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Demographics and life history traits of red snapper from south Texas, a historically under-sampled region
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Description:This project was conducted to augment biological data and stock demographics of red snapper (Lutjanus campechanus) from south Texas and U.S. waters in the U.S./Mexico maritime boundary. Fish were sampled from a contracted fishing vessel from June through September of 2017, using a vertical line rigged with 30 hooks. Sampling stations were selected from industry-supplied red snapper fishing locations or located via exploratory fishing within statistical reporting grid 21. The sampled red snappers were processed to obtain length, weight, internal temperature, both sagittal otoliths, and gonadal tissue. The highest proportion of captured red snapper measured between 400 and 500 millimeters FL. Ages were determined from traverse sections of otoliths for 1871 individuals, with the highest proportion of ages at age 5 years, and the oldest fish at 19 years. Trends for ages increased with both weight and length. Weights were collected for 1904 gonads, and the trends for both male and female increased with length. Macro staging of the gonads revealed the highest proportion of running ripe females occurred in late July, and running ripe males in early July. Maturity assignations for 705 female red snapper yielded 18 immature, 670 mature, 13 of uncertain maturity and four were discarded. A maturity ogive was not estimated due to the lack of contrast between smaller and younger individuals, and larger and older ones. Batch fecundity estimations of 58 female red snapper averaged 39459 eggs per individual. Batch fecundity trend increased with age and size; however the relative batch fecundity for grid 21 was lower if compared with the relative batch fecundity for other published estimates. The results of spawning fraction also support lower reproductive outputs for grid 21 females when compared with publications of other areas in the Gulf of Mexico. The reproductive outputs estimated for this project were lower than previous estimations that assessed the western Gulf of Mexico, potentially due to the diversity in the age composition and demographics of the stock of grid 21. Overall, this project provided biological parameters for the red snapper fisheries in the western Gulf of Mexico that will aid in the understanding of the stock in this under-sampled area.
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