Abstract
Gulf Menhaden, Brevoortia patronus, in the northern Gulf of Mexico support a large commercial fishery and are thought to play an important trophic role in the coastal ecosystem. The temporal dynamics of both fatty acid and oil content have a direct impact on the value of Gulf Menhaden to predators and to the fishery. In this work, we describe how oil content of Gulf Menhaden varies with season, sex, age, condition, and tissue and investigate how fatty acid composition of mature (≥137.5 mm FL) female tissues varies with season, month, and tissue type. We found pronounced temporal (January to October) variation in mean oil content ranging from 0.062 to 0.579 mg g−1 that exhibited a significant (p < 0.001) seasonal pattern. We observed significant differences in oil content between tissue (muscle vs. ovary) of mature females and these exhibited a significant seasonal contrast, indicating that females were provisioning eggs in the fall. PERMANOVA analysis indicated the existence of significant differences (p < 0.001) in the composition of fatty acids of muscle tissue collected in different months. Mean eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and long chain polyunsaturated fatty acid (LC-PUFA) levels exhibited significant seasonal differences (p < 0.05), and in the case of DHA and LC-PUFA, both exhibited mean tissue-specific differences (p < 0.05). This work indicates that the value of Gulf Menhaden as prey and a fishery resource in the region varies during the year and we propose that trophic models of the Gulf of Mexico ecosystem should account for this variation.
Highlights
The ecosystem impacts of removing forage fishes has garnered much attention in recent years (Hilborn et al, 2017; Pikitch et al, 2018)
We evaluate the intra-annual dynamics of lipid content and fatty acid composition of Gulf Menhaden, Brevoortia patronus, in
We report the presence of significant seasonal variation in the temporal dynamics of oil content and fatty acid composition of Gulf Menhaden collected in the northern Gulf of Mexico (nGOM)
Summary
The ecosystem impacts of removing forage fishes (schooling, high biomass finfish and invertebrate stocks that occupy low trophic levels and are prey to a variety of avian, fish, and mammal predators) has garnered much attention in recent years (Hilborn et al, 2017; Pikitch et al, 2018). An outstanding issue is to determine to what extent the abundance of a single forage fish species in an ecosystem mediates the population growth rates of predator taxa. Hilborn et al (2017) analyzed 50 forage fish stocks and concluded that predator population growth rates are not correlated to forage fish abundance, highlighting the role of the environment in influencing forage fish population dynamics which has been reported by others (Szuwalski and Hilborn, 2015). We evaluate the intra-annual dynamics of lipid content and fatty acid composition of Gulf Menhaden, Brevoortia patronus, in the northern Gulf of Mexico (nGOM). We seek to understand the intra-annual dynamics of these components, which will improve understanding of the importance of this taxa to the diets of predator species. Leaf et al / Regional Studies in Marine Science 24 (2018) 1–9 carbon from the methyl end of the fatty acid molecule; n−3), eicosapentaenoic acid (20:5n−3,2 EPA), and docosahexaenoic acid (22:6n−3, DHA), all of which are known to be involved in a number of physiological processes related to the cardiovascular and neurological systems, immunity, and reproduction (DeMeester, 2013; Glencross, 2009)
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