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Today on Animal Fact Files we’re discussing convict blennies. These fish are also known as engineer gobies, however, recently published molecular evidence suggests convict blennies are neither blennies nor gobies. Currently, it's believed these marine dwellers are most closely related to freshwater cichlids! For this reason, some authorities have changed to calling them convict fish to avoid confusion. There are two convict fish species. They range from the Philippines to the Solomon Islands although only one species, the snake convict fish, is known from the shores of Australia. These are reef-living fish often swimming no deeper than 100 feet (33 m) on coral reefs, rocky coasts, or muddy bottom areas. 

Convict fish are also known as engineer fish because they manipulate their habitat a lot as adults. They'll construct long, twisting tunnel systems in the sediment and it's here their babies spend their nights. There's very little known about convict fish breeding, but what is known is that the adults typically remain in the tunnel where their offspring reside. During the day, the babies form tight aggregations that look almost like a single large organism. They collect plankton from the water column and return to their parent's burrow shortly afterwards. What they do here is still not fully understood. The parent rarely leaves the burrow, merely keeping it free of sediment while the babies are out. One hypothesis is that the babies actually feed the adult regurgitated food as the adults have been found with a green slime in their stomach! In captivity, adult convict fish are known to eat small shrimp and crabs, as well.

These fish get the name "convict" from their striped pattern. Convict fish juveniles are dark with white stripes running down their sides starting from their head and finishing at their tail. This may be a form of mimicry as they closely resemble venomous striped catfish who also form tight schools! The convict's black and white pattern persists into adulthood, however, it switches! Once they reach adult size, convict fish have white stripes running from their dorsal fin to their belly, perpendicular to the stripes they had as juveniles. These fish reach reproductive maturity around 6 inches (15 cm) in length, but they can more than double this at full size! As adults, convict fish somewhat resemble moray eels with their secretive nature and long, eel-like body.

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