Munroe: Systematics of western Atlantic Symphurus 
155 
spectrum and variety of organisms that these fishes 
include in their diets (Stickney, 1976). Some inver- 
tebrates exhibit strong substrate preferences and are 
differentially distributed with respect to substrate 
types (Hedgpeth, 1953; 1954; Williams, 1958; 
Butman, 1987). Hence, substrate selectivity (either 
by passive or active means) exhibited by inverte- 
brates that are preferred food sources of tonguefishes 
would in turn be mirrored by tonguefishes through 
their selective foraging activities. This hypothesis is 
also untested, because, beyond descriptive studies for 
those few species where diets have been examined, vir- 
tually nothing is known concerning the relative degree 
(if any, see Toepfer and Fleeger, 1995) of dietary selec- 
tion or preference exercised by these flatfishes. 
Size-related life history information 
Adult western Atlantic symphurine tonguefishes 
span a size continuum from ca. 25 to 320 mm SL, 
encompassing the entire size range within the ge- 
nus. In these waters, both the largest (S. jenynsi, at- 
taining maximum sizes ca. 320 mm and maturing at 
sizes of ca. 120 mm or more) and smallest (S. arawak, 
maximum sizes ca. 50 mm and maturing at sizes as 
small as 25 mm) members of the genus occur. Most 
western Atlantic tonguefishes, however, are interme- 
diate in size, usually reaching maximum sizes 
smaller than 200 mm (usually between 80-180 mm) 
and maturing at sizes between 50 and 110 mm. Al- 
though no western Atlantic tonguefish attains sizes 
large enough to support directed commercial fisher- 
ies, several species have been used when taken in 
industrial fisheries (Roithmayr, 1965). 
Species of Symphurus are the smallest members 
of the Cynoglossidae. For example, adults of five spe- 
cies of Paraplagusia range in size from 184 to 334 
mm SL (Chapleau and Renaud, 1993), whereas adult 
sizes of 49 species of Cynoglossus range between 99 
and 530 mm SL (Menon, 1977). 
Despite superficial similarities in overall external 
morphology and general body plan, western Atlantic 
Symphurus display striking differences in body sizes 
and the relative sizes at which maturity is attained 
in individual species (Figs. 6-9). Although species of 
western Atlantic Symphurus more or less form a con- 
tinuum along a size gradient, marked differences in 
size-related features between species are apparent 
when overall maximum sizes (based on the largest 
specimen observed for the species) and minimum 
sizes at sexual maturity (based only on females) are 
compared (Figs. 6-9). Based on these parameters, 
species were assigned to one of four size categories. 
Dwarf tonguefishes are those with adult sizes rang- 
ing up to ca. 80 mm and attaining sexual maturity 
at sizes usually of 40 mm or less. Six western Atlan- 
tic tonguefishes categorized as dwarf species are (in 
order of increasing maximum size) <S. rhytisma (ca. 
45 mm), S. arawak (ca. 50 mm), S. ommaspilus (60 
mm), S. pelicanus (70 mm), S. pusillus (77 mm), and 
S. minor (78 mm). Symphurus arawak, which ma- 
tures at sizes as small as 25-30 mm, is one of the 
smallest tonguefish species. Only a small number of 
the S. minor studied actually exceeded 70 mm (most 
in fact were smaller than 65 mm), and maturity in 
this species is reached at sizes (29-40 mm) compa- 
rable to those noted for other dwarf tonguefishes. 
Several species of dwarf tonguefishes, such as S. 
arawak, S. ommaspilus , and S. rhytisma, which at- 
tain lengths of only 35-60 mm and mature at sizes 
as small as 25-30 mm, are among the smallest of 
pleuronectiform fishes. The small adult sizes in these 
species are comparable with those of S. lubbocki 
(Munroe, 1990), known only from two mature females 
of ca. 28 mm collected at Ascension Island. Among 
other western Atlantic flatfishes, only the bothid 
Citharichthys gymnorhinos, from the Gulf of Mexico, 
approaches such small sizes, attaining maximum 
lengths usually less than 55 mm and reaching sexual 
maturity at ca. 30 mm (Topp and Hoff, 1972). Other 
small species of flatfishes, such as members of the 
bothid genus Etropus (Leslie and Stewart, 1986), the 
paralichthyid Tarphops (Hoshino 10 ) and perhaps 
some freshwater achirid soles ( Achirus spp.), mature 
at sizes ca. 50-60 mm, and reach maximum lengths 
only slightly greater than this. 
Three diminutive tonguefishes are species reach- 
ing maximum sizes from ca. 80 to 100 mm and ma- 
turing at sizes greater than 40 mm, but usually less 
than 70 mm. Smallest of species in this category is 
S. parvus (maximum lengths ca. 88 mm, maturity at 
40-45 mm). The other species in this category (S. 
ginsburgi and S. nebulosus) attain similar maximum 
sizes (ca. 90 mm) but mature at somewhat larger 
sizes (50 and 60-65 mm) than S. parvus. Diminutive 
tonguefishes inhabit a variety of substrates in rela- 
tively deepwater habitats on the middle and outer 
continental shelf (S. ginsburgi and S. parvus ), or 
outer continental shelf and upper continental slope 
{S. nebulosus). 
Medium-size species reach maximum sizes of ca. 
110 to 150 mm and mature at ca. 70 to 90 mm. Me- 
dium-size western Atlantic species are S. marginatus 
(ca. 146 mm, matures at ca. 79-90 mm), S. billykrietei 
(ca. 113 mm, matures at ca. 80 mm), S. stigmosus 
(ca. 127 mm, matures at ca. 80 mm), S. piger (ca. 
10 Hoshino, K. 1996. Laboratory of Marine Zoology, Faculty of 
Fisheries, Hokaido Univ., 3-1-1 Minato-cho, Hakodate, Hokaido 
041, Japan. Personal commun. 
