[5] The cephalon posterior margin is not trilobed, once again typical characteristic of organisms found in Elthusa.

[7] In adult females, the pleotelson is as wide as its length, which fits the typical description of the genus.

[5] In juveniles, the color pigment granules are concentrated in the melanophores, thus giving its lack of distinct pattern appearance.

[5][8] E. californica is an ectoparasite and has been found on many reported host species, including the actinopterygian fishes Cymatogaster aggregate and Atherinops affinis, Artedius lateralis, Clinocottus analis, Oligocottus maculosus, S. marmoratus, and Fundulus parvipinnis.

[8][9] Once it finds a suitable host, it attaches inside the opercular cavity of the gill chamber, making a protruding shape.

To ensure secure attachment to the host, the isopod uses seven pairs of sharply hooked legs and its specialized mouthpart.

[9] The presence of E. californica in host fish may subject them to lower levels of vitality when encountering a decrease in the seawater salinity.

[9] The species has an ecological preference, selecting hosts that live in the benthic or that belong to a demersal school.