Post-mortem Examination
and the Recognition of Tissue Abnormalities
3
Abstract
Necropsy is an essential part of an investigation of fish health of wild and farmed
fish. Information on management practices and diet, detailed history of mortality, changes
in fish behaviour, stock weight and length, management practices (recent or former
transport, grading or treatments) as well as feeding response, are all important factors
normally available with farmed fish. For wild fish, as much information as possible should
also be collected and in both scenarios, water temperature, chemical and physical
characteristics should be recorded with notes of any concurrent or recent event affecting
other species in the area. The chapter describes the procedures of necropsy with particular
reference to obtaining samples of the most common tissues collected for histological
examination.
Keywords
Fish necropsy
3.1
Introduction
Post-mortem examination or necropsy (from the Greek
‘nekros’: ‘corpse, dead’ and ‘opsis’: ‘eye’, ‘to see’), corresponds to the term autopsy when performed on the human
body, namely the medical procedure of examining a body
with the objective of assessing the cause of death and the
lesions present. This is achieved through a systematic
approach and observation of external and internal structures,
organs or tissues, assisted by the collection of samples for
further analysis. Necropsy plays a major role in the investigation of fish health of wild and farmed fish, both at the
individual or the population level. Fish health assessment
begins when the fish is alive in their habitat, when important
observations can be made covering aspects related to
clinical signs, the water and the environment. Under farming
conditions, information on management practices and diet also
become of particular relevance. Records of the number or the
best estimate of affected individuals within the population
should be ascertained to establish the morbidity rate and pattern of the spread of the disease or abnormality observed. If
disease is associated with mortality, a detailed history of the
daily and total mortality is required, taking into account age,
class, and stock origin. Changes in fish behaviour including
swimming pattern, position in the water column and respiratory patterns should be noted. Additional information on the
stock average weight and length, management practices
(recent or former transport, grading or treatments) as well as
feeding response, are all important factors normally available
with farmed fish. For wild fish, as much information as possible
should also be collected and in both scenarios, water temperature and chemical and physical characteristics should be
recorded with notes of any concurrent or recent event affecting
other aquatic or terrestrial species in the area.
Compared to terrestrial animals there are limited laboratory
tests applicable for live fish and therefore, generally clinical
diagnosis is not enough for a conclusive diagnosis. This
emphasises the need of the post-mortem examination as an
essential step towards diagnosing disease in fish. The description provided in this chapter describes the procedures of necropsy with particular reference to obtaining adequate samples
of the most common tissues collected for histological examination. This is on the understanding that during necropsy,
other samples will also be taken e.g. for microbiological
D.W. Bruno et al., A Colour Atlas of Salmonid Diseases,
DOI 10.1007/978-94-007-2010-7_3, # Springer Science+Business Media B.V. 2013
27
and the Recognition of Tissue Abnormalities
3
Abstract
Necropsy is an essential part of an investigation of fish health of wild and farmed
fish. Information on management practices and diet, detailed history of mortality, changes
in fish behaviour, stock weight and length, management practices (recent or former
transport, grading or treatments) as well as feeding response, are all important factors
normally available with farmed fish. For wild fish, as much information as possible should
also be collected and in both scenarios, water temperature, chemical and physical
characteristics should be recorded with notes of any concurrent or recent event affecting
other species in the area. The chapter describes the procedures of necropsy with particular
reference to obtaining samples of the most common tissues collected for histological
examination.
Keywords
Fish necropsy
3.1
Introduction
Post-mortem examination or necropsy (from the Greek
‘nekros’: ‘corpse, dead’ and ‘opsis’: ‘eye’, ‘to see’), corresponds to the term autopsy when performed on the human
body, namely the medical procedure of examining a body
with the objective of assessing the cause of death and the
lesions present. This is achieved through a systematic
approach and observation of external and internal structures,
organs or tissues, assisted by the collection of samples for
further analysis. Necropsy plays a major role in the investigation of fish health of wild and farmed fish, both at the
individual or the population level. Fish health assessment
begins when the fish is alive in their habitat, when important
observations can be made covering aspects related to
clinical signs, the water and the environment. Under farming
conditions, information on management practices and diet also
become of particular relevance. Records of the number or the
best estimate of affected individuals within the population
should be ascertained to establish the morbidity rate and pattern of the spread of the disease or abnormality observed. If
disease is associated with mortality, a detailed history of the
daily and total mortality is required, taking into account age,
class, and stock origin. Changes in fish behaviour including
swimming pattern, position in the water column and respiratory patterns should be noted. Additional information on the
stock average weight and length, management practices
(recent or former transport, grading or treatments) as well as
feeding response, are all important factors normally available
with farmed fish. For wild fish, as much information as possible
should also be collected and in both scenarios, water temperature and chemical and physical characteristics should be
recorded with notes of any concurrent or recent event affecting
other aquatic or terrestrial species in the area.
Compared to terrestrial animals there are limited laboratory
tests applicable for live fish and therefore, generally clinical
diagnosis is not enough for a conclusive diagnosis. This
emphasises the need of the post-mortem examination as an
essential step towards diagnosing disease in fish. The description provided in this chapter describes the procedures of necropsy with particular reference to obtaining adequate samples
of the most common tissues collected for histological examination. This is on the understanding that during necropsy,
other samples will also be taken e.g. for microbiological
D.W. Bruno et al., A Colour Atlas of Salmonid Diseases,
DOI 10.1007/978-94-007-2010-7_3, # Springer Science+Business Media B.V. 2013
27