Gulf menhaden, continued 



after hatching, reaching a plateau at five to eight days, 

 then declining after 14 days (Grimes and Isely 1996). 

 In estuarine and marine waters, juvenile and adult gulf 

 menhaden are prey items for several fish species. 

 Piscine predators include sported seatrout, silver perch, 

 silver sea trout (Cynoscion nothus), red drum, Spanish 

 mackerel, king mackerel (Scomberomorus cavalla), 

 bluefish, and sharks (Simmons and Breuer 1964, 

 Fontenot and Rogillio 1 970, Reintjes 1 970, Swift et al. 

 1 977, Etzold and Christmas 1 979, Levine 1 980). Men- 

 haden are also thought to be an important forage 

 species for piscivorous birds such as brown pelicans, 

 and are known prey of the osprey and common loon 

 (Ahrenholz 1 991 ). Marine mammals are also reported 

 to prey on menhaden. 



Factors Influencing Populations : Gulf menhaden are 

 frequently involved in "fish kills" along the Gulf coast. 

 They are extremely sensitive to hypoxia, which is 

 common in Gulf estuaries during the summer months. 

 Dead-end sloughs, bayous, and harbors are particu- 

 larly dangerous to menhaden during the summer. 

 Postlarvae and juveniles are highly susceptible to such 

 kills, as their mobility and ability to avoid hypoxia is 

 limited (Lassuy 1983, Shipp 1986). Decaying menha- 

 den remove still more oxygen from the water which can 

 cause a fish kill to spread over a larger area. Gulf 

 menhaden are susceptible to parasitic copepods and 

 two major diseases, "spinning disease" and ulcerative 

 mycosis (UM). Ulcerative mycosis was previously 

 thought to be associated with infection by oomycete 

 fungi (Noga et al. 1988), but it is now suspected to be 

 a condition resulting from the destruction of epidermal 

 tissue by the toxins released by the dinoflagellate 

 Pfiesteria piscicida (Burkholder et al. 1 995, Ahrenholz 

 pers. comm.). 



The timing of migrations from nursery areas to open 

 bay habitats varies between different estuarine sys- 

 tems. This may be a response to differences in timing 

 of primary productivity and thus food availability (Deegan 

 1990). Larvae occur in high concentrations at the 

 Mississippi River plume front (Govoni et al. 1 989). This 

 may provide larvae with an enhanced feeding environ- 

 ment, but may also make them more susceptible to 

 predation. The construction of water control structures 

 in wetlands may seriously affect the recruitment of 

 young gulf menhaden into nursery areas (Marotz et al. 

 1 990). Some gulf menhaden are landed as bycatch on 

 commercial shrimping vessels, but the impact of these 

 landings on the menhaden population has not been 

 studied, and remains largely unknown (Vaughan pers. 

 comm.). 



Gulf menhaden are generally shorter-lived and have 

 higher natural mortality than Atlantic menhaden (B. 

 tyrannus), resulting in high interannual variation in 



fishable stock (Vaughan et al. 1 996). The gulf menha- 

 den population is considered stable and capable of 

 supporting an annual harvest, although declines in 

 landings have been noted since the peak landings of 

 the 1 980's (Christmas et al. 1 988, NOAA 1 992, Vaughan 

 et al. 1996). To maintain this valuable resource, the 

 Menhaden Advisory Committee and the Gulf States 

 Marine Fisheries Commission impose fishing limits to 

 regulate the fishery and monitor development activities 

 that impact the population (Christmas et al. 1988, 

 NOAA 1992). 



Personal communications 



Ahrenholz, Dean W. NOAA National Marine Fisheries 

 Service, Beaufort, NC. 



Lowery, Tony A. NOAA SEA Division, Silver Spring, 

 MD. 



Smith, Joseph W. NOAA National Marine Fisheries 

 Service, Beaufort, NC. 



Vaughan, D.S. NOAA National Marine Fisheries Ser- 

 vice, Beaufort, NC. 



References 



Allshouse, W.C. 1983. The distribution of immigrating 

 larval and postlarval fishes into the Aransas-Corpus 

 Christi Bay complex. M.S. thesis, Corpus Christi St. 

 Univ., Corpus Christi, TX, 118 p. 



Ahrenholz, D.W. 1981. Recruitment and exploitation 

 of gulf menhaden, Brevoortia patronus. Fish. Bull., 

 U.S. 79(2):325-335. 



Ahrenholz, D.W. 1991. Population biology and life 

 history of the North American menhadens, Brevoortia 

 spp. Mar. Fish. Rev. 53(4): 3-19. 



Ahrenholz, D.W., J.F. Guthrie, and C.W. Krouse. 1 989. 

 Results of abundance surveys of juvenile Atlantic and 

 gulf menhaden, Brevoortia tyrannus and B. patronus. 

 NOAA Tech. Rep. NMFS 84. 



Burkholder, J.M., H.B. Glasgow, Jr., and C.W. Hobbs. 

 1995. Fish kills linked to a toxic ambush-predator 

 dinoflagellate: distributions and environmental condi- 

 tions. Mar. Ecol. Prog. Ser. 124:43-61. 



Chapoton, R.B. 1971. The future of the Gulf Menha- 

 den, the United States' largest fishery. Proc. Gulf 

 Coast Fish Inst. 24:134-143. 



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