Grenadiers

What it is

Grenadiers, also known as rattails, are marine fish characterized by large heads, wide mouths, and slender bodies that taper into thin tails. This distinctive tail shape gives them their common name. They possess small scales, a tall pointed first dorsal fin, and a second dorsal fin extending along the back. Their eyes are large, adapted for low-light environments. Sizes vary significantly, ranging from small species around ten centimeters to the giant grenadier, which can reach two meters in length. These fish belong to the order Gadiformes and form the largest family within the suborder Macrouroidei.

Where it lives

These fish are found worldwide in deep ocean waters, spanning from the Arctic to the Antarctic. They typically inhabit benthic zones between two hundred and seven thousand meters deep. While most species live on the sea floor, they are attracted to structural features like hydrothermal vents, cold seeps, and shipwrecks. Two genera prefer midwater habitats rather than the bottom. As a group, they may constitute up to fifteen percent of the total deep-sea fish population, making them among the most abundant deep-living vertebrates.

How it lives

Grenadiers act as generalist predators and scavengers in the deep sea. Their diet includes smaller fish, shrimp, amphipods, cumaceans, and occasionally cephalopods. They use well-developed lateral lines and chemoreceptors on their heads and barbels to locate food. Some species form large schools, while others remain solitary. Benthic species have swim bladders with muscles that allow them to produce sounds, possibly for communication. Light-producing organs called photophores are present in some species near the abdomen.

Breeding and life cycle

Reproduction involves releasing vast numbers of tiny eggs, often exceeding one hundred thousand per female. Lipid droplets make these eggs buoyant, allowing them to float toward the thermocline where development occurs. Juveniles start in shallower waters and migrate deeper as they age. Spawning timing varies by species, with some being seasonal and others not. Certain species, like Coryphaenoides armatus, are semelparous, meaning adults die after reproducing. Nonsemelparous species can live for over fifty-six years.

Fish and people

Attempts to establish commercial fisheries for larger species, such as the giant grenadier, have largely failed because the meat is considered unpalatable. Despite this, commercially exploited species face risks of overfishing due to low resilience. The family contains twenty-eight recognized genera, with diversity concentrated in Coelorinchus, Coryphaenoides, and Nezumia. There is no significant aquarium trade or cultural usage mentioned for this group.

Status and threats

The macrourins generally exhibit low resilience to environmental changes and fishing pressure. Species targeted by commercial interests may be overfished, potentially leading to rapid fishery collapse. Conservation data is limited, but their abundance suggests ecological importance.

Relatives and look-alikes

Grenadiers are closely related to other gadiform fish. Within their family, they share traits with genera like Albatrossia and Malacocephalus. They are distinct from shallow-water cods despite sharing an order. Confusion may arise with other deep-sea fish, but their unique tail structure and head morphology differentiate them. The family's diversity is highlighted by the presence of many genera, some with very specific morphological adaptations.

Questions people ask about Grenadiers

Good reading and sources

• Grenadiers (fish) on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data