In an effort to escape the snail pace of cubicle work I reached out to my Marine Biology professor at Hatfield Marine Science Center to discuss possible field opportunities. I was very fortunate that professor Itchung Cheung (also how I learned about the Summer Scholars internship) recommended an upcoming NOAA event at Hatfield. So on his recommendation, last week I was fortunate to attend the NOAA Fish Cutting party 2018 during which we processed 1981 salmonids (primarily coho and chinook). The goal of the Fish Cutting party is to process the samples that are collected annually during the Juvenile Salmon Sampling Program. To process a juvenile salmon a number of samples and measurements are needed.
To begin, a length and weight are often collected and then the fish is scanned on a metal detector to indicate presence of a coded wire tag, pit tag, or combination of both. Coded wire tags (CWT) provide information regarding the origin of the fish or which hatchery it was released from. These metal tags are smaller than a grain of rice and usually inserted into the snout of the fish. Pit tags, about the size of a grain of rice, provide information such as migration patterns, migration timing, and growth rates by comparing size/length between when the fish was initially tagged and when it was collected. These tags are usually inserted beneath the skin on the abdomen of juveniles. Pit tags use passive technology, utilizing scanning arrays that are placed in their migration corridor within dam fish ladders and on the bottoms of streams. When a fish with a pit tag swims across the array, the information is automatically uploaded to a global database. You can literally track a fish migrating downstream and returning through the database each time the tag is scanned, assuming the fish survives the perilous journey. Coded wire tags require removal of the tag to read which is lethal to the fish and does not provide information about migration patterns, rather just hatchery origin.
Volunteers during the Fish Cutting party had the tasks of removing fish snouts for CWT and pit tags (if present) as well as any combination of the following: removal of the stomach, otolith (ear bone), intestines, and fin. Each specimen serves a purpose in the ongoing ecological monitoring of salmonids in the Pacific Northwest. Stomachs provide valuable information regarding what salmonids are eating out at sea and where certain foods are available. Plastics have also been observed in stomach contents which is a concern especially moving into the future. Otoliths are the tree rings of fish and provide information regarding how rapidly a fish is growing. Otoliths can also have a distinctive mark that is formed during the early stages of life during hatchery rearing by controlling water temperature fluctuations. These distinctive marks can be an alternative to CWTs and provide information about hatchery origin. Intestines can be used to further analyze diet intake although determining the prey source at this stage of digestion is far more difficult. A portion of a fin is also removed primarily for genetic sampling. Other data that is collected includes any observations of parasites and visceral fat which develops on the outside of the stomachs in hatchery origin fish due to the high protein content of their diet within the hatchery.
Performing this kind of sampling on an annual basis allows ecologists to monitor the health of different populations as well as the species as a whole. This was my first experience dissecting fish for biological sampling although I have gutted many fish in my free time to take home and eat. I would recommend the next Fish Cutting party to anyone interested in helping out with the monitoring effort but I do have some reservations for those not experienced with handling fish. My first reservation is to hold off on eating lunch until you get past the nausea that is induced by the smell of hundreds of fish being processed and digging through goopy brains to find otoliths. I would also recommend that you prepare yourself for having fish tissue flung at your face as well as handling a dead animal with feces extruding from its body. Some of these fish are hosts for parasites so if that freaks you out maybe fish cutting parties are not for you.
Overall I had a great three days in Newport meeting people from the NOAA Science Center, hanging out with fellow scholars, immersing myself with fish guts, and learning new skills. Thanks to the fellow Sea Grant Scholars who showed up to help and those scholars that helped make our experience at Hatfield enjoyable.