Rhinogobiops

Lore & Background

The blackeye goby was first described in 1882 by American ichthyologist Tarleton Hoffman Bean from a specimen collected in Departure Bay, British Columbia, by Captain Henry E. Nichols aboard the survey vessel Hassler. Bean named it Gobius nicholsii. It was later moved to the genus Rhinogobius in 1907 by Edwin Chapin Starks and Earl Leonard Morris, and then to its own genus, Rhinogobiops, in 1926 by Carl Leavitt Hubbs. The name Rhinogobiops derives from Greek, meaning 'resembling Gobius'.

In 1960, James E. Böhlke and C. Richard Robins synonymized Rhinogobiops with Coryphopterus, though they noted differences in fin rays and scales and suggested treating it as a subgenus. John E. Randall expressed doubts about this synonymy in 1995, supported by Ray S. Birdsong and even Robins himself. A 2002 phylogenetic study by Christine E. Thacker and Kathleen S. Cole confirmed that blackeye gobies are more closely related to Lophogobius cyprinoides than to other Coryphopterus species, and the genus Rhinogobiops was reinstated.

Abundant otolith fossils from the Pliocene epoch (5.3 to 3.6 million years ago) have been found in Lomita Marl, and Pleistocene fossils have been recovered from other California localities. The species is protogynous hermaphroditic, with all individuals born female and capable of transforming into males under the right conditions. Males maintain harems of two to eight females and are highly territorial.

Reader's Guide

Rhinogobiops nicholsii is the only goby species known to occur in Alaskan waters, making it a significant biogeographic outlier among gobies. Its northern range was extended in a 2000 survey that recovered specimens from Sitka and Klawock in southeastern Alaska, though subsequent aquarium observations suggest it cannot survive temperatures below 4 °C, limiting further northward expansion. The species is extremely abundant along its range and occupies a distinct ecological niche at the border between reefs and sand bottoms, where it rests motionless near shelters and darts back when threatened.

Its taxonomic history reflects ongoing debates in goby systematics. The 1960 synonymization with Coryphopterus was questioned for decades and ultimately overturned by molecular phylogenetics in 2002, underscoring the value of genetic data in resolving relationships among morphologically similar fishes. The blackeye goby's ability to rapidly change color for social signaling and camouflage, its protogynous hermaphroditism, and its elaborate courtship and territorial behaviors make it a well-studied model for understanding social structure and sex change in marine fishes. Its fossil record from the Pliocene and Pleistocene provides insight into the historical distribution of gobies along the Pacific coast.

Did You Know?

• The blackeye goby is the only goby species found in Alaskan waters.
• All blackeye gobies are born female and can later transform into males.
• The species was originally named Gobius nicholsii after Captain Henry E. Nichols, who collected the type specimen.
• Males have a black spot on the first dorsal fin that remains visible even when the fish changes color.