• Bridget Berg

    Bridget Berg
    Humboldt State Univ
    Worked on reproductive biology of Atka mackerel.

    This summer I had the opportunity to work at NOAA's Alaska Fisheries Science Center with Susanne McDermott on a project studying Atka mackerel. The Atka mackerel is a schooling, semi-demersal species whose center of abundance is located in the Aleutian Islands region. The project involved analyzing histological slides of Atka mackerel ovaries collected during three different National Marine Fisheries Service scientific cruises.

    Samples were collected in two major Atka mackerel aggregations in the Aleutian Islands: Kiska Island and Seguam Pass during 2006 and 2007. Using the Atka mackerel histological guide created by 2009's intern Elizabeth Wackenhut, I was able to decipher the maturity stages of each fish as well as the presence of atresia (amount of egg absorption in the ovary) and postovulatory follicles. I used a Leica Microsystems microscope to capture images of each ovary. I also measured the diameter of 10 oocytes of the most advanced stage from every sample to find an average egg size for each fish.

  • Figure 1

    Figure 1.


    Once I had entered all the maturity stage data into Microsoft excel, I used ArcMap to create maps that show the percentage of fish in each maturity stage per haul. (Figure 1 and Figure 2).

    In addition, I mapped the spatial and temporal difference of surface and bottom temperature as well as temperature gradient between surface and bottom. I then examined the spatial and temporal differences of maturity stages with respect to the water temperature data. Understanding variability in reproductive biology of Atka mackerel is important to understand timing of spawning and larval hatching for this fish species.

  • Figure 2

    Figure 2.


    During my time at the Alaska Science Center I also worked with Ingrid Spies (RACE) on a project using genetics to distinguish the larval arrowtooth flounder from Amchatka flounder by comparing DNA strands. Both species have very similar larval stages and are therefore difficult to identify using morphological methods. This project uses genetic methods to groundtruth the morphological classification of fish larvae. This is part of a larger study to examine mechanisms responsible for climate-mediated transport of larval walleye Pollock, Pacific cod, and arrowtooth flounder.

  • Sampling entailed the removal of one eyeball from each larval flounder so we could run polymerase chain reaction (PCR), and preserve the fish for morphological and morphometric examination. PCR is a process that duplicates thousands of copies of a particular DNA strand of interest, in this case the cytochrome oxidase gene (COI). There are fixed differences in the COI gene of arrowtooth flounder and Kamchatka flounder and these are identified using a restriction length fragment polymorphism test. By observing banding patterns of the gene fragments after we run them on a gel, we were able to identify the two different species.

    Working at NOAA this summer has provided me with various new skills and incite. Among other things, I learned how to use microscope software, Microsoft excel, and Arcmap, and how to write a scientific paper. I also learned genetic laboratory skills including microscope skills, DNA extraction, polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP), pipetting skills, and electrophoresis. Overall this summer has further prepared me to pursue a career in the marine field. Now I know first hand what to expect in a scientific research environment and I am very thankful for that!