along the texas and louisiana shelf of the gulf of mexico interannual variation in landings of brown shrimp farfantepenaeus aztecus is negatively correlated with size of the hypoxic zone o connor and whitall however texas fisheries regulations may contribute to the apparent strength of this correlation as fishing is prohibited on the inner shelf that serves as a refuge from hypoxia during much of the summer when northern gulf of mexico hypoxia is most extensive hypoxia already forces movement of wild stock from large areas both inshore and offshore and at times can cause extensive mortality