Characterizing the migratory strategies of Atlantic lumpfish to improve stock assessment of this commercially important species

Atlantic lumpfish is a semipelagic fish that spawns in shallow coastal areas and migrates offshore to feed. It sustains two types of fisheries: one targeting females for their roe, consumed as imitation caviar and the other targeting mature individuals to produce cleaner fish for salmon aquaculture. The main obstacle to stock assessment and management of lumpfish comes from the lack of knowledge concerning its population structure and migration patterns. For example, it is unknown whether adult lumpfish reproduce where they are born (homing) or whether they spawn elsewhere. Some individuals also seem to skip migrating to the open ocean and remain in fjords. Project ECOLUMP aims to better understand the life cycle of lumpfish, its migratory behavior, and the genetic structure of the population. We will use an interdisciplinary approach including population genetics and analyses of otoliths, the fishes’ “black box”. This will allow us to determine whether there are several subpopulations in Norway and to retrace the migratory history of the fish. Methods to determine age in lumpfish will also be investigated. A non-lethal biopsy tool will be developed to inform on their past migratory behavior. This tool will be used to quantify the proportion of resident and migratory lumpfish targeted by the commercial fishery. Coastal lumpfish will be tagged (acoustic tags) to study their coastal-offshore movements and behavior after spawning. We will also test whether lumpfish display different innate orientation and migratory tendencies by comparing their swimming behaviors and orientation cues (visual or magnetic) in the sea and in a laboratory. Knowledge of population structure and the underlying factors shaping it, are crucial for sustainable use of marine organisms including safeguarding their viability and maximal adaptative capacities to allow them to face future environmental changes.

The main impediment to stock assessment and management of Atlantic lumpfish comes from the lack of knowledge concerning its population structure and migration patterns. Lumpfish sustains two types of fisheries: one targeting females for their roe, the other targeting mature individuals to produce cleaner fish for salmon aquaculture. Studies on lumpfish population genetics so far have been somewhat contradictory. Some have shown little to no structure along the Norwegian coast, while others have revealed clear genetic differences and cryptic groupings even at a local level. Lumpfish is semipelagic fish that spawns in shallow coastal areas in the spring. The rest of its life cycle is spent offshore in pelagic feeding areas. However, the presence of immature adults in coastal areas as well as anecdotal spawning events in autumn question the current description of the lifecycle. In project ECOLUMP, we hypothesize that some individuals do not migrate offshore but feed in coastal areas and that these individuals constitute a separate subpopulation or ecotype than the migratory individuals. To uncover this alternate life strategy, we will use an interdisciplinary approach including population genetics, and methods that will allow us to retrace the migratory history of the fish (i.e. microchemistry of calcified structures and stable isotope analyses). A non-lethal biopsy will be developed to determine individual ecotypes. The proportion of resident and migratory lumpfish targeted by both types of fisheries will be quantified during the project. Acoustic telemetry will be used on coastal lumpfish to further document their coastal-offshore movements and behavior after spawning. We will also test whether lumpfish display different innate orientation and migratory tendencies by comparing their swimming behaviors and orientation cues (visual or magnetic) in the sea and in a laboratory.