Diet Analysis of Offshore Istiophorid Billfishes in the Western Atlantic
Abstract
Istiophorid billfishes are apex predators found in epipelagic tropical and temperate waters worldwide. Managed internationally following population declines due to overfishing, these fishes continue to be targeted by recreational anglers and are caught as bycatch by offshore commercial fisheries targeting tunas, resulting in a slow population recovery. Despite their ecological importance, knowledge of Western Atlantic billfish diets is lacking; no information exists regarding roundscale spearfish (Tetrapturus georgii), for white marlin (Kajikia albida) information is extremely limited, and the last Western Atlantic sailfish (Istiophorus platypterus) diet study was in 1977. To address this knowledge gap, Istiophorid diets were analyzed using stomachs collected opportunistically from billfish found dead at gear retrieval by pelagic longline vessels fishing offshore of the Carolinas. To date, stomachs have been examined from white marlin, roundscale spearfish, and sailfish, as well as swordfish (Xiphias gladius). White marlin and roundscale spearfish consumed the greatest diversity of prey items, a mix of epipelagic and mesopelagic species. White marlin stomachs contents included teleost fishes, crustaceans, cephalopods, and urochordates. Roundscale spearfish stomachs contained teleost fishes, crustaceans, and cephalopods. Swordfish and sailfish stomachs examined revealed only cephalopods and teleosts. These results resemble past studies claiming the most abundant prey items to be teleosts then cephalopods and crustaceans, respectively. A novel finding was the presence of a urochordate in the white marlin stomachs. These results further knowledge of Istiophorid diets, facilitating the ongoing shift from single-species measures towards ecosystem-based management, and sets the stage for diet comparisons of billfishes caught coastally and offshore.
Faculty Sponsors
Dr. David Kerstetter
Project Type
Event
Location
Alvin Sherman Library
Start Date
4-6-2021 12:00 PM
End Date
4-9-2021 12:00 PM
Diet Analysis of Offshore Istiophorid Billfishes in the Western Atlantic
Alvin Sherman Library
Istiophorid billfishes are apex predators found in epipelagic tropical and temperate waters worldwide. Managed internationally following population declines due to overfishing, these fishes continue to be targeted by recreational anglers and are caught as bycatch by offshore commercial fisheries targeting tunas, resulting in a slow population recovery. Despite their ecological importance, knowledge of Western Atlantic billfish diets is lacking; no information exists regarding roundscale spearfish (Tetrapturus georgii), for white marlin (Kajikia albida) information is extremely limited, and the last Western Atlantic sailfish (Istiophorus platypterus) diet study was in 1977. To address this knowledge gap, Istiophorid diets were analyzed using stomachs collected opportunistically from billfish found dead at gear retrieval by pelagic longline vessels fishing offshore of the Carolinas. To date, stomachs have been examined from white marlin, roundscale spearfish, and sailfish, as well as swordfish (Xiphias gladius). White marlin and roundscale spearfish consumed the greatest diversity of prey items, a mix of epipelagic and mesopelagic species. White marlin stomachs contents included teleost fishes, crustaceans, cephalopods, and urochordates. Roundscale spearfish stomachs contained teleost fishes, crustaceans, and cephalopods. Swordfish and sailfish stomachs examined revealed only cephalopods and teleosts. These results resemble past studies claiming the most abundant prey items to be teleosts then cephalopods and crustaceans, respectively. A novel finding was the presence of a urochordate in the white marlin stomachs. These results further knowledge of Istiophorid diets, facilitating the ongoing shift from single-species measures towards ecosystem-based management, and sets the stage for diet comparisons of billfishes caught coastally and offshore.
