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|The Starry Flounder (Platichthys stellatus) in the Fraser River Estuary
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|Retired DFO Scientist
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|twitter @cdlevings website colinlevings.ca
|Western Division/WA-BC Chapter
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The Starry Flounder (Platichthys stellatus) in the Fraser River Estuary
In this paper we give data from early studies on migration rates of Starry Flounder in the Fraser River estuary using ultrasonic and radio tags, feeding habits, age data, and habitats. In a preliminary study with a small sample size (n=11) a mixture of radio tagged and ultrasonic tagged fish showed movement upstream and downstream. A larger study (n=36) with only radio tagged submature flounder (average weight 40 g) showed mainly movement downstream and detections up to 42 days post release. Average daily movement was 0.6 km d -1 and average distance moved from the release site was 12.2 km. Trawl catch data suggested Starry Flounder are more abundant on sand substrate relative to mud, with smaller fish (<10 cm) more common on mud habitats. Stomach contents of Starry Flounder caught within the salt wedge area were dominated by polychaetes while fish above the salt wedge ate mostly chironomid larvae. Forty-six Starry Flounder were aged using otoliths; age range was from 0 (1st year of life) to 9 y, with 52% of aged fish in the 0 year class. Starry Flounder are known to spawn in the winter and early spring in estuaries. Importantly, it appears that in the lower Fraser River, juvenile Starry Flounder are likely resident within the estuary up to age 2, which may indicate an intolerance to elevated salinity levels prior to this age. If elevated salinities restrict the estuarine distribution of juvenile Starry Flounder, resource managers would need to take into account potential habitat loss given salinity encroachment in lower estuaries as a result of in-channel dredging and development. The last detailed studies of Starry Flounder in the Fraser River estuary were done over 25 years ago; additional studies are needed to update and expand data on the ecology of this important species.