A study of food habits of two species of silverside, Menidia beryllina (Cope) and Membras martinica (Valenciennes), in upper Galveston Bay, Texas.
The food habits of the tidewater silverside, Menidia beryllina, and the rough silverside, Membras martinica, from upper Galveston Bay, were investigated. Both species of fishes were found to be omnivorous and opportunistic, feeding upon available or abundant food items. Both species changed their food habits with successive increases in size. Important foods for M. beryllina 10-49 mm consisted of Acartia tonsa, nauplii, polychaetes, and some harpacticoids. Important foods for M. beryllina, 50 mm and larger consisted of some insects, polychaetes, and smaller fish. Smaller M. martinica 10-49 mm used Acartia tonsa, nauplii, insects, algae, and invertebrate eggs, with the 50 mm and larger fish switching to a diet of mostly insects and insect larvae. Both species demonstrated late morning peaks in feeding activity, however, only M. beryllina displayed a pronounced late afternoon peak. Both species appear to avoid competing with each other through the use of different food types. Those food items that were used by both species tended to be those organisms which were present in high abundances during certain times of the year. M. beryllina appeared to feed from all areas of the water column possibly favoring the benthic and mid-water zones. M. martinica appeared to favor the mid-water and surface portions of the water column.