Terwilliger and Munroe: Age, growth, longevity, and mortality of Symphurus plagiusa 



351 



B. 



c 



0) 



measured 140-180 mm TL. Lengths 

 of fishes collected within the Bay sys- 

 tem completely overlap those taken 

 from the nearby shelf. Munroe ( 1998 ) 

 noted that most blackcheek tongue- 

 fishes in collections from throughout 

 the species' geographic range were 

 usually much smaller than the larg- 

 est sizes known for the species be- 

 cause only 4% of 568 fish he exam- 

 ined exceeded 164 mm TL. Wenner and 

 Sedberry (1989) sampled 8780 black- 

 cheek tonguefishes from coastal habi- 

 tats ( < 10 m depth ) between Cape Fear, 

 North Carolina, and the St. Johns 

 River, Florida, and reported that 

 length composition of trawl-caught S. 

 plagiusa was consistent from season 

 to season, with mean sizes ranging 

 between 140-150 mm TL. The larg- 

 est specimens taken during that 

 study were 210 mm TL, and few fish 

 <100 mm TL were caught, possibly 

 because fish smaller than this inhab- 

 ited a different habitat as juveniles or 

 because they did not recruit to the fish- 

 ing gear until 100 mm TL. On the con- 

 tinental shelf off Tampa Bay, Florida, 

 lengths (124-174 mm TL) for black- 

 cheek tonguefishes were also similar 

 to those reported for fish from Chesa- 

 peake Bay (Moe and Martin, 1965). 



Although age estimates are not 

 available for other populations of 

 blackcheek tonguefish, a general 

 comparison of growth between black- 

 cheek tonguefishes occurring in 

 Chesapeake Bay with those from 

 other areas is provided by examination of length- 

 weight parameters derived for different populations. 

 Dawson (1965) generated a length-weight relation- 

 ship for 3504 blackcheek tonguefish (43-148 mm TL) 

 occurring in Gulf of Mexico waters. With this rela- 

 tionship, weights were generated from 510 randomly 

 selected lengths between 43 and 148 mm TL and 

 these were then compared with a similar number of 

 weights generated for fishes of the same size range 

 by using the length-weight relationship derived for 

 blackcheek tonguefishes from Chesapeake Bay. No 

 significant differences (^=0.53; df=1010;P=0.60) were 

 evident in this comparison between weights of fishes 

 of these two regions, indicating that growth in weight, 

 at least, is similar for fishes of this size range occur- 

 ring in these widely separated areas within the spe- 

 cies' range. 



Age (years) 



Figure 9 



Plot of back-calculated and predicted lengths from the von Bertalanffy growth 

 model for blackcheek tonguefish, Symphurus plagiusa, from lower Chesapeake 

 Bay and major lower tributaries: (A) males; (B) females. 



Annuli form on the otoliths of blackcheek tongue- 

 fishes from late spring through early summer (mostly 

 June), coincident with the summer warming period 

 and also at the initiation of the spawning season 

 (Terwilliger, 1996). For C. abbreviatus, a tonguefish 

 occurring in temperate seas off eastern China (Zhu 

 and Ma, 1992), annuli form on otoliths during March- 

 May, a period also corresponding to seasonal timing 

 of gonad maturation and warming of water tempera- 

 tures. Koski (1978) reported that annuli form on 

 scales of hogchokers in the Hudson River from April 

 to mid-June, which is a period of increasing water 

 temperature, and for mature fish this also corre- 

 sponds to the time just prior to and overlapping the 

 early spawning season. 



Flatfishes typically exhibit sexual dimorphism in 

 size at age (Roff, 1982; and others, see below) — 



