Guidelines for the Selection of Biological SSSIs Part 2: Detailed Guidelines for Habitats and Species Groups Chapter 19 Freshwater Fish Authors Bean, C.W., Mainstone, C.P., Hall, R.A., Hatton-Ellis, T.W., Lee, A.S.L. and Boon, P.J. To view other Part 2 chapters and Part 1 of the SSSI Selection Guidelines visit: http://jncc.defra.gov.uk/page-2303 Cite as: Bean, C.W., Mainstone, C.P., Hall, R.A., Hatton-Ellis, T.W., Lee, A.S.L. and Boon, P.J. 2018. Guidelines for the Selection of Biological SSSIs. Part 2: Detailed Guidelines for Habitats and Species Groups. Chapter 19 Freshwater Fish. Joint Nature Conservation Committee, Peterborough. © Joint Nature Conservation Committee 2018 Guidelines for the Selection of Biological SSSIs - Part 2: Chapter 19 Freshwater fish 2018 (revision, v1.0) Cover Note This chapter updates and replaces the previous Freshwater Fish SSSI Selection Guidelines chapter (Nature Conservancy Council 1989). It was prepared by Colin Bean, Phil Boon and Alison Lee (Scottish Natural Heritage), Chris Mainstone and Ruth Hall (Natural England) and Tristan Hatton-Ellis (Natural Resources Wales), and provides detailed guidance for use in selecting freshwater fish sites throughout Great Britain to recommend for notification as SSSIs. It should be used in conjunction with Part 1 of the SSSI Selection Guidelines, as published in 2013 (Bainbridge et al 2013), which detail the overarching rationale, operational approach and criteria for selection of SSSIs. The main changes from the previous version of the chapter are that it: • reflects our greater understanding of fish diversity within the British Isles, and within- species diversity in particular. All of the data sources have been updated to reflect this; • provides better alignment between the identification of valuable freshwater fish populations and fish assemblages and the protection of the habitats which support them. Linkages are made between this chapter and SSSI Selection Guidelines for Freshwater habitats where appropriate; • provides a better context for the geographical selection of sites for the protection of native freshwater fish or fish communities of conservation value. It also provides more detailed guidance relating to the identification of site boundaries; and • separates freshwater fish from those normally associated solely with estuaries; and • includes a glossary to provide clarity in relation to the technical terms used within the chapter. This chapter has been subjected to appropriate levels of evidence quality assurance. It is compliant with the JNCC Evidence Quality Assurance Policy (2014, and has been subjected to external peer review by Professor Peter Maitland. 1 Guidelines for the Selection of Biological SSSIs - Part 2: Chapter 19 Freshwater fish 2018 (revision, v1.0) 1 Introduction 1.1. This guidance covers selection for any eligible native fish species in Great Britain that inhabit freshwater systems for all or part of their life cycle (Table 1), including migratory species that spend part of their life cycle at sea (i.e. diadromous species). Those species that use rivers, estuaries and marine environments must have free movement between them if they are to complete their life cycles. Linked and contiguous notifications for river and estuarine habitat, including the river’s saline transition zone, are therefore the best means of protecting the full range of characteristic fish assemblages. This guidance covers the same habitats as SSSI Selection Guidelines for Freshwater habitats and aligns with the guidance in that chapter. 1.2. Fish assemblages in the fresh waters of Great Britain vary naturally owing to a combination of environmental tolerances, competitive interactions and barriers to colonisation. The last glaciation and the associated post-glacial period were highly influential in shaping British fish communities (Davies et al 2004). This has resulted in the establishment of a north/west–south/east gradient in the number of native fish species present in British freshwater habitats. 1.3. Fresh waters to the south east of Great Britain that were directly connected to the European mainland contain a greater variety of species than are present in the north or west of the country. These communities contain a variety of species (particularly cyprinids and percids) which are naturally absent from elsewhere on these islands. To the north and west (including islands), fish colonised fresh water from the sea, and species that have marine affinities (such as the salmonids) dominate. Even in southern Great Britain, however, many European fish species are missing from natural assemblages and some European species (such as spined loach, barbel and grayling) are only naturally present in certain southern and eastern catchments. In northern and western Great Britain, natural gaps in the fish community allow other species such as trout and Arctic charr to exploit vacant niches, so creating unique freshwater communities. The absence of cyprinid fish, in particular, allows certain freshwater plant and invertebrate communities to develop, particularly in standing waters. 1.4. Freshwater fish communities, probably more than any other biological group, are heavily influenced by human introductions. A wide range of fish species have been introduced to rivers and lakes outside their native range. These may be fish which are native to other parts of Great Britain, or have been introduced from other parts of the world. Although such introductions are now regulated, many took place before legislation existed, and accurate records are often not available. Therefore, great care should be taken when designating any non-migratory fish species as a specific SSSI feature or part of an assemblage. This is discussed further below. 1.5. Some debate surrounds the status of crucian carp (Carassius carassius L.) as a native species in Great Britain. This species was until recently thought to be native to southeastern England and under threat (Sayer et al 2011). However, recent genetic evidence suggests that it was introduced to England as recently as the 15th century (Jeffries et al 2015). For this reason, there is currently no basis for including Crucian carp in the list of native freshwater species (Table 1). 2 Guidelines for the Selection of Biological SSSIs - Part 2: Chapter 19 Freshwater fish 2018 (revision, v1.0) Table 1. Native fish recorded in freshwater habitats in Great Britain (adapted from Maitland 2004). Order Family Common name Scientific name Petromyzoniformes Petromyzontidae River lamprey3 Lampetra fluviatilis (L.) Brook lamprey Lampetra planeri (Bloch) Sea lamprey3 Petromyzon marinus L. Acipenseriformes Acipenseridae Common sturgeon1,3 Acipenser sturio L. Anguilliformes Anguillidae European eel1, 3 Anguilla anguilla (L.) Clupeiformes Clupeidae Allis shad3 Alosa alosa (L.) Twaite shad3 Alosa fallax (Lacépède) Cypriniformes Cyprinidae Silver or white bream Blicca bjoerkna (L.) Common bream Abramis brama (L.) Bleak Alburnus alburnus (L.) Barbel Barbus barbus (L.) Gudgeon Gobio gobio (L.) Chub Leuciscus cephalus (L.) Dace Leuciscus leuciscus (L.) Eurasian minnow Phoxinus phoxinus (L.) Roach Rutilus rutilus (L.) Rudd Scardinius erythrophthalmus (L.) Tench Tinca tinca (L.) Cobitidae Spined loach Cobitis taenia L. Balitoridae Stone loach Barbatula barbatula (L.) Esociformes Esocidae Pike Esox lucius L. Osmeriformes Osmeridae Smelt3 Osmerus eperlanus (L.) Salmoniformes Coregonidae Vendace Coregonus albula (L.) Pollan Coregonus autumnalis (Pallas) Whitefish (Powan, Gwyniad or Schelly) Coregonus lavaretus (L.) Houting1,2,3 Coregonus oxyrinchus (L.) Salmonidae Atlantic salmon3 Salmo salar L. Trout (incl. sea trout3) Salmo trutta L. Arctic charr Salvelinus alpinus (L.) Thymallidae European grayling Thymallus thymallus (L.) Gadiformes Gadidae Burbot2 Lota lota (L.) Gasterosteiformes Gasterosteidae 3-spined stickleback Gasterosteus aculeatus (L.) 9 or 10-spined stickleback Pungitius pungitius (L.) Scorpaeniformes Cottidae Bullhead Cottus gobio L. Perciformes Percidae Ruffe Gymnocephalus cernuus (L.) Perch Perca fluviatilis L. Moronidae Sea bass4 Dicentrarchus labrax (L.) Mugilidae Thick-lipped grey mullet4 Chelon labrosus (Risso) Thin-lipped grey mullet4 Liza ramada (Risso) Golden grey mullet4 Liza aurata (Risso) Gobiidae Common goby4 Pomatoschistus microps (Kroyer) Pleuronectiformes Pleuronectidae Flounder4 Platichthys flesus (L.) Key: 1 = Species that spawn in freshwater but for which no spawning record exists for Great Britain. 2 = Species that are extinct in the wild in Great Britain. 3 = Diadromous species. 4 = Predominantly estuarine species. (In this context ‘estuarine’ means species that spend most of their life cycle in the estuary but periodically use the tidally influenced lower reaches of the river. 1 Guidelines for the Selection of Biological SSSIs - Part 2: Chapter 19 Freshwater fish 2018 (revision, v1.0) 2 International and national importance 2.1. Great Britain supports a sub-set of the European fish fauna, within which many of the species present occupy more prominent positions than they occupy on the continent. This has led to the development, in some cases, of unique fish communities. Several species which may be relatively common in a European context may be rare in Great Britain, where they are at the limit of their European range. 2.2. A range of British fish species appear on UK and international lists of conservation importance (Table 2). Presence on these lists is considered in the notification advice below. 2.3. Houting (C. oxyrinchus)