The Role of Fishery-Independent Surveys in Assessment of Marine Fish Stocks

Assessments of marine fish and shellfish provide the information needed to set annual catch limits that prevent overfishing and provide for a sustainable fishery.  For the near 500 managed stocks in U.S. Fishery Management Plans, over 100 stocks get  updated assessments each year in order to adjust annual catch limits.  An important assessment data component is information on the abundance of the stocks.  This abundance information comes from a variety of methods ranging from highly standardized, statistically deployed fishing methods such as bottom trawls or longlines; to imaging surveys using acoustics and/or optics, and plankton surveys for eggs and larvae.   These surveys are conducted from either NOAA survey vessels, or chartered research or fishing vessels.  The great diversity is necessitated by the range of habitats in which fish are found, and the regional availability of different classes of vessels.  Historically, most surveys have strived only to provide a relative index of abundance (similar to a fishery catch per unit of effort) to track trends, hence leaving the inference of absolute abundance to the population models that analyze these trends.  Increasingly, NOAA seeks to attain full survey calibration directly in terms of absolute abundance.