 Excavations may be simple depressions dug up in the substrate, such as the nests of bowfin, smallmouth bass, and Pacific salmon, but it can also consist of fairly large burrows used for shelter and for nesting.Burrowing species include the mudskippers, the red band-fish "Cepola rubescens" (burrows up to 1 m deep, often with a side branch), the yellowhead jawfish "Opistognathus aurifrons" (chambers up to 22 cm deep, lined with coral fragments to solidify it), the convict blenny "Pholidichthys leucotaenia " whose burrow is a maze of tunnels and chambers thought to be as much as 6 m long, and the Nicaragua cichlid, "Hypsophrys nicaraguensis", who drills a tunnel by spinning inside of it.In the case of the mudskippers, the burrows are shaped like a J and can be as much as 2 m deep.