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Fishery Bulletin 97(2), 1999 



females usually growing larger than males. In the 

 Chesapeake Bay population, male and female 

 blackcheek tonguefishes attain similar maximum 

 sizes (mean value for oldest females=181.2 mm TL; 

 mean value for oldest males=177.8 mm TL). In sum- 

 marizing size information for blackcheek tongue- 

 fishes collected throughout the geographic range of 

 the species, Munroe (1998) also reported no signifi- 

 cant size differences between males (to 174 mm TL) 

 and females (to 172 mm TL). For 23 other species of 

 western Atlantic tonguefishes, females reached 

 larger sizes than males in 11 of these species, in six 

 others a larger size was reported for males, whereas 

 in seven other species similar maximum sizes were 

 attained by both sexes (Munroe, 1998). However, 

 since no age estimates have been made for these other 

 species of Syryiphurus. comparative data on dimor- 

 phism in lengths at age for these symphurine 

 tonguefishes are unavailable. For other cynoglossids 

 with accompanying age data, considerable variation 

 exists in the degree of sexual dimorphism evident in 

 sizes attained by the sexes. In the Malabar sole 

 iCynoglossus serriifasciatus) off India, females grow 

 larger than males, although reported differences in 

 maximum sizes between sexes were relatively small 

 (Seshappa and Bhimacher, 1954). Similarly, although 

 female C. abbreviatus ( to 348 mm TL) from Jiaozhua 

 Bay, China, were larger than males (to 321 mm TL), 

 average total lengths at age between the sexes were 

 not significantly different (Zhu and Ma, 1992). Fe- 

 males of C. biUneatiis and C. arel were also reported 

 to be larger than males sampled from the same popu- 

 lations (Hoda and Khalil, 1995), whereas sizes for 

 adult female (83-173 mm TL) and male (84-168 mm 

 TL) C. macrostomus were found to be similar (Victor, 

 1981). Female C. canariensis also grow larger than 

 males (Chauvet, 1972). For C. semilaevis inhabiting 

 the Bohai Sea, China (Meng and Ren, 1988), quite a 

 different situation exists. In this species, females at- 

 tain lengths (to 638 mm TL) slightly more than twice 

 those reached by males (to 312 mm TL). In other es- 

 tuarine flatfish, such as the hogchoker, which occurs 

 throughout much of the geographic range of the 

 blackcheek tonguefish, females grow to larger sizes 

 than do males from the same population (Koski, 1978). 

 For most species of the Pleuronectidae, females also 

 typically grow larger and have both a later age and 

 larger size at maturity than do males (Cooper^). 



Back-calculated lengths-at-age for blackcheek 

 tonguefishes were consistently less than observed 

 lengths-at-age for all age groups combined, which 

 may be attributed to Lee's phenomenon. The princi- 



■* Cooper, J. A. 1998. National Marine Fisheries Service, Na- 

 tional Systematics Laboratory, Wa.shington, DC 20.560. Per- 

 sonal common. 



pal cause of Lee's phenomenon in unexploited fish 

 populations, such as that of blackcheek tonguefish 

 inhabiting Chesapeake Bay, is that faster growing 

 fish tend to mature and die earlier than do smaller 

 members of the same year class (Gerking, 1957; 

 Ricker, 1975). When a larger proportion of older fish 

 die, the result is a smaller estimated size for fish at 

 younger ages than the true average size at the age 

 in question. Since blackcheek tonguefishes are not 

 harvested commercially or recreationally within the 

 Bay, the presence of Lee's phenomenon in the back- 

 calculation estimates may be due to higher mortal- 

 ity of larger individuals within an age class, or pos- 

 sibly this finding may reflect the fact that larger fish 

 move out of the Bay system and onto the nearby shelf 

 region. The ages of blackcheek tonguefishes occur- 

 ring on the continental shelf throughout the species' 

 range are unknown. No offshore samples of black- 

 cheek tonguefishes were collected during this study, 

 and it is unknown if any of these fish are older than 

 those occurring in Chesapeake Bay. 



Although female blackcheek tonguefishes captured 

 in Chesapeake Bay gi-ew at a slightly faster rate than 

 did males, observed differences in back-calculated 

 lengths between male and female blackcheek 

 tonguefishes beyond age 4 were not statistically sig- 

 nificantly different. However, our sample sizes for 

 older fish were small and interpretation of data for 

 this oldest age class is limited. In other cynoglossids, 

 such as Malabar sole, faster growth has also been 

 observed in females compared with that for males 

 (Seshappa and Bhimachar, 1954). Rajaguru (1992) 

 found that female C. arel grew faster than males, 

 but no significant differences in growth patterns were 

 found between female and male C. lida. After their 

 first year, female hogchokers in the Hudson River 

 also grew faster than males (Koski, 1978). In some 

 species of the Soleidae, such as the Agulhas sole 

 (Austroglossus pectoralis) occurring off South Africa 

 (Zoutendyk, 1974) and Solea solea in Spanish wa- 

 ters (Ramos, 1982), females also have a faster growth 

 rate than do males within the same populations. A 

 faster growth rate for females compared with that of 

 males has also been reported in a variety of other 

 flatfish species (Chen et al., 1992; Santos, 1994). 



Estimates of the growth parameter /C( Table 5) for 

 blackcheek tonguefish are relatively high, indicat- 

 ing that these fish reach their asymptotic length rela- 

 tively rapidly (Francis, 1996). Few estimates of K- 

 values are available for other tonguefishes, but for 

 those species studied, growth rates are relatively 

 high. Where data are available, all, except two spe- 

 cies, have higher growth coefficients reported for fe- 

 males. In r. arel, AT-values were 0.315 for females 

 and 0.238 for males, and in C. lidci A'-values of 0.233 



