yellow eel ecology
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Yellow eel ecology. After Metamorphosis. Staging in estuaries/river mouths Later by increasing latitude (March-May) Size 50-70 mm (increases with latitude) Movement upstream related to tidal height, temperature(10-12) and temperature differential (river and bay), and discharge

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PowerPoint Slideshow about ' Yellow eel ecology' - hilel-mccarty


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after metamorphosis
After Metamorphosis
  • Staging in estuaries/river mouths
    • Later by increasing latitude (March-May)
    • Size 50-70 mm (increases with latitude)
    • Movement upstream related to tidal height, temperature(10-12) and temperature differential (river and bay), and discharge
    • Upstream movement
      • up to 2.3 km/day (St Lawrence River)
      • ‘many years’ (Atlantic coast drainages)
slide3
Size
  • Recently metamorphosed
    • TLx~61 mm (range 50-70 mm)
    • TL increases with increasing latitude
  • Max
    • > 1m (large migratory females)
    • Males typically smaller than females
habitat use
Habitat Use
  • Brackish (estuarine)
  • Freshwater (lakes, rivers, streams)
  • Multimodal (FW then estuarine, growth advantage?)
habitat use1
Habitat use
  • Highly variable
    • Leaf packs, debris, undercut banks in rivers
    • Small mountain streams, ‘trout habitat’ (pools with structure)
    • Sheltering in winter (large cobbles, under stream banks)
home range
Home range

High site fidelity - short time (GA, VA, NE); multi years (VA)

Range Size – greater in FW than brackish (GA), seasonal

migrations in FW; VA mountain year-round residents

may vary with food availability, habitat type, density

of conspecifics

activity
Activity
  • Varies by season, time of day
    • Spring, summer, early fall longer periods of activity in mountain streams (crepuscular/night)
    • Winter (VA) largely inactive except for brief periods late night/early morning
slide8
Diet

Top predator

individuals often largest predators and eels comprise significant proportion of total fish biomass in a community

Diet opportunistic, related to availability and eel size - larger eels, larger prey

  • Small eels FW: insects
  • Large eels FW: crayfish and fish
  • Small eels Brackish: microcrustaceans
survival mortality
Survival/mortality
  • From Anguilla anguilla:
    • Age related, age 1-2 increase 35-80% then approaches 90% through age 10
  • Predation presumed
  • Fisheries (all life stages), Hydro facilities, diversions, pollution
growth
Growth
  • ME
    • 18-31 mm/yr
  • RI
    • Coastal streams 23-33 mm/yr
  • GA
    • Coastal plain 67-62 mm/yr
  • VA
    • Mountains 19-26 mm/yr
demographics
Demographics
  • Related to distance inland
    • Density declines with distance
    • Riverine eels longer than estuarine (GA, VA, NE)
    • Further inland more likely to be female (NE, GA, SC, VA)
    • Closer to coast sex ratios disparate but males often predominate
    • Lacustrine habitats greater proportions of females
demographics con
Demographics (con.)
  • Southern eels > 300km inland (e.g. Shenandoah) similar to northern eels (Lakes Ontario and Champlain)
    • Females, max size > 1m
    • Far upstream eels take 2+ years longer to mature
    • 15% increase in maturation time yields 65-93% increase in fecundity
demographics con1
Demographics (con.)
  • Distribution & abundance: Scale dependant
    • Large scale predictive models based on local habitat features highly variable, not transferable. Habitat relations a function of distance from ocean
      • Density not related to habitat type, substrate, etc. NC, SC, NE, VA
    • Large scale (physiographic or river-basin) patterns better described by random upstream dispersal (diffusion) model
yellow to silver
Yellow to Silver
  • Morphology
    • Change in skin color from yellow to silver or bronze
    • Thickening of integument
    • Increased length and weight
    • Relative lengthening of pectoral fins
    • Increased eye diameter
  • Physiology
    • Change in gill structure/cell composition
    • Degeneration of alimentary canal
    • Increased oocyte diameter and developmental stages
    • Increased gonadal weight
    • Changes in muscle properties
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