Upstream migration, reproduction and fishery of sea lamprey (Petromyzon marinus Linnaeus, 1758) in the River Ulla (NW Spain)

Abstract

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After a juvenile haematophagous stage developed mainly at sea, the sea lamprey Petromyzon marinus Linnaeus, 1758 stop feeding and return to the river to spawn. One of the main pressures in this stage is the presence of obstacles that reduce the accessible habitat, the mobility of individuals within this section and the energy resources available for gonad development and spawning. In addition, in the River Ulla, adults are targeted in a commercial fishery, using fyke-nets in the upper estuary and fishing in pesqueiras, which are stone constructions placed on the river bed, in the low section of the river. This study advances in the knowledge of the upstream migration (and related impact of barriers), reproduction and fishery of P. marinus in the River Ulla. The study combined fieldwork (radiotelemetry tracking of 19 adults in years 2012 and 2013 and inventory and characterization of obstacles), with information on the capture of lampreys (years 2000 to 2010) by commercial fishing and by a fixed trap located in the middle section of the river. The migration period in this river runs from January, or even December, until June, followed by reproduction in May and June. A total of 48 anthropogenic obstacles (all small-medium sized barriers except the last three, which are impassable), including 20 pesqueiras, were identified as a relevant obstacle for sea lamprey migration (which joins the impact of fishing performed in these sites). Hence, still more attention must be paid to "small" barriers, as pesqueiras, and to fisheries to properly conserve and manage populations of this and other anadromous lamprey species.

Keywords

• Telemetry
• Spawning Migration
• barriers
• Habitat Fragmentation
• fishery
• Ulla River