Blue-spotted jawfish

Lore & Background

The blue-spotted jawfish was first discovered in the Tropical Eastern Pacific by Gerald Allen and David R. Robertson in 1991. It belongs to the class Actinopterygii. The species is named after Richard H. Rosenblatt, an ichthyologist at the Scripps Institution of Oceanography who contributed to the study of eastern Pacific fishes.

This jawfish has electric-blue spotting over a yellow or orange body with an elegant yellow dorsal fin. Males have stark white on their anterior halves, while females and non-courting males are dark brown with larger blue spots. Younger individuals are uniformly yellow with blue spots. They have large eyes that make them look 'alien.'

Jawfish are named for their large mouths, which allow them to catch food and dig burrows by taking big mouthfuls of sand. The blue-spotted jawfish feeds on tiny benthic and planktonic invertebrates. They are colonial and social among their own species, living in colonies of up to several hundred fish with minimal spacing of 1 to 3 m (3.3 to 9.8 ft) between individuals. They cover their burrow entrance at dusk and rebuild it every morning. Unlike Opistognathus aurifrons, they only spend time above their burrows during the warm summer season.

Reader's Guide

The blue-spotted jawfish is significant as a colonial reef species native to the Gulf of California, first documented in 1991. Its notable behaviors include sealing its burrow entrance at night and rebuilding it each morning, as well as being a mouth brooder that incubates eggs for 5 to 7 days. Males display bright white coloration and dash 3 to 4 feet above their burrows in summer to attract females. The species is also found in the aquarium trade. Two diseases affect it: Brooklynellosis, which causes peeling skin and color loss and can be fatal within 24 hours but is treatable with malachite green and formalin; and 'blue spot jawfish disease,' caused by rough handling, coarse substrate, bare glass, or temperatures above 21°C. Its discovery by Allen and Robertson and its naming after Rosenblatt highlight its place in ichthyological study. The species feeds on benthic and planktonic invertebrates and lives in cold water at deeper depths in sandy rubble and reef areas.

Did You Know?

• The blue-spotted jawfish seals its burrow entrance completely at night and rebuilds it every morning.
• Males become stark white on their anterior halves during summer to attract females.
• It incubates eggs in its mouth for 5 to 7 days.
• Brooklynellosis can cause death within approximately 24 hours if untreated.