Managing fishes' environment and climate change (L9)
- 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)
- habitat reconstruction
- 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
- causes
- 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
- temperature/ rate processes
- 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
- achieve smolt size threshold > younger, smaller, more smolts, higher proportion of ISW (at sea) adults (less marine mortality exposure)
- 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
- in sea
- salmon smolt (juvenile growth)
- 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
- bankside tree planting
- (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
- effect on fish
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