caught in the fall of 1963, near the end of their 

 first year of life, had an average of 41,200 eggs. 

 The diameter of eggs was 0.02 to 0.72 inm. and 

 averaged 0.34 mm. Hildebrand and Cable (1930) 

 indicated that a mature egg probably has a diam- 

 eter less than 1 mm. The eggs in the large yellow 

 ovaries had fat globules. 



ABUNDANCE AT THE SAMPLING STATIONS 



Atlantic croakers are most abundant in low- 

 salinity areas in tlie Pensacola Estuary. Young 

 (O-groujj) enter the estuaiy in the winter and 

 spring and move out in the fall. Fish in the estuary 

 are rarely moi-e than 10 months old. 



Montlily changes in abundance (table 7) are 

 caused primarily by migrations and, to a lesser 

 extent, by natural mortality. In the winter young 

 croakers move rapidly from the Gulf to the upper 

 estuary; catches were largest at the station of 

 lowest salinity. The number of fish increases to a 

 maximum in May or June. Yearly differences in 

 abundance were small at station III but croakers 

 were most numerous at station IV in 1965. 



SUMMARY 



Life histories of pinfish and Atlantic croaker in 

 tile Pensacola Estuary were studied from August 

 1963 to December 1965. Their food, growth, age 



composition, migrations, reproduction, and abun- 

 dance were studied from fish collected at intervals 

 of about 1 month for 21/^ years. Each species was 

 sampled 22 times at each of two stations. 



Feeding, migrations, and other aspects of the 

 biology of pinfish from the Pensacola Estuary 

 change seasonally. They spawn in the Gulf of 

 Mexico in winter. Young and adults enter the 

 estuary in the winter and spring where they con- 

 gregate on grass flats and feed primarily on ani- 

 mals — crustaceans, polychaetes, and cliordates — 

 and attain maximum abundance in June. From 

 June until the fall migration pinfish apparently 

 move only short, distances over the grass flats and 

 are primarily herbivores. The amount of food in 

 tlie stomachs is at its highest level at this time. 

 The gonads of all fish except the smaller ones in 

 their first year of life begin to develop in the fall ; 

 ovaries contain about 22,000 developing eggs. The 

 maturing pinfish school and leave the estuary in 

 the fall. Food of the remaining fish includes fewer 

 plants, and the amount of food in their stomachs 

 decreases. Usually pinfish fonn the first annulus 

 on their scales in April of their second year of life. 



The life histoi-y of Atlantic croakers from this 

 area is similar to that of pinfisli. Croakers spawn 

 in the Gulf of Mexico in the late fall and winter, 



Table 7. — Atlantic croakers caught per 30-minute trawl-haul in the upper Pensacola Estuary at stations III and TV, 1963-66'- 



Date 



Station III 



Station XV 



Average 



Confidence 

 Interval 

 95% 



Range 



Confidence 

 Average Interval 



95% 



ms 



August 22-29 



October 21-24 



1964 



January 6-14 



February 24-27 _ 



May 5-11 



June 22-25 



July 27-30- 



August 24-27 



September 21-24 



October 26-29 



December 8-10 



1B66 



January 5-7. - 



January 26-28 



February 23-Maich 2 



March 22-31 



May 3-7-- 



May 25-28 



June 21-24-.. _ 



July26-30- - 



August 24-27. 



September 20-21 



December 1-2 



Number 



107 



3 



6 



85 



102 



221 



93 



27 



4 







Number 



63-150 



2- 6 



0- 5 



0- 1 



0- 4 



3- 8 



43-127 



80-124 



145-297 



17-170 



18- 36 



0- 8 



Number 

 25-229 

 0- 8 



'0 20-0 0-1 







280 218-342 202-463 



228 81-375 11-527 



74 54- 94 27-110 



48 21- 74 1-134 



11 3- 18 1- 26 



-- ---- 







0- 3 



0- 1 



1- 3 



2- 14 

 3-172 



67-172 

 67-436 



1-378 

 10- 47 



0- 8 



Number 



22 



2 



20 



5 



9 



62 

 13 

 41 



2 



. 

 11 



22 



28 



16 



6 



174 



496 



332 



149 



50 



. 



3 



Number 

 18- 27 



20- 



0- 10 

 7- 12 



37- 87 



9- 21 



28- 64 



1- 4 



1- 22 



8- 36 

 6- 50 



0- 33 



1- 12 

 128-220 

 349-642 

 284-380 



87-212 

 35- 65 



0- 10 



Range 



Number 



11- 34 



1- 2 



0- 1 

 0- 16 

 5- 16 



19-100 

 5- 26 



13- 74 

 0- 7 



0- 38 



3- 66 



0- 77 



0- 83 



0- 26 



89-320 



136-801 



239-408 



76-363 



17- 86 



0- 13 



Average 



both 



stations 



Number 

 64 



20 



2 

 144 

 146 

 44 

 44 



17 



20 



12 



6 



130 



298 



276 



121 



38 



2 



2 



' 10 trawl-hauls were made at each station per month with the following exceptions (number of hauls in parentheses): Station ni, 1964— Dec. 8-10 (3); 1966— 

 Jan. 6 (3), Jan. 28 (4), Mar. 2 (3), Sept. 21 (5), and Dec. 2 (2); Station IV, 1965— Sept. 20 (5), and Dec. 1-2 (6). 

 2 Less than 0.6. 



LIFE HISTORIES OF PINFISH AND ATLANTIC CROAKER 



145 



