New article on The Kroyer’s lantern fish

The Kroyer’s lantern fish (Notoscopelus kroyeri). Picture: Svanhildur Egilsdóttir

The Kroyer’s lantern fish (Notoscopelus kroyeri) is one of the most common species of mesopelagic fish around Iceland, but it has been little studied so far. Gaining knowledge of the species' biology is a prerequisite for its sustainable exploitation in the future. In recent years, the Marine and Freshwater Research Institute has participated in two international research projects funded by the European Commission on mesopelagic organisms.

The mesopelagic ecosystem consists of diverse organisms and a large biomass that could potentially be used for fishing. Among them are many species of mesopelagic fish. They live between 200 and 1000 m deep and show vertical diurnal behavior, i.e. they go up to a depth of about 200-400 m at night to feed but are found deeper during the day to avoid predators. The result of one of these projects is, among other things, a new scientific article on the biology of Kroyer’s lantern fish.

Length and age distribution were studied on fish collected in 2020 and 2021 (Figure 1). Three different length groups were distinguished in the samples (Figure 1a,b), which corresponded to three different age groups (Figure 1d). The largest fish were 4 to 9 years old. The relationship between otolith and fish length was also determined, which is useful for assessing predation on the species by length, when only otoliths are found in the stomach contents of predators. The article is based on Charlotte Matthews' master's thesis at the University of Iceland. Her co-authors, who are all working experts at the Marine and Freshwater Research Institute, were supervisors in the project. Charlotte is currently pursuing a doctoral degree at Memorial University in Newfoundland in Canada, where she is still studying mesopelagic fish and trying to assess their importance in the ecosystem.

The article can be found here.

Figure 1. Standard length (mm) distribution of Notoscopelus kroyeri caught during the IESSNS survey in (a) 2020 and (b) 2021. Three group sizes were detected when a K-means clustering analysis performed on the Gutted weight-standard length relationships. The three group sizes are represented by the different colors. Reading the age from the otolith confirmed that these three groups represented different age groups (d). The smaller fish (yellow) were between 2-3 years old, while the medium fish (blue) size corresponded to fish between 3 and 6 years old and the longer fish (grey) were between 4 to 9 years old.