Juvenile Salmon Usage of Nearshore Habitats along

City of Seattle Marine Shorelines

Wetland Ecosystem TeamSchool of Aquatic and Fishery Sciences

University of WashingtonSeattle, WA

Jason Toft

Charles SimenstadJeff Cordell

Lia Stamatiou

Funded by the Seattle Public Utilities Department

Main Objective:Quantify the abundance and behavior of juvenile salmonids and other fishes directly along marine shoreline habitat types.

Sampling Methods: High tides 5/12 - 8/1/03Spring Tides: Enclosure nets and snorkeling - sand, cobble, riprapNeap Tides: Snorkeling - all sites

Enclosure Nets (n=48):- Samples entire water column- Minimal problems with

obstacles on substrate- Holds fish for 2.75 hours, good

for fish diet analysis- Mesh size not good for small

forage and larval fish- Time and labor intensiveSnorkeling (n=442):- Fish not captured- Dependent on water clarity - Onsite specific behavior and

location patterns- Good at small forage/larval

fish and rare fish- Not so good at juvenile flatfish- Ease of replication

Pros and Cons

All Results are PRELIMINARY!:First detail fish densities from above 3 habitat types (modifications just to intertidal), then include the 2 below (modifications extend into subtidal).

Fish Densities:Between cobble beaches, sand beaches, and rip-rap that ends at the high intertidal, we see minimal differences -all in bottom fishes.

Enclosure Nets: Flatfish (juv. English Sole) at Sand Beaches

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

CobbleBeach

SandBeach

Rip-Rap

Fish

Den

sity

(#/m

3 )

Juvenile Salmon

Forage Fish

Other NearshoreFishesSurfperches

Flatfish

Other DemersalFishesGunnels

Crabs

*

Fish Densities:Between cobble beaches, sand beaches, and rip-rap that ends at the high intertidal, we see minimal differences -all in bottom fishes.

Snorkeling: Crabs at Cobble Beaches, Sculpins at Rip-Rap

0.000

0.001

0.002

0.003

0.004

0.005

CobbleBeach

SandBeach

Rip-Rap

Fish

# /

(Sec

chi d

epth

(m)*

Tran

sect

leng

th(m

)) Other NearshoreFishes

Flatfish

Other DemersalFishes

Gunnels

Crabs

Unknown Fish

* * *

Less Abundant FishAbundant Fish

0.0

0.1

0.1

0.2

0.2

0.3

0.3

0.4

CobbleBeach

SandBeach

Rip-Rap

Fish

# /

(Sec

chi d

epth

(m)*

Tran

sect

leng

th(m

))

JuvenileSalmonForageFishSurfPerchesOtherFish

Fish Densities:When shoreline modifications extend into the subtidal, we see more differences - in pelagic fishes.

Snorkeling: Overall at Overwater and Deep Rip-Rap, Juvenile Salmonids at Overwater, Surfperches at

Deep Rip-RapAbundant Fish

0.0

0.2

0.4

0.6

0.8

CobbleBeach

SandBeach

Rip-Rap Deep Rip-Rap

OverwaterStructure

Fish

# /

(Sec

chi d

epth

(m)*

Tran

sect

leng

th(m

))

JuvenileSalmon

Forage Fish

SurfPerches

Other Fish

* *

*

*

Fish Densities:When shoreline modifications extend into the subtidal, we see more differences - in pelagic fishes.

Snorkeling: Other Nearshore Fishes and Gunnels at Deep Rip-Rap

Less Abundant Fish

0.000

0.005

0.010

0.015

0.020

CobbleBeach

SandBeach

Rip-Rap Deep Rip-Rap

OverwaterStructure

Fish

# /

(Sec

chi d

epth

(m)*

Tran

sect

leng

th(m

))

Other NearshoreFishes

Flatfish

Other DemersalFishes

Gunnels

Crabs

Unknown Fish

*

** * *

Snorkeling: Juvenile Salmonid species groupings at Overwater and Deep Rip-Rap, also greater school sizes at Overwater (numbers above bars)

Salmon Densities and School Sizes:When shoreline modifications extend into the subtidal, we see differences in juvenile salmonids.

0

0.05

0.1

0.15

0.2

0.25

CobbleBeach

SandBeach

Rip-Rap Deep Rip-Rap

OverwaterStructure

Fish

# /

(Sec

chi d

epth

(m)*

Tran

sect

leng

th(m

))

Other SalmonidGroupings

Chum

Chinook/Chum

Chinook/Coho

Chinook

44

12

879

*

*

*

**

Overwater Structure

Deep Rip-Rap

Rip-Rap

Sand Beach

ChumChinook/

CohoChinook/

ChumChinook

21

4

195

998

249 415

203

79

291

518

1380

38

38

77

309

2103

Cobble Beach

Salmon Locations in Water Column:Deep Rip-Rap and Overwater Structures can affect positions.

surface

middle

bottom

Fish Location:Juvenile salmonids found 70% > 1m away from edge, or 30% at edge, rare underneath Overwater Structures.

23.7 b5.4 bc4.4 c3.4 dOverwater Structure

27.5 a5.9 c2.4 b4.8 dDeep Rip-Rap

28.8 a4.7 a1.7 a7.7 cRip-Rap

28.7 a4.8 ab1.7 a12.9 bSand Beach

28.7 a4.3 a1.6 a17.2 aCobble Beach

Surface Salinity

(ppt)

Average Secchi

Depth (m)

Average Water

Depth at Fish (m)

Average Transect Distance

from Shore (m)Habitat Type

Habitat Measurements:Shoreline modifications truncate the shallow water zone, gradual slope is lost. Pelagic fish that are typically spread-out along a large area may be forced to inhabit deep water directly along shore.

low tide

Sand Beach

Cobble Beach

Rip-Rap

DeepRip-Rap

OverwaterStructure

Diet Analysis:Gastric lavage of juvenile chinook shows less terrestrial/riparian input (insects) at sites with retaining structures at intertidal or supratidal.

0

20

40

60

80

100

Unretained(n=26)

Retained -Supratidal

(n=13)

Retained - HighIntertidal

(n=40)

% IR

I

Other

Terrestrial Riparian

Supralittoral/Marsh

Plant Matter

MarinePlanktonic/Neritic

MarineBenthic/Epibenthic

Overwater Structure

Deep Rip-Rap

Rip-Rap

Sand Beach

ChumChinook/ Coho

Chinook/ ChumChinook

21

4

195

998

249 415

203

79

291

518

1380

38

38

77

309

2103

Cobble Beach

Salmon Behaviors:Mostly schooling or swimming away. Fish are feeding on neuston at modified habitats, but getting less terrestrial input = limited.

Prey Resources:Unretained shorelines have a greater input of terrestrial insects into the diets of juvenile chinook salmon.

Timing and Size:- As compared to Lake Washington: juvenile chinook avoid

armored banks (Roger Tabor).- Juvenile chinook are larger and more pelagic in marine

waters, less dependent on shallow water (Casey Rice).- Differences are related more to indirect rather than direct

effects of shoreline modifications, such as changes in water depth, substrate, and shoreline vegetation.

0

0.03

0.06

0.09

0.12

0.15

0.18

5/19 6/2 6/16 6/30 7/14 7/28Date

Sum

Den

sity

(#/m

3 )

Chum

Coho(unmarked)

Coho(marked)

Chinook(unmarked)

Chinook(marked)

0

40

80

120

160

200

5/19 6/3 6/18 7/3 7/18 8/2Date

Fork

leng

th (m

m)

Coho -marked

Coho -unmarked

Chinook -marked

Chinook -unmarked

Chum

Concluding Remarks:- Shoreline modifications have the greatest effect on marine nearshore fish

communities when they extend from the supratidal through the subtidal.- Cumulative effects could be important, as 84-97% of the shoreline is

modified by retaining structures.

Future Research:- Further examine the effects of shoreline modifications on ecological

communities in regard to bank type, tidal height, and salinity regimes.- Look at landscape level patterns, especially in areas with high degrees of

alteration.- Investigate specific characteristics of Overwater Structures, such as

density, size, distance extending from shore, height above water, etc.

low tide

e-mail: tofty@u.washington.edu Pilot Study Report #301: www.fish.washington.edu/Publications/frireps.htmlFinal Report: due March 30, 2004Ongoing Research:

1. Ferry Terminals2. Monitoring of Salmon Bay Natural Area

Thanks: Funding by Seattle Public Utilities Department (Judith Noble, Gail Arnold Coburn, Julie Hall, Keith Kurko, Ed Connor, Maggie Glowacki, Albert Ponio); Casey Rice for fish permits; stellar fieldcrew (Lia Stamatiou, Carl Young, Danielle Potter, Katie Dodd, Trina Miller, Mike Cooksey, Kathryn Sobocinski, Mark Stamey); Scott Wilson and The North Beach Club for beach access.