Northwestern Coast Of Mexico Research Articles

Serodiversity, antibiotic resistance, and virulence genes of Vibrio parahaemolyticus in oysters collected in coastal areas of northwestern Mexico between 2012 and 2020

This study aimed to determine the prevalence of V. parahaemolyticus in oysters from the northwestern coast of Mexico and to identify the serotypes, virulence factors, and antibiotic resistance of the strains. Oyster samples were collected from 2012 to 2020 from the northwest coast of Mexico; biochemical and molecular methods were used to identify V. parahaemolyticus from oysters; antiserum reaction to determine V. parahaemolyticus serotypes, and PCR assays were performed to identify pathogenic (tdh and/or trh) or pandemic (toxRS/new, and/or orf8) strains and antibiotic resistance testing. A total of 441 oyster samples were collected and tested for V. parahaemolyticus. Forty-seven percent of oyster samples were positive for V. parahaemolyticus. Ten different O serogroups and 72 serovars were identified, predominantly serotype O1:KUT with 22.2% and OUT:KUT with 17.3%. Twenty new serotypes that had not been previously reported in our region were identified. We detected 4.3% of pathogenic clones but no pandemic strains. About 73.5% of strains were resistant to at least one antibiotic, mainly ampicillin and ciprofloxacin; 25% were multi-drug resistant. In conclusion, the pathogenic strains in oysters and antibiotic resistance are of public health concern, as the potential for outbreaks throughout northwestern Mexico is well established.

Effect of gillnet selectivity on elasmobranchs off the northwestern coast of Mexico

The regulation of mesh size is important for the effective and sustainable management of fisheries using gillnets, which are the main fishing gear used in artisanal elasmobranch fisheries throughout northwestern Mexico. Gillnet selectivity studies focusing on elasmobranchs have generally evaluated the impact on target species, and information on bycatches remains scarce. This study assessed the impact of gillnet selectivity on both target elasmobranch species and bycatches, by varying the mesh size of gillnets. Sampling was performed from 2009 to 2015 in five artisanal fishing grounds located along the northwestern coast of Mexico. The species composition and ecological parameters of the elasmobranch communities that were caught, as well as the size structure and estimated selectivity models for the main species caught, were compared between four mesh sizes: 10.16, 15.24, 20.32 and 25.4 cm (stretched opening). Overall, 32 elasmobranch species were caught, nine of which were common to all mesh sizes. Our results indicate that the species composition of the catch varied with mesh size. While the small-sized sharks Mustelus californicus and M. henlei were the main species caught by gillnets with the smaller mesh sizes, the guitarfish Pseudobatos productus and Zapteryx exasperata, and the Pacific angel shark Squatina californica were the main species caught gillnets with the largest mesh sizes. Gillnet selectivity was estimated for these latter four species as well as for the horn shark Heterodontus francisci. Optimum length for these species varied widely, increasing proportionally to mesh size. These findings emphasize the difficulty of determining an optimal minimum mesh size for multi-species fishery in this area. Finally, recommendations for future directions according to the species' vulnerability to fishing are discussed, focusing on the development of effective strategies to initiate or strengthen the recovery of elasmobranchs of the northwestern coast of Mexico.

Detrital zircon record of Mesozoic volcanic arcs in the Lower Cretaceous Mural Limestone, northwestern Mexico

The northwestern part of Mexico, southern Arizona, and southern California witnessed extensive arc magmatism during Late Triassic to Early Cretaceous. Here, we present results from petrography, whole‐rock geochemistry (major and trace including rare‐earth elements), and detrital zircon geochronological studies that were carried out on sandstones and shales of the Mural Limestone exposed in the Rancho Bufalo area. Based on the petrography, sandstones are classified as sublitharenite, litharenite, feldspathic litharenite, and lithic arkose. The sandstones contain higher proportion of monocrystalline quartz than polycrystalline quartz. Sandstones and shales from the various members of the Mural Limestone show large variations in major and trace elements concentrations. The average concentrations of ΣREE (total ΣREE) are lower in sandstones than in shales. The chondrite‐normalized REE patterns of the sandstones and shales are moderately fractionated with light REE (LREE) enrichment relative to heavy REE (HREE) and with flat to slightly depleted HREE patterns. The chemical index of alteration values and A–CN–K relationships of sandstones indicate low to moderate intensity of weathering in the source region; however, shale samples suggesting the source rocks were subjected to moderate intensity of chemical weathering. The chondrite‐normalized REE patterns, Al2O3/TiO2ratio, elemental ratios like Cr/V, Y/Ni, and Eu‐anomaly (Eu/Eu*), and bivariate plots suggest that the sandstones and shales were derived mainly from felsic source rocks. Detrital zircon U–Pb geochronology of sandstones from Fronteras, Rancho Bufalo, and Cerro La Ceja members of the Mural Limestone show five main groups of detrital zircon age populations: (a) Proterozoic, (b) Palaeozoic, (c) Triassic, (d) Jurassic, and (e) Early Cretaceous. Our study suggests that continental volcanic arcs in northwestern Mexico, southern Arizona, and southern California served as the provenance for the Late Triassic‐Jurassic detritus, whereas the Early Cretaceous zircon grains were derived mainly from the active Alisitos volcanic arc along the northwestern coast of Mexico.

Detecting Opisthonema libertate (Gunther, 1867) phenotypic stocks in northwestern coast of Mexico using geometric morphometrics based on body and otolith shape

Stock discrimination is essential for biomass population assessment and essential for the fisheries management. The analysis of shape differences in anatomical structures ( e.g ., body shape, otoliths, scales) has been relevant issue in the study of population structure. We evaluated the hypothesis on the existence of a stockstructured population of Pacific thread herring Opisthonema libertate in the northwestern coast of Mexico. Geometric morphometric methods were used to analyze body and otolith shape. Samples come from at three commercial fishery-landing sites: Magdalena Bay, Guaymas, and Mazatlan, Mexico. Results based on body and otolith shape support the existence of different morphotypes by location. Body shape allowed better discrimination than otolith shape. The differences observed between the phenotypic stocks suggest seasonal movements, which are linked to the marine current system in this region, particularly to the California Current and the North Equatorial Counter Current.

Caligus fajerae n. sp. (Copepoda: Caligidae) parasitic on the Pacific sierra Scomberomurus sierra Jordan & Starks (Actinopterygii: Scombridae) in the Pacific Ocean off Mexico.

A new species of parasitic copepod, Caligus fajerae n. sp. (Caligidae), is described from Scomberomorus sierra Jordan & Starks (Scombridae) caught off the northwestern coast of Mexico. The new species morphologically resembles Caligus cybii Bassett-Smith, 1898, Caligus kanagurta Pillai, 1961, Caligus pelamydis Krøyer, 1863 and Caligus robustus Bassett-Smith, 1898, all of which have been reported from scombrid hosts. Caligus fajerae n. sp. differs from these species by having spinules on the abdomen and caudal ramus, two processes on the proximal antennulary segment, fine striations on the claw of the antenna and maxilliped, a stouter and more recurved maxillulary dentiform process, shorter tines on the sternal furca, two additional patches of spinules on the distal endopodal segment of leg 2, a sclerotised lobe on the anteromedian surface of the leg 3 protopod and serrations on both margins of the first exopodal spine of leg 3. Analysis of the DNA sequences of the mitochondrial cytochrome c oxidase subunit 1 gene for Caligus fajerae n. sp. and 28 congeners, including C. pelamydis and C. robustus, showed that the new species grouped with Caligus belones Krøyer, 1863 (with 20% divergence), a species known to occur predominantly on needlefishes. Caligus fajerae n. sp. is the fifth species of Caligus reported from S. sierra. An updated host-parasite list for Caligus spp. on scombrids is provided.

Population structure of the Pacific angel shark (Squatina californica) along the northwestern coast of Mexico based on the mitochondrial DNA control region

Population structure has direct consequences on species evolution, local adaptation, and the capacity of a metapopulation to adapt to climate change. In this study we assess the genetic structure and demographic history of the Pacific angel shark, Squatina californica, along the northwestern coast of Mexico using the mitochondrial control region. Results showed high levels of genetic diversity and reveal genetic differentiation between the samples from the Pacific coast of the Baja California Peninsula and those from the Gulf of California. These genetic differences are consistent with ontogenetic differences previously reported for S. californica off the northwestern coast of Mexico. Our findings can be explained by the low dispersal ability and habitat preference of the angel shark and by the complex geomorphology off the northwestern coast of Mexico. Contrasting historical demographic patterns were observed: population expansion in the gulf and population stability, with a declining trend, in the Pacific; however, more studies are required to corroborate demographic patterns in both populations. Our results point to 2 distinct management units of the Pacific angel shark in the study area, and this may have direct implications for the management and conservation of this species in Mexico.

A Potential Role of Shrimp Farms for the Conservation of Nearctic Shorebird Populations

Shrimp aquaculture farms have greatly expanded at tropical areas worldwide, especially during the past three decades. One of the main core areas of this expansion was the northwestern coast of Mexico, prompting conservation concern for the shorebird populations that spend the nonbreeding period (October to March) in the region. We conducted a series of counts and behavioral observations to evaluate the importance of a shrimp farm as foraging habitat for shorebirds, relative to adjacent intertidal areas, during and after the shrimp harvest period at a tropical wetland in Sinaloa, Mexico, 2012 and 2013. Overall, low-tide counts within the entire wetland had an average of 3,168 ± 605 (SE) shorebirds during the shrimp harvest period (October–November) and subsequently dropped to 1,408 ± 373 birds following harvest (December to January), when shrimp ponds were emptied and foraging opportunities were reduced. The proportion of counts at the shrimp farm relative to total counts over the entire wetland ranged from 10 to 80 % for different shorebird species and dropped to 0 to 10 % in the postharvest period. During the harvesting period, black-necked stilt, American avocet, willet, and whimbrel selected shrimp ponds over intertidal areas to forage during low tide, while marbled godwit, western sandpiper, and dowitchers did not. The proportion of shorebirds observed feeding at the shrimp farm ranged between 60 and 90 % for most species and did not differ between low- and high-tide counts. These results suggest that shrimp farms can provide ephemeral but important complementary foraging areas for shorebirds, and appropriate management of existing farms may aid in conservation efforts for these species.

A new species of Euryhaliotrematoides Plaisance & Kritsky, 2004 (Monogenea: Dactylogyridae) from the gills of the spotted rose snapper Lutjanus guttatus (Steindachner) (Perciformes: Lutjanidae)

Euryhaliotrematoides mehen n. sp. (Monogenea: Dactylogyridae) is described based on specimens collected from the gills of the spotted rose snapper Lutjanus guttatus (Steindachner) off Mazatlan, Sinaloa, on the northwestern coast of Mexico. The synapomorphy of this genus is the presence of a funnel-shaped base of the male copulatory organ. This new species differs from all other species of the genus by possessing a male copulatory organ with a base with a thickened margin and a membranous accessory piece resembling a scarf and covering about 60% of its distal region. PCR products of the 28S rRNA (831 bp) and 18S rRNA (662 bp) genes were sequenced and submitted to GenBank (accession numbers HQ615997 and JF938069, respectively). BLASTn searches revealed no 100% identical hits with the previously registered monogenean sequences.

Genetic population structure of red mangrove (Rhizophora mangle L.) along the northwestern coast of Mexico

This study contributes to our understanding of population genetic diversity and connectivity in the red mangrove of northwestern Mexico. We evaluated the population genetic structure and the patterns of gene flow of the red mangrove, Rhizophora mangle, along the northwestern coast of Mexico. We analyzed samples taken from the northern Pacific distribution range limit, discuss the main mechanisms that probably have shaped the current genetic composition. The results show significantly reduced genetic diversity in northern populations, which can be attributed to very low effective population size, inbreeding, and high environmental pressure at distribution margins. Private alleles were found to be present at very low frequency on both the Pacific coast of Baja California and inside the Gulf of California, which suggests heterogeneity in genetic composition. Although we detected gene flow that was apparently associated with marine currents, we believe that the Baja California peninsula and the convergence of marine currents at the mouth of the Gulf of California are acting as effective barriers that limit gene flow. Cluster analysis supports this hypothesis, showing two main areas of genetic composition (inside and outside the Gulf of California). These findings were confirmed by significant genetic differentiation (FST=0.26; RST=0.50) between these regions; the findings also show that R. mangle presents low genetic diversity at margins without a random distribution and is present in at least two genetic population units along the northwestern Mexican coast.

Reproductive cycle of the leopard grouper Mycteroperca rosacea in La Paz Bay, Mexico

The leopard grouper Mycteroperca rosacea is an endemic species from the northwestern coast of Mexico and, like other serranid fishes, it has a high commercial value; hence, it is a good candidate for cultivation. This study aimed to describe the reproductive cycle of the leopard grouper in the wild as a step toward evaluating its aquaculture and restocking potential. From March 2008 to February 2009, 197 specimens were collected in the Gulf of California, Mexico. Overall sex ratio was 3.6 females to 1.0 male. Significant differences (P < 0.05) in total length and body weight were found between sexes. Group-synchronous ovarian development was observed with one yearly spawning period from May to June. Males matured two months earlier than females. The reproductive cycle was divided into four periods: (1) maturation, (2) spawning, (3) post-spawning, and (4) resting. Significant variations in the gonadosomatic index, hepatosomatic index, visceral fat index, and condition factor were observed throughout the study period. In addition, nine individuals were classified as immature bisexuals and one grouper presented evidence of sex change.

Seasonality of Parasitic Copepods on Bullseye Puffer, Sphoeroides annulatus (Pisces: Tetraodontidae), From the Northwestern Coast of Mexico

Seasonal occurrence of parasitic copepods in wild bullseye puffer, Sphoeroides annulatus (Pisces: Tetraodontidae), was analyzed in conjunction with variation of biotic and abiotic factors. Eleven samples were taken between February 2007 and February 2008 in Santa María La Reforma lagoon (northwestern coast of México). In total, 337 fish was examined; 5 parasitic copepod species were observed, including Acantholochus zairae , Caligus serratus , Lepeophtheirus simplex , Pseudochondracanthus diceraus , and Parabrachiella sp. The most common species were L. simplex , P. diceraus, and C. serratus (overall prevalence, 59, 53, and 35%, respectively), which significantly varied in prevalence and mean intensity between sampling months. A seasonal pattern was only observed for L. simplex, with higher infection levels in the warmest month than in the coldest month. Statistical analyses indicated that the intensity of L. simplex was positively correlated with water temperature. There were no significant differences in prevalence and intensity of infection among female and male hosts. At the component community level, species richness ranged between 4 and 5 during most of the study period, and no seasonality was observed in the number of individuals, Shannon diversity index, evenness index, or the Berger-Parker dominance index. At the infracommunity level, 4 descriptors used (mean species richness, mean number of individuals, mean Brillouin's diversity index, and mean Berger-Parker index) varied significantly between sampling months, but no seasonality was observed, except for a slight increase in the number of individuals during the warmest month. A significant positive association was detected between number of individuals and water temperature and between host size and both species richness and number of individuals. This is the first account of the ecology of these 5 parasitic copepods. Although no significant association was detected between fish condition factor and the burden of parasitic copepods, given the high occurrence of the caligid copepod L. simplex , we suggest that this copepod could represent a threat for the culture of S. annulatus .

A tropical assemblage of benthic macroalgae on rocky reefs in a temperate zone on the western Baja California peninsula, Mexico

Abstract We analyzed rocky reef benthic macroalgae on the western coast of the Baja California peninsula, Mexico. To describe the assemblages, we sampled two reefs that are geographically proximate but influenced by different oceanographic conditions, leading to potential differences in factors that could affect the macroalgal assemblage. Using analyses of similarities, we found significant differences between sites and seasons. Additionally, composition changed seasonally, but was not related to depth. Using SIMPER analysis, the species that defined the assemblages at “Arvin”, Tortugas Bay were Macrocystis pyrifera, Sargassum muticum and Plocamium cartilagineum; in contrast, the key components at “Queen” were Padina caulescens, Polysiphonia johnstonii var. concinna and Dictyota coriacea, showing how oceanographic conditions can influence the biogeographic pattern of macroalgal assemblages along the northwestern coast of Mexico.

Parasite diversity of Nyctiphanes simplex and Nematoscelis difficilis (Crustacea: Euphausiacea) along the northwestern coast of Mexico

The diversity of parasites found on Nyctiphanes simplex and Nematoscelis difficilis (Order Euphausiacea) was compared during 10 oceanographic cruises made off both coasts of the Baja California peninsula, Mexico. We tested the hypothesis that N. simplex has a more diverse parasitic assemblage than N. difficilis because it is a neritic species, has larger population abundance, and tends to form denser and more compact swarms than N. difficilis. These biological and behavioral features may enhance parasite transmission within swarms. We detected 6 types of ectoparasites: (1) epibiotic diatoms Licmophora sp.; (2) Ephelotidae suctorian ciliates; (3) Foettingeriidae exuviotrophic apostome ciliates; (4) an unidentified epicaridean cryptoniscus larvae (isopoda); and 2 castrators: (5) the ectoparasitic Dajidae isopod Notophryxus lateralis and (6) the ellobiopsid mesoparasite Thalassomyces fagei. We also detected 7 types of endoparasites: (1) an undescribed Collinia ciliate (Apostomatida); 3 types of Cestoda: (2) a Tetrarhynchobothruium sp. (Trypanorhyncha), (3) Echinobothrium sp. (Diphyllidea: Echinobothyriidae), and (4) unidentified metacestode; (5) a Trematoda Paronatrema-like metacercaria (Syncoeliidae); (6) the nematode Anisakis simplex (L3); and (7) Polymorphidae acantocephalan larvae (acanthor, acanthella, and cystacanth larval stages). N. simplex is affected by all types of parasites, except the isopod N. lateralis, having a considerably larger parasitic diversity and prevalence rates than N. difficilis, which is only infested with 3 types of ectoparasites and T. fagei. Euphausiid swarming is an adaptive behavior for reproduction, protection against predators, and increased efficiency in food searching, but has a negative effect due to parasitism. Although the advantages of aggregation must overcome the reduction of population and individual fitness induced by parasites, we demonstrated that all types of parasites can affect approximately 14% of N. simplex individuals. Collinia spp. endoparasitoids must occasionally have a significant influence on population mortality with potential epizootic events.

Two new species of Dactylogyridae (Monogenoidea) on rose spotted snapper, Lutjanus guttatus (Osteichthyes: Lutjanidae), from the coasts of Nayarit and Sinaloa, Mexico

Two new species, one each in Haliotrema and Euryhaliotrema, from the gills of the rose spotted snapper, Lutjanus guttatus, Steindachner, 1869, in Nayarit and Sinaloa, northwestern coast of Mexico, are described. Haliotrema guttati n. sp. is differentiated from its congeners H. longihamus and H. heteracantha by the presence of a delicate membranous envelope at the base of the copulatory organ, ventral and dorsal anchors with a prominent bulge on the inner face of the shaft, the base of the dorsal anchors simply fenestrated, ventral and dorsal bars having wide ends, and the ventral and dorsal bars W-shaped. Euryhaliotrema perezponcei n. sp. is characterized by a coiled male copulatory organ with three counterclockwise rings.

Morphology and distribution of Corallina vancouverensis (Corallinales, Rhodophyta) in Northwest Mexico

The morphology and distribution of Corallina vancouverensis Yendo was studied in order to determine its distribution limits and morphological variations in the northwestern coast of Mexico. Two hundred specimens were collected and analyzed, as well as samples from several herbaria, representing an overall total of 65 localities. The bibliographic records of this species in the Baja California Peninsula and mainland Mexico were also analyzed. Populations of C. vancouverensis are distributed from Alaska to Las Cabrillas, which is located South of Todos Santos, BCS. Several new localities are recorded for this species in the Gulf of California, and its southern limit in the Northeast Pacific is considered to lie within 23ºN on both sides of the Baja California Peninsula. Furthermore, the taxonomic relationship of this species with C. pinnatifolia and C. fiondescens is questioned based on morphological, ecological and distributional tendencies.