Fishery Bulletin 96(1 ), 1998 
1 12 
species include copepods, amphipods, ostracods, 
cumaceans, brachiopods, crabs, polychaetes, and pele- 
cypods. The most extensive study of food habits of 
this species (Stickney, 1976) reveals that S. plagiusa 
of all sizes fed on over 40 different plant and animal 
taxa but primarily consumed benthic molluscs, small 
crustaceans, and organic matter. Plant detritus was 
only a minor component of the diet, indicating this 
material was not actively sought as a nutrient source. 
Possibly, <S. plagiusa benefit from this food source, 
however, because low levels of cellulase activity oc- 
cur in the digestive tract of this species (Stickney 
and Shumway, 1974). About one-half of the 588 
tonguefish examined contained sand grains in their 
digestive tracts, implying that feeding is nondirected, 
senses other than vision are used in food capture, 
and food selection is not as precise as in other flat- 
fishes (Stickney and Shumway, 1974). In a Louisi- 
ana estuary, juvenile S. plagiusa (10-49 mm) col- 
lected near the marsh-edge environment fed prima- 
rily on epibenthic and hyperbenthic harpacticoid 
copepods (Toepfer and Fleeger, 1995). Other lesser 
important items ingested by these fishes were poly- 
chaetes, bivalves, amphipods, and tanaids. Infaunal 
organisms such as nematodes and foraminiferans 
were rare in diets of these juvenile tonguefishes. 
Little is known about which fishes prey upon S. 
plagiusa. However, blackcheek tonguefishes consti- 
tute a minor component of the diets of both juvenile 
(Meyer and Franks, 1996) and adult (Franks et al., 
1996) cobia, Rachycentron canadum, in the north- 
central Gulf of Mexico, and elsewhere (Smith 8 ). 
Throughout its geographic range, S. plagiusa ap- 
parently has a protracted spawning season coincid- 
ing with periods of seasonal thermal maxima. Based 
on occurrence of larvae in plankton collections, 
spawning occurs in late spring and throughout the 
summer period in Chesapeake Bay (Olney and Grant, 
1976). Hildebrand and Cable (1930) reported a 
spawning season extending from May to October, 
with peak spawning probably occurring in June, for 
S. plagiusa in North Carolina waters. More recently, 
Hettler and Barker (1993) collected S. plagiusa lar- 
vae during monthly sampling from May through 
January in inlets at two barrier islands off North 
Carolina. Peak densities of S. plagiusa larvae, however, 
occurred in August and September. No larvae of this 
species were collected February through April. Reichert 
and Van der Veer (1991) reported that settling of S. 
plagiusa juveniles in a Georgia estuary occurred on 
muddy substrates from mid-May and extended at least 
8 Smith, J. 1994. Southeast Fisheries Science Center, National 
Marine Fisheries Service, NOAA, Beaufort, NC 28516. Per- 
sonal commun. 
into September. Off Tampa, Moe and Martin (1965) 
reported collecting ripe fish ( 145-168 mm) from March 
through June, whereas on the west Florida shelf, Topp 
and Hoff (1972) noted a protracted spawning season 
beginning as early as February and continuing to Sep- 
tember. Shealy et al. (1974) noted a lower abundance 
of this species in the South Edisto River during May to 
August, which they believed probably coincided with 
seaward spawning migration of adults. 
Hildebrand and Cable (1930) described larval de- 
velopment purportedly of this species, but Olney and 
Grant (1976) reported that the specimens on which 
this description was based apparently included more 
than one species. Working with specimens taken from 
plankton collections in lower Chesapeake Bay, where 
S. plagiusa is the only tonguefish known to occur, 
Olney and Grant (1976) provided a more accurate 
description of larval stages and development of this 
species. In that study, recently hatched larvae (1.3- 
2.9 mm NL) represented the majority of the S. 
plagiusa larvae taken, and these were most abun- 
dant in the deepest and most saline portions of the 
Bay. In fact, 76% of all tonguefish larvae taken were 
found in salinities of over 23%e, and no larvae were 
collected at stations having an average salinity less 
than 16.5%e. Olney and Grant (1976) also emphasized 
that large estuaries may be more significant spawn- 
ing areas for S. plagiusa than previously reported. 
Reichert and Van der Veer (1991) reported that in a 
tidal creek of Duplin River estuary, Georgia, all lar- 
vae of S. plagiusa collected in plankton samples were 
postmetamorphosed juveniles. Settlement occurred 
at sizes as small as 9 mm TL (range 9-13 mm TL), 
and most specimens (70%) were taken in extremely 
shallow water (usually 1.5 m or less). 
Geographic variation Variation in meristic features 
among S. plagiusa segregated into seven areas of the 
geographic range was slight (Table 31). No clinal 
trends in variation were evident for any features 
examined, although counts of dorsal- and anal-fin 
rays and total vertebrae for S. plagiusa collected in 
areas of the southeastern U.S. and Gulf coasts were 
slightly higher than, but not significantly different 
from, those of S. plagiusa collected off Mexico. Counts 
for specimens from the Bahamas were lower than 
those of S. plagiusa from continental areas, but a 
small sample size (n=5) from this region prevented 
detailed comparisons. Ginsburg (1951) also found 
comparatively little geographic variation in meris- 
tic features for S. plagiusa he examined. He analyzed 
counts of dorsal- and anal-fin rays for fishes segre- 
gated into three geographic regions, Gulf of Mexico, 
West Florida (Key West to Tampa), and southeast- 
ern United States. Symphurus plagiusa from the 
