In tropical regions, temperature is the fundamental environmental factor controlling the reproduction-related physiological activities of fish. Tropical fish are particularly sensitive to climate change since they develop in a relatively stable thermal environment. A review was done to assess the potential effect of temperature rise on reproduction and population structure in the commercially important hermaphrodite grouper and wrasse species, and in gonochoric snapper species in the southern Gulf of Mexico. Temperature increase can disturb the aromatase synthesis and/or activity, which can affect the reproductive cycle and sexual differentiation in all studied species and the sexual inversion process in sequential hermaphrodites. Moreover, a mistiming or discontinuity in spawning seasonality could occur, with an alteration in the sex ratio in favor of males and a consequent reduction in populations’ fecundity. Furthermore, if the level of fishing exploitation enhances species’ sensitivity to environmental changes, then the stock of red grouper Epinephelus morio would be more affected by temperature increases than other species because it is the only fish population in the Campeche Bank currently assessed as overexploited.

On Campeche Bank (CB) in the southern Gulf of Mexico, Gags Mycteroperca microlepis are captured as part of a sequential multispecies fishery. Limited scientific data suggest that the Gag is the third most important commercial species in the region, contributing 21% (total weight) of the overall grouper catch. Neither age nor stock data are currently available for Gags in this region, making it impossible to determine how this species is affected by current fishing practices. Such information is vital for the CB stock since it acts as a genetic source for a mixed Gag population on the west Florida shelf through a constant unidirectional flow of larvae. The goal of this study was to generate baseline age and stock structure data for Gags on CB. Age was quantified from otoliths by counting the number of annuli (indicated by the number of opaque zones from the otolith core to the margin) in thin sections. Otolith shape was analyzed by using discrete wavelet transforms, linear otolith morphometrics, and shape indices. In each of 198 specimens, age was determined based on examination of the right sagittal otolith, and shape analysis was conducted on the left sagittal otolith. Individual age ranged from 4 to 17 years, and otolith opaque band deposition occurred annually between December and February. Using principal components analysis and linear discriminant analysis, two distinct groups were identified (discrimination success = 98%), indicating the presence of substructure in the CB stock of Gags. Otolith analysis clearly assisted in achieving a better understanding of the CB Gag stock and in identifying the complexity within the stock, demonstrating that otolith analysis is a useful tool in characterizing fish populations. The study results highlight the urgent need for Gag stock assessment in this region and for the application of a cautious approach to fishery management given the immense gaps in biological data for this species.Received January 13, 2016; accepted July 18, 2016 Published online October 7, 2016

Based on their morphological and genetic similarity, several studies have proposed that Lutjanus campechanus and Lutjanus purpureus are the same species, but there is no confirmed consensus yet. A population-based study concerning otolith shape and genetic analyses was used to evaluate if L. campechanus and L. purpureus are the same species. Samples were collected from populations in the southwestern Gulf of Mexico and the Venezuelan Caribbean. Otolith shape was evaluated by traditional and outline-based geometric morphometrics. Genetic characterization was performed by sequencing the mtDNA control region and intron 8 of the nuclear gene FASD2. The otolith shape analysis did not indicate differences between species. A nested PERMANOVA identified differences in otolith shape for the nested population factor (fishing area) in morphometrics and shape indexes (p = 0.001) and otolith contour (WLT4 anterior zone, p = 0.005 and WLT4 posterodorsal zone, p = 0.002). An AMOVA found the genetic variation between geographic regions to be 10%, while intrapopulation variation was 90%. Network analysis identified an important connection between haplotypes from different regions. A phylogenetic analysis identified a monophyletic group formed by L. campechanus and L. purpureus, suggesting insufficient evolutionary distances between them. Both otolith shape and molecular analyses identified differences, not between the L. campechanus and L. purpureus species, but among their populations, suggesting that western Atlantic red snappers are experiencing a speciation process.

Yellowtail snapper Ocyurus chrysurus is commercially important throughout its distribution range. In southern Gulf of México, it is caught as part of a largely undocumented multispecific snapper fishery. Samplings were done at three fishing sites with the highest landings volume of Yucatán, México: Celestún, Dzilam de Bravo, and Río Lagartos. Age and growth parameters were generated with the von Bertalanffy growth model via annuli counts in otolith thin sections of 1,124 individuals. Marginal increment analysis confirmed that opaque zone formation is annual and occurs from July to September. Overall age range was 0⁺ to 12 years (17.7 to 38.9 cm fork length) but differed between Celestún (0⁺ to 9 years), Dzilam de Bravo (1 to 12 years), and Río Lagartos (2 to 12 years). Growth parameters and lifespan for combined sexes also varied between sites: Celestún (L_∞ = 41.59 cm, K = 0.11 year^-1, t_max = 22.41 years); Dzilam de Bravo (L_∞ = 38.36 cm, K = 0.16 year^-1, t_max = 15.5 years); and Río Lagartos (L_∞ = 40.28 cm, K = 0.12 year^-1, t_max = 20.01 years). Age at maturity was 1.3 years for females and < 1 year for males. Natural mortality based on t_max was 0.28 year^-1 overall. A principal coordinates analysis identified morphometric variables as explaining 92.2% of otolith differentiation by fishing site, with average centroid distances: Celestún, 1.98; Dzilam de Bravo, 2.22; and Río Lagartos, 2.75. Differences in growth rate, lifespan, natural mortality and otolith shape indicate that O. chrysurus in southern GoM exhibits structural complexities that suggest the occurrence of repercussions from fishing-induced demographic changes.