Environmental and Trophic Determinants of the Spatial/Temporal Distribution of the Brief Squid (Lolliguncula Brevis) in the Apalachicola Estuary (North Florida, USA)

A long-term (8-year) study of spatial and temporal distributions of the brief squid, Lolliguncula brevis, was conducted in the Apalachicola estuary with emphasis on trophic relationships and physico-chemical control. The spatial distribution of squid was strongly associated to salinity and habitat structure. Within a salinity range of 20‰–30‰, squid inhabited the relatively deep passes and/or channels where current velocity was usually high. The timing of squid migration into the estuary in spring was largely influenced by both temperature and salinity, while fall emigrations were associated with declines in water temperature. Monthly variations in squid abundance were closely associated with seasonal fluctuation in zooplankton abundance and not with the environmental variables which were studied. Annual totals in squid abundance indicate a sharp decline in recent years, which was associated with lower baywide salinities and with the cold winter of the past 3 years.