Managing fishes' environment and climate change (L9)

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  • Created by: hanRose
  • Created on: 01-01-22 17:31
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  • habitat loss/ degeneration
    • causes
      • urbanisation/ infrastructure  engineering
      • farming/ drainage/ trampling/ fertiliser
      • forestation/ de-forestation (especially coniferous monoculture)
      • gravel extraction
      • flood defence/ land drainage/ channelisation
    • effects
      • in channel features loss habitat complex (eg gradient/ cover)
      • eutrophication
      • siltation: smothering gravels/ vegetation/  block o2 delivery to egg/ invest     (major issue in south wales/ south-west England)
      • bankside: loss tress/ root system/ organic + food input loss/ shade/ insolation
      • effects permeate downstream through catchment
    • solution
      • habitat reconstruction
        • flow deflection/ weirs/ artificial spewing beds/ bank protection/ reconstruction
      • buffer strips/ fencing
        • keep stock off bank/ decrease erosion/ increase revegetation (benefit aquatic/ terrestrial  taxa)
      • planning control/ guidelines (est farm/forest)
      • EU habitat directive (HD)
      • water framework directive (WFD)
    • cautions
      • benefits rarely monitored
      • poorly targeted scheme
      • instream structure are vulnerable to washout/ stream channels naturally dynamic
      • soft engineering more effective than hard structures
      • insufficient maintenance
      • upstream activities cause downstream effects
      • need catchment scale assessment/solutions
  • climate change
    • effect on fish
      • temperature/ rate processes
        • metabolism/ maturation/ embryo development/ growth/ swimming/ stress resistance
        • by 2100: temperature  up 1-6oC globally. ectotherm metabolic rates up by 10-75%. effects feeding, excretion, growth, production
      • flow regime: habitat migration/ loss space (low flow)/ washout + displacement (floods) connectivity
      • invasive non-native species (INNS): competition / path
      • phenology (biological timing): extended growing season/ mismatch in seasonal development/ migration/ change in cue timing
      • ecosystem  changes: niche available/ shift in primary production assemblages/ competition/ trophic webs
    • conflicting processes= hard to predict  - life history not in a straight line in response + geographically variable
      • salmon smolt (juvenile growth)
        • achieve smolt size threshold > younger, smaller, more smolts, higher proportion of ISW (at sea) adults (less marine mortality exposure)
          • but smolts migrating earlier because cue happen earlier = sea arrival mis match = net outcome uncertain
      • post-molt (adult salmon)
        • in sea
          • thermal habitats shifts in North Atlantic
          • ocean currents/ migration routes
          • new competitors (mackerel)
          • prey available /energy quality
          • "skinny salmon"
        • in estuaries/ rivers
          • low flows delay migration (tracking studies)
          • high temperature = thermal stress, disease, displacement back to sea, mortality
          • decrease Vitello genesis/ egg survival in salon
    • what to do??
      • bankside tree planting
        • optimal shade, cooling (decrease max temperature 2-3oC)
        • bank stability, inverts, leaf litter
      • max migration
        • reservoir flow releases for salmonid (+ local cooling effect)
        • remove barriers to max connections
      • control invasive species
      • limit abstraction/ protect ground water (help temperature management )
      • human policy and beavhioue
    • (potential) brown trout (sotrutta)
      • summer temperature = growth rate/ maturation/ competition/ trophic web
      • winter temperature = incubation rate and emergence date advance/ productivity
      • winter rainfall/ flow: gravel stability  and washout
    • effects on environments
      • vary geographically
      • UKCP18 projects: dyer, warmer summer (=5.4oC by 2070, high); wetter, warmer winters (=4.2oC); more variation and extremes of temperature
      • sea level rise 0.53m -> 1.15m by 2100
      • water quality (less dilution of contaminants/ sedimentation/ acidification)
      • habitat change: direct (flow) and indirect (plant growth/ invasive species/ communities)
      • freshwater ecosystem- sensitive indicators, due to tight air-water temperature links

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