Lindsay Knippenberg: Going Fishing! September 4, 2011


NOAA Teacher at Sea
Lindsay Knippenberg
Aboard NOAA Ship Oscar Dyson
September 4 – 16, 2011

 

Mission: Bering-Aleutian Salmon International Survey (BASIS)
Geographical Area: Bering Sea
Date: September 4, 2011

Weather Data from the Bridge
Latitude: 54.13
Longitude: -166.41
Wind Speed: 24.10kts
Wave Height: 4-6 ft
Surface Water Temperature: 9.0°C
Air Temperature: 8.8°C

Science and Technology Log

The station grid for all of the proposed sampling sites.

The station grid for all of the proposed sampling sites.

Yeah! Today we left Dutch Harbor and began the second leg of the Bering-Aleutian Salmon International Survey (BASIS). The purpose of the BASIS Study is to assess the status of marine species in the Eastern Bering Sea and support the decision making process for commercially important fisheries. The scientists on my team are accomplishing this goal by combining their knowledge of fisheries, oceanography, and acoustics. While I am onboard I will be helping out the scientists in all these different areas to get a broad view of all the science going on during our cruise.

There are specific sampling locations called stations that we will be going to throughout the Eastern Bering Sea. The map on the left shows the locations of these stations. The green dots are the stations that we are sampling during leg 1 and leg 2 of the BASIS survey. Leg 1 is already complete and they sampled at all the stations east of Unalaska. We will be picking up where they left off and sampling at all of the remaining green stations. The black dots are stations that will be sampled by another vessel named the Bristol Explorer.

The trawl net being let out behind the ship.

The trawl net being let out behind the ship.

For the first station I got to help out the fisheries team in the fish lab. We did a surface trawl by letting out a large net out the back of the boat with floats on it to keep it at the surface. By adjusting the floats and weights on the trawl, the fishermen can choose what depth they fish at. While the net is out, the OOD (Officer of the Deck) slowly motors the ship for about 30 minutes and the net catches the fish that are swimming in that area and depth. For this station we want to see the fish that are swimming within the top 30 meters of our sampling area. At later stations we might also do a mid level or deep trawl to see the fish that live at those depths.

We found some Salmon!

We found some Salmon!

After the 30 minutes were up, the fishermen slowly brought in the net and we immediately saw salmon caught in the net. Yeah! We caught something! As more and more net was brought in the fish began to pile up on our sorting table. There were a lot more fish than I had expected and the majority of them were salmon. It was now our job to sort the fish by species and I will admit that I am pretty slow at identifying the species. They may all look like fish, but they each have identifiable features like the color of their gums (black for Chinook Salmon), type of gill rakers, or color patterns on their body or tails. At this station we were lucky enough to pull in four out of the five salmon species in Alaska. We caught Chinook, Sockeye, Chum, and Pink Salmon. We also caught several different species of jellyfish and some squid.

That is a lot of salmon to sort.

That is a lot of salmon to sort.

After we caught the fish, we had to process them. In order to learn about the fish and the health of their population, we took samples and collected data from the fish we caught. Here is a description of the data we collected and what the scientists can learn from that data.

Weight and Length – Weight and length are an index of fitness for the fish. The scientists multiply how fat the fish is by how long it is to determine its lipid (fat) content. In cold waters the fish tend to have a higher lipid content than in warmer waters where the fish have to use more energy to metabolize. Additionally, if a fish has a higher lipid content, it might also mean that it is healthy and finding prey easily.

Gill rakers (white hairs on top of the red gills) from two different salmon. Can you see the difference?

Gill rakers (white hairs on top of the red gills) from two different salmon. Can you see the difference?

Axillary Process – We cut the axillary process off the fish we caught for genetic studies. The scientists know the baseline genetic sequence for the salmon that come from different regions of the world. By looking at the genetics of the fish we caught, we can tell where the fish came from and reconstruct their migration and distribution. For instance, the scientists have used the genetics from the axillary processes to determine that a large percentage of chum salmon caught in the Eastern Bering Sea are from Japan.

Sexual Maturity – By looking at the testes and ovaries of the fish, the scientists can determine if the fish were immature or mature and when they were going to spawn. Using this information along with the results from the axillary process genetics, the scientists can determine migration patterns and growth rates.

Determining the sex, stomach contents, and sexual maturity of the fish we caught.

Determining the sex, stomach contents, and sexual maturity of the fish we caught.

Male vs. Female – The scientists also use the testes and ovaries to determine if the fish was a female or male. This is helpful in looking at the ratio of males to females in their population.

Stomach Contents – By removing the stomach of the fish and analyzing its stomach contents, the scientists can determine what the fish was eating. This is can be very helpful when comparing warm years to cold years and the effect that climate change can have on prey sources and the nutrition of the fish.

All of this information can then be extremely useful to fisheries managers who are assessing the stock of the fish that are important to commercial fishermen. One of the species that we hope to collect as we sample at other stations is Pollock. Pollock is the largest US fishery by volume. Each year around 2.9 Billion pounds of Pollock are harvested. To learn more about the Pollock fishery check out this link to NOAA FishWatch. The scientists  on my team are assessing the health of the Pollock fishery by looking at the total lipid content of Age 0 Pollock in late summer. Their lipid content is important at this time of year because winter in coming and they will need lipids to survive the cold winter. By looking at the lipid content of the Age 0 Pollock that we collect, the scientists can predict how many Age 0 Pollock will survive to become Age 1 Pollock and eventually mature to become Age 3 or 4 Pollock that can be harvested.

Personal Log

The fluke of a whale as it dives.

The fluke of a whale as it dives.

Whales! I was hanging out on the bridge getting my last look at land for a couple of weeks when I thought I saw a whale out of the corner of my eye. I couple of minutes later a huge Humpback Whale breached right next to the ship. I have seen whales before, but it was just their dorsal fin of flukes. This was crazy. An entire whale was out of the water and it kept on breaching over and over again like it was playing. I wanted to take a picture, but I was too mesmerized to even take my eyes away from it for a moment. Then as I started to look farther out to sea, I saw even more whales. There were about a dozen whales flapping their tails and rolling on to their sides. It looked like they were having a good time playing on a beautiful day.

The weather forecast for September 4 - 6. It doesn't look good...

The weather forecast for September 4 - 6. It doesn't look good...

That beautiful day, however, did not last very long. We managed to sample at two different stations when the wind started to pick up and the waves began to get a little larger. The forecast was calling for a Gale Warning with gusts of up to 50kts and 20-24 ft seas. Those conditions are far too dangerous to fish in, so we turned around and headed back to Dutch Harbor. Hopefully the storm will pass quickly and we will only have to hide out a couple of days until it is safe to fish again.

One response to “Lindsay Knippenberg: Going Fishing! September 4, 2011

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