This report describes the results of 3 years of research on the market squid, Loligo opalescens. A number of questions concerning this species were addressed by this research program; particularly those concerned with fisheries management. Areas of study included spermatogenesis and oögnesis; age and growth; feeding dynamics and prey of market squid; marine fish, bird, and mammal predators of this species in Monterey Bay; assessment of total population size and structure (number of stocks), and possible morphological indicators of stocks; the properties of market squid with respect to acoustic identification and quantification; and the relationship of the availability of this species to the commercial fishery in relation to the physical oceanographic conditions in Monterey Bay.