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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Yellow eel ecology

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Yellow eel ecology

Yellow eel ecology


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)


Yellow eel ecology

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


Yellow eel ecology

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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