Munroe: Systematics of western Atlantic Symphurus 
95 
1951; Topp and Hoff, 1972), and on the inner conti- 
nental shelf of South America to about Isla de Flores 
(34°56'S, 55°53'W), Uruguay (Ginsburg, 1951; 
Menezes and Benvegnu, 1976; Menni et al., 1984; 
Correa et ah, 1986). 
Off the southeastern United States and in the east- 
ern Gulf of Mexico, S. diomedeanus is numerically 
the most common tonguefish in depths greater than 
18 and shallower than 80 m. In a study assessing 
potential fishery resources along the southeastern 
United States (Struhsaker, 1969, Appendix B), S. 
diomedeanus was present at more than 50% of shal- 
low stations sampled by trawls and was considered 
to be very common in these areas. In the Gulf of 
Mexico, S. diomedeanus occurs from the southern tip 
of Florida and Dry Tortugas region in the east (Topp 
and Hoff, 1972), to southern Texas and the Gulf of 
Campeche in the west (Hildebrand, 1955; Gaspar- 
Dillanes and Espinosa-Perez, 1989). It has been re- 
ported to be the most common tonguefish between 
37 and 73 m on the southwest Florida shelf (Topp 
and Hoff, 1972), whereas in the Caribbean Sea, this 
species has been collected at continental locations 
off Yucatan (Hildebrand, 1955; Topp and Hoff, 1972; 
this study), Nicaragua, and Panama. It is rare in the 
Antilles with records from only the shallow waters 
south of Jamaica (Caldwell, 1966) and off the Virgin 
Islands (Appendix). In the southern Caribbean, S. 
diomedeanus is taken commonly in shallow seas off 
Colombia and Venezuela (Cervigon, 1966). Along 
northeastern South America, there are numerous 
captures of this species from Guyana to northern 
Brazil. Although this species was recorded as far 
south as Isla de Flores, Uruguay (Ginsburg, 1951), 
Menezes and Benvegnu (1976) noted that when com- 
pared with more northern areas of Brazil, the abun- 
dance of S. diomedeanus diminishes substantially in 
waters south of about Rio de Janeiro. 
Bathymetric distribution Symphurus diomedeanus 
occurs on a variety of inner continental shelf sub- 
strates at depths of 6-183 m (Table 10). The center 
of abundance for this species occurs between 21 and 
80 m, where 284 out of 315 (90%) of the specimens 
were collected. Topp and Hoff (1972) reported a simi- 
lar depth range for S. diomedeanus collected during 
cruises on the west Florida shelf. Most fish they ex- 
amined were taken at 37 m or deeper. These authors 
also noted that S. diomedeanus abundance declined 
noticeably at both the very deepest and the shallow- 
est stations, indicating that it inhabits a rather nar- 
row depth range on the inner continental shelf off 
west Florida. The deepest recorded capture of this 
species is a single specimen (UMML 34377) collected 
at 183 m off Tortugas, Florida (Longley and 
Hildebrand, 1941). Other deep collections of S. 
diomedeanus recorded herein are single specimens 
taken at 145 m and 146 m. 
As noted previously (Topp and Hoff, 1972), this 
species usually does not inhabit shallow inshore or 
estuarine areas. Only three specimens examined in 
this study were taken in waters 20 m or shallower 
(Table 10), with one specimen (UMML 35206) col- 
lected at 6 m off Key Biscayne, the shallowest cap- 
ture depth. Moe and Martin (1965) collected three 
other specimens at 3-5 m off Tampa Bay, Florida. 
Cervigon ( 1966) reported that in Venezuelan coastal 
waters, S. diomedeanus is occasionally collected at 
less than 30 m, but most captures of this species typi- 
cally occur in deeper waters. Occurrence of the small- 
est specimen (33 mm; UMML 35268) at 27 m may 
indicate that newly settled individuals occur in off- 
shore habitats similar to those occupied by adults. 
Ecology On the continental shelf off west Florida, 
Topp and Hoff (1972) collected S. diomedeanus at 
bottom temperatures ranging from 17.5° to 28°C and 
at salinities of 32.3-36.7%o. Springer and Bullis 
( 1956) reported capturing this species on substrates 
with a high mud component. Hildebrand ( 1954) noted 
that in the western Gulf of Mexico the species was 
rarely caught on soft mud bottoms but was more com- 
mon on hard bottoms, such as those comprising the 
snapper banks. Later ( 1955), he noted the capture of 
four specimens in the western Gulf of Mexico on sub- 
strates with a high shell and coral content. Topp and 
Hoff ( 1972 ) collected most specimens off west Florida 
on calcareous substrates, noting also that S. diomede- 
anus was not taken where appreciable proportions 
of quartz sand were present. The majority of speci- 
mens examined in the present study were also col- 
lected on substrates consisting of calcareous mud, 
calcareous sand, and those with a large component 
of shell hash. 
Topp and Hoff (1972) reported that 49 of 140 speci- 
mens of S. diomedeanus examined for diet composi- 
tion contained a broad spectrum of benthic inverte- 
brates. Crustaceans, particularly small crabs, were 
most frequently encountered, followed in importance 
by polychaetes, gastropods, bivalves, gastropod eggs, 
and amphipods. 
Geographic variation Variation in counts of dor- 
sal- and anal-fin rays and total vertebrae for S. 
diomedeanus divided into 13 geographic regions 
(from southeastern United States to Uruguay) was 
comparatively small (Table 28). No significant dif- 
ferences in meristic characters of fishes from any 
segment of the geographic range were evident, al- 
though S. diomedeanus from the southernmost re- 
