Northwest Fisheries Science Center

Newportal Blog

A gateway to oceanographic adventures from the Newport Line and beyond

Blog on ocean conditions along the Newport Line and the northern CA Current.

Sampling the Columbia River Plume

By Kelsey Swieca and Ric Brodeur
Posted on June 28, 2016


Larval fish (possibly tomcod) seen in ISIIS images.

We successfully completed a survey of the Columbia River plume using ISIIS. Over the duration of 10 hours we conducted four north/south cross-sections of the plume with catching both an ebb and flood tide. Salinity values ranged from 18-33 psu. Attached is the plot for the first transect (x axis is distance from start so the values are negative). At first glance our samples consisted mainly of a variety of gelatinous zooplankton (with on very dense layer of Mitrocoma near 20 m depth) and the images were saturated with small phytoplankton and detritus. We did not closely examine the real time images because we were in a shallow area and were concentrating on our flying pattern and bottom depth, however we did spot a good size (~3 cm) fish that Toby Auth believes is a Pacific tomcod (see image).

 

Large catch of northern anchovy (and one hake) collected in midwater trawl collection.

In the early hours of the morning, the night crew finished sampling their last station. Having completed all the regular grid stations, they had some extra time and filled it with some experimental mid-water trawls. Because of the low rockfish catches in the southern stations, we wondered if juvenile rockfishes were at a different depth than the standard tow depth or if most of the rockfishes were closer to shore than our normal sampling grid. So we fished at three depths, (shallow, standard, and deep) at one Columbia River station where we caught a number of rockfish in our earlier sampling. The shallow tow had 1 juvenile rockfish, the deep tow had 55 juvenile rockfishes, whereas the normal depth caught 131 rockfishes which suggests that we are sampling the bulk of the population.  We also did a nearshore tow (~20 km) inside of our nearest station on this transect and we caught 19 rockfishes. We also caught a lot of adult herring, northern anchovy, and smelt that we hadn’t sampled much of before, along with some Pacific butterfish.  The dominant taxa in terms of biomass were water jellies (Aequorea sp.) which in normal years are generally distributed farther offshore than this station.

Thanks to great weather throughout the cruise we finished everything earlier than expected and will conduct some additional depth-stratified tows tonight. We also have enough time to complete an ISIIS transect of the Newport Line tomorrow during the day, thus completing the ISIIS transect series of the entire Oregon coast.


Tagged: Prerecruit

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