5:15 PM - 7:15 PM
[AOS15-P08] The Potential of Using Environmental DNA to Estimate Lanternfish Diel Vertical Migration<gdiv></gdiv>
Keywords:eDNA, DVM
Diel vertical migration (DVM) in fish is a critical ecological phenomenon in marine ecosystems. Understanding its mechanisms is essential for effective ecosystem management and resource conservation. Myctophids (family Myctophidae) are the most diverse and abundant group of mesopelagic fishes. Although many Myctophids have been reported to inhabit subsurface layers during the day and ascend to surface waters at night for feeding, knowledge of species-specific DVM characteristics remains limited. Previous studies have primarily focused on vertical distribution surveys using net sampling of larvae and juveniles; however, net-based methods are expensive, require substantial time and labor, and introduce negative selective bias against fish capable of evading capture. Moreover, such net surveys exert stress on a wide range of marine organisms, rendering them unsustainable as a long-term monitoring approach. In light of these constraints, the present study aims to explore the feasibility of employing environmental DNA (eDNA), a cost-effective and noninvasive survey technique, to investigate the diel vertical migration patterns of Myctophids.
Observed samples were obtained during the KH-23-3 “Hakuho-Maru” research cruise in the western North Pacific from July 2 to July 29, 2023. Continuous observations were conducted at the K2 station (subarctic region) for 40 hours and at the S1 station (subtropical region) for 48 hours. Every four hours, 10 L of seawater for eDNA analysis from seven different depths between the surface and 200 m using Niskin bottle samplers. Simultaneously, environmental data, such as water temperature and salinity, were recorded using a CTD sensor.
A comparison of day–night fish assemblages at each station showed that at K2, the Myctophid fish Stenobrachius leucopsarus—which is known to perform semi-diel vertical migrations—was detected more frequently at the surface at night. At S1, the Myctophid fish Diaphus gigas also showed higher surface occurrence during the night, consistent with previous findings that this species undergoes diel vertical migration. These observations suggest that eDNA can effectively capture diel vertical migration behavior in fishes. However, the diel vertical migration patterns at K2 were less pronounced than at S1. One factor could be that water temperatures at K2 are significantly lower than those at S1, and it is known that colder temperatures slow the degradation rate of eDNA. Consequently, environmental conditions such as water temperature must be considered to conduct more accurate eDNA-based surveys. In this presentation, we will discuss the diel vertical distribution of eDNA observed during the KH-23-3 “Hakuho-Maru” cruise, using a one-dimensional model that incorporates these environmental conditions.
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Observed samples were obtained during the KH-23-3 “Hakuho-Maru” research cruise in the western North Pacific from July 2 to July 29, 2023. Continuous observations were conducted at the K2 station (subarctic region) for 40 hours and at the S1 station (subtropical region) for 48 hours. Every four hours, 10 L of seawater for eDNA analysis from seven different depths between the surface and 200 m using Niskin bottle samplers. Simultaneously, environmental data, such as water temperature and salinity, were recorded using a CTD sensor.
A comparison of day–night fish assemblages at each station showed that at K2, the Myctophid fish Stenobrachius leucopsarus—which is known to perform semi-diel vertical migrations—was detected more frequently at the surface at night. At S1, the Myctophid fish Diaphus gigas also showed higher surface occurrence during the night, consistent with previous findings that this species undergoes diel vertical migration. These observations suggest that eDNA can effectively capture diel vertical migration behavior in fishes. However, the diel vertical migration patterns at K2 were less pronounced than at S1. One factor could be that water temperatures at K2 are significantly lower than those at S1, and it is known that colder temperatures slow the degradation rate of eDNA. Consequently, environmental conditions such as water temperature must be considered to conduct more accurate eDNA-based surveys. In this presentation, we will discuss the diel vertical distribution of eDNA observed during the KH-23-3 “Hakuho-Maru” cruise, using a one-dimensional model that incorporates these environmental conditions.
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