Contribución al conocimiento del origen y distribución de la ictiofauna del Golfo de California, México

Abstract

This contribution reviews and proposes some theorical models to explain several aspects about the origin and distribution of the ichthyofauna of the Gulf of California. After a brief descripction about its coastal developments, hidrology and geological history, the zoogeographical relationships of the Guls ichthyofauna are analyzed. It is emphasized the afinity between the fish-groups of this mare nostrum and other tropical regions of the world, mainly with the Caribbean and, in general, with the northwestern Atlantic and Indo-Pacific. It is posed the hypothesis that the actual ichthyofauna of the Gulf it seems not differ much from that shaped out by the end of Pliocene and early Pleistocene. It is suggested that the origin of the ichthyofauna of this sea go back to the late Cretaceousc and early Paleocene, when probably appeared the "protogulf". When the actual Peninsule completed its develompent would happen many phenomena resulting in the characteristic actual ichthyofauna, a complex of tropical and subtropical, temperate and even arctic-boreal species. In this context the proposed hypotheses to explain such kind of phenomena are analyzed, combining the dispersalist ideas with the propositions of the vicariant theory. The existing zoogeographic barriers inside the Gulf and their effects on some fish ensembles are discussed. It is stressed the relationships that the therminc fluctuation together with the bottom coastal type (rocky, sandy, mud-clayey) have with the ichthyic composition and their distribution and abundance. Those successful transpacific populations in colonizing the Mexican Pacific coasts, including some localities of the Gulf of California, are documented. In relation to the neritic ichthyofauna of the Gulf, some ecological and geographical considerations mainly related to the processes of endemism, more remarkable in rocky and coralline environments, are settld. The hypotheses intending to explain the pesence of various populations of artic-boreal affinities are discussed. Likewise, the relationships between the three charactristics type of environment of this sea (north, center and south of the Gulf) and the distributional patterns of the different fish ensembles are analyzed.