How to preserve and how to exploit natural populations to be sustained for the future. Plain questions without equally plain answers Applied freshwater fish biology An introduction to methods of research and management Arne N. Linløkken, ass. professor Inland Norway University of Applied Sciences Arne N. 1 CONTENT INTRODUCTION .................................................................................................................................................. 3 Prehistory and evolution ......................................................................................................................................... 3 Short on construction and function ......................................................................................................................... 4 Morphology ........................................................................................................................................................ 4 Anatomy and physiology .................................................................................................................................... 5 European freshwater fish species ............................................................................................................................ 6 Immigration and distribution of freshwater fish in western Scandinavia ........................................................... 7 Western immigrants ........................................................................................................................ 8 Southeastern immigrants to Norway ............................................................................................... 8 Northeastern immigrants to Scandinavia ........................................................................................ 9 Biotops and habitats.............................................................................................................................................. 23 Streams and rivers ............................................................................................................................................ 23 Lakes................................................................................................................................................................. 24 Clear water lakes ........................................................................................................................... 27 Boreal lakes and tarns ................................................................................................................... 27 Eutrophic lakes .............................................................................................................................. 28 Acidification affecting aquatic life ................................................................................................................... 29 Fish management .................................................................................................................................................. 30 Issues and action ............................................................................................................................................... 31 Reducing density/biomass to increase individual growth ............................................................. 31 Stocking ........................................................................................................................................ 32 Habitat Enhancement .................................................................................................................... 33 Fish Surveys ..................................................................................................................................................... 34 Test fishing ................................................................................................................................. 34 Sampling in running water ............................................................................................................ 35 Sampling in lakes .......................................................................................................................... 36 Calculations ................................................................................................................................ 40 Length and weight relationship ..................................................................................................... 40 Back calculation of length............................................................................................................. 41 Growth rate ................................................................................................................................. 42 Hydroacoustics .............................................................................................................................. 47 Age distribution and mean age ...................................................................................................... 48 Survival and mortality ................................................................................................................... 49 Nutrition and prey species of fish ................................................................................................. 51 Genetic surveys ............................................................................................................................. 54 Pollutants and contamination ........................................................................................................ 55 Fish parasites and diseases ............................................................................................................ 56 Creel surveys .................................................................................................................................................... 60 2 CURRENT TOPICS ............................................................................................................................................. 61 Temperature increase ........................................................................................................................................ 61 EU’s habitat directive .................................................................................... Feil! Bokmerke er ikke definert. Water framework .............................................................................................................................................. 62 3 INTRODUCTION This is a short introduction to freshwater fish biology and applied research, with a presentation of freshwater fish species in Norway, their immigration, distribution and ecological roles. It is based on Norwegian and Scandinavian conditions, with an environment characterized by pronounced seasonal variation, with annual ice cover and cool summer temperatures. Due to topography and postglacial history of freshwater organism invasion, the number of species is actually low, and a lot of lakes and streams have only one or two fish species. This makes them especially vulnerable to introduction of new species, like minnow or other cyprinids which may affect the native population dramatically. PREHISTORY AND EVOLUTION Life on Earth originated in the sea, about 3 billion years ago, with living organism defined as "something" with combustion and an ability to multiply. After additional one billion years, some organisms developed ability to harness energy from sunlight and build organic molecules of carbon dioxide and water, with oxygen in molecular form (O2) as a byproduct. The first bacteria to have photosynthesis, the basis for most of what we know of life on the planet today, started the "oxygen revolution". The sea slowly received oxygen from these organisms, and environmental conditions were changed perpetuity. This meant disaster for organisms that do not tolerate oxygen (the strictly anaerobic), being forced to retreat to oxygen free areas in sediments of oceans and lakes. For others, this offered new opportunities and future success. Most multicellular and advanced forms of life are depending on oxygen, produced by algae and plants. The oldest known multicellular organisms are left in 600 million year old fossils, some of them with living descendants, but numerous forms have emerged in the meantime. The earliest fish, known until now, is an almost 500 million years old fossil. These were the first chordates provided with vertebra for attachment of limbs and muscles and for protection of the important spinal nerve. The first skeletons were of cartilage, which is still found in sharks. Sharks have inhabited the world's oceans for 400 million years, and they were from the beginning a 4 success having existed with minor changes since then. The bony fish appeared concurrently but the modern ray finned bony fish developed during the last 200 million years. After Michael Benton: Vertebrate palaeontology (1st edition, 1990; 2nd edition, 1997; 3rd edition, 2005; 4th edition, 2014) SHORT ON CONSTRUCTION AND FUNCTION MORPHOLOGY Bony fish have their skin covered by scales and a protective slime layer, a tailfin, dorsal fin(s), anal fin and the paired pectoral and pelvic fins, pairs pointing towards the more advanced vertebrates, the tetra pods with two pairs of limbs, the amphibians, reptiles, birds and mammals. Design of fins, with or without rays, spiny fins or soft fins, and location relative to each other characterize species and groups, as do the shape of