Bay Gobies – Conservation Genetics and Conflicts in the Restoration of California Estuaries

The North Pacific "bay gobies" (Gobiidae: Gobionellinae) include approximately 17 eastern Pacific temperate and subtropical largely estuarine species with the greatest diversity found from California to the Gulf of California. These species prefer discrete types of estuarine habitat.  The federally endangered tidewater goby, Eucyclogobius newberryi, is exclusive to the coast of California and strongly prefers seasonally closing habitat. Reproduction is confined to the summer months, when estuaries close and freshen; consequently, oceanic larval dispersal is lacking. Microsatellite data document hydrologic control of dispersal, where significant rainfall and resultant stream-flow events opens estuaries to the sea, permitting adult movement along sandy coasts.  Our data indicate that rocky headlands function as impassible barriers yielding a dozen local isolated units that have not experienced gene flow for millennia, resulting in the greatest local genetic subdivision of any west-coast vertebrate. Furthermore, tidewater goby from Orange and San Diego Counties are deeply divergent (1 to 2 million years) in both mitochondrial and nuclear sequence and are morphologically distinct from populations to the north.  This southern lineage (southern tidewater goby) is a separate species by any reasonable criterion, and it is under immediate threat of extinction as it persists in only three to five ephemeral sites in any given year.  On the order of a billion dollars has been spent on estuary “restoration” in southern California.  In every case this involves type conversion from historically closing systems to fully open tidal estuaries.  Such “restoration” has been conducted or is planned for virtually all historic and potential habitat for the southern tidewater goby beyond its very limited current range on Camp Pendleton.  As a consequence “restoration” of estuaries in southern California has to be recognized as a primary threat to the recovery of the southern tidewater goby.  These “restorations” conflict with natural geomorphic process on the coast and as a consequence have additional negative effects, on the coastal water table, on other endangered species, on public health, and have high maintenance costs. These potential consequences have gone largely unrecognized, and need to be assessed in restoration planning.  Habitat specificity influences dispersal, genetic structure and endangerment of bay gobies. Increased understanding of formative processes in estuaries, combined with a better understanding of the ecology and genetics of these species on the West Coast and in the Gulf of California, should provide the basis for habitat based conservation of the bay gobies.

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