Currents and Connections Post #7

Juvenile Pacific cod attracted to a baited camera system set in kelp habitat. All cod have three dorsal fins, but you can tell these are Pacific cod because of their "leopard" markings and large chin barbel - which I think is so cute! Credit: NOAA Fisheries.

We welcome back guest blogger, Ella Kelly, to Currents and Connections. Ella is an undergraduate student attending the University of Alaska Southeast in Juneau, Alaska. Ella is currently interning at Alaska Fisheries Science Center's Auke Bay Laboratories. She is participating in the NOAA Fisheries juvenile Pacific cod research survey in the Gulf of Alaska. The objective of this research is to increase our understanding of how juvenile Pacific cod use nearshore coastal habitats and what factors influence their survival through winter. By collecting detailed data on the early life stages of Pacific cod, scientists are refining a computer model that predicts how larval cod disperse and where they settle. Incorporating these findings into stock assessments can improve estimates of Pacific cod population size, fishing pressure, and the number of young fish entering the fishery each year, ultimately leading to more accurate and sustainable fisheries management. Read on to learn more about Ella's adventures aboard the Lady Sea.

Lights, Camera, Cod!

Katharine Miller, Research Fisheries Biologist at Auke Bay Laboratories, leads the baited camera component of this research that I mentioned briefly in my first blog post. In today's post we get to learn more about her process and see some of the amazing images captured!

Camera Sampling

Two cameras are mounted to a metal platform that has four weighted legs, a light, and a bait cage at the end of a 2.5 foot long rod positioned in front of the cameras. One camera takes photos every 5 seconds, while the other records continuous video. The bait is a mixture of mackerel, herring, and vegetable oil. Each camera rig deployment lasts 15 minutes, which provides enough time for the bait to attract Pacific cod in the immediate area. There are six camera rigs, which we deploy at different locations within each bay we sample. In most bays, there is space and time to deploy each camera rig twice, thereby generating a total of 12 video sets and 12 photo sets each with 180 pictures to process back in Juneau after the cruise.

Josh and Katharine setting cameras in vegetated sites in Kukak Bay, Alaska. They work with GIS data that Josh reviewed this year to find the best spots with the most vegetation. Credit: NOAA Fisheries.

Camera Deployment

Finding the perfect camera spot can be tricky. You need kelp or eelgrass where young of the year cod live but you need to place the camera right on the edge of the vegetation to make sure you have footage of more than just eelgrass waving in the water or covering the camera's lens.

Above water view of an eelgrass bed in Wide Bay, Alaska. Credit: NOAA Fisheries.

When setting cameras Katharine sits up front, baiting and deploying the rigs, while the driver, whether that be me, Josh, Johanna or anyone else, navigates the cove. Together, we are able to find the perfect spots for clear pictures of fish!

Johanna sitting in the skiff loaded with the camera systems. Credit: NOAA Fisheries.

Once we find the perfect spot, Katharine prepares the cameras. She opens the bait canisters and deposits a small cup of ground up mackerel bait that was prepared before the trip. Once the bait is in there, she secures the canister, turns on the cameras, does a quick light check, and drops the cameras!

Prior to camera deployment, Katharine removes bait from plastic wrap (left) and places it inside a bait cage (right). The bait we use is mostly mackerel, a very oily (and stinky!) fish. Katharine keeps it wrapped and bagged up to keep the smell contained. Credit: NOAA Fisheries. Katharine preparing to deploy a camera system into the water on a rainy day. Credit: NOAA Fisheries. Katharine deploys the camera system into the water by slowly letting out line. The camera is attached to a 15 foot line with a buoy for easy retrieval. Credit: NOAA Fisheries.

Camera Retrieval and Video Analysis

Josh and Katharine retrieve a camera rig from aboard the Lady Sea. Katharine grabs the buoy with a boat hook, and Josh stretches over to get the camera aboard. Credit: NOAA Fisheries.

After recovering the cameras and returning to the Lady Sea, Katharine removes the SD cards from the video and still cameras and downloads the data onto a drive for analysis back at the lab in Juneau. Katharine reviews each camera deployment to count the number of Pacific cod that were attracted to her baited cameras. To avoid counting the same fish twice, the abundance is based on the photo frame with the highest number of cod in the set (MaxN). This number is summed for each camera set to estimate the relative abundance of cod in the bays we sample. These observations will be compared to predictions of juvenile cod abundance in nearshore nursery habitats from the IBM mentioned in the first blog post. We are looking at a range of habitats in the bays, mainly eelgrass beds and sugar kelp beds.

A Pacific cod taking a closer look at the baited camera in a kelp bed. Credit: NOAA Fisheries. Lots of Pacific cod swimming around the bait cage in a kelp bed. Credit: NOAA Fisheries.

Sampling has been the focus of what we are doing, but we also take breaks to enjoy beach combing, seeing beautiful sights, and exploring the dramatic landscape. There has been lots of excitement with the recent earthquake and tsunami warning in our area. Stay tuned for my next blog post, where I debrief after getting home, and get to reflect on my time aboard the Lady Sea.

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