POPULATION AND FISHERY CHARACTERISTICS OF 

 GULF MENHADEN, BREVOORTIA PATRONUS 



Walter R. Nelson 1 and Dean W. Ahrenholz 2 



ABSTRACT 



Landing data from 1964 to 1978 for the purse seine fishery in the north-central Gulf of Mexico for gulf 

 menhaden, Brevoortia patronus, were analyzed to determine growth rate, yield-per-recruit and spawner- 

 recruit relationships, and maximum sustainable yield (MSY). Estimates of stock size, year-class size, and 

 rates of fishing were obtained from cohort analysis. The fishery is characterized by high rates of both 

 fishing and natural mortality. During the period studied, an average of 40% of the population of age-1 

 and older fish were taken by the fishery and 47% was lost to other causes annually. Although there was 

 substantial scatter about the fitted curve, a Ricker-type spawner-recruit relationship was found to be 

 suitable The number of age-1 recruits fluctuated annually between 7.5 and 25.4 billion during the period 

 studied. Maximum biomass of a year class is reached at an age of about 1.5 years. Yield-per-recruit estimates 

 were obtained for an array of fishing mortalities and ages of entry. A deterministic simulation model 

 incorporating growth, the spawner-recruit relationship, and age-specific rates of fishing provided an 

 estimate of MSY at 585,118 t with 127% of the current mean rate of fishing. Implications for the current 

 and future status of this fishery are discussed. 



Gulf menhaden, Brevoortia patronus, are filter-feed- 

 ing, surface-schooling clupeids that are subjected to 

 an intensive purse seine fishery in the northern Gulf 

 of Mexico. Although annual landings have fluc- 

 tuated, there has been a general increase since the 

 inception of the modern fishery in 1946 to a high 

 of 820,000 metric tons (t) in 1978. The fishery con- 

 sists of about 80 refrigerated vessels serving 11 

 reduction plants at 6 ports in Mississippi and Loui- 

 siana. The fishing season is currently set by State 

 law from mid-April to mid-October. Although a 

 majority of the catch is taken off Louisiana and 

 Mississippi, vessels range west into eastern Texas 

 coastal waters and east to the coastal waters of the 

 Florida panhandle Vessels, aided by spotter aircraft, 

 land from 6,000 to 10,000 t/6-mo fishing season. Ex- 

 cellent background information and descriptions of 

 the fishery have been published by Christmas and 

 Etzold (1977) and Nicholson (1978). 



Considerable literature exists on the general 

 biology of gulf menhaden (Reintjes et al. 1960; Rein- 

 tjes 1964; Reintjes and Keney 1975; Christmas and 

 Etzold 1977); however, information is scarce on the 

 population dynamics of gulf menhaden and on the 

 dynamics and impact of the fishery. Chapoton (1972) 



'Southeast Fisheries Center Beaufort Laboratory, National 

 Marine Fisheries Service, NOAA, Beaufort, NC; present address: 

 Southeast Fisheries Center Miami Laboratory, National Marine 

 Fisheries Service, NOAA, 75 Virginia Beach Drive, Miami, FL 

 33149. 



Southeast Fisheries Center Beaufort Laboratory, National 

 Marine Fisheries Service, NOAA, Beaufort, NC 28516-9722. 



and Schaaf (1975a) estimated maximum sustainable 

 yield (MSY). Ahrenholz (1981) described recruitment 

 patterns and estimated natural and fishing mortality 

 rates from returns of tagged juvenile and adult 

 menhaden. 



Gulf menhaden have a life history similar to many 

 other estuarine-dependent coastal species. Spawn- 

 ing takes place in coastal and offshore waters in the 

 winter (Christmas and Waller 1975 3 ; Lewis and 

 Roithmayr 1981). Larvae move onshore into Gulf 

 estuaries in winter and early spring, transform to 

 juveniles, and remain in the nursery areas until the 

 following fall. Juveniles move offshore during the 

 winter and back into coastal waters the following 

 summer. Spawning occurs for the first time at the 

 end of their second year. 



A joint State-Federal-Industry plan developed for 

 gulf menhaden identified the lack of a reliable mea- 

 sure of effective effort and questionable MSY 

 estimates as major concerns in evaluating the gulf 

 menhaden stock and fishery (Christmas and Etzold 

 1977). Problems encountered in determining the 

 status of gulf menhaden stocks and estimating a 

 long-term yield from catch-effort data on schooling 

 species subjected to a purse seine fishery are com- 

 pounded by the "dynamic aggregation process" 

 described by Clark and Mangel (1979). Basically, they 



3 Christmas, J. Y, and R. S. Waller. 1975. Location and time 

 of menhaden spawning in the Gulf of Mexico. Unpubl. manuscr., 

 20 p. Gulf Coast Research Laboratory, Ocean Springs, MS 39564. 



Manuscript accepted July 1985. 



FISHERY BULLETIN: VOL. 84, NO. 2, 1986. 



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