When we ended leg 1 of the Winter Survey on 1/26, we had:
Obviously the (at times) poor weather affected our transect distance, but why so little fishing? Ask the hake. We were ready to fish right out of Newport, but didn’t see any acoustic hake “echosign” (i.e. characteristic patterns in shape or depth of the aggregations that we look for across frequencies) on which we could fish. We eventually found, and fished on, juvenile hake near Crescent City, CA, and saw similar juvenile echosign further south. However, juveniles were not our quest.
We had seen very weak echosign for adult hake at times as we headed south, but nothing substantial enough to fish on. The two post-weather delay trawls that caught adult hake offshore of San Francisco were the most substantial adult echosign of the trip…and this echosign was still not as strong as we had seen in 2016. Frustrating, but scientifically pretty interesting given how far north we found hake last year.
Leg 2 is ready to go and we will continue to work our way south. Our colleagues from Southwest Fisheries Science Center (SWFSC), who were out on the NOAA Ship Rueben Lasker, were kind enough to watch their bongo tows for signs of hake larvae, and their fish-egg-collector for signs of hake eggs. If the adult hake are still in the area where SWFSC found a few larvae and eggs, Leg 2 of Winter Survey could find adults quite quickly…and be very busy!
Good thing we have a new all-star team of scientists coming aboard. Daytime Wet Lab is Melanie (Lead), Dan, and McVeigh. Nighttime Wet Lab is Doug (Lead), Chelsea, and Uriel. We’ve got Abi doing a special eDNA project. Finally, in the Acoustics Lab we have Chu, Steve (Field Party Chief), and me (Chief Scientist).
Weather forecast looks good for next few days, so it’s time to go!
While in San Francisco for our inport, we have been docked at the Exploratorium. The description of the Exploratorium (https://www.exploratorium.edu/) as a “public learning laboratory” is perfect. It is laboratory, workshop, museum, curiosity shop, and science playground all wrapped into one.
The Explainers (http://explainers.exploratorium.edu/) play a big role in the Exploratorium experience, and during the inport it was my pleasure to spend time with both the Field Trip Explainers and the High School Explainers. While the Explainers deal with cool science stuff every day, this was my chance to show them the cool stuff we are doing at sea, why we’re doing it, and the amazing science platform that is the Bell M. Shimada.
We started at the Bridge (with a great introduction by ENS Manougian) and worked our way around the science spaces, talking through a typical operation: using the acoustics to watch for hake echosign, breaking transect for a trawl, preparations on the back deck, how the trawl works, how the catch is processed and what is collected, and how the oceanographic operations are performed (and why we care about those data).
At the end of the tour, we also had a bit of time to talk about life at sea, including how we handle 24-hour operations from food and sleep perspectives. We visited the Mess Deck, everyone crowded into a stateroom, and we stopped by the lounge so the High School Explainers could check out the comfy chairs. These tours reminded me how awesome, and sometimes weird, it is to be at sea.
My thanks to the Exploratorium and the Explainers for the opportunity to engage with them – I had a blast. For the Field Trip Explainers – the “many successful hake trawls” good luck chocolate has been added to the table in the Acoustics Lab (i.e. the science, and chocolate, epicenter of the ship).
After our weather delay, the Winter Survey got right back to business and found adult hake!
The echogram (38 kHz, -69 dB threshold) shows time along the top (x-axis), with vertical lines at 30-minute intervals. The left side is 3:00 pm local time and the right is 6:30 pm. Along the side (y-axis) is depth below the surface. Depths of 0-600 m are shown, with a horizontal line at 300 m.
The black rectangle shows the hake aggregation that was the target of our trawling. As trawl targets go, this wasn’t super dense (or it would have had more orange and red color in it). But, we fished it, confirmed it was hake, and got adult fish ~45 cm in length.
As we were wrapping up the trawl, the sun began to set and everything in the water column headed for the surface. The hake in the echogram head upward and then disperse from their layer - not so easy to fish when you can’t find them! Above the hake are three other bands, likely lanternfish or other small fish or squid, and those also head for the surface as it gets dark. In the morning, we watch the opposite pattern as everyone heads down to spend their day in the deep.
While hiding from the weather, we did a calibration of our echosounders near Sausalito, CA (which isn’t far from the Golden Gate Bridge). Before and after the calibration, we did casts with the Conductivity-Temperature-Depth (CTD) rosette, and the data were very different than from the open ocean a few days earlier.
“Saltwater” is typically defined as water with salinities (i.e. dissolved salt) of ~30 to 35. Data from the Pacific Ocean near Bodega Bay (north of San Francisco) are shown as an example. The rightmost line (dark gold) is from an offshore station with a bottom depth of 150 m. Here, the water has a uniform salinity of 32 down to 20 m below the surface. The next line in (light gold) is from a station that was closer to shore with a bottom depth of 60 m. At this site, water within 12 m of the surface is slightly fresher than the water below.
Our anchorage outside of Sausalito was “brackish,” often defined as having salinity levels between 0.5 and ~29. The two casts from near Sausalito are shown in blue. The large differences between the surface and 20 m (differences of 20 and 15) indicate that the surface waters are fresher than the water below, likely due to river and/or stormwater runoff. Another interesting note is that the two casts are quite different from one another, likely influenced by tidal cycles.
Many lakes and rivers are “freshwater” and have salinity values <0.5. As an example, I’ve shown data from Lake Washington in the figure (leftmost, in red). Salinity levels are <0.1 from the surface down to 20 m.
Now that the weather has dropped, we’re heading out of brackish and back into saltwater!
The week before coming out to sea, I was thrilled to be able to go talk to kids about ocean pressure in two classrooms at Bryant Elementary school: Ms. Regalado’s 2nd grade class and Ms. James 4th grade class. Thanks for welcoming me! I love revisiting the wonder of science through kid’s eyes.
We talked about pressure in the ocean, how it goes up as you get deeper, and different kinds of cool animals that live in deeper parts of the ocean. We got things a bit wet with a pressure experiment using a big plastic jug with three holes drilled in it to show how water shoots further from the bottom hole due to the water pressure. Wheee! The kids took over from there, using permanent markers to draw their own designs on Styrofoam cups. They were also excited to explore the idea that their cups would shrink once we took them down to 500 m.
The cups came onto the ship with me in Newport, OR. A few days ago, off the coast of Northern California, Survey Tech Scott helped attach the mesh bag with cups from Ms. Regalado’s class to the CTD (an instrument that measure salinity, temperature, and depth in the ocean). We sent the cups down to just shy of 500 m. They came back looking great!
Check out the difference in shrinkage between the two cups! The one on the left hasn’t gone down to 500 m yet, and the one on the right has. So cool.
Ms. James’ class cups were scheduled for the next CTD, but weather came up, and we weren’t able to do CTD’s for a few days. We’ll put the cups for her class on the next deep CTD after we come out of San Francisco. I’m excited to give the cups back to the kids after the survey – it’s so fun to see how tiny the drawings have become.
Although the NOAA Ship Bell M. Shimada is a formidable vessel, there are still limitations to the conditions we can work in due to safety or data quality. The winds and sea state work in unison to kibosh our best plans.
High winds and waves make deploying expensive, often heavy, gear unsafe. We don’t want our trawl, which looks like an enormous spider web, to get twisted and/or damage the net sounders or camera/sensors that are strapped to it. Side ops have the same challenges, with the CTD with its numerous sensors and the zooplankton nets. In all operations, the safety of the crew handling the gear is paramount.
As wave height increases, our acoustic data quality decreases. When our echosounder sends out a downward “ping” of sound energy, it needs to hear that ping reflected back after it hits a fish (or a krill, squid, etc.). If we send out a ping, and the ship pitches (bow-to-stern, or front-to-back) or rolls (port-to-starboard, or side-to-side) too far, the echosounder doesn’t receive the return ping. That can lead to gaps (vertical white stripes) in our data called “drop-outs.” In addition to drop-outs, high seas can also create a lot of bubbles below the echosounders which can affect the sent and returned ping.
We enjoyed some great weather early in the survey but winds and seas have picked up beyond our threshold for operation. So, it’s into San Francisco to let this storm pass and then back out as soon as we can!
We finally found some hake, but not the adults that we were hoping to find. What we saw on the acoustics was an aggregation (i.e. a group of fish, but not necessarily swimming in unison like a school of fish) of juvenile hake. These age-1 fish, which were born last year, had an average length of 19 cm from tip of snout to tail.
The 120 kHz echogram shows the worm-y, blue-green aggregation that we saw. From left to right, the echogram shows ~2 nmi and from top to bottom it’s ~225 m. The other two acoustic frequencies we watch, 18 and 38 kHz, also showed the aggregation very clearly. Once we identified that the aggregation was large enough (left to right) and far enough off bottom (the bright green line over top of the dark red-brown), we called the ship’s Bridge and requested to fish.
The phone call to the Bridge brings into play many other things: preparation of our underwater video camera, starting the temperature-depth sensor that goes on the net, a watch for marine mammals, attachment of the ship’s net sounders which allow us to watch what’s going into the net, discussion of how deep the net needs to go, maneuvering of the vessel, and finally deployment of the net. Even before the net goes it in the water preparation to fish is an involved process, with Scientists, Deck Crew, Survey Techs, and Bridge Officers all involved.
Food is an important part of being at sea. You’re probably tired, you might be wet (or smell fishy), and you could even be sea sick. However, if you walk into the Mess and a certain food is there, things seem better.
I asked crew and scientists about their at-sea comfort food, and here’s what I heard:
When the weather picks up, as it is for us now, the more liquid-y of these comfort foods (soup, stews, etc) become a challenge to carry across the Mess Deck.
The photo shows the epicenter for snacks on the ship (including the ice cream stash!). During certain times of day, particularly if the Galley has been baking, this can be a busy place.
Four days of running transects…four days without a substantial hake sighting. The echogram screen capture, with a total size of 6.5 nmi across by 400 m deep, has not a hake in sight.
Many scientists and crew used the large survey map in the Acoustics Lab to vote on where they thought we would have our first confirmed hake sighting. As of now, we’ve breezed passed by 8 of those vote locations.
In the pre-cruise blog post, I mentioned that we didn’t know where the hake would be this year. We are currently south of where we found adult hake in 2016, so 2017 is a different beast. Interesting.
While the zeros (=no hake) are frustrating because we want to fish (and the Wet Lab crews are getting restless), surveys (and science in general) can work like this. You leave the dock with a survey design and sampling plan, but the hake have other ideas. If we want to understand where hake are, the zeros tell us where hake are not, so are just as important!
The search for hake continues…
We’ve been running the acoustic transects (more to come on that topic) and have been stopping for side operations (aka “side ops”). The side ops are an important part of this survey as they allow us to measure attributes of the water, and collect the small creatures in it, across the survey area. For some researchers, these data are the core of their work!
All side ops start with lowering a Conductivity-Temperature-Depth (CTD) package through the water to measure temperature, salinity, dissolved oxygen, pH, and other attributes from the surface to 500 m (or 5 m off bottom if we’re in shallow). From the photo you can see that the CTD “rosette” also has 12 large, grey cylinders strapped it. These “Niskin bottles” can be triggered to close at specific depths, allowing us to collect water at those depths.
We also use small nets at some side ops stations to collect zooplankton samples – zooplankton are small animals without spines (i.e. invertebrates) that, while important in their own right, are a key part of the food web as food for many fish species. If zooplankton numbers are low because of water conditions, or if there are different species present, fish and other creatures that eat zooplankton can be affected. Small stuff, but important.
In the last blog I mentioned we are using two types of zooplankton nets – a vertical net and a bongo net. The image shows a 333 um (i.e. micron which is 1×10−6 of a meter) mesh bongo net on the deck before deployment. The large can-shaped weight helps it to sink and keeps the net stable. While we are towing the net upwards through the water, zooplankton are collected in both sides of the net. When the net is back on deck, both samples are filtered in the lab, frozen, and saved. The small bag in the photo contains the sample from a shallow (150 m) station. Note that you can see our label floating inside!
The side ops will continue throughout the survey and provide us with an interesting snapshot of what’s happening in the California Current Large Marine Ecosystem (CCLME) this winter.
I wanted to take a moment to introduce the Science Party on this survey. In the Acoustics Lab we have Rebecca, Steve (Field Party Chief), Ben, and me (Chief Scientist). Daytime Wet Lab crew is Victor (Lead), Jeff, Cassandra, and Rachel (who is also doing a couple of special projects). Nighttime Wet Lab is in the capable hands of Aaron (Lead), Nick, and Brittney. I’m lucky to be sailing with an all-star Science Party!
We are officially underway and will soon put gear in the water, make sure everything works, and then start our operations.
Our goals for the 2017 Winter Hake Survey are to:
(1) Characterize the winter distribution of Pacific hake, hake aggregations, and the fish within those aggregations, to support evaluation of the feasibility/design of a potential future winter hake biomass survey, and
(2) Increase our understanding of the winter ecology and biology of hake in the California Current Ecosystem
From the survey map, you can see that we plan to cover the area between Newport, OR and San Diego, CA. The acoustic transects (shown) will take us ~175 nmi offshore over bottom depths from 50 to 4,500 m. We’ll use midwater trawling to verify that we’re seeing hake on the acoustics and check whether any other fish species are also present in those aggregations/schools. Fish we collect will be used for many measurements and collections – length, weight, age, sex, macro and microscopic maturity, diet, genetics, and some other projects.
Along the transects, we’ll stop at stations and use a Conductivity-Temperature-Depth (CTD) sensor to measure temperature, salinity, dissolved oxygen, and other things that may ultimately help us to understand why we find hake where we find them. A 0.5 m diameter net pulled vertically through the water, and a pair of 0.5 m diameter nets (a “bongo”) pulled obliquely through the water, will tell us about the invertebrate zooplankton species that are here.
You can always use the link to the left “Track the NOAA Ship Bell M. Shimada” to see where we are. The science fun is just beginning!
The 2017 Winter Hake Survey is gearing up and we leave Newport aboard the NOAA Ship Bell M. Shimada on 11 January.
In 2016, a warm El Niño year, we found hake all the way from southern California to Newport, OR. Interestingly, upcoming conditions for 2017 are La Niña or Neutral according to the National Weather Service Climate Prediction Center. What will that mean for where we find hake in 2017?
The short answer is that we don’t know.
There are so many things to consider in predicting how 2017 will compare to 2016 – Do colder surface waters matter to hake if they’re down deep? Are conditions different down deep where hake are found, say with currents? What role does The Blob play, since it’s back (or it never left)? Does the observation of juvenile hake in the north in spring 2016 mean that we’re more likely to find hake in the north this winter? These are questions that keep Winter Hake Survey scientists up at night, but soon we’ll be out there!
Follow all the Winter Hake Survey 2017 action here on the FEAT team’s new blog, The Main Deck.