Abstract
The ecological and distributional status of the continental fishes of <br /><br />northwestern Baja California, Mexico, was seasonally monitored between Feb- <br /><br />ruary 1996 and March 1997. A review of records in literature and of specimens <br /><br />collected between 1983 and 1995 in the study area, provide the data upon which <br /><br />this report is based. A total of 23 species (19 native and 4 exotic) belonging to <br /><br />22 genera and 15 families was registered. This fish fauna is ecologically composed <br /><br />of species of marine derivation (78.9% sporadic and 21.1% diadromous) and by
8 permanent species (34.8%), 9 tidal visitors (39.1%) and 6 occasional visitors <br /><br />(26.1%). From the ichthyogeographical point of view, most of the species are of <br /><br />Calif omian affinity (68.4%) and the remaining related to northeastern Pacific <br /><br />(15.7%), Holarctic (5.3%) and circumtropical (5.3%) regions. Only one taxon <br /><br />{Oncorhynchus mykiss nelsoni) is endemic (5.3%) to the study region. Ten species <br /><br />are new continental records for Baja California [Norte], and seven taxa reach their <br /><br />southernmost continental ranges in northwestern Baja California. The conserva- <br /><br />tion status of Gasterosteus aculeatus microcephalus is considered as threatened. <br /><br />The main problem that affects the ecosystemic integrity of the streams of this <br /><br />region is the progressive alteration of the aquatic and riparian habitats caused by <br /><br />anthropogenic impact.
