TROPHIC RELATIONSHIPS AND LIFE HISTORY OF FORAGE FISH IN THE US SOUTH ATLANTIC
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Michael, Christine Eliana
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Abstract
Ecosystem-based fisheries management (EBFM) requires that analysts and managers account for multiple species, usually from several trophic levels, to better understand and predict how targeted species are affected not only by fishing but also by competitors, predators, and prey. The objectives of this study were to describe basic life history and diet compositions of small marine fish species that are common prey of targeted species within the snapper-grouper management unit of the South Atlantic Fishery Management Council (SAFMC), including Sand Perch (<i>Diplectrum formosum</i>), Spottail Pinfish (<i>Diplodus holbrookii</i>), Pinfish (<i>Lagodon rhomboides</i>), Tomtate (<i>Haemulon aurolineatum</i>), and small porgies (<i>Stenotomus</i> spp.). This study also tests the validity of grouping these species as forage fish, or mid-trophic level species, which is a commonly utilized term to refer to several small marine species. Morphological measures, including overall body size and gape size, were measured and compared among species using multiple linear regressions and MANOVA. Diet overlap was verified by using the Schoener and Morisita-Horn resource overlap indices, a CVA analysis with cross-validation frequencies, and analysis of variance using distance matrices. The traditionally used resource overlap indices produced inconsistent conclusions in terms of extent of diet overlap; however, the CVA analyses confirmed that all study species belong to a single forage fish trophic guild with structure consistent with morphological variation and had significant trophic overlap with small (≤ 200 mm total length) Black Sea Bass (<i>Centropristis striata</i>), a potential reference species. Several species in one guild can be monitored using a reference species, such as small Black Sea Bass, to expand management to a multispecies approach. Trophic guilds can simplify the stock assessment process so that EBFM can be achieved in the future.