62
CARL J. SINDERMANN
strongly suspected. It is easy, however, to over-extend any point of
view, so there is no implication here that every decrease in abundance
can be blamed on disease.
Although supporting data are sometimes inadequate and fragmentary, the author believes that the following hypotheses about the
role of disease in marine fish populations can be stated :
(1) Disease may exert profound effects on population size, and
may a t times be one of the most important factors of environmental
limitation to the biotic potential of certain marine fish species.
(2) Epizootic disease in one species may have pronounced negative
or positive effects on other species-predators,
scavengers or competitors.
(3) Disease levels may be influenced by a number of factors,
including change in susceptibility of the host population, or increase
in infection pressure on the host population.
(4) Certain diseases and parasites common in one geographic area
may be rare or absent in other areas. Microhabitats within hosts with
cosmopolitan distribution may be occupied by different representatives
of a genus or family of parasites in different parts of the world.
(5) Some of the great past fluctuations in sea fisheries may have
been caused by disease.
(6) Epizootics in marine fishes may occur a t times of high population
density.
( 7 ) Disease may affect fish of any age. There are some indications
that earliest life history stages-eggs, larvae and juveniles-may at
times be seriously affected.
(8) Close scrutiny of a marine fish species usually discloses one or
more diseases which might be considered " characteristic " of that
species in a given geographic area, although other diseases may occur.
(9) At least some disease problems in marine fish populations seem
amenable to solution.
Although it is difficult to predict the future course of research and
the development of knowledge about marine fish diseases, it is comparatively easy to itemize areas that require exploration. One of the
greatest needs is for continuity of observations, so that changes in
prevalence of recognized diseases, particularly those known to occur
in epizootic proportions, can be documented over extended periods.
These observations should be accompanied by detailed studies of such
factors as food and temperature in the environment of host populations
and of mechanisms of resistance to known pathogens. Acquisition of
continuous information about the size of the host populations would
also be an important facet of the studies.
CARL J. SINDERMANN
strongly suspected. It is easy, however, to over-extend any point of
view, so there is no implication here that every decrease in abundance
can be blamed on disease.
Although supporting data are sometimes inadequate and fragmentary, the author believes that the following hypotheses about the
role of disease in marine fish populations can be stated :
(1) Disease may exert profound effects on population size, and
may a t times be one of the most important factors of environmental
limitation to the biotic potential of certain marine fish species.
(2) Epizootic disease in one species may have pronounced negative
or positive effects on other species-predators,
scavengers or competitors.
(3) Disease levels may be influenced by a number of factors,
including change in susceptibility of the host population, or increase
in infection pressure on the host population.
(4) Certain diseases and parasites common in one geographic area
may be rare or absent in other areas. Microhabitats within hosts with
cosmopolitan distribution may be occupied by different representatives
of a genus or family of parasites in different parts of the world.
(5) Some of the great past fluctuations in sea fisheries may have
been caused by disease.
(6) Epizootics in marine fishes may occur a t times of high population
density.
( 7 ) Disease may affect fish of any age. There are some indications
that earliest life history stages-eggs, larvae and juveniles-may at
times be seriously affected.
(8) Close scrutiny of a marine fish species usually discloses one or
more diseases which might be considered " characteristic " of that
species in a given geographic area, although other diseases may occur.
(9) At least some disease problems in marine fish populations seem
amenable to solution.
Although it is difficult to predict the future course of research and
the development of knowledge about marine fish diseases, it is comparatively easy to itemize areas that require exploration. One of the
greatest needs is for continuity of observations, so that changes in
prevalence of recognized diseases, particularly those known to occur
in epizootic proportions, can be documented over extended periods.
These observations should be accompanied by detailed studies of such
factors as food and temperature in the environment of host populations
and of mechanisms of resistance to known pathogens. Acquisition of
continuous information about the size of the host populations would
also be an important facet of the studies.