98' 



FISHERY BULLETIN: VOL 79. NO 2 

 86° 84! 82° 



30' 



28 



26' 



TEXAS 



98° 



Figure l. — Location of Gulf of Mexico ports where catches of Gulf menhaden are currently landed idots), major fishing and tagged 

 adult release areas (vertical lines), and division of the U.S. gulf coast into tagged juvenile Gulf menhaden release areas (numbered 

 circles and dashes). 



Methods of tagging and tag recovery are well 

 documented ( Pristas and Willis 1973; Parker 1973; 

 Dryfoos et al. 1973). Numbered stainless steel 

 ferromagnetic tags, 7.0 x 2.5 x 0.4 mm for juve- 

 niles, and 14.0 x 3.0 x 0.5 mm for adults, were 

 injected into the body cavity. Juveniles were 

 tagged in estuaries during late summer or early 

 fall just before emigration. Adults obtained from 

 fishing vessels on the fishing grounds were tagged 

 during late spring. 



Tags were recovered on magnets located in re- 

 duction plants; however, not all tags that entered a 

 plant were recovered. To estimate the fraction of 

 tags recovered at each plant, 100 tagged fish were 

 put in the catch of a selected vessel each week. 

 Field recoveries were adjusted for loss rates within 

 a plant by multiplying the inverse of the test re- 

 covery fraction by the number of field tags actually 

 recovered at each plant. 



For analyzing juvenile tag recoveries, the 

 northern Gulf of Mexico coast was divided into 10 

 release areas, numbered, and geographically 

 named for reference (Figure 1, Table 1). In some 

 areas, fish were tagged in only one estuary; in 

 other areas, they were tagged in several estuaries. 

 For analyzing adult tag recoveries, the coast was 

 divided into three areas: western, central, and 

 eastern (Pristas et al. 1976) (Figure 1). 



MOVEMENT AND RECRUITMENT OF 

 JUVENILE TAGGED FISH 



The eventual distribution of fish tagged in 

 326 



Table l. — Numbers of taggedjuvenile Gulf menhaden released 

 in estuarine vv-aters by area and year, 1970-72. Areas are 

 depicted in Figure 1 . 



specific estuaries would be an indication of the 

 degree and direction of movement offish from each 

 estuary. Because there is no way of knowing 

 exactly where a tagged fish was caught, and be- 

 cause levels of effort may vary between ports (and 

 thus numbers of fish actually landed), the dis- 

 tributions must be inferred from estimates of the 

 relative availability of tagged fish to each port 

 rather than from just the distribution of recoveries 

 of tagged fish to each port. Because vessels tend to 

 fish more intensively in areas near their home 

 ports, most tags recovered at a specific port were 

 assumed to have been from fish caught in waters 

 closest to that port. The measure of standardized 

 effort (f) used in availability calculations is the 

 vessel-ton-week (computed as net-registered- 

 tonnage times number of weeks fished), the unit of 

 fishing effort currently employed for this fishery 

 (Chapoton 1972; Schaaf 1975), adjusted for differ- 

 ences in vessel catch efficiency in numbers offish 



