Genetic Structure and Gene Flow of Octopus maya (Mollusca: Cephalopoda) in the States of Yucatan and Campeche, Mexico / Estrutura genética e fluxo gênico do polvo maya (Mollusca: Cephalopoda) nos Estados de Yucatan e Campeche, México

It was determined the population genetic structure of the red octopus Octopus maya in the states of Campeche and Yucatan in Yucatan Peninsula, Mexico, through the expression of isozymes in polyacrylamide gels. Mantle samples from 25 octopuses, captured in nine sites of the Yucatan Peninsula, were used to characterize the genotypic expression revealed by the expression of 26 loci in thirty enzyme systems. Program TFPGA version 1.3 (Tools for Population Genetic Analyses), was used to process data of allozyme gene frequencies of the studied populations. The parameters determined were: descriptive statistics, F statistics, genetic distances, Hardy - Weinberg, UPGMA and the number of migrants as an indicator of gene flow. The average number of alleles per locus, percentage of polymorphic loci, average and direct and direct heterozygosity were: 1.08 ± 0.05 to 1.15 ± 0.04. P95 26.9231% to 34.6154, Have 0.1142 to 0.1390 and Hdir = 0.0354 to 0.0938 respectively. Heterozygosity values in a range of 0.3506 to 0.4793 and G6PDH for ARGK with an average heterozygosity value of 0.1824, Fisher average value of 0.5313 and 0.0140 Fst indicates a heterozygous deficiency but it is within the ranges reported for marine invertebrate species. The number of migrants derived from the Slatkin equation is 1824 per generation, globally indicates some degree of variability between sites and is consistent with the low values of Nei genetic distance found, particularly the node showing the separation of the population of Lagartos River and Dzilam Bravo from the other locations with an obtained value of 0.0004. From the results of this study, it is concluded that locations of Octopus maya have a certain level of interpopulation genetic variability that does not reflect its fragility.

Potential biomass and distribution of octopus in the eastern part of the Campeche Bank (Yucatán, Mexico)

The octopus fishery on the Campeche Bank (Yucatán, Mexico) is considered the third largest in the world. In Yucatán, two fleets target this resource: an artisanal fleet and a semi-industrial fleet. The artisanal fleet only catches Octopus maya, while the semi-industrial fleet catches two species, O. Maya and O. “vulgaris” Type II, because it operates at deeper waters ( > 30 m). Since there is no information on the abundance of O. “vulgaris” Type II, management is based only on O. Maya. In order to generate information about the abundance of this species, four fishing research cruises were carried out in the northeastern area of the continental shelf off the Yucatán Peninsula. Four methods (a stratified random method, a swept area, geostatistics and a weighted swept area) were applied and compared to determine the instantaneous abundance and biomass of both species in the study area. The lowest potential biomass was calculated with the geostatistical method, with values between 18.5% and 36.7% lower than the other three methods. O. “vulgaris” Type II showed the lowest biomass (37.8±3.36 t) during May and July and the highest (189.56±11.6 t) in December. Our findings revealed that the total abun­dance of both species was similar in the study area, with a geographic overlap whose amplitude changed throughout the year according to the geographic position: O. Maya dominated at approximately 88°W, while O. “vulgaris” Type II dominated towards the southeast at 87°W.