until the next trawl-haul was completed, and only 

 fish that seemed healthy were released. The area of 

 release was not fished again for at least 15 minutes. 

 Fish movement could be noted if fish fin-clipped at 

 one station were recaptured at any of the other 

 three stations or at other locations sampled spo- 

 radically. I also marked 284 pinfish by attaching 

 an Atkins tag in front of the dorsal fin with 

 nickel wire. 



I estimated numbers of eggs in ovaries by meas- 

 iiring the volume of eggs in both ovaries (after 

 most ovarian tissue had been removed) and divid- 

 ing that value by the average volume of an egg 

 as estimated from measurement of 25 eggs. 



PINFISH 



Pinfish are one of the dominant animals in the 

 fauna of vegetated areas in the lower Pensacola 

 Estuary. Therefore, I investigated the seasonal 

 and annual change in the food, growth, migration, 

 reproduction, and abundance at two locations from 

 August 1963 to December 1965. 



FOOD 



Pinfish were omnivorous feeders on the grass 

 flats where stations I and II were located. Gunter 

 (1945) and Reid (1954) on the Gulf of Mexico 

 Coast and Linton (1904) on the east coast of the 

 United States found a large variety of food orga- 

 nisms in pinfish stomachs. I identified 10 phyla of 

 animals and a wide variety of vegetation (includ- 

 ing diatoms, filamentous algae, and vascular 

 plants). The type of food varied witk season and 

 fish size (table 1), but not by station. 



Vegetation contributed 40.6 percent of the total 

 volume of identifiable items (including sand) in 

 the stomachs. It was the dominant food in the sum- 

 mer and fall ; the amount usually increased in late 

 spring or early summer and decreased in the late 

 fall. Diatoms were most imi^ortant in fish less than 

 76 mm. long, and filamentous algae and vascular 

 plants in larger fish. 



Crustaceans, polychaetes, and chordates were 

 dominant in pinfish stomachs in the winter and 

 spring. Small pinfish usually contained a higher 

 total number and volume of small crustaceans than 

 large pinfish. The crustaceans were mainly amphi- 

 pods, copepods, crabs, cyprids, isopods, mysids, 

 and shrimp. Chordates — amphioxus and (second- 

 arily) fish — were most abundant in large fish. 

 Other animals eaten in smaller amounts were 

 brachiopods, bryozoans, chaetognaths, echino- 

 derms, moUusks, and nemerteans. 



The mean volume of food in pinfish stomachs 

 was highest during the summer and early fall 

 (table 2) . The increase in the volume usually began 

 in May or June for both size groups of fish and 

 came with increase in ingestion of vegetation. The 

 volume decreased in the fall as fish became more 

 carnivorous. In the fall most fish over 90 mm. long 

 leave the estuary. Amounts of food in the stomachs i 

 decrease during the spawning season, as is common 

 in many si^ecies of fish. 



The mean volume of food in pinfish stomachs 

 was generally low and nearly constant from late 

 fall until late spring, except for a short-term in- 

 crease in February, when large numbers of caprel- 

 lid amphipods and polychaetes were found in 

 stomaclis of small fish. 



Table 1. — Percentage of lolal volume contributed by differ en 

 items in pinfish stomachs collected in the lower Pensacola 

 Estuary at stations I and II in different seasons, 1963-66 



1 Numbers of stomachs from both stations are shown in parentheses. 



2 Other items include brachiopods, bryozoans, chaetognaths, echlnoderms, 

 moUusks, and nemerteans. 



Table 2. — Average volume of stomach contents of small 

 and large pinfish collected in the lower Pensacola Estuary 

 at stations I and II in the months of sampling, 1963-65 



Fish length class 



Month 



<76 ram. 



76-173 mm. 



Stomachs Stomachs 



Examined Average Examined Average 

 contents contents 



January 



February... 



March 



April 



May 



June 



July 



August 



September- - 



October 



November.. 



No. 



Ml. 



No. 



Ml. 



138 



U.S. FISH AND WILDLIFE SERVICE 



