Species description and status: Sea lamprey (Petromyzon marinus) is a species of primitive, jawless fish that migrates between freshwater and marine habitats. Similar to many migratory species in Europe, sea lamprey are threatened by habitat modification in their natal rivers and migration barriers that restrict their access to their spawning grounds (Hansen et al. 2016). They may also suffer from physical damages caused by turbines and other infrastructure installed in rivers. Unlikely many migratory species for which river restoration efforts are generally designed, sea lamprey require slow flowing habitats and soft sediments, which may often be undervalued compared to fast flowing riffles and gravel substrate generally associated with salmon spawning success. Lamprey also depend on estuaries as conditioning habitats as they transition between salt and freshwater habitats. However, estuaries throughout Europe are highly degraded and require restoration efforts in order to provide high quality habitat to species such as lamprey that rely on such habitats (Lotze et al. 2006). (Image above by Ine Pauwels ©)
Sea lamprey are born in rivers and migrate to the ocean after years living burrowed in soft substrate and filter feeding on drifting particles. Distinguished by having a relatively long larval life stage (Hansen et al. 2016), sea lamprey larvae will remain in freshwater for several years before metamorphosis, at which point they exit the gravel and migrate to sea. Metamorphosis is characterized by changes to both the morphology and physiology of sea lamprey. At sea, sea lamprey are parasites that feed on tissues of fishes and sharks as well as cetaceans, leaving a distinct mark that, in the Great Lakes, is used to estimate the impact of sea lamprey on salmonids. The juvenile lamprey grow much more rapidly at sea and will return to rivers to spawn during spring and summer. Males build nests in sandy or graveled bottoms of the river from which larvae will emerge to find soft substrates that they themselves will then burrow in to filter feed. The semelparous adults die, fertilizing the natal streams with the marine-derived nutrients.
Knowledge gaps: Lamprey research is a diverse field including research on physiology, ecology, and ecology through the lenses of conservation and invasive species control. Sea lamprey being a primitive species of fish and an early product of vertebrate evolution, they are a species that is significant to the field of evolutionary biology. Sea lamprey telemetry projects have been mostly limited to studies in the Great Lakes where their invasion is considered a significant threat to biodiversity and it is therefore the subject of a binational, multi-million dollar, multi-decade control program. Much of our understanding of lamprey physiology and behaviour have emerged from research supported by efforts to assist control efforts. However, conservation of sea lamprey is a substantial field of interest in Europe where they are important coastal species requiring more research. Changes to sea lamprey populations during climate change, responses to restoration efforts in rivers, and marine behaviour are key areas requiring data for better management of coastal and freshwater systems used by sea lamprey. These questions can be addressed using telemetry tools to track the habitat selection and behaviour of lamprey in the wild and therefore the European Telemetry Network represents a critical partnership among institutions that will facilitate the necessary infrastructure for larger scale research on sea lamprey biology.
Regions of interest: Although sea lamprey is an invasive species in parts of North America, it is a threatened species in Europe that has been a focal point of many conservation efforts. Sea lamprey are found in rivers along the Atlantic coast of Europe into the Mediterranean and Baltic Seas. Sea lamprey distribution arches to Iceland and across the Atlantic to North America where it occurs all along the coast of North America but not the Gulf of Mexico or Central America (see figure reproduced from Hansen et al. 2016). The species is listed in Europe as a species needing special areas of concern under the EC habitats directive (Nunn et al. 2017) and as threatened in Portugal, Spain, and France (Hansen et al. 2016). As a semelparous species, sea lamprey perform important ecosystem services by bringing marine nutrients into freshwater rivers and contributing to ecosystem fertilization. They also have cultural importance as they are exploited as a food resource and some populations have been threatened by the effects of overexploitation (Hansen et al. 2016).
Figure 1. Reproduced from Hansen et al. (2016) showing the native range of the sea lamprey Petromyzon marinus in black.
Telemetry tools: Lamprey larvae are small and can only be tagged with small PIT tags and the smallest acoustic transmitters (Quinetella et al. 2005). Capturing juvenile lamprey at sea is challenging and little is known about their behaviour in the marine realm including how far they move, how they identify hosts, and how they identify and move back towards home rivers to spawn. Maturing lamprey can be trapped in estuaries and rivers to track their upstream migration to spawning grounds (e.g. Almeida et al. 2002). Using biologging tags to study juveniles is challenging because of the weak or non-existent homing of sea lamprey, which do not necessarily return to the natal river to spawn and can therefore be difficult to recover tags from.
Benefits within ETN: European Telemetry Network arrays in major rivers in southern Europe (e.g. Adour, Minho, Douro) could be used for tracking sea lamprey in freshwater. In the marine environment, tracking lamprey in the Baltic Sea where arrays are active for studies on northern pike, tuna, salmon, and sea trout has the potential to be used to expand understanding of the movements of juvenile sea lamprey if challenges related to capturing and tagging sufficient numbers can be resolved. Difficulties from tracking juvenile lamprey will include separating active and passive movement as they spend time attached to hosts while they suck the blood; accelerometer tags could be calibrated to detect this. Given that sea lamprey are not considered to have high site fidelity, they may be relatively fast to respond to climate change by moving their distribution northward, strengthening their numbers in rivers of central and northern Europe relative to southern nations. Sea lamprey telemetry may therefore provide an interesting index of climate change.
References
Almeida, P. R., Quintella, B. R., & Dias, N. M. (2002). Movement of radio-tagged anadromous sea lamprey during the spawning migration in the River Mondego (Portugal). In Aquatic Telemetry (pp. 1-8). Springer, Dordrecht.
Hansen, M. J., Madenjian, C. P., Slade, J. W., Steeves, T. B., Almeida, P. R., & Quintella, B. R. (2016). Population ecology of the sea lamprey (Petromyzon marinus) as an invasive species in the Laurentian Great Lakes and an imperiled species in Europe. Reviews in fish biology and fisheries, 26(3), 509-535.
Lotze, H. K., Lenihan, H. S., Bourque, B. J., Bradbury, R. H., Cooke, R. G., Kay, M. C., ... & Jackson, J. B. (2006). Depletion, degradation, and recovery potential of estuaries and coastal seas. Science, 312(5781), 1806-1809.
Nunn, A. D., Taylor, R. J., Cowx, I. G., Noble, R. A. A., Bolland, J. D., & Harvey, J. P. (2017). Demography of sea lamprey (Petromyzon marinus) ammocoete populations in relation to potential spawning‐migration obstructions. Aquatic Conservation: Marine and Freshwater Ecosystems, 27(4), 764-772.
Quintella, B. R., Andrade, N. O., Espanhol, R., & Almeida, P. R. (2005). The use of PIT telemetry to study movements of ammocoetes and metamorphosing sea lampreys in river beds. Journal of Fish Biology, 66(1), 97-106.