OLLA, BEJDA, and MARTIN: ACTIVITY OF TAVTOGA ONITIS 



Table 1. — Locations and diiralit)n of stay (h) of individual tautog during their daily movements as determined by ultra- 

 sonic tracking, continued. 



Night 



G ( 8.0) D ( 7.9) 



D ( 7.9) D ( 7.9) 



A5(10.2) A5( 8.3) 



' Location as presented in Figures 1 and 2. 



- Hours given in parentheses. 



^ Age estimated from calculated total lengths by Cooper ( 1967) . 



stage of tide, cloud cover, water temperature, 

 and water transparency. Current velocity was 

 measured either with a Beauvert midget cur- 

 rent meter or by the float method. The current 

 velocity ranged from 0.65 to 1.75 m/s. Temper- 

 ature was measured with a thermistor and 

 transparency with a secchi disk. Cloud cover 

 was visually estimated. 



In conjunction with our tracking, we directly 

 observed tautog in the study area with scuba 

 for a total of 135 h (90 h daytime and 45 h 

 nighttime). 



To identify periods of feeding as well as the 

 types and amounts of food ingested, we ex- 

 amined the digestive tracts of fish collected at 

 different times of the day and night. We mea- 

 sured the relative dige.stive tract fullness of each 

 volumetrically with the fullness index being 

 the quotient of displacement volume of empty 

 tract/displacement volume of tract with con- 

 tents. 



Determination of the maximum size of mussel 



that the tautog could ingest and of the maximum 

 size it could crush was made by inserting dif- 

 ferent size mussels into the mouth and into the 

 anterior opening of the pharyngeal mill. The 

 maximum ingestable size was defined as the 

 largest mussel that could be completely enclosed 

 in the mouth. The maximum crushable size was 

 the largest mussel that could be partially 

 grasped by the pharyngeal teeth. 



To aid in describing the method of feeding 

 on mussels, at infrequent intervals over a 16-mo 

 period, we directly observed and used cine anal- 

 ysis of three individuals 25 to 38 cm, held in a 

 2,200-liter aquarium. 



RESULTS 



Activity and Movements 



The fish which we tracked were active during 

 the day and inactive at night. There was some 



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