Trophic ecology of barrelfish (Hyperoglyphe perciformis) in oceanic waters of southeast Florida

Abstract

Deep-water demersal fishes represent an understudied but ecologically important group of organisms. Select species of demersal fishes rely on pelagic prey items, representing a direct transport of surface carbon to greater depths. Barrelfish,Hyperoglyphe perciformis (Mitchell, 1818), which inhabit deep slope waters, are a species that has been suggested to fill this role, as congeners consume primarily pelagic gelatinous zooplankton. However, there is a dearth of information on the trophic ecology of barrelfish. Stomach content and stable isotope analyses were conducted on 29 barrelfish caught by recreational fishers from November 2014 to November 2015 off Miami, Florida, to improve our understanding of the feeding of this species.Pyrosoma atlanticum Peron, 1804, a pelagic, vertically migrating tunicate, represented 89% of the barrelfish diet by weight. Mesopelagic fish and shrimp contributed much smaller proportions. Standard ellipse areas corrected for sample size (SEAc ) showed a substantially smaller isotopic niche width for barrelfish (n = 26, 0.606 ‰2) than dolphinfish, Coryphaena hippurus Linnaeus, 1758 (n = 36, 2.16 ‰2), king mackerel,Scomberomorus cavalla (Cuvier, 1829) (n = 17, 3.04 ‰2), or wahoo,Acanthocybium solandri (Cuvier, 1832) (n = 12, 1.97 ‰2). Coupled with dependence on a singular prey item, the low SEAc of barrelfish suggests they occupy a limited trophic niche space. Overlap of barrelfish SEAc with dolphinfish (99.5% overlap) and king mackerel (100% overlap) indicate that the carbon sources and the number of trophic steps for barrelfish are similar to king mackerel and dolphinfish, and are linked to surface waters. This trophic linkage suggests that barrelfish may play a role in carbon export and further study of their behavior and daily consumption rates is warranted for quantifying this role.