Forage fish play a pivotal role in marine ecosystems and economies worldwide by sustaining many predators and fisheries directly and indirectly. We estimate global forage fish contributions to marine ecosystems through a synthesis of 72 published Ecopath models from around the world. Three distinct contributions of forage fish were examined: (i) the ecological support service of forage fish to predators in marine ecosystems, (ii) the total catch and value of forage fisheries and (iii) the support service of forage fish to the catch and value of other commercially targeted predators. Forage fish use and value varied and exhibited patterns across latitudes and ecosystem types. Forage fish supported many kinds of predators, including fish, seabirds, marine mammals and squid. Overall, forage fish contribute a total of about $16.9 billion USD to global fisheries values annually, i.e. 20% of the global ex‐vessel catch values of all marine fisheries combined. While the global catch value of forage fisheries was $5.6 billion, fisheries supported by forage fish were more than twice as valuable ($11.3 billion). These estimates provide important information for evaluating the trade‐offs of various uses of forage fish across ecosystem types, latitudes and globally. We did not estimate a monetary value for supportive contributions of forage fish to recreational fisheries or to uses unrelated to fisheries, and thus the estimates of economic value reported herein understate the global value of forage fishes.
The Gulf Menhaden Brevoortia patronus is frequently cited as playing a predominant role in the trophic structure and function of the northern Gulf of Mexico (GOM) marine ecosystem, yet much work remains in quantifying its ecological importance. We performed a meta‐analysis of diet studies to quantify the trophic role of Gulf Menhaden within this ecosystem. Of the 568 references consulted, 136 identified predator–prey interactions involving Gulf Menhaden, menhaden Brevoortia spp., or unidentified clupeid prey items. Overall, 79 species were reported to consume menhaden, and no significant difference was detected between the Atlantic Ocean and the GOM in the mean occurrence of Brevoortia spp. in predator stomachs. We employed a probabilistic approach using maximum likelihood estimation to quantify trophic interactions within the northern GOM, with a focus on the trophic role of Gulf Menhaden. The estimated contribution of identifiable menhaden to the diets of all predators generally ranged between 2% and 3%; the largest dietary contribution was identified for Blacktip Sharks Carcharhinus limbatus (8%), and lower estimates (<2%) were obtained for oceanic species, including sharks, billfishes, and tunas. When diet compositions were adjusted for unidentified prey by using the proportion of fish species biomass in the ecosystem, five predator groups showed a relatively large dependence on menhaden prey: juvenile King Mackerel Scomberomorus cavalla, juvenile Spanish Mackerel Scomberomorus maculatus, adult Spanish Mackerel, Red Drum Sciaenops ocellatus, and Blacktip Sharks. The quantification of trophic linkages and key predators identified herein will be fundamental to future modeling efforts focused on the northern GOM ecosystem.Received March 24, 2015; accepted September 3, 2015
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