RECRUITMENT AND EXPLOITATION OF 

 GULF MENHADEN, BREVOORTIA PATRON US' 



Dean W. Ahrenholz 



ABSTRACT 



Gulf menhaden, Brevoortia patronus, range along the Gulf of Mexico coast from Cape Sable, Florida, to 

 Veracruz, Mexico, and are exploited by a purse seine fishery from Alabama to eastern Texas. Rates of 

 exploitation, population movement, and recruitment into the fishery were estimated from returns of 

 tagged juveniles and adults. The annual instantaneous rate of natural mortality (M = 1.0935) was 

 estimated from recoveries of tagged adults. Recruitment patterns were determined and exploitation 

 rates were estimated from returns offish tagged as juveniles in specific geographic regions along the 

 northern Gulf of Mexico. During 1971-73, fish tagged as juveniles from either the eastern or western 

 extremes of the northern gulf coast were exploited as 1-year-olds at a mean rate of only 57c. The rate 

 increased to a high of 51 % for 1-year-olds tagged near the Mississippi Delta, the center of the fishery. 

 During 1972-74 , 2-year-old fish tagged as juveniles were exploited at rates ranging from 18 to 55*%^ . Fish 

 from the eastern and western ends of the range dispersed toward the center of the range as they grew 

 older. 



Gulf menhaden, Brevoortia patronus , range along 

 the coastline of the Gulf of Mexico from Cape Sa- 

 ble, Fla., to Veracruz, Mex. (Reintjes 1969). They 

 are exploited from April to October by a purse 

 seine fishery that operates in nearshore waters 

 from Alabama to Texas. Gulf menhaden move 

 offshore in the fall before spawning in the winter. 

 The larvae move into estuaries in late winter and 

 spring, where they metamorphose into juveniles 

 and remain there until the following autumn. 



The fishery is dependent on age-1 and age-2 fish, 

 with few fish being taken that exceed 3 yr of age. 

 The catch, processed into meal and oil, increased 

 from 8,900 t in 1946 to 728,500 t in 1971, and has 

 fluctuated between 447,000 and 820,000 t since 

 then. Yellowfin menhaden, B. smithi, and fine- 

 scale menhaden, B. gunteri, occur in the area 

 fished, but Gulf menhaden compose approxi- 

 mately 99% of the landings. At present, catches 

 are processed at 11 reduction plants, located at six 

 ports along coastal Louisiana and Mississippi 

 (Figure 1). Large, refrigerated purse seine vessels, 

 supported by spotter aircraft, range up to about 

 320 km from port. During recent years the number 

 of operating plants has varied from 10 to 13, and 

 the number of active ports has varied from 6 to 8 

 (Nicholson 1978). 



'Southeast Fisheries Center Contribution No. 81-31B. 

 ^Southeast Fisheries Center Beaufort Laboratory, National 

 Marine Fisheries Service, NOAA, Beaufort, NC 28516. 



To determine if fish reared outside the range of 

 the fishery are exploited and to determine the rate 

 of exploitation of individuals reared within the 

 range, juvenile menhaden (young-of-the-year) 

 have been tagged since 1970 in selected estuaries 

 from Florida to the Mexican border. I analyzed 

 returns from fish tagged as juveniles from 1970 to 

 1972 to determine if fish reared outside the range 

 of the fishery contribute to landings and to esti- 

 mate rates of exploitation by age and estuarine 

 area of origin. 



I also analyzed returns from a second (indepen- 

 dent) adult tagging program to obtain an estimate 

 of natural mortality and a preliminary estimate of 

 rate of fishing on fully recruited fish to comple- 

 ment my analysis of the first (juvenile) tagging 

 program. In the second study, reported by Pristas 

 et al. (1976), Gulf menhaden were tagged as re- 

 cruited fish (adults) on the fishing grounds from 

 1969 to 1971. 



TAGGING METHODOLOGY 



Since all tags that are recovered from both tag- 

 ging programs are from "adult" fish caught by the 

 fishery, a distinction in terminology is made in this 

 paper for clarity in separating results: "tagged as 

 adults" or "adult recoveries" refers to the study 

 reported by Pristas et al. (1976) and "tagged as 

 juveniles" or "juvenile recoveries" refers to the 

 present study. 



Manuscript accepted September 1980. 

 FISHERY BULLETIN; VOL. 79, NO. 2, 1981. 



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