FAQ:Transport vs Bypass
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How to determine if fish are transported or bypassed at detection sites
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Overview
During the smolt transportation season, fish collected from the smolt bypass systems at Lower Granite, Little Goose, Lower Monumental, and McNary dams are either trucked or barged to an in-river release point below Bonneville Dam. PTAGIS maintains PIT tag interrogation equipment in these bypass and collection facilities, with site names of GRJ, GOJ, LMJ, and MCJ, respectively. The following discussion is pertinent to these four smolt transportation sites only. All fish passing through the smolt bypass systems at all other hydroelectric facilities are immediately returned to the river by default.
At all smolt bypass facilities, the juvenile salmon are routed from the collection channel at the powerhouse through a large (36-48") pipe that conveys the fish to the tailrace below the dam. At the four transportation facilities, the juvenile fish pass through a size and/or debris separator, and are then routed into the collection facility. (Adult salmon "fallbacks" are diverted from the separator and returned to the dam's tailrace as, incidentally, are some smolts.) While fish without PIT tags can be bypassed back to the tailrace after they leave the separator, the majority of those fish are generally (see Caveats) routed into raceways where they are held until loaded onto a barge or tanker truck. Under some circumstances, the fish are "direct-loaded" to a barge as soon as they pass over the separator. A sample portion of the fish exiting the separator are routed to the facility's lab, where the facility biologists determine the species composition and densities of the group(s) of fish to be transported. The sampled fish are also transported.
Beginning in 1993, PIT-tagged fish exiting the separator at these four sites have been preferentially bypassed directly back to the river, rather than routed to transportation. The detection of the PIT tag automatically activates a gate that diverts the PIT-tagged fish into a separate route back to the river. Since 1996, this automated selection and diversion capability has been expanded to allow the identification and segregation of specific PIT-tagged fish. This selective segregation of PIT-tagged fish is called "Separation by Code", and is abbreviated as "SbyC". Some groups of PIT-tagged fish are now intentionally routed to transportation instead of being automatically diverted back to the river. Other individual PIT-tagged fish are collected in tanks after their intial "diversion" or a second diversion at a separate PIT-tag activated gate.
PTAGIS maintains PIT tag detectors in all of these routes through the smolt collection facilities. This redundancy not only ensures that essentially every PIT-tagged fish is detected as it transits a facility, it also provides the means to track the movement of each fish through the facility. From this detailed information, PTAGIS provides a summary of where the fish was first and last detected at it passed through the collection facility.
Using the "Last Monitor Name" to infer disposition
The Interrogation Summary Report, available through the Query Builder application on the PTAGIS Web Portal, returns a single record for each PIT tag code detected at a single detection site. In addition to providing the complete tagging and release information available for the tag code, the query also returns a summary of the detection events (also called "interrogation" or "observation" events) at the site. This summary information includes:
1) the time stamp of the first detection;
2) the individual antenna ("coil") ID of the first detection;
3) the antenna group ("monitor") name of the first detection;
4) the time stamp of the last detection;
5) the individual antenna ("coil") ID of the last detection;
6) the antenna group ("monitor") name of the last detection; and,
7) the total number of detections reported as that tag transited the site.
The "Last Monitor Name" from item (6) above can be used to determine which PIT-tagged fish were bypassed back to the tailrace to continue their down-stream migration. The "Last Monitor Name" can also be used to infer (see Caveats) which tagged fish were transported from the facility. Below, in descending order of certainty, is how to classify the disposition of PIT-tagged fish at the transportation sites.
1) Tags with a "Last Monitor Name" of "FULL FLOW BYPASS", "ADULT FISH RETURN", "DIVERSION RIVER EXIT", "SBYC RIVER EXIT", "RIVER-1 EXIT", or "RIVER-2 EXIT" are definitely bypassed back to the tailrace.
2a) Tags with a "Last Monitor Name" that contains "RACEWAY" or "[SUB]SAMPLE", and are detected during the transportation season, are probably transported from the facility.
2b) Tags with a "Last Monitor Name" that contains "RACEWAY" and "EXIT", and are detected outside of the transportation season, are probably bypassed back to the tailrace.
3) Fish last seen at a "DIVERSION GATE" or "SBYC GATE" were definitely not transported, but may not have been returned to the river.
4) At LMJ, tags with a "Last Monitor Name" of "A-EXIT" or "B-EXIT" were either direct-loaded to a barge or bypassed back to the river. Contact the Corps' Site Biologist at Lower Monumental Dam for more information about these specific operations.
5) Tags with a "Last Monitor Name" other than those listed above were last detected at some intermediate point in the collection facility, and have an unknown disposition.
Caveats
There are a number of caveats to be noted and addressed when assigning the disposition of PIT-tagged fish at the four smolt transportation sites. These caveats include:
1) The transportation season at a site may be shorter than the collection season. Fish may be "collected" (passed through the separator) to obtain a subsample with which to monitor species composition and run timing. Outside of the transportation season, all of the sampled and non-sampled fish, PIT-tagged or not, are returned to the river. Contact the Corps' Site Biologist to confirm the dates of transportation activities.
2) In recent years, a "Spread the Risk" policy has been implemented at McNary Dam that calls for the bypass of most fish during the Spring, and transportation of most fish during "Summer-like" conditions. During the Spring, only PIT-tagged fish marked for the Corps of Engineer's Smolt Transportation Evaluation study are targeted for transportation from MCN. All other PIT-tagged fish, any non-tagged fish, and all sampled fish (tagged or not), are routed back to the tailrace and bypassed. Contact the Corps' Site Biologist at MCN to confirm the dates of the various "study" and "normal" transportation activities.
3) Even within the transportation season, not all fish last seen at a "Raceway" monitor are transported. On occasion, and for a variety of reasons, raceways are intentionally drained to the river. If the fish in these raceways are routed through a pipe without a PIT tag monitor, or pass through a monitored pipe at a high density, they may exit the facility without a last "River" detection. These raceway releases are generally well documented. Contact the Corps' Site Biologists to ascertain if any raceway bypass events occurred.
4) If a gate below a "Raceway" monitor leaks or fails, then fish may be routed out to the barge loading dock and dropped into the river. At each site this is a different exit location than the various "River" exits listed above, but the result is the same, such that the "transported" fish are actually "bypassed". Again, contact the Corps' Site Biologist at each site for more information about any possible operational anomalies at their site.
In summary, while it is possible to determine with great confidence that specific PIT-tagged fish have been bypassed back to the river at one of the four transportation sites, it is not possible to confirm, from the "Last Monitor Name" alone, that a PIT-tagged fish was transported from that site. However, there have been relatively few instances where a PIT-tagged fish was presumed transported and then observed downstream at or above Bonneville Dam. By contacting the Corps' site biologists, it is possible to identify and segregate these and similar data anomalies from the vast majority of tags with known, or at least probable, transportation histories.
Additional Information
To obtain the contact information for the Corps Site Biologists at Lower Granite, Little Goose, Lower Monumental, and McNary dams, or for more information about the layout of the PIT tag detection systems at those sites, browse to the SbyC page under the support section of the PTAGIS Web Portal (www.ptagis.org/ptagis). A sample portion of that information is displayed below.
