tailieunhanh - Lake Trout Ecosystems in a Changing Environment - Chapter 12

Hồ cá hồi thả trong hồ nhỏ: các yếu tố ảnh hưởng đến thành công Còn hàng truyền thống được xem như một giải pháp chính cho các vấn đề quản lý nghề cá. Một điểm chung giữa các công nhân thủy sản đầu sinh sản tự nhiên là không hiệu quả, và đó trồng cấy nhân tạo và thả giống cẩn thận của các quần thể cá chiên đảm bảo lành mạnh (Nevin, năm 1892, Fullerton, 1906). Các nút cổ chai xuất hiện sẽ diễn ra trên các bãi đẻ. Nam và nữ đến và chín tại các thời điểm. | chapter twelve Lake trout stocking in small lakes factors affecting sUccess Michael J. Powell Ontario Ministry of Natural Resources Leon M. Carl Great Lakes Science Center Contents Introduction Stocking objectives Environment Stocking location and method Variation among stocks Size at release Stocking rate Species interactions Management implications Acknowledgment References Introduction Stocking has traditionally been viewed as a primary solution to fisheries management problems. A common view among early fisheries workers was that natural reproduction was inefficient and that artificial propagation and careful stocking of fry guaranteed healthy fish populations Nevin 1892 Fullerton 1906 . The bottleneck appeared to take place on the spawning grounds. Males and females arrived and ripened at different times when spawning finally occurred the manner in which eggs and milt were released into the environment seemed to ensure that few eggs were ever fertilized. This prevailing view was affirmed by Nevin 1898 p. 20 Nature s provisions for the survival and increase of the several species of fish are not adequate. To rectify this apparent error in nature s laws we have resorted to artificial propagation with gratifying results. As in the past the decision to stock may seem eminently logical given that problems such as habitat loss overexploitation and species introductions share the common symptom 2004 by CRC Press LLC of decreased fish. It is understandable then that topping up the population would be perceived as a positive action. However the objectives of many stocking programs are often not well articulated and might best be described rather vaguely as increasing the population so more fish can be caught. With no clear objectives it is difficult to set quantifiable measures of success and therefore determine if the stocking program is achieving the desired results. Although the value of fish stocking has traditionally gone unquestioned the potential negative .