The juvenile demersal fish assemblage along the Pacific Northwest coast has received little attention relative to adult life history stages since pioneering work in the 1970s.

Increasing severity of hypoxia along the Oregon coast in recent years has prompted investigations into the response of biota in this region. Reserchers used summer data (2008e2013) from a beam trawl survey targeting juvenile demersal fishes in soft-bottom habitats along the Oregon coast to describe patterns of distribution and abundance at fixed sampling stations (from 30m to 100m depth). They relate the assemblage and abundance of the common species to environmental variables and analyze condition of recently settled fish (<50mm SL). 

Most of the captured fishes were young-of-the-year flatfishes, dominated by Butter Sole (Isopsetta isolepis), English Sole (Parophrys vetulus), Speckled Sanddab (Citharichthys stigmaeus), and Pacific Sanddab (Citharichthys sordidus). Community analysis of the full dataset showed some variation in species richness among years and high evenness across all sampling sites and years. Depth was a structuring variable for the community, indicated by multivariate nonmetric multidimensional scaling analysis. Generalized additive models for common flatfish species abundances during the summer months indicated depth preferences, with Butter Sole, English Sole, and Speckled Sanddab at shallower locations and Pacific Sanddab occurring at deeper locations farther offshore. Additionally, while most common species were collected in high abundances in hypoxic conditions, dissolved oxygen was a significant factor in determining flatfish abundance. Condition factor was weakly negatively impacted by low dissolved oxygen for the species assessed, but the strength of the relationship varied by species.

Increased sampling frequency and spatial coverage would improve researchers understanding of this community, especially in light of changing environmental drivers such as decreasing pH, warming water, and episodic periods of low dissolved oxygen coinciding with settlement for many species.

Authors: Sobocinskia, Kathryn L.;  Ciannellia, Lorenzo; Wakefield, W. Waldo; Yergey, Matthew E.; Johnson-Colegrove, Angela

Short Description: 
Researchers investigate the effects of summer hypoxia and other environmental variables along the Oregon coast on the distribution and abundance of juvenile demersal fish that live and feed on or near the bottom of the ocean and coastal shelf.
Product Number: 
ORESU-R-18-008
Entry Date: 
Thursday, May 10, 2018
Length: 
16 pages
Year of Publication: 
2018