Topsmelt

The Topsmelt (Atherinops affinis) is a schooling marine and estuarine fish in the family Atherinopsidae, the New World silversides, found along the eastern Pacific coast from British Columbia, Canada, to the Gulf of California, Mexico. It is one of the most common nearshore silversides in this region, frequently encountered in bays, estuaries, and kelp forest habitats. Topsmelt tolerate a wide range of salinities, allowing them to move between fully marine waters and brackish estuarine environments. The species plays a significant ecological role as a schooling forage fish and is also used in scientific research and environmental water quality testing due to its sensitivity to certain pollutants.

Topsmelt are slender, elongated fish typically reaching about 15-20 cm, occasionally larger.

• Body: slim, moderately compressed, olive-green to silvery-green above
• Markings: a bright, prominent silver stripe runs along the midline of each flank
• Mouth: small and slightly upturned, adapted for surface feeding
• Fins: two separate dorsal fins typical of silversides
• Tail: forked Topsmelt closely resemble the Jacksmelt but are generally smaller and have a shorter snout and fewer lateral line scales; the two species are often distinguished by relative body proportions and precise scale counts rather than coloration alone.

Topsmelt range along the eastern Pacific coast from British Columbia to the Gulf of California, inhabiting nearshore marine waters, bays, estuaries, and kelp forests. They tolerate a broad range of salinities, moving freely between fully marine conditions and brackish estuarine waters, and are often found in shallow, sheltered coastal zones. The species associates closely with kelp beds and eelgrass, using these habitats for shelter and foraging. Topsmelt occur from the surface down through the upper water column, typically in relatively calm, productive coastal waters rather than the open ocean.

Topsmelt form large, active schools near the surface of bays, estuaries, and kelp forest edges, frequently seen shoaling in shimmering groups. They are omnivorous, feeding on a mix of small invertebrates, fish eggs, algae, and organic material picked from the water column and surface. Spawning occurs over extended periods, with adhesive eggs deposited among algae or eelgrass, where fine filaments anchor them until hatching; there is no parental care afterward. As an abundant schooling species, Topsmelt serve as an important forage fish for a wide range of coastal predators, including larger fish, seabirds, and marine mammals.