Environmental Effects on Recruitment of Northern Shrimp in the Gulf of Maine

Environmental Effects on Recruitment of Northern Shrimp

in the Gulf of MaineAnne Richards

Michael Fogarty

David Mountain

NOAA National Marine Fisheries Service

Woods Hole, MA

• stock-recruit-environment relations

• mechanisms for recruit-env’t relation

Outline

Northern ShrimpPandalus borealis

• Boreal distribution• Gulf of Maine=southern

limit• Locally important

fishery

from Shumway et al. 1985

Life history

Fishery

Impetus

• Conventional wisdom: temperature = primary regulating factor

• will “…not respond well to attempts to control exploitation”

(Apollonio et al. 1986)

0

2

4

6

8

10

12

14

55 57 59 61 63 65 67 69 71 73 75

Year

Lan

din

gs

(00

0 m

t)

7

8

9

10

11

12

Landings Temperature lag 4

Stock-Recruitment Series1968-2002

Northern Shrimp S-R

-2.0

-1.0

0.0

1.0

2.0

3.0

-1.5 -0.5 0.5 1.5 2.5SSB Index

Rec

ruit

Environmental Variables• Temperature anomalies (W Gulf of Maine)

– fall bottom: developmental rates, egg parasitism

– spring bottom: developmental rates, hatch timing

– spring surface: larval development

• NAO winter index

Analysis• Box-Jenkins TSA to ID factors affecting

recruitment

• S-R with environmental inputs

Results – TSASignificant crosscorrelations with recruitment

1

-4Spring Bottom TA

-1NAO

-Spring Surface TA

+2SSB

Lag Sign

without 2002

Planktonic larvae

Male maturation, gender transition

Stock-Recruitment Models

Time period Variables tested Model r2

1968-2001 SSB

Spring surface TA

Spring bottom TA

r2=0.46

1968-2002 SSB

Spring surface TA Spring bottom TA

r2=0.29

Stock-Recruit-TemperatureShrimp S-R

0

1

2

3

4

5

6

0 1 2 3 4 5 6

SSB Index

Rec

ruit

Inde

xS-R observed TA=-1.5 TA=0 TA=+1.5

Conclusion

• Shrimp recruitment dependent on SSB and spring temperatures (surface and bottom)

Mechanisms: Spring SST

• Spring surface temperature effect (larvae):– Appears intuitively correct– But counters laboratory studies: better growth

and survival at warmer temperatures.– Indirect effect, e.g. match-mismatch?

Match-Mismatch Hypothesis

• Coastal Gulf of Maine: Bloom timing determined by solar insolation (Townsend and coauthors)

• Shrimp development: temperature-dependent

Match-Mismatch Hypothesis– Bloom timing– Hatch timing – Survival rates

Bloom Timing• Townsend and Cammen

(1988): 1971-1980

• CZCS and SeaWifs

’78-’86, ’98-’03

Timing of Bloom OnsetTownsend and Cammen (1988)

30

35

40

45

50

55

71 72 73 74 75 76 77 78 79 80

Year

Julia

n D

ay

Hatch Dates

• Maine DMR fishery sampling, 1980-1983 and 1989-1993

• Probit analysis: 50% hatch, duration of hatch

Proportion Hatched1980

0.00

0.20

0.40

0.60

0.80

1.00

0 20 40 60 80 100

Julian Day

Pro

po

rtio

n H

atch

ed

Hatch Timing

Hatch Timing and Duration

10

20

30

40

50

60

70

80

90

100

80 81 82 83 89 90 91 92 93Year

Juli

an

Da

y

90% 10% 50%

Shrimp Development• temperature-dependent

Hatch Timing vs. Ocean Temperature1980-1983, 1989-1993

y = -0.038x + 169.6

R2 = 0.54

40

45

50

55

60

65

70

75

2500 2600 2700 2800 2900 3000 3100 3200

Cumulative Temperature May 1- Julian Day 40

Ju

lian

Day o

f 50%

Hatc

h

Bloom Onset and Hatch Timing

Bloom vs. Hatch Dates

30

40

50

60

70

70 72 74 76 78 80

Hatch Year

Julia

n D

ay

Bloom Hatch

Survival

Survival Ratio (R/S) vs. Mismatch

0.000.501.001.502.002.503.003.504.004.505.00

-2 3 8 13 18 23 28

Days between Bloom Onset and Hatch Timing

Su

rviv

al

Ind

ex

(R

/S)

Larval Shrimp Diet• Zooplankton bloom ~ one month later

(Townsend 1984)

March 6

no food

small diatoms

large diatoms

zooplankton

March 26

no food

small diatoms

large diatoms

zooplankton

March 13no food

small diatoms

large diatoms

zooplankton

April 1 no food

small diatoms

large diatoms

zooplankton

Stickney and Perkins (1980)

Stage I larvae

ImplicationsCumulative SST during Developmental Period

Boothbay Harbor SST

2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

1905 1915 1925 1935 1945 1955 1965 1975 1985 1995Year

Cum

Tem

p '0

00s

Julian Day 120 - 40

Application

• Management:

Adjust fishing effort to allow higher egg deposition in warmer years

Stephen H. ClarkSummary

1) SSB and spring temperatures affect GoM shrimp rcrt

2) Spring SST effect may be mediated through match-mismatch

Ongoing Work

• Bloom timing– Solar insolation, 1982-

1999

– CZCS / SeaWiFS, ‘83-’91, ‘97-’03

• Hatch timing