Red snapper (Lutjanus campechanus) demographic structure in the northern Gulf of Mexico based on spatial patterns in growth rates and morphometrics
Red snapper (Lutjanus campechanus) in the United Stateswaters of the Gulf of Mexico (GOM) has been considered a single unit stock since management of the species began in 1991. The validity of this assumption is essential to management decisions because measures of growth can differ for nonmixing populations. We examined growth rates, size-at-age, and length and weight information of red snapper collected from the recreational harvests of Alabama(n=2010), Louisiana (n=1905), and Texas (n =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 differed significantly among all states; Texas, however, had a much higherproportion of smaller, younger fish. All red snapper showed rapid growth until about age 10 years, after which growth slowed considerably. Von Bertalanffy growth models of both mean fork length and mean total weight-at-age predicted significantly smaller fish at age from Texas, whereas nodifferences were found between Alabama and Louisiana models. Texas red snapper were also shown to differsignificantly from both Alabama and Louisiana red snapper in regressions of mean weight at age. Demographicvariation in growth rates may indicate the existence of separate management units of red snapper in the GOM. Ourdata 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.
| Main Authors: | , , |
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| Format: | article biblioteca |
| Language: | English |
| Published: |
2004
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| Subjects: | Fisheries, Management, |
| Online Access: | http://hdl.handle.net/1834/30939 |
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| Summary: | Red snapper (Lutjanus campechanus) in the United Stateswaters of the Gulf of Mexico (GOM) has been considered a single unit stock since management of the species began in 1991. The validity of this assumption is essential to management decisions because measures of growth can differ for nonmixing populations. We examined growth rates, size-at-age, and length and weight information of red snapper collected from the recreational harvests of Alabama(n=2010), Louisiana (n=1905), and Texas (n =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 differed significantly among all states; Texas, however, had a much higherproportion of smaller, younger fish. All red snapper showed rapid growth until about age 10 years, after which growth slowed considerably. Von Bertalanffy growth models of both mean fork length and mean total weight-at-age predicted significantly smaller fish at age from Texas, whereas nodifferences were found between Alabama and Louisiana models. Texas red snapper were also shown to differsignificantly from both Alabama and Louisiana red snapper in regressions of mean weight at age. Demographicvariation in growth rates may indicate the existence of separate management units of red snapper in the GOM. Ourdata 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. |
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