NOAA Teacher at Sea
Aboard NOAA Ship Reuben Lasker
July 17 – 30, 2017
Mission: West Coast Pelagics Survey
Geographic Area of Cruise: Pacific Ocean; U.S. West Coast
Date: July 22, 2017
Weather Data from the Bridge:
Date: 07/22/2017 Wind Speed: NW at 8 Knots
Time: 20:20 Latitude: N 43 53.78
Temperature: 18.5 C Longitude: W 124 38.7
Science and Technology Log:
After steaming north out of San Francisco, the Reuben Lasker arrived on location just south of Newport, Oregon early Wednesday (07/19) morning ready to begin the 2nd leg of the West Coast Pelagics Survey (WCPS). The survey is targeting coastal pelagic species (CPS). The Southwest Fisheries Science Center (SWFSC) uses the following characteristics to describe CPS. CPS have relatively short life spans, high reproductive potential, responsivity to climate change, schooling or swarming behavior, and inhabiting the upper or mixed layer of the water column (swfsc.noaa.gov/). The survey uses a combination of methods to try to locate the target species for sampling. The primary fish target species for the survey include Pacific sardine (Sardinops sagax), Pacific mackerel (Scomber japonicus), jack mackerel (Trachurus symmetricus), and the northern anchovy (Engrraulis mordax). In addition to these fish species, the market squid (Doryteuthis opalescens) is also included as a target species for the survey. These coastal pelagic species are critical to the ecology of the California Current pelagic ecosystem.
A very important part of the survey involves using the acoustic trawling method (ATM) to locate and sample CPS. This method of sampling uses a systematic approach to help locate the target species that are being monitored. The area for the survey is laid out using a transect system. Transect lines (perpendicular to the coast) are latitudinal at 10 mile intervals and approximately 30-40 miles long. During the day, the ship follows these transect lines while using a continuous underway fish egg sampler (CUFES) and “listening” for CPS using some of the most advanced acoustics systems in the world. CUFES pulls water in from below the ship at a rate of 640 liters/ minute. As the water moves through the sampler it passes through a fine mesh filter that is continuously agitated. Any plankton or fish eggs that are larger than 505 microns are screened out, collected, and analyzed at 30 minute intervals. The CUFES requires constant monitoring and an experienced eye to be able to identify the various organisms in the sample. That responsibility falls on the shoulders of the lead scientists on the survey, Dave Griffith and Sue Manion. As this information is coming in it is entered into a computer that plots the results in relationship to the transect line that is being traversed. Of particular interest to the scientists on this survey are Pacific sardine eggs due to declining populations of this important forage fish over the last 10 years.
Along with the CUFES data, the survey is being guided by a complex array of sonars and split beam eco-sounders. Dan Palance, is the ships acoustician. Dan monitors and collects data from 2 split beam echo-sounders, the EK60 and the EK80 and 3 multi-beam sonars, the MS70, ME70 and the SX90. As the ship moves down the transect line information from the eco-sounders and sonars is being monitored and analyzed. The images from the acoustics system provide insight into what types of fish or other marine organisms may be present near the transect line. Dan and the lead scientists use the data from CUFES and acoustics system to determine the best locations to trawl for the target species. Once the likely target areas are determined, the lead scientist will consult with the NOAA Corps officers to eventually determine where the boat will trawl. There is an incredible amount of information and data that is being generated to direct the survey. Each group of people involved bring their own unique skill set to the table, and communication between these groups is essential to the success of the survey.
Once the location for sampling areas has been determined, a series of trawls will be conducted in those areas. The trawls are done at night to provide the best opportunity to catch the target species which are migrating up in the water column following the plankton species that they feed on. Since arriving on location we have been able to average 2-3 tows per night. The Reuben Lasker is equipped with trawl net (13 X 20 meter fishing mouth) with progressively smaller mesh as you move towards the cod end. The net is deployed behind the boat and fishes from the surface down to a depth of about 13 meters for 45 minutes. As the net is hauled back the excitement and anticipation about what may be inside grows. Over the course of the last 3 days we have found 3 of the 4 CPS fish species that are being monitored and market squid. The target fish species that we have seen so far include the Pacific sardine, jack mackerel, and Pacific mackerel. We have not found northern anchovies yet, but we have seen a variety of other marine organisms (listed below). Once the haul is collected from the net it is brought into the wet lab to be “worked up.” Everything that comes up in the net will be weighed and/or measured. In addition to weight and length measurements, gender is determined and DNA samples and otoliths are collected for the target fish species.
Along with CUFES there is another process in place for collecting plankton using a “bongo net.” These paired nets are lowered into the water over the starboard side paying out 300 meter of cable before beginning the retrieval process. Once 300 meters of cable have been released the ship will set a speed to establish a 45O angle in the cable connecting to the bongos. As ship is underway the nets will be retrieved at of 20 meters/minute. Once at the surface the nets contents are washed down into a fine mesh collecting bag at the bottom of the net. This sample is preserved and will be analyzed to gain a better understanding of the planktonic community found in the water column. The data from the bongo nets is used to help calibrate the acoustics systems. The sampling protocol for the bongo nets has been well established and consistently followed for a long period of time leading to a reliable data set. There is also a system in place using a conductivity, temperature and depth (CTD) probe for collecting water chemistry data at regular intervals. The data collected from the various sampling methods is used to help direct the management of CPS in the California Current.
As we push south down the Oregon coast the science team is settling into a routine and becoming more efficient at processing the hauls. I feel fortunate to be part of such an eclectic group of people. The team is made up seven members with a variety of backgrounds and experience, but all sharing the common goal of provide consistent, reliable data that can be used to help protect the ecological integrity of our oceans. In up-coming posts I hope to be able to provide a brief summary of the individual team members.
Tonight (7/24) will be the fourth set of trawls for this leg. Despite some of the challenges of switching over to an 8:00 pm to 8 am schedule the teams’ morale is high and everyone on the team is always eager to pitch in and lend a helping hand whenever it is needed. Although there have been some long shifts and the weather has been pretty rough over the last few days, the people I have met are making this an incredibly rewarding experience. Please find below a tentative list of common names for some of the species that we have seen since leaving San Francisco…
Taxa list from the net (common names):
Pacific sardine pacific mackerel
jack mackerel market squid
clubhook squid hake
northern spearnose poacher pomfret
American shad ctenophores
blue shark lions mane jellyfish
egg yolk jellyfish pyrosomes
blue lantern fish steelhead
northern lantern fish chum salmon
California lantern fish pink salmon
Observed from the deck:
humpback whale albatross