embryo_survival 2

Developmental rate and

survival of embryos

• Temperature and rate of incubation

• Survival of embryos

– Disturbance by other females

– Gravel quality – water flow

– Dissolved oxygen

The number of days from fertilization to hatching

or emergence is fundamentally controlled by

temperature, but also varies between species

0 50 100 150 200 250 300

0 5 10 15

Temperature (oC)

day

s a

fte

r fertilization

coho emergance coho hatch

sockeye hatch

Temperature Units and development

Temperature Units = number of days x temperature

There is a general equivalence between time and temperature, such that embryos achieve about the same stage of development after

10 days at 5 degrees or

5 days at 10 degrees

10 x 5 = 50

Ecological importance of temperature

Sept Nov Jan Mar May

C um ul at ive T em per at ur e U ni ts Normal spawning times of two

populations

Straying to a warmer creek would lead to premature emergence

Straying to a cooler creek would delay emergence

spawn

hatch emergence

Cool = spawn early Warm = spawn late

Temperature Units and development: Part II

colder water, but the difference is not as great as

would occur if development required a fixed number of temperature units.

The ecological effect is to allow

embryos that start late (in cold water) to “catch up” a bit, and to “slow down”

those that started early (in warm water).

Variation in TUs needed for development

at different temperatures: Nadina River

sockeye salmon

0 5 10 15

Degrees C T em p er at u re u n it s t o yo lk a bs or bt ion

TU to yolk absorbtion constant 800 TU

Nadina River sockeye salmon yolk

absorption rate in relation to temperature

Brannon 1987 0 100 200 300 400 500 600

1.6 2.3 3.4 5.6 7.6 9.7 12.1 13.1 14.2

Temperature D ays t o yo lk ab so rp ti o n

Nadia R. days to yolk absorbtion

constant 800 TU

Simulated, if 800 TUs were required at all temperatures

Survival to emergence: average

and sources of variation

Density Dependent Factors

1. Redd “superimposition” (digging up) 2. Water Quality

• Dissolved oxygen

• Disease

Other Mortality – Biotic

Physical Factors

• Low D.O. Delivery rate

• Removal of metabolic wastes

2. Scour from high flow:

Percent Survival to Emergence

Pink

11.5%

Chum

12.9%

Sockeye

12.7%

Coho*

25.3%

Steelhead* 29.3%

Chinook*

38.0%

% are averages of data for wild populations

* = weak data

These values reflect

Density-dependence: Chilko River sockeye

0 10 20 30 40 50 60

0 100,000 200,000 300,000 400,000

Spawning adults

F

ry

(

m

ill

io

n

s

Density-dependence:

Weaver Creek Spawning Channel

0 10 20 30 40 50 60 70 80 90 100

0 10000 20000 30000 40000

Number of females (all species)

0 20 40 60 80 100

0 3 6 9 12 15

coho Chinook sockeye

Temperature

%

s

ur

v

iv

al

t

o

em

er

genc

e

Relationship between coho survival to

emergence and % fine sediment

0 10 20 0 10 20 30 40 50 Artificial

redds

Natural redds 80

70 60 50 40 30 20 10 0

%

S

ur

vi

val

t

o E

m

er

gence

Percent Fines < 0.85 mm

Survival of coho salmon embryos to

emergence in relation to % fine material

Coho (lab)

Coho redds (Koski)

Coho redds (Cederholm)

80

60

40

20

Survival to emergence in relationship

to particle size for salmonids

Chinook

Steelhead

Sockeye

Coho

5 10 15 20 Particle diameter (mm)

100

80

60

40

20

0

P

er

cent

sur

vi

Gravel particle size is important for embryo

survival, but how do we sample it?

1) Pebble count: measure the median axis of a random sample of particles from the surface of the stream (quick but superficial)

2) McNeil cylinder: collect, dry and weigh a bulk sample of gravel including surface and deeper material (more effort)

3) Freeze-core: collect a sample revealing the vertical profile of gravel sizes (most

Low dissolved oxygen levels reduce

survival: rainbow and steelhead trout

0

10

20

30

40

50

60

70

0

2

4

6

8

10

Mean DO level (mg/l)

% su

rviva

l of embryos

Estimated critical levels of dissolved oxygen* for

chum salmon embryos: older embryos need more DO

0 1 2 3 4 5 6 7 8

0 10 20 30 40 50

Days at 10 C

C rit ic a l D O le v e l ( m g /l)

Alderdice et al. (1958)

Chronic low oxygen levels slow

development and reduce alevin weight

Shumway et al. (1964)

0 5 10 15 20 25 30 35 40 45

0 3 6 9 12 15

Dissolved oxygen (mg/l)

D

ay

s

t

o hat

c

h or

w

ei

ght

days to hatch

alevin weight

0 20 40 60 80 100 socke ye

coho pink _chum

steel head rainb ow cutthr oat Dolly Var den Arct ic ch arr Atla ntic C onc ent rat ion ( m ic ro -g ra ms/ g ra m)

Concentrations of carotenoid pigments in eggs

of different salmonid species (Craik 1985)

100 80 60 40 20 10 5 15

Micrograms of carotenoid per gram of egg

% f er ti liz at ion and em br y o/ al ev in s ur v iv al

Fertilization success and survival of embryos and alevins may be enhanced by carotenoid concentration (Craik 1985).

0 25 50 75 100

Bright orange Pale orange Bright yellow Pale yellow

4

6

7

8

%

m

or

tal

it

y

t

o

hat

c

hi

ng

At moderate temperatures (4 – 8 C), rainbow trout

embryo mortality was associated with reduced

carotenoid pigment concentration (Craik 1985)

Fine sediment does not reduce DO levels,

only the transport rate of the water

2.0 mg/l

5 10 15 20 25 30 15

10

5

0

Percent fines (< 4 mm)

D

issol

ved oxy

gen

(m

g/

DO levels in chum salmon redds

declined from spawning to emergence

20

10

0

Spawning

0 1 2 3 4 5 6 7 8 9 10

Dissolved Oxygen mg/l

P

er

cent

30

20

10

0

Egg to fry survival is reduced

by high flows during incubation

0

5

10

15

0

100

200

300

Cedar River peak flow (m

/s)

E

gg t

o f

ry

s

ur

v

iv

a

l (

%

)

Scour and egg burial depth:

Kennedy Creek chum salmon redds

50 40 30 20 10 0

30 20 10 0

P

er

cent

scour

or

egg pocket

s

Scour

Egg Pockets

The depth of scour varies among

habitat types: Kennedy Creek

0% 10% 20% 30% 40% 50%

Riffle Lower

Riffle

Glide Pool

Tailout

Pool Lat.Bar

All Sites

%

m

oni

tor

s

s

c

our

ed t

o 0.

2m

Site A

What is the cause of mortality

from flooding?

•

Dislodgement of embryos that drift

downstream, get eaten, etc.

•

Crushing of embryos within the gravel

•

Disruption of normal development from

mechanical shock at sensitive periods

•

Sedimentation of the egg pocket and

Salmon embryos are very vulnerable to

handling or other mechanical disturbance

during a period in their development

0 25 50 75 100

0 50 100 150 200 250 300

Temperature units after fertilization

%

s

ur

v

iv

a

l a

ft

e

r ha

ndling

8.9 C 10.5 C 12.7 C

Johnson et al. (1989)

Winter flows in Carnation Creek in

relationship to coho egg to fry survival

R2 = 0.71

0 5 10 15 20 25 30 35 40

0 20 40 60 80

Winter discharge (cm)

%

egg

f

ry

s

ur

v

iv

al

Egg to fry survival in relation to an index of

gravel quality: Carnation Creek coho

R2 = 0.54

0 10 20 30 40

2.5 3 3.5 4 4.5

Fredle index of gravel quality

%

eg

g

f

ry su

rvi

val

Complex effects of flooding

• Gravel mobilizes during high flows,

crushing and dislodging embryos in

vulnerable habitats

Fine

sediment

Low

ambient DO

Density

Scour

Birds

Desiccation or freezing

Dig up

Suffocation

Female

size

Female

timing

Low flows

High flows

Fishes