Shorefishes of the Eastern Pacific online information system

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Species: Microdesmus affinis, Olivaceous goby, Short-tail worm-goby

All Families:   All Genera:   All Species:

eyes - not tiny, on sides of head
plain color
thin lips
chin - knob
pectoral: 12
A 41
scales 19 radiating lines

Microdesmus affinis Meek & Hildebrand, 1928

Olivaceous goby, Short-tail worm-goby

Slender, wormlike, body height 3-9% of SL; tail (without fin) 48% of SL; eyes small but not tiny, not skin covered, on side of head; snout and lower jaw with well defined ridges; mouth small, oblique; lower jaw strongly projecting, with small fleshy lump at chin, lips thin, with small side flanges; teeth small, close-set, in 2 rows; gill opening large (not tubular), about length of base of pectoral; dorsal fin spines evenly spaced, 69 elements, origin over rear 1/3 of pectoral; anal II, 41; pectoral 12 rays; pelvics I, 3, shorter than pectorals; tail fin rounded, short; dorsal and anal fins confluent with tail fin; scales small, non-overlapping, well separated; scales with 19 radiating lines; snout and lower jaw scaleless.

(Preserved fish) uniform olive; tail slightly dusky, other fins clear.

Size: 11 cm.

Habitat: estuaries.

Depth: 0-10 m.

SW and eastern Gulf of California to Ecuador.

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  • Brackish
  • Non Marine
  • Inshore Only
  • Inshore
Water Column Position
  • Bottom only
  • Bottom
  • Soft bottom only
  • Soft bottom (mud/sand/gravel/beach/estuary/mangrove/seagrass)
  • Mud
  • Sand & gravel
  • Estuary
FishBase Habitat
  • Demersal
Feeding Group
  • Carnivore
  • No Data
  • No Data
  • Mobile benthic worms
  • Mobile benthic crustacea (shrimps/crabs)
Egg Type
  • No data
  • Pelagic larva
  • Benthic
Global Endemism
  • East Pacific endemic
  • All species
  • Tropical Eastern Pacific (TEP) endemic
Regional Endemism
  • TEP endemic
  • Continent
  • All species
  • Continent only
  • Continental TEP endemic
  • 3 provinces (Cortez + Mexican + Panamic) endemic
  • Resident
Climate Zone
  • Northern Tropical (Mexican Province to Nicaragua + Revillagigedos)
  • North Temperate (Californian Province &/or Northern Gulf of California)
  • Equatorial (Costa Rica to Ecuador + Galapagos, Clipperton, Cocos, Malpelo)
  • Northern Subtropical (Cortez Province + Sinaloan Gap)
IUCN Red List
  • Listed
  • Data deficient
  • Not listed
Length Max
  • 11
Depth Range Min
  • 0
Depth Range Max
  • 10