Rainbow Smelt
Overview
The rainbow smelt (Osmerus mordax) is a small schooling fish that is native to watersheds of the northwest Atlantic ocean. They are anadromous (ie. adults live in saltwater, migrating to freshwater to spawn), however some populations live permanently in lakes due to human introduction (ex. The Great Lakes). Rainbow smelt are predatory, consuming mainly zooplankton and even young fishes. They live for 5-6 years and survive in various environments, including waters from -1.8ºC to 20ºC!
Appearance
Slender/streamlined body, averaging 6-8 inches long.
Deeply forked caudal fin (i.e., tail), 1 dorsal fin, and a small adipose fin.
Olive green back and silvery white belly.
Bright silver sides with a ‘rainbow’ (blue, purple, and pink) iridescence.
Long and pointed snout
Large mouth with a protruding lower jaw and canine-like teeth on the roof of their mouth and tongue.
If you observe rainbow smelt please consider reporting your sightings to https://www.inaturalist.org/ or use our smelt data form.
Additional data from sightings helps wildlife managers monitor the health of the population.
SAWIG Smelt Data Form 2023.pdfLife Cycle
Rainbow smelt are sexually dimorphic; this means that females grow larger and live longer than males. Smelt migrate into freshwater streams right after ice out (around mid-April) and usually spawn at night.
They first spawn at around 1-2 years old, and need access to cool, slow-flowing waters with a clean gravelly bottom.
Females will lay upwards of 50,000 eggs, depending on their size. These eggs are very sticky, clinging to bottom vegetation and substrate, and hatch after 5-30 days.
Once the eggs hatch, the young smelt, who are only ¼ inch long and are translucent, rely on the stream's current to carry them back to sea, where they will grow and mature. They will return to freshwater streams after 1-2 years, repeating the spawning cycle.
Fun Facts
Rainbow smelt have what is referred to as an ‘antifreeze’ gene - this means they can survive in icy coastal waters and extreme temperatures (<5ºC). Studies have shown that smelts obtained this gene from herring, despite the two species not being closely related! It’s believed that smelts obtained the gene around 20 million years ago through a process called ‘horizontal gene transfer’; this process has rarely been identified in complex organisms such as vertebrates.
There are 2 unique subspecies of rainbow smelt that exist only in Lake Utopia, New Brunswick. These small-bodied and large-bodied rainbow smelt are genetically distinct from each other. Both populations are listed as endangered.
Why Monitor Rainbow Smelt?
Smelt are an important food source for larger predatory species like Atlantic salmon and Atlantic cod. They’re also a popular recreational fish on PEI, being eaten by humans and also used as bait.
Rainbow smelt populations face a number of threats. Habitat degradation, acid precipitation, and blocked culverts can lead to poor water quality, which can negatively impact their reproduction and survival. Smelt are also poor swimmers, meaning they can't easily use fish ladders to access upstream habitats. This can impact their spawning success.
How To Monitor Smelt
The easiest way to monitor for the presence of smelt is to locate the first culvert up from a stream’s connection to the ocean. Smelts are most likely to spawn in the first area of freshwater they come across. Checking both upstream and downstream of the culvert will give you a good indication of smelt abundance in the stream. Look for dark patches near the stream’s bottom; smelts congregate in schools, so they’ll be tightly packed together.
Another great way to protect smelt populations is by protecting their habitat. This means doing what you can to minimize runoff of pollutants, fertilizers, and sediments into your local stream. This will help to maintain a good water quality and ideal bottom substrate.
Check out this video to learn how to identify smelts from the riverside!
Catching Smelt on PEI
Did you know that you don’t need a license to fish rainbow smelt on PEI?
The dip net fishery for smelt runs from April 1st to June 15th of each year.
Angling for smelt in inland waters is also permitted from April 15th to September 15th.
The catch limit is 60 smelts per person, per day.
When fishing for smelt, you should only take what you need.
Be mindful of entering the stream, and remain on the shore when possible to avoid trampling eggs.
The smelt fishery is regulated to ensure that this important species isn't overfished. Smelts are relatively vulnerable to this, especially since they're weak swimmers and are easy to catch.