Table 6. — Standard lengths of Atlantic croakers of age-groups and I in the upper Pensacola Estuary at stations III and IV, 



1963-66 



Age-group 



Age-group I 



Date 



Length 



Length 



Fish Average Range 



Average Range 



I96S Number 



August 22-29-..- --- 1,291 



October 21-24 -- 49 



1964 



January 6-14 - - - 2 



February 24-27-..- - ----'-■ ---- 60 



May 6-11.. - 2,336 



June 22-26 - - - -• 1,909 



July 27-30. --- -- 891 



August 24-27 ..: --1--- ...-. -. 847 



September 21-24 -- 129 



October 26-29. .'--- - 



December 8-10 - Ill 



January5-7 220 



January 26-28 - 274 



February 23-March 2 - ._-,-. 157 



March 22-31 - - -. 122 



May 3-7 --Lj--.:. -- 2,269 



May 25-28 - 2,211 



June 21-24. - .- - -.■.---- 2,999 



July 26-30- - 2,422 



August 24-27 - - - 767 



September 20-21 --- --- 21 



December 1-2--- - 13 



Mm. 



107 

 117 



32 

 38 

 65 

 76 

 91 

 94 

 102 



Mm. 



91-162 



24- 40 

 20- 66 

 36-117 

 45-128 

 61-131 

 70-140 

 86-125 



35 



41 

 46 



64 

 61 

 67 

 68 

 74 

 99 

 111 

 118 

 47 



24- 50 



17- 60 

 15- 64 

 21- 74 

 30- 79 

 34-113 

 34-123 

 51-136 

 68-151 

 93-155 

 106-129 

 38- 63 



Number Mm. Mm. 



--.- --. 







. 











1 166 



- -.- 











- 



3 106 94-118 



3 93 91- 96 



5 102 94-118 



-. 



1 112 







1 132 .- 



2 163 163-173 

 2 164 161-168 



- 



- 







therefore, they were larger in the winter, and from 

 January through August grew at a faster rate 

 (0.30 mm. per day in 1964, 0.36 mm. per day in 

 1965) so that in August they averaged 17 mm. 

 longer than in 1964. Growth was greatest in the 

 spring in 1964 and in the summer in 1965, and 

 maximum growth was in July in both years (0.60 

 mm. per day). 



MIGRATION AND REPRODUCTION 



Migrations of Atlantic croakers are extensive. 

 In December and January the young begin to 

 enter the estuary from spawning grounds in the 

 Gulf of Mexico and move to areas of low salinity. 

 Haven (1957) noted that these fish move up the 

 estuary in the salt-water "wedge" near the bot- 

 tom. Two days of trawling (February 10-11, 1964) 

 at all depths near the mouth of the Pensacola 

 Estuary, however, caught no young croakers. 



Atlantic croakers of age-group O appeared ear- 

 lier and were more abundant at station IV in the 

 years when estuarine water temperatures were 

 relatively high in November and December. The 

 average temperatures in November-December 

 were : 1963—14.0° G., 1965—16.4° C., and 1964— 

 19.2° C. In the winter of 1963-64 the first young-of- 

 the-year croakers were caught in early January. 

 In the winter of 1964-65 and 1965-66 they ap- 

 peared in late November and early December (in 



the greater numbers in the winter of 1964-65). 

 Young fish appeared first and in greatest abun- 

 dance in areas of low salinity (station IV). They 

 moved to areas of higher salinity as they grew 

 and appeared in the lower estuary (stations I and 

 II) in late spring. Fish cauglit at stations I and II 

 were never as small as fish captured in the upper 

 estuary near the beginning of the fry migrations. 



Of 5,269 fin-clipped Atlantic croakers only 6 

 (0.1 percent) were recaptured, and only 2 of tliese 

 liad l)een marked at least 1 month before recap- 

 ture. None liad left the area of marking. 



The migration of Atlantic croakers out of the 

 estuary begins in late summer and ends before No- 

 vember. All fish probably leave the estuary; no 

 croakers have been captured after the period of 

 gulfward migration until the newly hatched fish 

 enter the estuary. 



Pearson (1928), Suttkus (1955), and Roith- 

 mayr (1965) foimd that, along the Gulf Coast, 

 Atlantic croakers spawn at the end of their second 

 year of life. In the Pensacola Estuary, most croak- 

 ers had developing gonads in the fall of their first 

 year of life. Most females and males examined had 

 well-developed gonads (stage 2 or 3 of Homans 

 and Vladykov, 1954). Although it is possible that 

 the developing eggs are retained, these croakers 

 may spawn in their first year of life. 



Ovaries of 18 croakers, 101 to 145 mm. long, 



144 



U.S. FISH AND WILDLIFE SERVICE 



