46
CARL J. SINDERMANN
C. Economic effects
Economic effects of disease in marine fishes may be categorized as
follows : reduction in numbers of food fish available to the fishery ;
weight loss of individuals ; rejection by consumers and subsequent loss
of interest in fishery products as food; and indirect effects, either
favorable or unfavorable, on survival of other species in a food chain.
Examples of economic effects in each of the categories have been
mentioned throughout this paper.
Second only to mortality induced directly or indirectly by disease
is the often significant weight loss of diseased fish. Williams (1963)
has drawn attention to possible losses of thousands of pounds of
fishery products annually because of nutrient requirements of fish
parasites or disruption of the host’s metabolism by disease organisms.
Lernaeocera branchialis, for example, usually causes significant weight
loss, so that parasitized fish are 20 to 30% below average weight. This
loss can be an important economic factor if 50 to 80% of fish landed
are parasitized, as is often true.
Rejection of diseased fish by dealers or consumers can also be
economically important. Mann (1954) has summarized some of the
economic effects of parasites and diseased conditions of fish from the
eastern North Atlantic ; he dealt particularly with fish as they appear
on the market. He indicated that protozoans, larval nematodes and
tissue-invading copepods created the most serious problems. Cited as
an example was microsporidean (Qlugea stephani) infection of the
intestine, gall bladder, liver and mesenteries of plaice. The parasitized
fish gradually became thinner, probably due to destruction of digestive
epithelium. Also considered was another microsporidean, Plistophora
ehrenbaumi Reichenow, which caused destruction of somatic muscles of
catfish, Anarrhichas lupus, and produced large unsightly tumors. Mann
mentioned a large catch of catfish landed a t Hamburg in 1952, from
West Iceland waters, of which 10% had to be discarded as unsuitable
for human consumption. Ulcers and cysts caused by Sphyrion invasion
of redfish and other species make it necessary to remove the diseased
areas during processing. Since up to 25% of the catch may be parasitized, the filleting operation is slowed and many pounds of fillets
must be discarded. Because of high frequency and intensity of parasitization of redfish in the Gulf of Maine, the resulting increase in processing costs, and the decrease in processed yield, it may soon be
necessary to downgrade the species in that area from a food fish to an
industrial fish, utilized only as a source of fish meal and oil.
Hargis (1958) has cited very interesting data from fish processors,
indicating that candling and trimming to detect and remove flesh
CARL J. SINDERMANN
C. Economic effects
Economic effects of disease in marine fishes may be categorized as
follows : reduction in numbers of food fish available to the fishery ;
weight loss of individuals ; rejection by consumers and subsequent loss
of interest in fishery products as food; and indirect effects, either
favorable or unfavorable, on survival of other species in a food chain.
Examples of economic effects in each of the categories have been
mentioned throughout this paper.
Second only to mortality induced directly or indirectly by disease
is the often significant weight loss of diseased fish. Williams (1963)
has drawn attention to possible losses of thousands of pounds of
fishery products annually because of nutrient requirements of fish
parasites or disruption of the host’s metabolism by disease organisms.
Lernaeocera branchialis, for example, usually causes significant weight
loss, so that parasitized fish are 20 to 30% below average weight. This
loss can be an important economic factor if 50 to 80% of fish landed
are parasitized, as is often true.
Rejection of diseased fish by dealers or consumers can also be
economically important. Mann (1954) has summarized some of the
economic effects of parasites and diseased conditions of fish from the
eastern North Atlantic ; he dealt particularly with fish as they appear
on the market. He indicated that protozoans, larval nematodes and
tissue-invading copepods created the most serious problems. Cited as
an example was microsporidean (Qlugea stephani) infection of the
intestine, gall bladder, liver and mesenteries of plaice. The parasitized
fish gradually became thinner, probably due to destruction of digestive
epithelium. Also considered was another microsporidean, Plistophora
ehrenbaumi Reichenow, which caused destruction of somatic muscles of
catfish, Anarrhichas lupus, and produced large unsightly tumors. Mann
mentioned a large catch of catfish landed a t Hamburg in 1952, from
West Iceland waters, of which 10% had to be discarded as unsuitable
for human consumption. Ulcers and cysts caused by Sphyrion invasion
of redfish and other species make it necessary to remove the diseased
areas during processing. Since up to 25% of the catch may be parasitized, the filleting operation is slowed and many pounds of fillets
must be discarded. Because of high frequency and intensity of parasitization of redfish in the Gulf of Maine, the resulting increase in processing costs, and the decrease in processed yield, it may soon be
necessary to downgrade the species in that area from a food fish to an
industrial fish, utilized only as a source of fish meal and oil.
Hargis (1958) has cited very interesting data from fish processors,
indicating that candling and trimming to detect and remove flesh