A Model for Early Life A Model for Early Life History Survival for History Survival for Pacific Herring in Pacific Herring in

Prince William SoundPrince William SoundBrenda Norcross, Seanbob

Kelly, Peter-John Hulson, Terry

QuinnSchool of Fisheries and Ocean

Sciences University of Alaska Fairbanks

Herring – An Important Herring – An Important SpeciesSpecies

Forage fish

Commercial fishery

Prince William SoundPrince William Sound

http://marine.alaskapacific.edu/octopus/pws-map.php

Recent History of Recent History of HerringHerring

Fishery closed in March 1989 following the Exxon Valdez oil spill

Stock collapsed 1993 due to (VHSV)

Species has not recovered to pre-oil spill abundance

Spawning and LarvaeSpawning and Larvae Herring spawn

onshore in April

Larvae herring are advected counter-clockwise through open water

Years 1 and 2Years 1 and 2 June-August metamorphosis Nursery habitats at heads of

bays In nursery bays for 2 winters Leave bays and join adult

schools

Early Life History to Age-1Early Life History to Age-1

4 stages - eggs, larvae, fall juveniles, winter juveniles

Know mortality changes as life stage changes

Determine which life stage is most influential

Early Life History ModelEarly Life History Model

Life-stage specific survival to age-1 Builds on an earlier range-based

study (Norcross & Brown 2001)

Statistical distributions of survival to account for uncertainty

Data input from published estimates

Standard Year-Class Standard Year-Class Model Model

((Quinn and Deriso 1999)Quinn and Deriso 1999) Cumulative mortality - z for each

stage multiplied by number of days per stage

Total mortality - combines mortalities of sequential life stages to age-1

,

Delta Method Delta Method (Seber 1982)(Seber 1982)

Converts standard error of survival to that of mortality

Assumed normal distribution Allows determination of 95%

confidence intervals.

Egg Stage - first 21 daysEgg Stage - first 21 days

(Haegele 1993) Subsurface oophagy - crabs, sea

anemones, and snails

(Rooper et al. 1999) Duration of air exposure -

exposure abiotic forces, and avian predation

Larval Stage - next 92 Larval Stage - next 92 days days

(McGurk et al. 1993) Larval mortality caused by advection,

predation, and inability to feed Data from Auke Bay, Southeast

Alaska Comparable to estimates from

British Columbia

Fall Juvenile Stage - next next 92 days92 days

(Stokesbury et al. 2002) Greatest mortality due to

predation Averaged over four bays and

two years

Winter Juvenile Stage - next next 135 days135 days

(Patrick 2000) Energy reserves (WBEC) and

water temperature affect survival

Age-0 winter mortality due to starvation

Averaged over 12 bays

>Age-3 spawn

first 21 daysmortality 0.07 d-1

next 92 daysmortality 0.07 d-1

next 92 daysmortality 0.01 d-1

Egg Stage Larval Stage

Fall Juvenile Stage

Winter Juvenile Stage

next 135 daysmortality 0.004

d-1

Age-1

hatch

drift

nursery bay

ResultsResults Total survival through age-1 118 herring out of 1 million eggs Compare to range-based – 1-

6,500

Consistent with the results of age-structured assessment (ASA)

Average ELH mortality is lower than ASA mortality ASA incorporates mortality ages-0 through -3 Greater uncertainty in the distribution of ELH

mortality

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

4 5 6 7 8 9 10 11 12 13 14

Total Mortality (Z)

Freq

uenc

yASA (age-3) ELH (age-1)

ELH ASA

Distribution of total mortality

Total mortality

Single-Stage Sensitivity Single-Stage Sensitivity AnalysisAnalysis

Altered mortality of each life stage by 10%

Total survival was most affected by the larval stage

Length of stage (92 days) and mortality level (* 0.07 d-1) is cause

Other life stages had an order of magnitude less effect

ConclusionsConclusions

Life stages did not contribute equally to mortality and survival

Larval stage has the largest influence on total survival

This model shows that there is high uncertainty in the early life history

AcknowledgmentsAcknowledgments Exxon Valdez Oil Spill Trustee Council Jeep Rice Mark Carls

Daily Survival and Daily Daily Survival and Daily Mortality Mortality

.

Results of single-stage sensitivity analysis. Both of the textured series are the results from increasing (left) or decreasing (right) daily mortality (zi) while the black series is the total survival estimated from the base early life history (ELH) model

0

0.00005

0.0001

0.00015

0.0002

0.00025

Invert Pred & Air Exp Larval Autumn Winter

Egg Drift Juvenile

Tota

l Sur

viva

l (S)

10% Increase of Mortality Base ELH Model 10% Decrease of Mortality

Interaction Sensitivity Interaction Sensitivity AnalysisAnalysis

Determined all possible paired combinations of life stages

Altered each pair of mortality estimates by 10%

Larval stage combined with any other life stage contributed the most to total survival

Total survival maximized by decreasing mortality for larval and egg stages