Theses and Dissertations

Copyright Statement

All rights reserved. This publication is intended for use solely by faculty, students, and staff of Nova Southeastern University. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, now known or later developed, including but not limited to photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author or the publisher.

Defense Date

5-22-2009

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology

Department

Oceanographic Center

First Advisor

David W. Kerstetter

Second Advisor

Kate Mansfield

Third Advisor

Jennifer Rehage

Abstract

The pelagic longline fishery in the western Atlantic Ocean targeting swordfish (Xiphias gladius) and tunas (Thunnus spp.) historically has a high frequency of interactions with marine mammals, particularly pilot whales (Globicephala spp.) in the Mid-Atlantic Bight (MAB) region. Typical pelagic longline hooks used in the MAB are size 16/0 "strong" hooks that straighten at 250 lb of pull (113 kg), while alternative "weak" hooks straighten at 150 lb of pull (68 kg). Taking advantage of the size difference between large bycatch and relatively smaller target species, these "weak" hooks could be implemented as a bycatch reduction agent. To test this within the tuna fishery of the MAB, 21 sets were made using size 16/0 hooks, targeting yellow fin tuna (Thunnus albacares) and bigeye tuna (T. obesus) alternating strong and weak hooks. To test these hooks in a swordfish targeted area, nine sets were made using larger size 18/0 hooks within the Florida East Coast statistical area (FEC) and the Charleston Bump of the Southern Atlantic Bight statistical area (SAB) alternating strong and weak hooks. Size 18/0 strong hooks straighten at 350 lb (159 kg) of pull, while the weak straightens at 225 lb (102 kg). Results for the tuna targeted sets showed no significant reduction in total catch (a < 0.05) of any target species, with weak hooks having higher trends for catch per unit effort (CPUE) for both tuna and swordfish. The only species to show a significant difference in total catch between strong and weak 16/0 hooks was the pelagic stingray (Pterplatytrygon violacea), with more individuals caught by the strong hook. The 18/0 hook sets had similar catches for all species except the target species swordfish. Swordfish CPUE trended higher for the strong hook, while also having significantly higher total catches. Seven weak hooks were retrieved straightened at haul back; one of these hooks was observed being straightened by a pilot whale at 10m distance from the vessel.

To access this thesis/dissertation you must have a valid nova.edu OR mynsu.nova.edu email address and create an account for NSUWorks.

Free My Thesis

If you are the author of this work and would like to grant permission to make it openly accessible to all, please click the Free My Thesis button.

  Link to NovaCat

Share

COinS