The responses of two Atlantic white-sided dolphins (Lagenorhynchus acutus) to objects: an analysis of behaviour patterns with respect to incidental entrapment in fishing gear

Nelson, Dawn Laurel (1992) The responses of two Atlantic white-sided dolphins (Lagenorhynchus acutus) to objects: an analysis of behaviour patterns with respect to incidental entrapment in fishing gear. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (22MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Incidental entrapment of cetaceans in fishing gear poses serious problems for fishermen due to the time required to disentangle the animals and to repair damaged gear. Entrapment can also result in drastic losses to cetacean populations. -- The factors which may influence entrapment are discussed in this paper. One basic question which has received little experimental attention is how cetaceans respond to fishing gear, or objects in general, and whether the response depends upon object type or familiarity. The main objectives of this study were to promote awareness of the work needed on this topic, to develop a workable methodology that will answer the questions involved, and to exemplify the types of information that can be gained. This study also served to categorize and quantify some aspects of the behavioural lexicon of two captive Atlantic white-sided dolphins (Lagenorhynchus acutus). The study animals had originally been found stranded, and were being rehabilitated at an aquarium for eventual release. They were housed together in an outside pool 12 m in diameter and 3 m deep. -- Introduction of an object to the pool appeared to increase the arousal level of the dolphins, and also resulted in avoidance of the object's immediate vicinity. Response was greatest to a rope lying across the surface of the water, which the dolphins would not swim underneath. Rope avoidance disappeared within several hours, although it reappeared on subsequent days for one of the dolphins. After four days, there was no response to the rope from either dolphin, and there was no dishabituation after the rope has been absent for twelve days. -- Objects in or under water were infrequently contacted. A rope stretched above the surface was repeatedly hit as the dolphins rose to breathe, although collisions decreased with time. All contacts with objects appeared to be accidental and seemed to be caused either by a lack of attention or through misjudging distances. Reactions to collisions were minimal. -- The dolphins exhibited a high degree of social cohesiveness and engaged in complex forms of social interaction which may not have been recorded before. Several other behaviours were also observed which do not seem to have been documented elsewhere. -- The results from this study must be viewed with caution, as the health of the dolphins was not stable while the experiment was conducted. -- Key Words: incidental entrapment; marine mammals; cetaceans; whales; Atlantic white-sided dolphin; Lagenorhynchus acutus; behavior; novel objects

Actions (login required)

View Item