356 



would be inflated compared with 

 those calculated for an older year 

 class. 



Sex ratio of tonguefishes 

 sampled during this study devi- 

 ated from 1:1 mostly due to large 

 single-sex catches of females dur- 

 ing the summer months in the 

 lower Bay. In lower Chesapeake 

 Bay, apparently some spatial 

 separation of the sexes occurs 

 (Terwilliger, 1996). Here, dense 

 concentrations of female black- 

 cheek tonguefishes were com- 

 monly found in the deeper areas, 

 and fewer males were taken in 

 the same trawls. Among sympa- 

 tric species of pleuronectiforms, 

 the hogchoker also reportedly 

 displays bathymetric separation 

 of the sexes in tributaries of 

 Chesapeake Bay during the sum- 

 mer months prior to spawning 

 (Mansuetti and Pauly, 1956), 

 when females occupy grass beds 

 and shoal regions, while males 

 are surmised to occupy deeper ar- 

 eas withm the estuary. This pattern of habitat seg- 

 regation by adult hogchokers, however, was not evi- 

 dent in the study conducted by Koski (1978) in the 

 Hudson River, although he noted that although the 

 overall sex ratio for fishes examined did not differ 

 from 1;1, some individual trawl catches were domi- 

 nated by or consisted entirely of one sex. Significant 

 differences in the sex ratios of catches of other 

 tonguefishes have also been reported. Seshappa and 

 Bhimachar ( 1955) noted that sex ratios of catches of 

 Malabar sole during the spawning period were mark- 

 edly different than those made during other times of 

 the year and attributed these differences to differ- 

 ential behavior of the two sexes during their spawn- 

 ing migrations. Hoda and Khalil ( 1995) also reported 

 skewed sex ratios (1.0:2.55 males to females) for 

 catches of^ Cynoglossus arel, whereas those (1.16:1) 

 for C. bilineatus were not significantly different from 

 1:1. A skewed ratio (1.56:1) favoring females over 

 males was also found for C. semilaevis (Meng and 

 Ren, 1988). Although some studies have inferred 

 spatial differences in movements of the different 

 sexes of cynoglossid tonguefishes based on fisheries 

 catch data, it is difficult to draw any general conclu- 

 sions from these data. Just as we lack reliable docu- 

 mentation concerning spatial movements for the two 

 sexes of blackcheek tonguefish, directed studies pro- 

 viding the detailed information necessary for inter- 



Figure 10 



Catch curve for blackcheek tonguefish, Symphurus plagiusa. collected by otter 

 trawl in lower Chesapeake Bay and major lower tributaries, 1993-95. Numbers 

 above plot represent numbers at each age. 



preting adult movements of any of these other 

 cynoglossid species have yet to be performed. 



North temperate estuaries, such as Chesapeake 

 Bay, are rigorous physical systems well known for 

 environmental extremes in temperature, salinity, and 

 dissolved oxygen, and for strong seasonal cycles of 

 primary and secondary production. However, the 

 extensive distribution within the Bay and its tribu- 

 taries of shallow, soft bottom sediments presents con- 

 siderable amounts of suitable habitat for flatfishes. 

 Twelve species of flatfishes have been recorded from 

 the Bay (Murdy et al., 1997). The unique geographi- 

 cal location of Chesapeake Bay at the northern end 

 of a warm temperate and southern end of a cold tem- 

 perate region (Briggs, 1974) may account for the oc- 

 currence within the Bay of diverse faunal compo- 

 nents, which have either warm or cold water affini- 

 ties. Among pleuronectiforms inhabiting Chesapeake 

 Bay, for example, are six species representing five 

 different families (Cynoglossidae, Achiridae, Para- 

 lichthyidae, Scophthalmidae, and Pleuronectidae). 

 This assemblage includes representatives of families 

 whose species occur primarily in cold temperate 

 or boreal areas (Scophthalmidae, Pleuronectidae) or 

 in warm temperate and tropical regions (Cyno- 

 glossidae, Achiridae, Paralichthyidae). Of the spe- 

 cies occurring within Chesapeake Bay are blackcheek 

 tonguefish, hogchoker, and smallmouth fiounder. 



