Fish diurnal

Topsmelt Silverside

Atherinops affinis

The shimmering acrobat of the Pacific shallows, the Topsmelt Silverside brings a flash of brilliant silver to coastal estuaries and kelp forests. A vital part of the marine ecosystem, these schooling beauties are a favorite for underwater camera enthusiasts.

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Quick Identification

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Size

6 to 14.5 inches (15–37 cm) in length; typically weighing 0.5 to 1 lb (0.2–0.45 kg).

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Colors

Silvery-green or blue on the back with a brilliant, wide silver stripe along the flank; white or pale silver belly; fins often exhibit a translucent or yellowish hue.

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Key Features

Broad silver band running horizontally along the side
Two separate dorsal fins on the back
Pointed snout with a small, terminal mouth
Slender, streamlined 'silverside' body shape

When You’ll See Them

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Activity pattern diurnal

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Peak hours 10 AM - 3 PM

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Season April - September

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Diet Omnivorous filter-feeders that consume zooplankton, small crustaceans, and larvae. They also frequently graze on algae and detritus found on kelp fronds or pier pilings.

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Habitat Coastal waters, kelp forests, estuaries, and bays. Often found near man-made structures like piers, docks, and rock jetties.

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Behavior

Topsmelt are energetic, schooling fish that are a hallmark of the Pacific coastline. They are most frequently observed in large, shimmering groups near the surface of the water, a strategy that helps protect them from predators while they forage for food. These schools can consist of hundreds of individuals, moving in synchronized patterns that create a dazzling display of reflected light.

During the spawning season, which typically occurs from spring through late summer, Topsmelt migrate into the shallow, calmer waters of estuaries, bays, and even tidal sloughs. Here, they attach their eggs to eelgrass or submerged vegetation using sticky filaments. They are relatively hardy fish, capable of tolerating wide ranges of salinity, which allows them to thrive in environments where other marine species might struggle.

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Camera Tips

To capture high-quality footage of Topsmelt Silversides, you will need an underwater camera setup, such as a GoPro in a waterproof housing or a dedicated submerged 'drop-cam.' Since these fish are surface-dwellers, the best placement for your camera is 1 to 3 feet below the water line. If you have access to a private dock or pier, mounting the camera to a piling or suspending it from a weighted line is highly effective. Angle the lens slightly upward toward the surface to catch the 'silverside' flash as they swim through the sunlight.

Lighting is the most critical factor for these metallic fish. Aim to record during peak daylight hours, typically between 10 AM and 2 PM, when the sun is directly overhead. The bright light penetrates the water column and makes their silver lateral stripes pop against the blue-green water. Avoid using artificial lights if possible, as the glare can wash out their reflective scales and may spook the school. In murkier estuarine water, high-contrast settings on your camera can help define their silhouettes.

While you shouldn't 'bait' the water in a traditional sense, placing your camera near structures with heavy algae growth or barnacles—like a boat slip or a kelp bed—naturally attracts Topsmelt. They are curious but easily startled by sudden movement. If you are using a trail-style underwater camera, ensure it is tethered securely to prevent it from swaying in the current, as a stable frame is necessary for the AI to correctly identify the fast-moving school. In the spring, focus your efforts on areas with submerged vegetation where spawning activity is highest.

Similar Species

Species that look similar or are commonly confused with Topsmelt Silverside.

Jacksmelt

Larger in size (up to 17 inches) with the first dorsal fin positioned further forward, in front of the anal fin.

California Grunion

Best known for spawning on beaches during high tides; they have a more rounded snout and lack the specific fin placement of the Topsmelt.

California Leuresthes

Similar in shape but possesses a more translucent body and different spawning habits.

Frequently Asked Questions

Topsmelt Silverside are strictly diurnal, meaning they are most active during daylight hours. You will see them most frequently during the middle of the day when the sun is high, as they use the light to forage for plankton near the water's surface.

If your 'backyard' includes a coastal dock or seawall, you can attract Topsmelt Silverside by maintaining a healthy environment for eelgrass or submerged aquatic plants. They are naturally drawn to structures like pier pilings where they can graze on algae and find cover from predators.

Topsmelt Silverside have a varied diet consisting of zooplankton, algae, and very small crustaceans. They use their small mouths to nip at organisms attached to kelp or pilings, or filter tiny life forms directly from the water column.

Yes, they are extremely common in suburban coastal communities along the Eastern Pacific, from British Columbia to Baja California. They are one of the most frequent species found around public fishing piers and marinas.

The easiest way to distinguish them is by looking at the dorsal fin. In Topsmelt, the first dorsal fin begins well behind the insertion of the pelvic fins. Additionally, Topsmelt have a smaller mouth and generally do not grow as large as the related Jacksmelt.

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