Habitat Use and Fishery Dynamics of a Heavily Exploited Coastal Migrant, Spanish Mackerel

Abstract

AbstractSpanish Mackerel Scomberomorus maculatus support important commercial and recreational fisheries in the Gulf of Mexico (GOM). Although federally managed because of interstate migrations, harvest, essential fish habitat consideration, and management are largely state issues. Contrary to the accepted paradigm of a well‐mixed stock from the GOM to the Atlantic, Spanish Mackerel have been suggested to exhibit reduced movement, and hence mixing, which could lead to areas of localized depletion within the larger stock. We addressed how local abundance patterns responded to changes in harvest pressure, evaluated migration patterns via examining temporal trends in abundance, and determined whether the spatial abundance patterns resembled habitat specialization or generalization. Abundance trends of Spanish Mackerel in Alabama have remained relatively constant from 2001 to 2011 despite a significant increase in commercial harvesting. Seasonal patterns of catch rates coincided with the proposed annual migration. We also observed adult Spanish Mackerel in low salinities (0–10‰) at the mouth of Mobile River during the fall when river discharge is relatively low. This extends the known range of estuarine habitat use by adult Spanish Mackerel. Because Mobile Bay includes various habitat types differing from surf zone and coastal ocean habitats typically inhabited by Spanish Mackerel, capturing Spanish Mackerel near the mouth of Mobile River provides evidence for a habitat generalist strategy. Based on a relatively constant abundance index and year‐class strength, the stock seems to be relatively stable even after a drastic increase in commercial harvests in Alabama and heavy exploitation of age‐1–3 Spanish Mackerel. The resilience of catch rate trends to changes in local harvest pressure as well as evidence of synchrony among areas in terms of migration suggest the Alabama fishery is influenced by population dynamics of a larger population.Received July 3, 2014; accepted January 12, 2015