Date of Award

2015

Degree Type

Thesis

Degree Name

Master of Science in Fisheries, Animal and Veterinary Science

Department

Fisheries, Animal and Veterinary Science

First Advisor

Terence M. Bradley

Abstract

The domestication of tuna species has proven to be one of the most challenging endeavours in aquaculture. Among the issues yet unresolved is the occurrence of ‘puffy snout syndrome,’ a condition in which tumor-like growths form on the head. Ultimately, vision and feeding are impaired and long-term afflictions typically result in mortality. Though few mentions of puffy snout exist in the literature, evidence suggests that it is not uncommon among facilities that hold tunas in captivity. The specific aims of this study were to: a) describe pathological features of puffy snout, and b) investigate its etiology through the evaluation of conditions and protocols at facilities rearing/holding tuna.

To describe pathological features of puffy snout, clinical signs were detailed by observing captive tunas in a land-based holding system, and examination of evidence of infection by parasites, bacteria, and viral agents was conducted on tissues collected from fish with and without puffy snout. Histological examination of tissue from normal and affected fish was also conducted. To investigate etiology, a survey was developed and sent electronically to 28 tuna-holding facilities globally. The survey inquired about the prevalence of puffy snout and the husbandry conditions and protocols employed (e.g., biological characteristics, capture and transport procedures, holding system design and water quality, feeding regime). These data were compared across facilities in an attempt to couple puffy snout prevalence with holding conditions and/or protocols.

Clinical signs of puffy snout included occlusion of the eyes and mouth, followed by changes to swimming and feeding behaviours. Parasitology, bacteriology, and virology examination all indicated no commonly-found pathological agents were responsible for inducing the condition. Histology showed that puffy snout is largely characterized by the apparent degeneration of muscle tissue with the replacement of a loose collagenous fibrosis and an undetermined fluid filling the interstitial space in tissues anterior to the eye. In dorsal musculature, collagenous growth may occur in the epidermal or hypodermal regions.

Based on survey data, the capture and transport process and feeding regime were unrelated to development of puffy snout. However, certain biological (e.g., fish size) and holding system (e.g., tank/pen size) parameters showed weak but non-dismissible coupling with puffy snout prevalence. Survey data and additional personal communication with field researchers confirmed that puffy snout in tuna is solely a captivity-related condition.

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