Management Of Fish Populations Research Articles

Effects of Introductions of Salmonids into Barren Lakes

There are still many lakes in the Palearctic that are barren of fish because of deglaciation history. Early transplantations of fish into such lakes have been documented, and there is a continuous activity of that kind going on for example in Scandinavia and at the North American west coast. Introductions of fish into barren lakes produce noticeable responses in the invertebrate fauna. For example, in a large mountain lake in northern Sweden the fairy shrimp Polyartemia forcipata disappeared after the introduction of Arctic char, and after a period of spectacular growth the fish now tend to get stunted. Changes in the invertebrate fauna after the introduction of new species of fish have been recorded also in many lakes with more complicated species compositions, and also in very large lakes such as Lake Michigan. In the Scandinavian mountain lakes there seems to be a correlation between the composition of fish species and the crustacean plankton. Further studies of introductions into barren lakes should provide a better understanding of predator–prey relations on the whole and, in the long run, of management of fish populations.

Fish Management Problems of Large Impoundments on the Missouri River

Dam construction on the Missouri River is creating a tremendous fishery resource in the million surface-acres of water being impounded in six large reservoirs. Major management problems include obtaining adequate harvest, developing efficient commercial gear and markets for fish products, and the threatening possibility of over-population of the reservoir with undesirable kinds of fishes. Each reservoir is unique in its basic physical and chemical characterstics and must be managed as a separate entity. Water level manipulation holds considerable promise as a tool of fish population management. Improvements in the physical design of tailwaters areas can improve sport fishing. More basic data on the fish habitat provided by these reservoirs is urgently needed if fish management methods are to be developed in time to make full and proper use of the tremendous fishery resource. At present, state fishery research and management programs are not adequate to deal with the problems at hand and little or no outside assistance has been received.

Notropis perpallidus, a New Minnow from Arkansas

dry season refractoriness of the Brazilian fish. Additional pituitary substance introduced by injection overcomes this refractoriness in both species. On the other hand our studies with rainbow trout showed that this species could be made to spawn at least two months in advance of the normal spawning time, provided injections are started that early. Our work here, however, did not include experiments to show if this were possible with muskellunge. While this work is of considerable physiological importance there are also certain features which make the methods here used of value in the conservation and management of fish populations in streams obstructed by dams, permitting the preservation of this species until arrangements can be made for fishways to be constructed around the dams, allowing them to pass to natural spawning grounds.