The relation between length (L) and weight (W) was estimated for 33 species representing 14 families of fishes from El Conchalito mangrove swamp, Gulf of California (Mexico). The parameter b estimated by nonlinear least squares of weight and length data, ranged from 1.41 to 3.68. Length -weight parameters can be used for several biological or fishery purposes to enable the derivation of weight estimates from given a value of length or vice versa. 1

Length-weight and length-length relationships were estimated for 10 freshwater, estuarine and marine fish species caught at the mouths of coastal sterams from northwestern Baja California (Mexico). The parameter b estimated by nonlinear least squares of weight and length data, ranged from 2.50 to 3.61. Size conversions (calculated total length from standard length) can be used in fishery for understanding several aspects of population dynamics.

The urohyal bone, located in the central part of the mandibular skeleton, plays an important role in the mouth openingclosing mechanism of fish, and is considered a synapomorphy in teleostean fish. Morphology of the urohyal bone in six species of Gerreidae (Diapterus brevirostris, D. auratus, Eugerres lineatus, E. plumieri, Eucinostomus entomelas and Gerres cinereus) from the Pacific and Atlantic coasts of México was compared, using size and shape measurements. The main goal of the study was to explore the effectiveness of urohyal measurements in discriminating Gerreidae species. Morphological variation of urohyal bones, in terms of size and shape parameters, allowed species differentiation. Discriminant function analysis (DFA) significantly separated the six species with high classification rates (overall mean 92%). The G-test and Cohen's kappa confirmed the high rates of classification success obtained by DFA. Circularity, Feret minimum, roundness, rectangularity and area were the main urohyal measurements explaining inter-specific variability. These results suggest the usefulness of urohyal bone morphology in differentiating Gerreidae species analyzed, highlighting the taxonomic value of the urohyal bone, until now never quantitatively evaluated as a diagnostic character in the classification of teleostean fish.

uero, J. (2014). Molecular and morphometric systematics of Diapterus (Perciformes, Gerreidae). -Zoologica Scripta, 43, 338-350. The fish belonging to Gerreidae are common representatives of the coastal ichthyofauna of the tropics and subtropics of the world. The genus Diapterus has a neotropical distribution and currently includes four species: two in the Atlantic Ocean [Irish mojarra D. auratus Ranzani 1842 and rhombic mojarra D. rhombeus (Cuvier 1829)] and two in the Pacific Ocean [short-beaked mojarra D. brevirostris (Sauvage 1879) and golden mojarra D. aureolus (Jordan & Gilbert 1882)]. This genus has uncertain taxonomy based on the remarkable and dissimilar morphology of D. aureolus. We evaluated the taxonomy and phylogeny of Diapterus with statistical (canonical discriminant analysis) and phylogenetic analyses (maximum parsimony, maximum likelihood and Bayesian inference) of geometric morphometric data (relative warps) and molecular data (12Sr RNA, 16Sr RNA, COI and RAG1 sequences). Our results indicate that the genus Diapterus as we currently conceive it is a polyphyletic group: [(Gerres cinereus -Eucinostomus spp. (D. aureolus -(Eugerres spp. (D. auratus -(D. brevirostris -D. rhombeus)))))]. Therefore, a taxonomic rearrangement is needed. To preserve the monophyly of the group, our proposal is to remove D. aureolus and place it in a new monotypic genus. A neotype is designated for D. aureolus as well as an artificial identification key for the genera and the species treated in this article.Our concept of a species is necessarily shaped by our understanding of the characters by which it attains objective and testable status in taxonomic research, [however] there is a disturbing trend to ignore deep thought about individual characters and to treat species as if they existed to be recognized by DNA barcodes rather than critically tested as evolutionary hypotheses. Those who misuse taxonomic information can answer for their own sins.(Valdecasas et al.

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The checklist presented in this study includes the latest taxonomic and systematic modifications and updates (early 2018) for the Chondrichthyes that inhabit the Exclusive Economic Zone (EEZ) of Mexico. The list is based on a literature review of field-specific books, scientific publications and database information from collections and museums worldwide available online such as, the Ocean Biogeographic Information System (OBIS), Global Biodiversity Information Facility (GBIF), Encyclopedia of Life (EOL), iSpecies, FishBase and the National Biodiversity Information System (SNIB–CONABIO). Information was cross-referenced with digital taxonomic systems such as the Catalog of Fishes of the California Academy of Sciences, the World Register of Marine Species (WoRMS), and the Integrated Taxonomic Information System (ITIS). There is a total of two subclasses two divisions, 13 orders, 44 families, 84 genera, and 217 species that represent approximately 18% of all living and described species of chondrichthyans worldwide. For the Mexican Pacific and the Gulf of California, 92 species of chondrichthyans are listed compared to 94 species for the Gulf of Mexico and the Caribbean Sea. Additionally, 31 species listed occur on both coasts of Mexico. The species richness of the Mexican chondrichthyans will surely continue to increase, due to the exploration of deep-water fishing areas in the EEZ.

Summary Stock discrimination in fishes is important for fisheries management. Morphometric analysis has been a viable approach when different structures (overall body, otoliths, and scales) are used. However, in cases where a single source of information may already differentiate among stocks, different conclusions may be obtained when using different sources of information. These have to be considered because they could lead to different management plans. Using geometric morphometrics, data was analyzed regarding the body and otolith shape of the Pacific sardine Sardinops sagax Jenyns, 1842 collected off the west coast of Baja California Peninsula, Mexico. Results confirm seasonal differences in body shape and otolith shape in stocks previously associated with sea surface temperature. Although both measures resulted in compatible conclusions, the shape of the body discriminated groups more appropriately; the data indicate that differential resolution could be thus obtained, depending on the source of the data. If possible, the application of more than one source of information is suggested in comparable cases because this would detect the extent of stock isolation with greater certainty.

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