DRAFT REPORT 


SIUSLA W DREDGED MATERIAL DISPOSAL SITE 


Benthic Infauna And Demersal Fish Evaluation 


Contract Number: W9127N-08-P-0259 


Prepared For: 


u.S. Army Corps of Engineers 


Portland District 


Portland, Oregon 


Prepared By: 


Marine Taxonomic Services, Ltd. 


5125 NW Crescent Valley Dr. 


Corvallis, OR 97330-9721 


January, 2009 

Table 1 

Table 2 

Table3A &B 

Table 4 

Tables 5A&B 

Table 6 

Table7A &B 

LIST OF TABLES 

Station Locations for the Siuslaw ODMDS Study 

Sediment Grain Sizes and Total Organic Carbon 

Statistical Data Summary Tables 

Relative Densities ofMajor Taxa 

Dominant Five Fauna from Each Station 

Density Data - Eight Most Dominant Species Each Cruise 

Trawl Data 

iii 
1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

Appendix 

Appendix 

Appendix 

Appendix 

Appendix 

Appendix 

Appendix 

Appendix 

Appendix 

Appendix 

Appendix 

LIST OF APPENDICES 

Station Locations 


List ofEquations Used in Analysis of Invertebrate Data 


Plot of Invertebrate Diversity (R') 


Plot of Shannon Diversity Value (SDV) 


Plot ofEvenness Value (1') 


Plot of Species Richness (SR) 


Relative Densities - Major Taxa Groups 


Five Most Dominant Species From Each Station 

Eight Most Dominant Species From Each Cruise 

Trawl Data 

Species Data By Station 

v 
METHODS AND MATERIALS 

The purpose of this study is to supplement the earlier benthic data and provide 

information about the fish and epibenthic species present in the study area (see map, 

Figure 1 and Table 1, Appendix 1 for station locations). 

This study consisted of two separate tasks. The benthic infaunal study (Task 1) used a 

modified Gray-O'Hara box core to take five biological cores and one geological core at 

each ofthe ten predetermined sampling sites. 

The demersal fish and epibenthic study (Task 2) used a 12 foot semi-balloon otter trawl 

with a ~ inch mesh liner to take twenty minute (bottom time) trawls at each of the six 

predetermined trawl tracks. Both studies were undertaken in early August and again in 

September of 2008. 

The geological samples were placed in a pre-labeled zip-lock style bag, cooled, and 

shipped to Columbia Analytical Services Laboratory in Kelso, Washington for grain size 

and sediment chemistry analysis. Geological samples were only taken during the early 

August cruise. 

Biological samples for both cruises were sieved through a 0.5 mm screen and the retained 

material was placed in a container and fixed with a 10% solution of buffered formalin 

and seawater for a minimum of 72 hours. The samples were then rewashed through a 

0.25mm screen to remove the formalin solution and transferred to appropriately sized 

containers. These containers were filled with a mixture of 70% isopropyl alcohol and 

Rose Bengal stain. Rose Bengal is a protein stain added to facilitate sorting the animals 

from any retained detritus. Each sample was sorted under a dissecting microscope and all 

animals were removed and placed in major groups, i.e. Polychaeta, Mollusca, Crustacea, 

Echinodermata and miscellaneous groups. Taxonomists then identified all organisms to 

the lowest practical taxa. 

3 
TABLE 2 


Sediment Grain Size and Total Organic Carbon Data 


Station Number % Sand 

1 98.3 

2 98.7 

3 99.2 

4 98.4 

5 97.2 

6 97.3 

7 98.6 

8 97.8 

9 88.0 

10 99.0 

% Total Organic Carbon 

0.07 

0.06 

0.07 

0.07 

0.14 

0.08 

0.05 

0.08 

0.40 

0.05 

Total organic carbon was also performed on the geological sediment samples. Low 

organic carbon numbers were present at all stations. The data ranged from 0.40-0.05 

percent ofthe total volume. 

The invertebrate fauna found in the box core samples were typical of the nearshore high 

energy environment found along the Oregon coast. The infaunal data were computer 

analyzed and the following components of community structure were calculated: a) H', 

the Shannon-Weaver diversity index (Shiumon-Weaver, 1963); b) SDV, the Simpson 

Diversity Value (Simpson, 1949); c) SR, species richness, defined by Margalef (1958) as 

the number of species in a sample; and d) J', evenness, defined as the distribution of 

individuals among species (Lloyd and Ghelardi, 1964) (see equations, Appendix 2). 

5 
These data also show several commercially and recreationally important species present 

in the study area. Most of the specimens are juvenile or sub-legal individuals. 

Commercially and recreationally important species include the following: 

Cancer magister (Dungeness crab) 


Citharichthys sp. (Sand dab) 


Isopsetta isolepis (Butter sole) 


Psettichthys melanostictus (Sand sole) 


Ophiodon elongates (Ling Cod) 


Parophrys vetulus (English Sole) 


7 
Many ofthe benthic species in this study are able to survive in this dynamic environment 

being either very mobile or being able to react both to natural or man made perturbations. 

They readily recolonize in disturbed areas such as dredging scars or disposal site events. 

Task II 

The trawl samples denote this near shore area as a nursery ground with an abundant food 

source. Most of the species encountered in the trawl samples were benthic feeders that 

tend to utilize the shallower areas both because of the abundant food and because of 

fewer predators. The majority of the fish and crabs captured in the trawls were juveniles 

and young of the year. However, larger crabs and fish have the ability to avoid the trawl 

net. 

CONCLUSIONS 

The variability noted throughout this study appears to be consistent with other areas of 

the Oregon Coast and does not necessarily indicate a man made impact on the study area. 

The variation seen could be related to several factors but was most likely an artifact of 

spatial and temporal sampling. The data includes many animals newly recruited into the 

system as juveniles which were either lost through natural mortality, or moved to 

"better" feeding sites. Those that are not mobile tend to stabilize disturbed sites with 

their tube or burrow structures thus allowing more colonization by more long lived 

species. Spiophanes species are known to produce sediment stabilizing tube structures. 

(J.A. Blake, ENSR, Pers Comm). 

13 
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Blake, J.A. 2002. Pers. Comm. 

Byrne, J. V. and D. A. Panshin. 1977. Continental Shelf Sediments Off Oregon. Oregon 

State University Extension Service. SG-8. 

Emmett, R. L. 2001. Pers. Comm. 

Hancock, D. R., P. O. Nelson, C. K. Sollitt, K. J. Williamson. 1981. Coos Bay Offshore 

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Report to U.S. Corps of Engineers, Portland District, Oregon for Contract No. 

DACW 57-79-C-0040. Oregon State University, Corvallis, Oregon. 

Hancock, D. R. 1989. Pers. Comm. 

Jones, K. K. 2002. Pers. Comm. 

Lloyd, M. and R. J. Ghelardi. 1964. A table for calculating the "equitability: component 

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