California halibut

The small tidal creeks and channels of the estuary support a relatively diverse population of fish including at least 29 species. Estuaries such as the Tijuana Slough NWR provide a "nursery" for these fish, and in turn provide food for a suite of other species in the food web.

Since 1987, fish assemblages have been sampled in the estuary. Catches are often dominated by topsmelt (Atherinops affinis), longjaw mudsucker (Gillichthys mirabilis; shown in photo below), arrow goby (Clevelandia ios), and California killifish (Fundulus parvipinnis). Adult striped mullet (Mugil cepalus) are also common. Abundance varies year to year, but total density tends to peak in the summer and declines in the winter. The tidal channels have been shown to function as a nursery for commercially important fish, such as the California halibut (pictured, above). Nordby (1982) found abundant eggs of the croaker family, topsmelt, and northern anchovy. Hence, the estuary appears to be providing nursery habitat for marine fishes; it may, therefore, be important for sport and commercial fisheries. Game fish such as kelp bass and sand bass, opaleye, and white croaker have also been found in the estuary (U.S. Department of Commerce and California Coastal Commission, 1981).

 Long jaw mudsucker fish