2 OO 

 8 « 

 6 ^ 

 4? 



2^ 

 > 



8 ui 

 6 J 



? ■* 



FISH LENGTH (mm SL) 



Figure 6. — Mean prey volume (cubic centimeters) and relative 

 prey size (x prey volume/x wet fish weight) for size classes of 

 Prionotus scitulus, Tampa Bay, Fla., 1972-73. 



selection of larger sized individuals within a 

 single prey kind. Only one prey item, B. floridae, 

 exhibited a broad enough size range to meaning- 

 fully test for differences between fish sizes. The 

 mean size of lancelets, however, did increase with 

 increasing fish size (P<0.001) (Figure 7), but the 

 rate of increase was quite low compared with the 

 overall increase in mean prey size (cf. Figure 5). 



55- 

 50 - 



'e 45- 



E 

 -- 40 H 



B 35-1 



0) 



30 - 



>» 25 - 

 o 



tL 20 - 



15- 



10 - 



5 - 



319 



150 337 



II 



69 



- {} ^^ ^^ 



154 



bB 



59 



/At 1 1 1 1 1 1 — 



85 95 105 115 125 135 145 



Fish Length (mm) 



FISHERY BULLETIN: VOL. 76. NO. 1 



Morphology and Growth 



Trophic changes showed a critical size interval 

 between approximately 60 and 100 mm, within 

 which the mean prey number decreased, and after 

 which the mean prey volume, length, and relative 

 volume increased. These trophic changes suggest- 

 ed the presence of certain morphological or de- 

 velopmental correlates, of which I examined jaw 

 size, intestinal length, and growth. 



Ontogenetic changes in mouth size were ex- 

 pressed by relative jaw width and relative jaw 

 length. Juvenile leopard searobins showed propor- 

 tionately greater mouth widths and lengths com- 

 pared with adults, but plots of both relative jaw 

 length and relative jaw width versus SL showed 

 considerably lower slopes by approximately 75 

 mm (Figure 8). Proportionate mouth length con- 

 tinued to decrease with increasing fish size for fish 

 >75 mm; however, proportionate mouth width 

 remained constant for fish >75 mm. Mouth size 

 thus increased rapidly with increasing fish size for 

 early juvenile P. scitulus, but by 75 mm the rela- 

 tionship between mouth size and fish length was 

 essentially fixed. 



Intestinal length increased rapidly between the 

 45- and 65-mm size classes. Fish <50 mm had 

 mean intestinal lengths of 70% SL, while fish >60 

 mm had mean intestinal lengths of 102% SL. 



Log transformed length-weight values of 

 leopard searobins showed an increase in the slope 

 of the regression line between approximately 55 

 and 75 mm (Figure 9). The fish were divided into 

 two size groups, <75 mm and >75 mm, and sepa- 



140 . 

 135 



130 



I 



i 125 J 



UJ 



_l 



^ 120 . 



CO 



"^ 115 . 



H 



z 



UJ 



o 110 



(E 



UJ 



^ 105 

 100 



^6--, 



o o Mouth Width /SL 



i i Mouth Length/SL 



^s:_ 



T- 



-r 



I I 1 I I 1 I 



30 40 50 60 70 80 90 100 110 120 130 140 

 FISH LENGTH (mm SL) 



Figure 7. — The relationship between lengths of the dominant 

 prey, Branchiostoma floridae, and its predator, Prionotus sci- 

 tulus. See Figure 5 for explanation of symbols. 



230 



Figure 8. — Relative mouth width and relative mouth length 

 versus fish length for Prionotus scitulus, Tampa Bay, Fla. Each 

 data point is based on the mean of 20 individuals. 



