# Eumicrotremus pacificus

Eumicrotremus pacificus, sometimes known as the spotted lumpsucker or the balloon lumpfish, is a species of lumpfish native to the Northwest Pacific. It can be found in the Sea of Okhotsk, the Sea of Japan, the East China Sea, and the Pacific Ocean off Hokkaido and the Kuril Islands. It may be confused with the closely related Eumicrotremus orbis, which overlaps with E. pacificus in range, although E. pacificus is larger, reaching 20 cm (7.9 inches) TL. This fish is generally yellow to orange in color with small dark spots and its tubercles are usually smaller and less pronounced than E. orbis, giving it a less spiny appearance.

## Taxonomy

The Spotted Lumpsucker is one species part of the family Cyclopteridae, alongside 23 other species. They are part of the genus Eumicrotremus which include species such as: Eumicrotremus Orbis (Pacific Spiny Lumpsucker), Eumicrotremus taranetzi, Eumicrotremus awae, and 15 other described species. This genus is mainly characterized by their distribution in Northern regions of oceans, spiny external skeleton, and lack of a swim bladder. Eumicrotremus pacificus was first described by The Spotted Lumpsucker and is often confused with E. Orbis (Pacific Spiny Lumpsucker) because of similar coloration, size, tubercles, and habitat range. However the Spotted Lumpsucker is typically smaller than the Pacific Spiny Lumpsucker and has distinct dark spots present all over its body.

## Description

The Spotted Lemonsucker (Eumicrotremus pacificus) is part of the family Cyclopteridae. E. Pacificus gets often confused with the Pacific Spiny Lumpsucker (E. Orbis) because of their spiny appearance and overlapping range in the Pacific. Like other species of Cyclopteridae, Spotted Lumpsuckers possess a sucker at the bottom of their body. This sucker is a highly modified pair of pelvic fins and is an important anatomical feature for the Cyclopteridae. The Spotted Lumpsucker has a globiform body plan, with an armored external skeleton. They have a ventral mouth and lack of a swim bladder. Most adult E. Pacificus are yellow and orange toned with small brown to black dots scattered all over its body. There are observations of juvenile E. Pacificus have a darker head and body, and then slowly transition into their yellow and orange hues as they develop into adults.
In addition to the vibrant coloration, E. Pacificus have body armor that is made up of bony tubercles and grows from different plaques on their body. These plaques are much less pronounced than the Pacific Spiny Lumpsucker (Eumicrotremus orbis). The structure of the individual spines are set into circular bases within the bony plaques. These bases form into the spines of the E. Pacificus. This armor serves multiple purposes such as camouflage, environmental protection, and reducing drag from water currents.
There are morphological differences between female and male E. Pacificus. A noticeable difference between the two is the anteanal distance. The anteanal distance is the distance from the anal fins and the fish vent/anus. Female E. Pacificus have a greater anteanal distance since they need to have more space to develop gonads and eggs for reproduction.
Another morphological difference found in the Spotted Lumpsucker is the external skeleton between spawning and non-spawning male E. Pacificus. There is a significant decrease in the external skeleton based on if the males are in a spawning stage or not. Spawning males showcase a lengthening in their upper and lower jaw, and their overall height is increased.

## Biology

Spotted Lumpsuckers are docile, solitary fish that have poor swimming abilities. There is no record of the average lifespan of Like other Cyclopteridae, but similar species have been recorded to live for about a year in aquariums. Spotted Lumpsuckers live most of their life attached to rocks, aquatic vegetation, and any other stable substrates. There is not a clear reason as to why the Cyclopteridae as a whole have their suction appendage besides sticking to their habitat. It has been observed that they use their suction ability to aid with their parental care and protection.
There is not much information about the diet of E. Pacificus, specifically. Other Eumicrotremus species have been observed to feed on small crustaceans, mollusks, plankton and other small fish. Juvenile Cyclopteridae have been observed to feed on crustacean larvae, and the larva of their own egg. Spotted Lumpsuckers are vulnerable to the predation of Hermit Crabs, Red King Crabs, and other large fish.

## Distribution and habitat

Spotted Lumpsuckers are found in Northern regions of the Pacific Ocean among coasts and tidal regions. They have been recorded in the East China Sea, Okhotsk, the Sea of Japan and the Hokkaido and Kuril Islands. There is no record of these fish preferring warm or cold water temperatures.
There is no research about where in these oceans Spotted Lumpsuckers inhabit. However, other Cyclopteridae species are typically found amongst rocks, stones, sea grass, algae growth and other solid substrate that they are able to stick onto. Because of their poor swimming ability, it is most likely that the Spotted Lumpsucker can inhabit in deeper ranges of the ocean, shallow waters, and intertidal zones.

## Conservation status

Spotted Lumpsuckers are not a threat to humans and are frequently kept in aquariums because of their docile nature. In the wild, they are under-researched and cryptic compared to other Lumpsucker species. Spotted Lumpsuckers have no conservation status on the IUCN Red List. They don't have any immediate threats to their population because more research is needed on their populations and life cycle. However, due to their range, activities such as habitat loss/degradation, bycatch, and climate change can potentially threaten their populations.