artedidraconids, Pogonophryne scotti and P. phyllopogon .
After nearly a century of exploration, it is surprising that the southern Ross Sea continues to yield distinctive new species and infrequently collected species. Previous bottom trawling in this area, however, usually employed small Blake trawls that occasionally captured a maximum of 12-14 species per trawl but usually considerably fewer (DeWitt and Tyler 1960; Reseck 1961; Iwami and Abe 1981). Use of a relatively large commercial trawl to scour the bottom on a shallow 300-meter bank may account for the especially great species diversity at station 93. These trawls will be used on future cruises.
I thank A.L. DeVries and J. Turnbull for their efforts in collecting fishes during this cruise. B. Kluckhohn of Antarctic Support Associates and the captain and crew of the R/V Nathaniel B. Palmer contributed greatly to the success of the trawling. J. Barry, J. Grebmeier, and M. Van Woert provided useful information on the bottom and oceanographic conditions at the fishing stations. This research was supported by National Science Foundation grant OPP 94-16870.
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