Aspects of the conservation biology of an exploited population of migratory European river lamprey (Lampetra fluviatilis)

Abstract

Populations of anadromous lampreys across the globe have declined in recent years as a result of anthropogenic impacts. One such species is the European river lamprey, Lampetra fluviatilis, which has declined due to the consequences of factors such as pollution, over-exploitation and anthropogenic barriers. The Humber River Basin contains one of Western Europe’s most important populations of L. fluviatilis but this population may be threatened by the impacts of anthropogenic barriers and commercial exploitation for angling bait.
This thesis’s objectives were two-fold. Firstly, to evaluate the efficiency of a semi-formalised nature like bypass specifically designed, but previously untested, to allow upstream passage of migrating river lamprey past a weir at the tidal limit. Secondly, to determine the proportion of UK coarse predator anglers who use lamprey as bait and to gauge their opinions and knowledge regarding the use of lamprey as bait.
Passive Integrated Transponder and acoustic telemetry indicated that although attraction efficiency into the bypass was high, up to 70.8 % (calculated as the number of acoustically tagged lamprey that entered the bypass as a percentage of those detected downstream of the weir), the bypass was very inefficient with an estimated passage efficiency of 5.4 % (calculated as the number of PIT tagged lamprey which successfully used the bypass to travel upstream of Naburn weir as a percentage of those that were detected within the bypass during the period of time that the most upstream PIT antennas was operational). Most lamprey that passed the weir directly when the weir was drowned rather than using the bypass. It appears that periods of high river stage increased attraction into the bypass but also created conditions unsuitable for passage through the bypass due to high velocities, especially at an undershot control sluice at the upstream end.
Telephone questionnaires of freshwater predator (principally pike, Esox lucius) anglers revealed that 67.8 % of participants used lamprey as bait to some degree and 39.1 % of participants would prefer lamprey to be sourced from the UK. Although participants knew little about the source of their lamprey, they generally agreed that bait companies should source their baits sustainably, that lamprey should be conserved and if lampreys were threatened by exploitation, a ban on their use as angling bait should be implemented. However, the results indicate the existence of a subset of anglers who highly value lamprey as bait and so may oppose conservation efforts or restrictions on use.
Overall, this thesis indicates that upstream passage solutions for weaker swimming fish should be focused on removing redundant barriers in waterways rather than creating novel designs for fishways. Additionally, the lack of knowledge surrounding the origin of angling baits combined with the widespread use of threatened species highlights the lack of transparency within the angling bait industry, an issue that deserves further investigation.