Noé Díaz-Viloria

Genetic Connectivity Among Pink Abalone Haliotis corrugata Populations

ABSTRACT The understanding of genetic connectivity among populations is important for the management of fisheries, particularly in overexploited benthic species such as the pink abalone Haliotis corrugata, which might have limited dispersal because of a short-term pelagic larval stage. Eight microsatellite DNA loci (Hco15, Hco16, Hco19, Hco22, Hco47, Hco97, Hco194, and Hka56) from specimens caught at five locations from the northeastern Pacific of Mexico and the United States were examined. H. corrugata showed a low to moderate genetic diversity. Most loci from the five sampling sites were in Hardy-Weinberg equilibrium, except for Hco47, which showed null alleles. Hierarchical AMOVA from seven loci showed highly significant population divergence between San Clemente Island and the Mexican locations (F ST = 0.021, P < 0.001) but not among Mexican subpopulations. The prevailing explanation for such divergence is the historical isolation by distance, but the presence of an oceanographic barrier (Southern California Eddy) and the insufficient mix between waters masses from both regions could preserve genetic differentiation.

Paralarvae of the complex Sthenoteuthis oualaniensis-Dosidicus gigas (Cephalopoda: Ommastrephidae) in the northern limit of the shallow oxygen minimum zone of the Eastern Tropical Pacific Ocean (April 2012)

The three-dimensional distribution of the paralarvae of the complex Sthenoteuthis oualaniensis-Dosidicus gigas (Cephalopoda: Ommastrephidae) was analyzed at the northern limit of the shallow oxygen minimum zone in the Eastern Tropical Pacific in April 2012. The upper limit of the oxygen minimum water (∼44 µmol/kg or 1 mL/L) rises from ∼100 m depth in the entrance of the Gulf of California to ∼20 m depth off Cabo Corrientes. Most of the paralarvae of this complex, dominated by D. gigas, were concentrated in the Gulf entrance, between the thermocline (∼20 to ∼50 m depth) and the sea surface, in the warmest (>19°C) oxygenated (>176 µmol/kg) layer. The highest abundance of paralarvae was detected in an anticyclonic eddy (∼120 km diameter and >500 m deep), which contained lower-salinity water (<35 g/kg), consistent with formation in the California Current. Lower paralarvae abundance was recorded further south off Cabo Corrientes, where hypoxic layers were elevated as water shoaled nearshore. Almost no paralarvae were found in the north of the study area beyond the strong salinity front (∼34.8–35.4 g/kg) that bounded the anticyclone. These results showed an affinity of the paralarvae for lower-salinity, oxygenated water, illustrated by the influence of the mesoscale anticyclonic eddy and the salinity front in their distribution. Based on this study, it can be concluded that the expansion of the depth range of hypoxic water observed in the Eastern Tropical Pacific may be increasing environmental stress on the paralarvae by vertically restricting their habitat, and so affecting their survival.

Assessment of Self-Recruitment in a Pink Abalone (Haliotis corrugata) Aggregation by Parentage Analyses

ABSTRACT The implementation of abalone aggregations as a tool for stock enhancement has been under discussion. For this purpose, understanding the self-recruitment capacity of managed reefs based on the amount of larval retention is an important task to evaluate potential success. Under the hypothesis that every reef is mostly self-restored within a short spatiotemporal scale because of a rather reduced planktonic period, the practice of aggregating mature adults of pink abalone in a reef would improve local recruitment. This study assessed local replenishment within an abalone reef of pink abalone Haliotis corrugata at Bahía Asunción (El Riíto reef), a location on the west coast of the Baja California Peninsula, where an aggregation of adult abalone was studied. A parentage analysis was carried out between adults transplanted to El Riíto and the juveniles collected from the same site by comparing their genetic profiles at 8 microsatellite DNA loci. The parentage tests defined successfully the status of more than 97% of the juveniles, revealing that approximately 4% of them could have been produced within the aggregation area. Because not all the potential parental abalone were collected, this self-recruitment proportion in the aggregation experiment was possibly underestimated. The suitability of parentage analyses, based on genetic markers as a robust alternative for the assessment of future aggregations, is discussed.

Molecular identification and morphological description of Micropogonias megalops, Cynoscion othonopterus, C. reticulatus and Menticirrhus nasus larvae, collected in the upper Gulf of California during Summer 2012

Abstract Sciaenidae fish larvae were collected from the upper Gulf of California during September 2012 using a conical net (505 μm) through surface tows. These were pre-classified into four larval morphotypes, based on external characteristics (mainly meristic and pigmentation). Partial sequences of cytochrome c oxidase, subunit 1 and 16S rRNA (16S) genes of mitochondrial DNA, were used in molecular genetic identification from each larval morphotype. Genetic results indicated the identification of four larval morphotypes as Micropogonias megalops, Cynoscion othonopterus, C. reticulatus and Menticirrhus nasus. Pigmentation patterns of larvae described after molecular genetic identification made it possible to distinguish between M. megalops, M. nasus and C. othonopterus (postflexion). However, pigmentation was not reliable for differentiating between preflexion larvae of C. othonopterus and C. reticulatus. From these results, both morphological and genetic approaches were proposed as complementary tools in taxonomic studies of ichthyoplankton, particularly in early fish larvae identification of congeneric species with similar morphological characteristics.

Morphological description of genetically identified Cortez bonefish (Albula gilberti, Pfeiler and van der Heiden 2011) leptocephali from the southern Gulf of California

Abstract Bonefish leptocephali of the genus Albula are difficult to identify to the species level due to morphological similarities between two different species present in the Northeastern Pacific Ocean, A. esuncula and A. gilberti. In this study, 22 bonefish leptocephali (premetamorphic and early metamorphic), collected from two locations in the southern Gulf of California were identified as Albula gilberti by comparing 459 bp of their mitochondrial cytochrome b gene sequences to those of four other species of bonefish. The characteristics of these A. gilberti leptocephali were compared to those of previously described bonefish leptocephali in the region. No distinctive morphological characteristics (meristic and pigmentation) were found that differentiate premetamorphic leptocephali of A. gilberti from those of other Albula species, making species identification by molecular-genetics a necessity. In early metamorphic leptocephali some differences in horizontal eye diameter-head length ratio, number of rays of pelvic and anal fins and myomere of pelvic-fin origin may help to differentiate A. gilberti from A. esuncula.

Proposed synonymy for Micropogonias altipinnis (Günther 1864), Micropogonias ectenes (Jordan & Gilbert 1882), and Micropogonias megalops (Gilbert 1890)

Abstract Within the Sciaenidae family, the genus Micropogonias is composed of three recognized species along the Pacific coast of Mexico: Micropogonias altipinnis, M. ectenes, and M. megalops. These species exhibit overlapping diagnostic characters, which make species identification difficult. This study ties morphological differences (meristic, morphometry of body, and otolith) with DNA sequences (CO1 and 16S fractions of mtDNA and 28S of nDNA) among Micropogonias species in the Pacific. Meristic analysis showed a latitudinal variation among the three species in the number of rays, the number of gill rakers, and length of the longest spine of the dorsal fin. Discriminant analysis of morphometric characters (body and otolith) showed three morphological entities (p < 0.001). However, the mean genetic divergences among the three species with partial sequences of mtDNA (CO1 and 16S), and nuclear (28S) were lower than those reported at the interspecific level (>2%). Genetic results suggest that the three species are one species and that the differences in meristics and morphometry could be the result of phenotypic plasticity or incipient speciation. In this sense, M. ectenes and M. megalops are proposed as junior synonyms of M. altipinnis.

Larval distribution and connectivity of the endemic Sciaenidae species in the Upper Gulf of California

Because the endemic Sciaenidae species (commonly known as drum or croakers) are important to the fishing industry in the Upper Gulf of California, their larval distribution and connectivity was analyzed in relation to hydrographic conditions during spawning periods (March, June and September). Totoaba macdonaldi, Micropogonias megalops, Menticirrhus nasus and Cynoscion othonopterus larvae were morphologically and genetically identified. Genetic analysis reveals for the first time the presence of Isopisthus remifer, which had not previously been morphologically identified. The most relevant hydrographic structure in the region was the permanent stratification front (Φ = 10 J/m) originated by the convergence of mixed water of the Northern Gulf (~20 m depth) and stratified water coming from the adjacent oceanic water (~200 m). Whereas T. macdonaldi larvae were only collected in the shallowest area in March, the other species were found mostly along the front in June and September. Connectivity matrixes showed high particle retention along the front (>80%) coinciding with the larval distribution. Results indicate that the stratification front might favor larval survival and prevent their advection toward the ocean. This type of retention likely enhances endemism, not only of these species but also of others coastal demersal species.

Development and characterization of 24 novel tetranucleotide microsatellite loci in green abalone Haliotis fulgens

Twenty-four new tetranucleotide microsatellite loci, obtained by 454 pyrosequencing, were found in the green abalone Haliotis fulgens. Genetic diversity ranged from 6 to 27 alleles per locus with 0.653–0.912 expected heterozygosity. This provides polymorphic markers for population genetics and parentage analysis focusing on the management and conservation of this species. Cross-amplification in H. corrugata and H. rufescens showed polymorphism in five and four loci, respectively.