Defense Date

12-1-2023

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

David W Kerstetter, Ph.D.

Second Advisor

Christopher A Blanar, Ph.D.

Third Advisor

Tracey T Sutton, Ph.D.

Keywords

Pelagic longline fishery, Mesopelagic, Bycatch, Endoparasites, New host records

Abstract

The ecology of the mesopelagic zone is an understudied area of the open ocean, with few diet studies even for dominant fish species. Since endoparasites are generally transmitted trophically, descriptions of the parasite communities within fishes can often provide additional insights on food web interactions. This project assesses the endoparasite faunal community of mesopredatory mesopelagic teleosts to better understand mesopelagic food webs in the South Atlantic Bight. Fishes in the Families Alepisauridae (lancetfishes), Gempylidae (snake mackerels), Bramidae (pomfrets), and Scombrolabracidae (longfin escolar) are frequent bycatch in the pelagic longline fishery targeting swordfish Xiphias gladius and thunnid tunas, yet the ecology of these mesopelagic species is poorly known. Fish specimens were collected onboard commercial vessels by observers, frozen, and examined in the laboratory. Of the 105 whole fishes examined to date, 96% were infected by at least one parasite taxon. Lancetfishes commonly hosted the cestode Pelichnibothrium speciosum (93% prevalence, n=37), and gempylids commonly hosted the nematode Anisakis sp. (69% prevalence, n=73). Lancetfishes are potentially a unique case due to their high rate of cannibalism (45%), which may allow for multiple developmental stages of P. speciosum to coexist in the same host. These co-occurring stages of cestode may help the worm to develop before entering the definitive host, blue shark Prionace glauca. Lancetfishes Alepisaurus spp. (n = 40) have a mean infection intensity of 151 per host, oilfish Ruvettus pretiosus (n = 23) have an infection intensity of 122 per host, and other gempylids combined (n = 33) have an infection intensity of 76 per host. The high infection intensities in lancetfishes and oilfish may indicate their role as intermediate hosts for parasites seen in apex predators targeted by the pelagic longline fishery. Additionally, endoparasites of two novel hosts were examined. These were Nesiarchus nasutus (Gempylidae) and Taractichthys longipinnis (Bramidae). Through all specimens, 20 new host records and nine ocean basin extensions are recorded.

Comments

This project was supported by NOAA Award NA19OAR4170414.

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