PRISTAS ET AL.: RETURNS OF TAGGED GULF MENHADEN 



91f ?«• ?V» 92'' 90 



30' 



28« - 



26" 

 98 



TEXAS 



Figure l. — Three areas in which adult Gulf menhaden, Brevoortia patronus, were tagged, 1969-71. 



vember to March, may arbitrarily be divided 

 into two broad age-classes, juveniles and adults. 

 Juveniles are less than a year old, inhabit the 

 estuaries and rivers during the summer, and 

 move into the open waters of the Gulf in autumn 

 when they are about 65 to 130 mm in fork length. 

 Except in late summer and autumn when some 

 of the larger fish become available, they are not 

 vulnerable to the purse seine fishery. Adults are 

 more than a year old (age 1 or older), inhabit the 

 larger sounds and inshore areas of the Gulf, and 

 are vulnerable to the purse seine fishery. 



Techniques for tagging adult Gulf menhaden 

 followed those developed for tagging adult At- 

 lantic menhaden (Pristas and Willis 1973). A 

 numbered internal ferromagnetic tag (14.0 x 3.0 

 X 0.5 mm) was injected into the body cavity with a 

 tagging gun developed by Bergen-Nautik,'* a Nor- 

 wegian firm. Fish were obtained from com- 

 mercial purse seine catches and were tagged 

 aboard the carrier vessels. 



Five percent of the fish tagged in 1969 and 

 10% of the fish tagged in 1970 were measured. 

 Because measuring fish reduced the number that 

 could be tagged, it was not done in 1971. Mean 

 lengths of fish released in the spring of 1969 

 ranged from 118 to 130 mm; means of those re- 

 leased in the spring of 1970 ranged from 157 to 

 171 mm; and means of those released in autumn 

 1969 ranged from 148 to 164 mm. 



Individual fish were not aged. On the basis of 



■•Mention of commercial firm does not imply endorsement 

 of product by National Marine Fisheries Service, NOAA. 



length frequencies, nearly all the fish tagged 

 were judged to be either age 1 or age 2. Most of 

 those tagged in spring 1969, probably were age 

 1. Since the mean lengths were greater in 1970 

 than in 1969, a greater proportion in 1970 prob- 

 ably were age 2. Nearly all of those tagged in 

 autumn 1969 were age 1. 



METHODS OF RECOVERING TAGS 



Magnets, installed in reduction plants to re- 

 cover tags moving along the conveyer system 

 with the fish scrap and meal (Parker 1973), are 

 classified as either primary or secondary, de- 

 pending on their location. They were cleaned 

 about once a week to remove tags and other 

 scrap metal. Primary magnets are located be- 

 tween the fish scrap dryers and the storage areas. 

 Since newly processed fish scrap moves across 

 the primary magnets, the date tagged fish were 

 caught can be estimated. Tags recovered on 

 these magnets are referred to as primary recov- 

 eries. Secondary magnets are usually located in 

 the storage, transfer, or loading areas for scrap 

 and meal. Since fish scrap or meal that moves 

 across the secondary magnets may have been 

 in storage for several months or may have been 

 moved from one plant to another, the date 

 tagged fish were caught cannot be estimated, 

 and the plant at which the tags were recovered 

 cannot always be determined. Tags recovered 

 on these magnets are referred to as secondary 

 recoveries. In this paper we combine both types, 

 since we are interested only in the fishing sea- 

 son a tag was recovered. 



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