• Patrick Hayden

    Patrick Hayden
    Oregon State Univ
    Organized, keypunched and validated data for the Pacific Cod Maturity Project.

    For my internship, I worked with the Fisheries Interaction Team on the Pacific cod maturity project by organizing, keypunching and validating data collected by biologist on board commercial fishing boats in Alaska. I also performed some preliminary analysis and helped prepare the maturity data for GIS mapping.

    Pacific cod are an important commercial and ecological species in the Bering Sea, though little research has focused on Pacific cod maturation processes and spawning behavior. Knowledge of these processes provides valuable insight to fisheries managers tasked with estimating recruitment success. Important information such as spawning location, duration, and seasonality require knowledge of the gonad developmental stages of individual fish.

    Investigation of these processes for Pacific cod require a quick and easily applicable tool, allowing for the large sample sizes and broad application necessary for this wide ranging species. A gross visual staging key based on the external and internal appearance of gonads can be applied inexpensively to obtain large sample sizes over a range of collection platforms. The Fisheries Monitoring and Analysis Division (FMA) of the AFSC monitors groundfish fishing activities in the Bering Sea and provides an opportunity to collect data through fishery effort from a greater space and time range than typically available to researchers. FMA observers currently employ a visual maturity key to evaluate the maturation stage of Pacific cod.

  • In the graph below, we see a progressive increase in GSI weight with advancing maturity stages:

    graph

    Though easily applicable, visual staging keys may provide subjective and often inaccurate data, especially for gonads in transitional stages of development. In this research, histological assessments have been used to verify visual maturity stages. Gonadosomatic index (GSI; ovary weight/ somatic weight) is also a good indicator of the developmental status of Pacific cod eggs (Hattori et al. 1992).

    With maturation, the weight of the ovary increases. As oocytes uptake water in the process of hydration and the weight of the ovary further increases (Hunter and Macewicz, 1985). In 2009, observers began collecting ovary and somatic weights to assess the amount of variability in GSI of females assigned to different maturity stages.

    Preliminary results show an increase in GSI for each maturation stage suggesting that GSI measures may be helpful in delineating maturation stages, especially between Developing and Prespawning which are difficult to differentiate with the gross visual maturity key.

  • References:
    -Hattori T, Sakurai Y, Shimazaki K (1992) Maturation and reproductive cycle of female Pacific cod in waters adjacent to the southern coast of Hokkaido, Japan. Nippon Suisan Gakkaishi 58:2245-2252

    -Hunter, J.R., and B.J. Macewicz. 1985. Measure of spawning frequency in multiple spawning fishes. Page 79-99 in R. Lasker, editor. An egg production method for estimating spawning biomass of pelagic fish: Application to the northern anchovy, Engraulis mordax, NOAA Technical Report NMFS 36. Seattle, WA.