Water quality

Water quality requirement of lampreys

Lamprey are recognised as being sensitive to water pollution (Maitland, 2003) and compromised water quality. The larvae of all three species are rarely found in areas of stagnant water or eutrophic conditions; in addition heavy siltation and slow currents have been noted as unfavourable for larval lampreys (Kelly and King, 2001). Pollution events can have major impacts on all lamprey species by smothering both spawning gravels and nursery silts (Maitland, 2003). When instream works are undertaken during the lamprey spawning season (March to July), similar effects can occur as would occur if such works were undertaken during the salmonid spawning season (October to May). On Natura 2000 rivers designated for lampreys particular instream works should only take place during August and September, taking cognisance of the existing close seaosn for salmonids.

Excessive filamentous algae growth as a result of eutrophication processes on the lower River Boyne
Excessive filamentous algae growth as a result of eutrophication processes on the lower River Boyne SAC

Eutrophication which is associated with lush growths of algae and bacteria associated with increased nutrients can also smother spawning gravels preventing spawning or killing eggs and creating anoxic conditions in nursery silts (Maitland, 2003).

The distribution of larvae is rarely affected by short-term low oxygen levels, as ammocoetes can tolerate low oxygen levels due to their low metabolic activity, their blood characteristics and branchial pumping ability (Maitland, 2003). The contributory factors leading to low oxygen levels, such as pollution and high temperatures, are more lethal to ammocoetes. Conversely adult lamprey do not have the same buffering with regard to oxygenation and adult Sea lampreys are known to have the same oxygen consumption as salmonids of comparable weight at various temperatures.

Although there is an apparent absence of legislation in relation to the avoidance of instream works during the lamprey spawning seaosn in Ireland, prosecutions are possible under European legislation and also the European Communities (Environmental Liability) Regulations 2008

Water temperature is an important regulatory factor for all three species of lamprey as it determines the onset of spawning and migration. The transformation of the larval stage to the macrophthalmia stage occurs over a very short period of three to four weeks and temperature may also be an influencing factor at this stage of development. Any developments directly or indirectly affecting the temperature within a river system must take consideration of the ecological requirements of lamprey species present.

Legislation

The key parameters in relation to water quality are set out in the European Communities Environmental Objective (Surface Waters) Regulations (2009 and Amendment Regulations 2012). However, there are no specific limits provided in these regulations for suspended solids, most often arising from the mobilisation of silt. Suspended solids are identified as a significant impact affecting both water quality and lamprey species directly and also indirect with siltation effectively blanketing spawning gravels and ova. The European Commission (Quality of Salmonid Waters) Regulations 1988 sets an annual average of ≤25mg/l for suspended solids in salmonid watercourses, this is considered an appropriate standard for lamprey with regard to the adult life stage and spawning requirements, where fluctuations may occur within this range. The primary legislation in the Irish context is therefore:

Visual elevation of suspended solids levels downstream a working machine. OPW works take place within lamprey spawning season.
Visual elevation of suspended solids levels downstream a working machine on the River Nore . Instream works should never take place during the lamprey spawning season.

Guidance

The requirement with regard to the protection of watercourses during instream works are set out in guidance which includes details of the primary pollution control measures to be employed when working near water. These publications, in addition to the guidelines set out by the National Roads Authority are the principle guidance for instream works in Ireland. Instream works should never be undertaken during the lamprey spawning season, especially in Natura 2000 rivers. Although there is an absence of legislation in relation to this issue in Ireland, prosecutions are possible under European legislation and also the European Communities (Environmental Liability) Regulations 2008. There it would be advisable to take this issue into account when working in rivers, and schedule works outside sensitive times. For more information see ECOFACT (2012).  It is noted that this would also apply to state agencies.

Pollution in Limerick City; this dye probably looks worse than it is to lampreys and other fish
Pollution in Limerick City; this dye probably looks worse than it is to lampreys and other fish

In Northern Ireland the Lough’s Agency have published guidance for the protection of water quality and fisheries, which, in addition to guidance published by the Northern Ireland Environment Agency; UK guidance published by the Scottish Environment Protection Agency and CIRIA guidance provides significant water quality protection measures for instream works which should be followed, taking specific regard to the differing requirements of Lamprey over salmonids.

Severe pollution of sediments downstream of Navan municipal water works, River Boyne and River Blackwater SAC
Severe pollution of sediments downstream of Navan municipal water works, River Boyne and River Blackwater SAC

General references

  • Maitland P.S. (2003) Ecology of river, brook and sea lamprey. Conserving Natura 2000 Rivers Ecology Series No. 4. English Nature, Peterborough.
  • Kelly, F.L. and King, J.J. (2001) A review of the ecology and distribution of three lamprey species, Lampetra fluviatilis (L.), Lampetra planeri (Bloch) and Petromyzon marinus (L.): A context for conservation and biodiversity considerations in Ireland. Biology and Environment: Proceedings of the Royal Irish Academy 101B (3), 165_/85.

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