Two-spotted goby
A small goby with lateral eyes and a black tail spot.
The two-spotted goby (Pomatoschistus flavescens) is a slender fish that grows up to 6 cm long. It lives in salty or slightly brackish waters along the eastern Atlantic, from the Faroe Islands and Norway down to northwestern Spain. It has also been spotted in Estonia, but reports from the Mediterranean are uncertain. This goby is common around all UK coasts.
These fish prefer areas thick with seaweed, such as overgrown structures, kelp beds, or eelgrass meadows. They can be found in tide pools and shallow water down to 20 meters deep.
Unlike most gobies, this species doesn't stay on the seafloor. Instead, it swims in shoals among seagrasses and seaweeds. Its eyes sit on the sides of its head, not on top. A black spot marks the base of the tail fin; males have a second, smaller black spot below the pectoral fins. Their color ranges from reddish to greenish brown, with paler undersides and dark net-like patterns on the back. Four light saddle-shaped marks run along the back from the head to the end of the second dorsal fin. A series of bluish markings line the sides, and these become very bright in males during breeding season.
This goby feeds on zooplankton, like crustacean larvae. Breeding happens in summer. Males become territorial and defend a nest—usually a natural cavity like an empty mussel shell or a folded kelp leaf. Males and females perform several stages of courtship displays, ending with the female visiting the nest to lay a batch of eggs. The male then guards, cleans, and fans the eggs of one or several females until they hatch. After growing through the summer, juvenile fish move into deeper water for the winter. Adults usually die after a single breeding season.
Quick Facts
- Scientific name
- Pomatoschistus flavescens
- Maximum length
- 6 cm (2.36 in) TL
- Depth range
- Intertidal pools to 20 m / 65 ft 7 in
- Habitat
- Areas with weed growth, overgrown structures, beds of Laminaria or Zostera
- Distinctive feature
- Eyes on the side of the head (lateral) rather than on top (dorsal)
Facts from the source article.
Lore & Background
The two-spotted goby is distinguished from other gobies by having its eyes positioned laterally on the head rather than dorsally. It is reddish to greenish brown in colour, paler on the undersides, with dark reticulations dorsally and four light saddle marks from the head to the end of the second dorsal fin. A black spot is present at the base of the tail fin, and in males a second, smaller black spot lies beneath the pectoral fins. Along the midline of the sides are a series of bluish markings that become extremely bright in males during the breeding season.
Unlike most gobies, this species does not live on the seabed but instead forms shoals among seagrasses and seaweeds. It feeds on zooplankton such as crustacean larvae. Breeding takes place in the summer, with males becoming territorial and defending a nest formed by a natural cavity such as an empty mussel shell or a folded kelp leaf. Males and females engage in several stages of mutual courtship displays, culminating in a visit to the nest where the female lays a batch of eggs. The male then guards, cleans, and fans the eggs of one to several females until they hatch.
After a period of growth in the summer, juvenile fish move into deeper water to spend the winter. Adults usually die after reproducing once.
Reader's Guide
The two-spotted goby is notable for its unique eye placement among gobies, with lateral rather than dorsal eyes, and its shoaling behaviour in seagrass and seaweed habitats rather than living on the seabed. Its distribution spans the eastern Atlantic from northern Europe to Spain, with uncertain records from the Mediterranean, and it is common around all coasts of the United Kingdom. The species plays a role in coastal ecosystems as a zooplankton feeder and as prey for larger animals. Its breeding strategy involves male territoriality and nest guarding, with males fanning and cleaning eggs from multiple females. The life cycle is annual, with adults typically dying after a single reproductive season, while juveniles overwinter in deeper water. The two-spotted goby is often found in intertidal pools and shallow waters up to 20 metres deep, favouring areas with Laminaria or Zostera beds and overgrown structures. Its distinctive black tail spot and the male's secondary spot beneath the pectoral fins aid identification, along with the bluish markings that intensify during breeding.
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