FRESHWATER FISHERIES MANAGEMENT |
| One of the concerns in environmentalism is the management of fish and other aquatic creatures usually those which are used for human consumption. This is a difficult task because all biotic and abiotic factors in the environment must be taken into account to achieve success. These factors include but are not limited to predator/prey relationships in the area, chemical composition and clarity of the water, water pollution, and the use of the area by several groups for different purposes (i.e. logging, recreation, etc.). |
ARTIFICIAL STOCKING
There are two types of stocking: 1)
adding to an existing fish population and
2) starting a new population in an area
where one did not exist.
| The first type of stocking often fails. It is also very expensive to raise the young fish to adulthood, making it prohibitive in many cases. Also hatchery-raised fish are often not suited for the environment into which they will be released. They may be weaker and more disease-prone than the natural stock in the area. Introducing these fish into the reproductive cycle of the existing population lowers the survival chances of the entire population. Catching native fish and breeding them in captivity creates essentially the same problem. By breeding only specific individuals, the genetic diversity available in the wild is lost. Once again, the result is a weaker population in general (Owen et al. 292). |
| Stocking of fish is most successful in newly-formed areas such as reservoirs created after a dam is built. There are no existing fish which will be harmed by this stocking. In addition, if a reservoir is deep, it can have two layers of inhabitants. In this case the top layer of warmer water can support warm water species while the lower cold layer can support cold water species. |
INTRODUCTION OF NEW SPECIES
| The practice of introducing a species to a populated area where it has not previously existedis often detrimental. The new fish will compete with existing species for resources, which may cause serious problems. If the new species is better suited to the environment and reproduces more quickly, the older populations of fish may be forced out of existence. |
| A good example of this is the huge problem caused by the sea lamprey in the Great Lakes. When the Welland Canal was constructed near the end of the 1800s, it offered ocean fish the possibility of entering Lake Erie for the first time. The sea lamprey, probably accidentally at first, gained access to the area. Within twenty years it had caused widespread destruction of the trout population in the entire Great Lakes region (Owen et al. 296). |
| Another problem which occurs with new species introduction is interbreeding. If the new fish species mates with an existing species, a hybrid species will emerge. Often hybrids are not viable species, and this could lead to the demise of the three species (the original one, the introduced species, and the hybrid). |
| If the introduced species can find a niche that is not being filled by an existing species, this practice can be successful. For example, if the original fish species live in one section of the water (i.e. a specific depth or temperature range) and the new fish lives in a different section, there will be little or reduced competition between them. It is possible that both species can survive. |
TRANSLOCATION
| This is a practice of taking
eggs from a species in one environment and intro- ducing them into another area where the same species already lives. An important element in this method is that the eggs come from an ecologically similar environment to the one in which they will be transplanted. When these eggs hatch in the new area, the population of fish which had been dwindling will have a new generation with which it can increase its numbers. The most important consideration in this maneuver is to determine why the original species was declining. If this is not done prior to the translocation of the new eggs, the new population may also decline due to the existing problems at the site (Owen et al. 298). |
REMOVAL OF DESTRUCTIVE SPECIES
| Often a fisheries manager may want
to rid an area of species that are detri- mental to game fish. Again, this is a touchy issue. Sometimes chemicals are dumped into the environment to kill the unwanted species. However, these poisons kill more than just the intended species. At other times commercial fishing is advocated of a particular fish to reduce its numbers. Sometimes nets are used to catch the undesired species to avoid more unpleasant manners of removal. |
| Studies have shown that less than 50% of these efforts are successful. Again, it is important to discover the underlying cause of a sudden increase in an undesired fish species. In this manner a long-term solution can be sought rather than a short-term treatment of the symptoms (Owen et al. 299). |
OXYGEN MAINTENANCE
| Often in the winter oxygen levels become depleted in lakes. This can cause death of many species of fish. To avoid this, snow can be removed from the frozen surface, allowing sunlight to penetrate. This allows the aquatic plants to continue to photosynthesize and produce oxygen. For larger bodies of water, it may be necessary to dynamite or bore holes through the ice so that atmospheric oxygen can enter the water or so that oxygen can be introduced with aerators. |
SELECTIVE BREEDING OF SUPERIOR FISH
| Sometimes the crossbreeding of two species can result in a hybrid that is stronger and more successful than either of its parent species. However, this practice is controversial because there is no way to predict ahead of time the consequences of introducing this new species into an environment. Therefore, this method must be given careful forethought before being implemented. |
FISHING REGULATIONS
| One of the most effective ways of maintaining fish numbers is through the regulation of fishing practices. Establishing minimum size limits and maximum quantity limits on fish species can provide these fish a chance for survival. In addition, fishing seasons can be imposed, with the species being off limit during crucial times such as reproductive periods. Certain types of fishing methods can also be controlled to give the fish a better chance of evading capture. For example, poisoning, dynamiting, or using multiple hooks are not means by which fish can be caught fairly. |