John H. Eiler

Riverine Spawning by Sockeye Salmon in the Taku River, Alaska and British Columbia

Abstract Radio telemetry was used to determine the distribution of sockeye salmon Oncorhynchus nerka returning to spawn in the glacial Taku River in 1984 and 1986, and to locate and characterize spawning areas used by this species. During the study, 253 sockeye salmon were tracked as they moved upriver; 204 of these were followed to spawning areas. Only 37% of the 204 fish traveled to areas associated with lakes; the remaining 63% returned to “riverine” areas – river areas without lakes (42% to the Taku River main stem, 17% to the Nakina River, and 4% to other rivers). Sockeye salmon spawning in riverine areas used a variety of habitat types, including main-river channels, side channels, tributary streams, and upland sloughs. Most (55%) of the radio-tagged fish that returned to the Taku River main stem were tracked to side-channel spawning areas. Half of the 471 adult sockeye salmon sampled in main-stem spawning areas had migrated to sea as juveniles before their first winter. This study showed that many ...

A Remote Satellite-Linked Tracking System for Studying Pacific Salmon with Radio Telemetry

Abstract A remote tracking system with a satellite uplink was used to study the movements of adult Chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch in the large, isolated Taku River in Alaska and British Columbia. Salmon were tagged with pulse-coded radio transmitters; 10 codes identified individual fish on each of 52 frequencies. Remote tracking stations automatically collected, processed, and transferred telemetry data via a computer-controlled receiver. A satellite uplink was used to retrieve the data for within-season analysis. Three hundred six Chinook salmon were tracked upriver in 1990 and 351 coho salmon in 1992. Coho salmon could not have been tracked with conventional methods due to the inclement fall weather and mountainous terrain typical of this area. The stations recorded 98–100% of the radio-tagged fish that moved past. Tracking success was much higher than in previous studies in which fish were tracked exclusively from aircraft. The remote tracking system is an effective ...

Collecting, interpreting, and merging fish telemetry data from an AUV: Remote sensing from an already remote platform

Chemical and hydrological AUV sensors (e.g. C, T, 02, CDOM, Chlorophyll a) collect information about water in contact with or in close proximity to the vehicle. Sonar (e.g. ADCF, side scan, dual beam, and multibeam) collect data about features distant on the scale of tens of meters away and linked to coordinates. In contrast, acoustic tags implanted in fishes or other marine fauna can be detected at distances greater than a kilometer away, which brings special considerations to data treatment and merging. In the case of telemetry systems that log sound pressure levels, relative signal strength can be used to produce proximity maps using regression. For systems with invariant signal timing, a synthetic aperture engine can calculate location of the tag if a suitable AUV path produces a good aperture. In the common case where both of these conditions are lacking, the tag position must be assigned to a place along the vehicles path. The use of tags that broadcast information from their own sensors (e.g. pressure, temperature) can help resolve both the position and environment of the distant tag. An empirically-fashioned hierarchical decision matrix based on numerous AUV-fish telemetry missions in shallow and deep (<3m to 600m) water assists in mission planning, data processing, and displaying AUV-collected data about telemetered fauna and their environment.

Comparing autonomous underwater vehicle (AUV) and vessel-based tracking performance for locating acoustically tagged fish

Autonomous underwater vehicles (AUV’s) are increasingly used to collect physical, chemical, and biological information in the marine environment. Recent efforts include merging AUV technology with acoustic telemetry to provide information on the distribution and movements of marine fish. We compared surface vessel and AUV tracking capabilities under rigorous conditions in coastal waters near Juneau, Alaska. Tracking surveys were conducted with a REMUS 100 AUV equipped with an integrated acoustic receiver and hydrophone. The AUV was programmed to navigate along predetermined routes to detect both reference transmitters at 20–500 m depths and tagged fish and crabs in situ. Comparable boat surveys were also conducted. Transmitter depth had a major impact on tracking performance. The AUV was equally effective or better than the boat at detecting reference transmitters in shallow water, and significantly better for transmitters at deeper depths. Similar results were observed for tagged animals. Red king crab, Paralithodes camtschaticus, at moderate depths were recorded by both tracking methods, while only the AUV detected Sablefish, Anoplopoma fimbria, at depths exceeding 500 m. Strong currents and deep depths caused problems with AUV navigation, position estimation, and operational performance, but reflect problems encountered by other AUV applications that will likely diminish with future advances, enhanced methods, and increased use.

Comparison of Radiotelemetry and Microsatellites for Determining the Origin of Yukon River Chinook Salmon

Abstract Chinook salmon Oncorhynchus tshawytscha support important subsistence and commercial fisheries throughout the Yukon River. Low returns and diverse user groups have made management of these fisheries contentious and have necessitated information on the origin of the spawning migration and harvest. Here we compare estimates of individual assignment and stock composition derived from genetic and radiotelemetry data collected from the same Chinook salmon. Radiotelemetry and genetic individual assignments were highly concordant. Agreement between methods for individual assignment was 79% to region and 93% to country when using the most probable genetic criterion, improving to 94% for region and 98% for country when using the ≥95% probability genetic criterion; however, under the more stringent criterion, fewer individuals could be assigned. Further analysis showed that estimates of stock composition based on radiotelemetry and genetic methods were within 6% of each other and were not significantly dif...

Fate of radio-tagged trawl web on an Alaskan beach

Thirty-five fragments of trawl web were radio-tagged on Kayak Island, Alaska, to determine their fate once stranded ashore. Tagged fragments placed in the immediate study area were monitored daily by a remote tracking station (RTS) from August 1994 to May 1995. Ground and aerial surveys in June 1995 located fragments that had moved out of the reception range of the RTS. Of the 35 tagged fragments, 18 (51%) remained on Kayak Island, whereas the whereabouts of 17 (49%) fragments were undetermined. Most fragments not relocated were lost during severe fall storms. Tagged fragments that remained on Kayak Island moved an average of 2.0 km from their original tagging location. Fragments not relocated were smaller (x = 1.25 kg) than those found (x = 6.28 kg). Missing fragments were likely washed back to sea. To reduce entanglement hazards to marine life, stranded trawl web should be removed from beaches during clean-ups to prevent possible reentry into the ocean.