593 



Abstract— Red snapper (Lutjanus 

 campechanus) in the United States 

 waters of the Gulf of Mexico ( GOM ) 

 has been considered a single unit 

 stock since management of the spe- 

 cies began in 1991. The validity of this 

 assumption is essential to manage- 

 ment decisions because measures of 

 growth can differ for nonmixing popu- 

 lations. We examined growth rates, 

 size-at-age, and length and weight 

 information of red snapper collected 

 from the recreational harvests of Ala- 

 bama (n=2010), Louisiana (re=1905), 

 and Texas (re=1277) from 1999 to 

 2001. Ages were obtained from 5035 

 otolith sections and ranged from one 

 to 45 years. Fork length, total weight, 

 and age-frequency distributions dif- 

 fered significantly among all states; 

 Texas, however, had a much higher 

 proportion of smaller, younger fish. 

 All red snapper showed rapid growth 

 until about age 10 years, after which 

 growth slowed considerably. Von Ber- 

 talanffy growth models of both mean 

 fork length and mean total weight- 

 at-age predicted significantly smaller 

 fish at age from Texas, whereas no 

 differences were found between Ala- 

 bama and Louisiana models. Texas 

 red snapper were also shown to differ 

 significantly from both Alabama and 

 Louisiana red snapper in regressions 

 of mean weight at age. Demographic 

 variation in growth rates may indicate 

 the existence of separate management 

 units of red snapper in the GOM. Our 

 data indicate that the red snapper 

 inhabiting the waters off Texas are 

 reaching smaller maximum sizes at 

 a faster rate and have a consistently 

 smaller total weight at age than those 

 collected from Louisiana and Alabama 

 waters. Whether these differences are 

 environmentally induced or are the 

 result of genetic divergence remains 

 to be determined, but they should be 

 considered for future management 

 regulations. 



Red snapper (Lutjanus campechanus) 

 demographic structure in the northern 

 Gulf of Mexico based on spatial patterns 

 in growth rates and morphometries 



Andrew J. Fischer 



Coastal Fisheries Institute 



School of the Coast and Environment 



Louisiana State University 



Baton Rouge, Louisiana 70803-7503 



E-mail address: afische g Isu edu 



M. Scott Baker Jr. 



Coastal Fisheries Institute 



School of the Coast and Environment 



Louisiana State University 



Baton Rouge, Louisiana 70803-7503 



Charles A. Wilson 



Coastal Fisheries Institute and 



Department of Oceanography and Coastal Sciences 



School of the Coast and Environment 



Louisiana State University 



Baton Rouge, Louisiana 70803-7503 



Manuscript submitted 6 May 2003 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 19 April 2004 by the Scientific Editor. 



Fish. Bull. 102:593-603 12004). 



Red snapper {Lutjanus campechanus) 

 in the United States waters of the Gulf 

 of Mexico (GOM) are heavily exploited 

 by both recreational and commercial 

 fishermen (Wilson and Nieland, 2001; 

 Shirripa and Legault 1 ). Harvest, how- 

 ever, has not proceeded without det- 

 rimental affects on the population. 

 Commercial landings have declined 

 substantially from 6048 metric tons (t) 

 in 1964 to 1207 t in 1990; recreational 

 landings exhibited similar declines 

 from 1937 t in 1981 to 481 t in 1990 

 (NMFS' 2 ). In 1991, harvest restrictions 

 including reef fish permits, seasonal 

 fishing, fish quotas, creel limits, and 

 minimum size limits were placed upon 

 the red snapper fishermen by the Gulf 

 of Mexico Fishery Management Council 

 (GMFMC 3 ) to increase the spawning 

 potential ratio to 20%, which is indic- 

 ative of recovery. These regulations 

 have also been adopted for state waters 

 in Alabama, Louisiana, and Texas. 

 Despite the management actions, GOM 

 red snapper remain overfished (Good- 

 year 4 ; Schirripa and Legault 1 ). 



1 Shirripa, M. J., and C. M. Legault. 

 1999. Status of the red snapper in the U. 

 S. waters of the Gulf of Mexico; updated 

 through 1998, 44 p. + appendices. Con- 

 tribution rep. SFD-99/00-75 from Sus- 

 tainable Fisheries Division. Miami 

 Laboratory, Southeast Fisheries Science 

 Center, National Marine Fishery Ser- 

 vice, 75 Virginia Beach Drive, Miami, 

 FL 33149-1099. [Not available from 

 NTIS], 



2 NMFS (National Marine Fisheries 

 Service). 2003. Fisheries Statistics 

 and Economics Division. Website: www. 

 nmfs.noaa.gov. 



3 GMFMC (Gulf of Mexico Fishery Man- 

 agement Council). 1991. Amendment 

 3 to the reef fishery management plan 

 for the reef fish resources of the Gulf 

 of Mexico, 38 p. Gulf of Mexico Fish- 

 ery Management Council, 3018 N. U.S. 

 Hwy 301 Suite 1000, Tampa, FL. 33619- 

 2272. [Not available from NTIS], 



4 Goodyear, C. P. 1995. Red snapper in 

 U.S. waters of the Gulf of Mexico. Stock 

 assesment report MIA-95/96-05, 171 p. 

 Miami Laboratory, Southeast Fisheries 

 Science Center, National Marine Fish- 

 eries Service, 75 Virginia Beach Dr., 

 Miami, FL, 33149-1099. [Not available 

 from NTIS]. 



