Mummichog Fish Size, Lifespan, Breeding, Habitat, Adaptations

The mummichog is a tiny killifish found off the coasts of the U.S. and Canada  These fish, also recognized as Atlantic killifish, mummies, gudgeons, and mud minnows, live in brackish and coastal waters such as estuaries and salt marshes. The species is known for its hardiness and capacity to withstand very fluctuating salinity, temperature changes ranging from 6 to 35 °C, extremely low oxygen levels (as low as 1 mg/L), and heavily contaminated environments. As a result, the mummichog is a favorite research subject in embryology, physiology, and toxicology. It was also the first fish to be launched into space, aboard Skylab in 1973.

Mummichogs swim in shoals of up to 100 individuals. Mummichogs hibernate in upstream tidal pools during the cold winter months in the northern portions of their habitat, where they burrow into the mud to levels of up to 20 cm to survive the harsh winter conditions.

If they become stuck in a drying tidal pool between spring tides, they can bury themselves in mud. They can even travel short distances on land to return to the water.

Mummichog Fish Size

Mummichogs have a sturdy body, a flattened head, a rounded or squared-off tailfin, pointed teeth, and a lower lip that protrudes beyond the upper one. This fish reaches a maximum length of 5 - 6 inches, with females being larger than males.

Mummichog Fish Lifespan

The majority of mummichogs reach sexual maturity at two years of age when they reach a length of approximately 3.8 cm (1.5 in). The average lifespan is 4 years.

Mummichog Fish Breeding

Spawning occurs between April and August, and males frequently exhibit aggressive behavior during this time. Females entice males by flaunting their silvery bellies. Females have the ability to spawn up to 460 eggs 8 times in a single season. When the tide is at its maximum during the new or full moon, females lay sticky eggs in empty mollusk shells or on dead plants. 

When the water recedes, the eggs become visible to the air. Eggs will not hatch until they are covered with water again during the next month's highest tide. Larvae are roughly 7 mm in length when they hatch. The majority of adults acquire full development during their second year and survive for a total of three years after that date.

Mummichog Fish Habitat

Mummichogs are found in a wide variety of coastal settings, including salt marshes, muddy streams, tidal waterways, brackish wetlands, eelgrass or cordgrass beds, and sheltered coastlines. It is found in coastal rivers, but only rarely beyond the high tide mark. It is possible that a few landlocked populations can be found in freshwater lakes close to the shore, such as on Digby Neck, Nova Scotia.

Mummichog Fish Adaptations

Killifish, despite its diminutive size and unpleasant name, has the potential to be a major player in the animal kingdom's evolutionary history. Researchers discovered that the mummichog is capable of adapting to significantly fluctuating salinity (the quantity of salt in the water) and temperature swings in its habitat.

The fish employs a process known as phenotypic plasticity. It is the potential of a particular species to alter traits in reaction to environmental changes - and to do so fast. To adapt to changing salinity levels, the killifish activates or deactivates salt secretion channels. This suggests that the fish may alter the processes that regulate the salt balance and hence survive in both salt and freshwater environments.