| Abstract/Description or Keywords |
The Skeena Watershed is the second largest Chinook salmon (Oncorhynchus tshawytscha) producing watershed in British Columbia. It hosts more than 30 populations of Chinook which spawn in over 56 census units. In 2010 we carried out the first watershed-wide radiotelemetry project for Chinook salmon in the Skeena River. Our objectives were to tag Chinook and trace them to their spawning sites, determine the effectiveness of the latest Skeena Chinook microsatellite DNA baseline in predicting travel to known stock spawning zones, and to develop information on Chinook populations in the upper Skeena. Chinook were captured, DNA samples taken, and tags applied near the head of the Skeena estuary with supplemental tagging at Kuldo above the Babine River. 451 tags were applied overall. Chinook location and migration were determined by 13 fixed stations along the Skeena and major tributaries and by 11 mobile surveys with a small airplane supplemented with boat and helicopter surveys. Radio-tag retention was 97% . Mobile surveys recovered 75% and 93% of the Chinook tagged at Kwinitsa and Kuldo, respectively, and 93% of the Chinook that were tagged at Kwinitsa that proceeded upstream of Oliver. Chinook movement up the Skeena River is fairly uniform, and in general the fish move steadily upstream at 15 to 25 km/day. As the various Chinook stocks separate and approach their destination tributaries they appear to slow down. This is particularly marked below the Kalum River. Chinook that traveled up major tributary rivers spent significantly more time at the river confluences than fish heading further up the mainstream ( p<0.0001 for the Bulkley, Sustut and Kispiox River confluences). The number of Chinook known to have been taken in fisheries is relatively low. Chinook tagged in the lower river experienced 14% capture above the tagging site. Most of the terminal and in-river fishing for Chinook is by First Nations (66% of the total fishing). The radio-tagged Chinook were analyzed and assigned to the 32 sub-populations defined in the Skeena Chinook baseline. The genotypes of 99% of the Chinook that were submitted for analysis were successfully obtained. The overall stock abundance for the radio tagged Chinook assemblage is similar to the abundances derived from analysis of the Tyee Test Fishery collections Recent improvements to the Skeena Chinook baseline has demonstrated the importance of the upper Skeena Slamgeesh and Squingula stocks which now appear to be among the 10 largest Skeena sub-populations. In the lower river, relatively few tags were tracked to the Kitsumkalum watershed. The tracking data and genetic analyses suggest that the Kitsumkalum run constitutes less than half the Chinook escapement of the lower Skeena. Most of the microsatellite DNA assignments agreed with the radiotelemetry results overall. Slightly over half (52%) of the Chinook returned to the specific sites predicted by the baseline genetics. If we take a less stringent view and divide the Chinook cladogram (Figure 6) into the five identified clades, then 77% of the Chinook went to predicted spawning localities. The widespread mobile surveys found Chinook present at all of the known spawning zones and widely distributed downstream of these sites. Of the 382 Chinook that were tagged and traced to an upstream position, 30% were found outside of known or appropriate seeming spawning areas. As the mobile surveys took place near the end of the spawning season and many tags were relocated in nearby localities weeks apart, it is unlikely that these Chinook spawned. It is apparent that there are considerable losses in transit and furthermore that many Chinook end up at unexpected spawning sites. The genetic evidence and radiotelemetry can be reconciled if the straying Chinook have low breeding success. The overall success of microsatellite DNA in predicting the clade and stock assignments of tagged fish, however modest, supports the continued use of genetic analysis of representative samples of Skeena Chinook such as the Tyee Test Fishery to determine escapements of the larger Skeena Chinook components. The migratory delays observed with radio-tagging were much more prominent at the lower Skeena tagging site located at the freshwater end of the estuary than at the upriver site at Kuldo. Nearly 90% of the tagged fish at the lower station dropped back for some period of time and 16% never came back upriver. At the upriver tagging site, only 10% of the fish (12 of 119) dropped back downstream. The more extreme reaction to capture and tagging of Chinook in the estuary is likely related to the osmoregulatory stress of fresh water entry. |
