44
CARL J. SINDERMANN
such an extent that their growth rate during the epizootic period
exceeded anything previously recorded. Cod landings in the southern
Gulf of Saint Lawrence almost doubled during the immediate postepizootic period, due almost entirely to increased weight of individual
fish caught, rather than to increased numbers of fish taken. Lobsters,
important bottom scavengers, showed a similar but less dramatic
increase in growth rate. Here then were both negative and positive
short-term effects of an epizootic in herring-the negative brought
about by increased infection pressure and mortalities of other species,
5 0
I
Y E A R
FIQ. 13. Annual landings of Atlantic herring in the southern Gulf of
Saint Lawrence, 1920-61. (From Sindermenn, 1963.)
and the positive by a temporarily increased food supply for important
predators and scavengers, resulting in accelerated growth of species
which in this case had a higher unit value to man.
B. " Background " effects
Epizootics provide the dramatic and obvious examples of disease
as a factor of resistance to the biotic potential of marine fishes. The
more pedestrian, less conspicuous, but probably more significant effects
of disease are those that have been variously described as " low level "
or " background " effects. Disease may cause continuous subtraction
of individuals by weakening and disorienting infected fish, reducing
CARL J. SINDERMANN
such an extent that their growth rate during the epizootic period
exceeded anything previously recorded. Cod landings in the southern
Gulf of Saint Lawrence almost doubled during the immediate postepizootic period, due almost entirely to increased weight of individual
fish caught, rather than to increased numbers of fish taken. Lobsters,
important bottom scavengers, showed a similar but less dramatic
increase in growth rate. Here then were both negative and positive
short-term effects of an epizootic in herring-the negative brought
about by increased infection pressure and mortalities of other species,
5 0
I
Y E A R
FIQ. 13. Annual landings of Atlantic herring in the southern Gulf of
Saint Lawrence, 1920-61. (From Sindermenn, 1963.)
and the positive by a temporarily increased food supply for important
predators and scavengers, resulting in accelerated growth of species
which in this case had a higher unit value to man.
B. " Background " effects
Epizootics provide the dramatic and obvious examples of disease
as a factor of resistance to the biotic potential of marine fishes. The
more pedestrian, less conspicuous, but probably more significant effects
of disease are those that have been variously described as " low level "
or " background " effects. Disease may cause continuous subtraction
of individuals by weakening and disorienting infected fish, reducing