ROSS TROPHIC ONTOGKNY OF l,KOI'ARD SEAROBIN 



I 



10 



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 o 



4. 



3 3. 



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 0. 



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 2 



Log W = -10.878 » 2.949 Log SL 



6 



75mm 

 65mml 

 55mm *^ 



i 



Log W= -9.083-2.451 Log SL 



N=77 



SE=0.328 



-P 



 I I I I < I I I I 



3.0 3.2 3.4 36 3.8 4.0 42 4 4 46 4.8 5.0 5.2 



LOGg FISH LENGTH (mm SL) 



Figure 9. — Length- weight relationships for size 

 classes of Prionotus scitulus, Tampa Bay, Fla. 



rate length-weight regressions were calculated. 

 The 75-mm size was chosen because of its associa- 

 tion with changes in relative mouth size. The 

 growth data showed that P. scitulus >75 mm were 

 gaining weight much more rapidly than smaller 

 fish, even after allowing for the expected exponen- 

 tial rate of increase by using the log transforma- 

 tion. 



Reproduction and Distribution 



Mean female GSFs remained below 0.4 for P. 

 scitulus between 20 and 90 mm and these fish did 

 not contain mature ova. Leopard searobins 100 

 mm and larger had mean GSI values between 3 

 and 6 and were sexually mature. Ross (1974, in 

 press) showed that mean female GSI values dur- 

 ing spring to summer spawning were 5 to 10. The 

 GSI values reported here are lower because the 

 fish were combined from all months of the study to 

 avoid possible bias due to differences of spawning 

 times of different size groups. Male searobins 

 showed the same size-related pattern. 



Spatial separation between immature and ma- 

 ture P. scitulus was quite pronounced (Figure 10). 

 Juvenile searobins consistently had high relative 

 abundances at Station 1 in Old Tampa Bay (5 m 

 deep), while mature fish had high relative abun- 

 dances near the mouth of Tampa Bay at Station 3 

 (7 m deep). Overlap between immature and ma- 

 ture searobins was greatest during summer and 

 fall 1972 at Station 2 ( 5 m). The percent occurrence 

 of juvenile fish in combined collections was high- 

 est between March and May (60-75%) and lowest 

 between June and November (25-47%). 



Annual mean salinities varied significantly be- 



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 o 



z 



Zi 

 CD 



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UJ 

 (T. 



O 



100 

 80 

 60 

 40 

 20 

 



Juveniles 



•:■>:■:■ .^^xN 58 



.^93 



June - 

 Aug. 

 1972 



1 



Sepl.- 

 Nov. 



J59 $a:^90 



581 



m 



■•■'■'■'• 



19! 



..M248 giM24l 



Dec- 



Feb. 

 1973 



m 



v/.v 



M 



m 



65 



March- 

 May 



310 



a::^:M95 



June- 

 July 



16 



-1M168 $;^^39 



I 2 3 



TAMPA BAY STATIONS 



FIGURE 10.— Spatial distribution of juvenile ( <100 mm SL), and 

 adult (>100 mm SL) Prionotus scitulus at three stations in 

 Tampa Bay, Fla., 1972-73. Percent relative abundance is based 

 on each sample site and date; numbers indicate sample sizes. 

 Adults are indicated by hatching; juveniles by cross-hatching. 



tween stations (P<0.05); respective means for 

 Stations 1-3 were 25.7, 28.1, and 33.2%o. Con- 

 sequently, small leopard searobins were occupy- 

 ing somewhat less saline water. Annual mean 

 temperatures did not vary between stations 

 (range = 13°-32°C). 



231 



