This invention relates to a method and apparatus for monitoring the movement of macro-organisms. More particularly the instant invention relates to a method and apparatus for tagging and retrieving fish.
For many years, biologists and fisheries managers have monitored the migratory habits of fish. In recent years, particular emphasis has been placed upon studying the migratory habits of anadromous and catadromous fish as these fish migrate past dams and hydroelectric facilities. This emphasis has focused, in part, on studying the effects which passage through a turbine or fishway may have on a fish population, as migratory and resident fish may suffer injury when passing through a hydroelectric facility. However, as discussed at length in Turbine Related Fish Mortality; Review and Evaluation of Studies AP-5480 Research Project 2694-4, Electric Power Research Institute 1987, no adequate or reliable methods for satisfactorily quantifying the effects of such facilities exists.
A hydroelectric generating area commonly consists of a dam and an associated reservior wherein a large quantity of river water is stored temporarily. The retained water passes through hydroelectric generating turbines and the like in a manner known to those skilled in the art. When a dam or other hydroelectric facility is constructed in a stream or river for such purposes as development of power or storage of water for industrial, municipal or irrigation purposes, certain types of fish may be attracted to or transported with the flow of water from the reservior through the turbines and other bypass routes. As these fish travel in and through the turbines, which rotate at high speeds, fish may suffer injury or be killed as they come into contact with rotating turbine blades or shear forces. Additionally, the fish may suffer injury or death as a result of the changes in water flow and pressure which occur during turbine passage.
Thus, although beneficial to man, some hydroelectric generation facilities have been implicated as being destructive to many types of fish. Overflow spillways may provide some method of escape from the foregoing, however, when there is a water shortage for hydroelectric or irrigation purposes, the spillways may only be opened infrequently, if at all. Moreover, some spillway configurations may be detrimental to a fish population where, for example, the fish are swept downwardly at a precipitous angle and dashed at high velocity against a concrete apron or into an extremely turbulent pool.
In the past there have been attempts to form fish passage structures for diverting fish both upstream and downstream, as well as to form conduits bypassing hydroelectric dams or the like for the intended purpose of attempting to protect fish from passing through hydroelectric turbines and the like. Attempts to save fish have also included the netting and catching of fish for transport downstream by way of tank trucks, barges or the like thereby averting passage through the dam. These and other methods for the diversion of downstream migrating fish are described in Koch, U.S. Pat. No. 4,437,431; Matthews, Park, Achord and Ruele, Static Seawater Challenge Test To Measure Relative Stress Levels in Spring Chinook Salmon Smelts, Trans. of Am. Fisheries Society, 115:236-244 (1986) and Matthews et al., Improved Bypass And Collection System For Protection Of Juvenile Salmon And Steelhead Trout At Lower Granite Dam, U.S. National Marine Fisheries Service, Marine Fisheries Review 39(2):10-14. The attempts made at saving fish described above have serious drawbacks, not the least of which is the significant cost of such measures. A fish way or other diversion device is costly to install. Additionally, where attempts have been made to divert fish via a downstream passage structure, large amounts of water, otherwise useful for hydroelectric generation are normally lost. Thus, the efficiency of the use of the water and of the facility is greatly reduced.
In light of the potential environmental impact which a hydroelectric site may have both upon migrating and resident fish populations and in light of the significant costs often associated with remedying such an impact, Federal and State regulatory and environmental authorities often require a developer or owner of a site to plan and conduct studies detailing the environmental effect which the hydroelectric site has on fish passing through the site. The primary object of these studies is often to measure the environmental impact of the facility by calculating the injury and mortality rate for resident and migrating fish passing through the facility. Federal and State environmental authorities often condition operating and renewal licenses for such facilities on the results of such studies and may deny an operating license to facilities which inflict an unacceptable level of harm on migrating and resident fish populations. Additionally, where the environmental impact has been determined to be high, a regulatory authority may require a developer or owner to implement one or more expensive remedial measures including the construction of fish ways or other diversions, as a precondition to the issuance of an operating permit or license. Such remedial construction measures can exceed tens of millions of dollars in cost.
Given the high cost of remedial measures and the fact that an operating license or permit may be denied if a particular facility has been determined to cause excessive harm to a certain fish population, the accuracy of the study evaluating the effect of the facility on populations which pass through it is of crucial importance. If, based upon such a study, a developer or owner can report that only a small percentage of fish are affected by passage through the facility, costly remedial measures may be avoided. Before such a report will be accepted by the appropriate governmental regulatory authority, however, the owner or developer may often need to explain the details of how the study was performed and to substantiate its accuracy.
Heretofore, in order to collect the mortality data needed for operating licenses or permits several techniques have been employed. These include tracking radio tagged fish past a hydroelectric facility as well as mass marking techniques. In mass marking (stains, fin clips, coded tags) large numbers of fish are introduced upstream of a facility and a portion of these are recaptured after their passage through the facility, usually in some type of nets or screening device. Methods for attaching identification or radio tags to fish are disclosed in U.S. Pat. No. 3,820,545 to Jefferts; U.S. Pat. No. 3,369,525 to Dbrotnic, et al.; U.S. Pat. No. 4,790,090 to Sharber; U.S. Pat. No. 4,646,455 to Gardner; and U.S. Pat. No. 3,313,301 to Jeffers et al.
Monitoring fish passage and associated mortality via radio telemetry normally requires that a miniature radio transmitter be fixed in a suitable waterproof enclosure. That transmitter is then either inserted into the fish's stomach, surgically implanted, or externally attached to the fish. The tagged fish are then introduced upstream prior to the hydroelectric facility. Radio receivers are then used to track the fish after passage through the turbines. The status of each fish is determined by monitoring its movements. A steady signal would indicate that the test specimen is stationary and is therefore presumed dead. This presumption introduces uncertainty into the study, as some stationary fish may be healthy, but simply inactive. In addition, in order to determine if there are any delayed effects due to turbine passage, tracking will have to transpire over a number of days, normally a 72-hour period. Additional uncertainty is also introduced, as there are instances when a test specimen is preyed upon during the tracking period.
One such method for telemetrically monitoring migration has been described in Knight, Marancik and Layzer, Monitoring Movements of Juvenile Anadromous Fish by Radio Telemetry, Prog. Fish Cult 39(3):148-150. The method disclosed by this reference suffers from a number of significant problems. First, the tagged fish are often difficult to locate quickly after passing through the turbines especially if they move into deep pools, as the strength of the signal will attenuate as the depth of the transmitter within the water increases. As a result, a third to a half of the tagged fish may go undetected. Of course, for each fish that goes undetected the uncertainty and margin for error introduced into the results of the study increases. In addition, it bears noting that the cost of each transmitter tag is substantial and typically few of these tags are ever recovered. Also, because of the inherent unreliability and unpredictability of this method, several seasons may be needed to complete a study. Finally, because of the man-power requirements of locating and tracking dispersed fish and because of the often protracted time period needed to determine delayed effects of turbine passage, the costs of conducting such studies are often substantial.
A number of modifications have been made to this known method, in an attempt to increase the percentage of fish recovered. While these modifications have to some extent increased the percentage of fish recovered, the modifications themselves have introduced additional uncertainty into the study with the result that the overall accuracy of the study has not been significantly enhanced. For example, in one such modification, nets are introduced in the tailwaters to collect the fish. Netting permits the recovery of a percentage of the test specimens but often the capture technique itself introduces additional uncertainty into the study. According to this method nets are deployed at the turbine port outlets or downstream a short distance so as to trap and recover the fish quickly after their turbine passage and before they may disperse. These nets themselves are expensive to construct and install and often require on-going maintenance and repair. More importantly, however, the fish are often injured as a result of the netting and when the fish are recovered it is often impossible to determine whether the injury resulted from the turbine passage or from the netting. As a result, those using this method typically assume that all fish recovered in a deceased state lacking visible damage were killed by the net and not by some other cause. This assumption ignores the possibility of suffocation, shock and other mortalities which do not manifest themselves visibly and externally, but which may occur as the fish passes through the turbine, thereby drawing into question the results of the study. Although water filled boxes with diminished water currents ("live cars") attached to the end of a collecting net have lessened the magnitude of injury associated with the capture net in some instances, these devices add to the cost in that they require considerable maintenance as well as a large sampling of fish. Additionally, high flow conditions and large debris loads in the water often make these live cars ineffective or inoperable.
Another modification which has been attempted is the attachment of buoyant floats, fishing floats, or the like to the fish prior to their introduction upstream. These floats tend to float and may bring the fish to the surface after their turbine passage thereby simplifying their recovery. However, the problem presented by this method is that there is no way to control the buoyancy of these floats. The float may inhibit or otherwise interfere with the natural movement of the fish as it approaches and passes through the turbine. Often, the fish surface before or during their turbine passage and may come into contact with stationary or moving parts of the turbine facility thereby causing severe, if not fatal injury to the fish. Since after recovery it is difficult to determine whether the injury resulted from factors associated with the float or from the turbine, the accuracy of this method is at best doubtful. Additionally, because of drag forces the float can be readily torn from the fish during passage.
Finally, it has been known to conduct fish migration studies wherein fish have been placed in sealed plastic bags containing water and some chemicals capable of producing a gas. The bagged fish are then introduced upstream of the dam as the chemicals in the bag react to form a gas. After passage through the turbines the formed gas forces the bags to the surface facilitating their recovery. This method has numerous drawbacks. By putting the fish in a sealed bag during the test fish may be deprived of oxygen thereby increasing the mortality rate. Furthermore, the movement of the fish within the bag may be difficult to control. Since this movement may increase the rate of any chemical/gas-producing reaction within the bag, it may cause inflation to incur prior to entry into the turbines. Finally, the bags themselves seriously impair the natural movement of the fish and its ability to propel itself within the water. To the extent this natural movement is altered by the surrounding bag, the accuracy and reliability of the study is drawn into question.
Of the known prior art methods discussed above, all have limitations which have been heretofore unsuccessfully addressed. Known methods have proved to be unreliable, inaccurate, expensive, and time-consuming.