Abstract

Gulf menhaden, Brevoortia patronus, are considered an important ecological component in the northern Gulf of Mexico (nGOM) and also supports a large commercial fishery in the region. An analysis of the fishery dynamics of the stock indicated that the stock was not overfished and that overfishing was not occurring (SEDAR, 2013). However, an analysis of the historical record of landings indicates that the fishery has consistently harvested, in the last ten years, ~400 to 450 × 105 metric tons (mt) of biomass in the coastal waters of Texas, Louisiana, Mississippi, and Alabama. Gulf Menhaden are caught nearshore, using purse seine vessels and processed in one of three reduction facilities in the nGOM. The products of the reduction processing are mainly fish meal which is used for animal feed in agriculture and aquaculture and high value fish oil that is used as a feed additive in these industries and also used for human consumption. In addition to its value in the commercial fishery, Gulf Menhaden are thought to play an important role as consumers and prey in the trophic food webs of the nearshore and coastal pelagic ecosystem. Olsen et al. (2014) documented, using stable isotope analysis that Gulf Menhaden < 125 mm TL have a mixed diet but feed primarily on phytoplankton and those larger than this size have a mixed diet and feed primarily on zooplankton. Because they feed at low trophic levels and transfer this energy to higher trophic levels, Gulf Menhaden have been termed a wasp-waste species or “forage fish” and are thought to be the prey of numerous coastal resident and transitory predator species in the region. Forage fish species are comprised of fast-growing, early-reproducing, small-bodied individuals and their population growth rates are thought to be determined, in part, by bottom-up processes. In this work we explore how such bottom-up processes, acting at the individual level, effect intra-annual and inter-annual variation in oil density and fatty acid characteristics. Specifically we describe the temporal variabil-ity of oil density in Gulf Menhaden, analyze and quantify the environmental determinants that determine the magnitude of this content, and evaluate the intra-annual variability in fatty acid components.

PDF Preview