Interim Report: Arrow Lakes Reservoir Burbot Life History and Habitat Use, 2008-2013

Author: D. Robichaud, G. Glova, S. Kingshott

The key management questions that BC Hydro wishes to answer from the findings of this five-year Burbot life history and habitat use monitoring program are: 1.Where do Arrow Lakes Reservoir Burbot spawn? 2.If spawning occurs in the mid-Columbia River, will the change in flow regime due to the addition of the fifth generating unit at Revelstoke Dam affect Burbot spawning migration and habitat in the river? 3.Does winter drawdown of the reservoir cause dewatering of Burbot spawning habitat and affect spawning success? 4.Can operation of the Arrow Lakes Reservoir be modified to protect or enhance spawning success of Burbot?

1.Where do Arrow Lakes Reservoir Burbot spawn?

Initially, we thought that Burbot would be spawning in relatively shallow tributary areas, which was why we began by using radio tags and aerial tracking. When the first years (aerial) surveys were unsuccessful, we realized that the Burbot must be spawning in relatively deep water, and we switched to acoustic tags.

In the next four study years, we continually documented the Beaton and Shelter Bays areas as the primary areas of Burbot aggregation during the spawning period (Feb/March). Trapping of fish in the aggregation areas showed that fish were expressing or spawned out by March. Plankton tows and egg mats in the aggregation areas did not, however, find Burbot eggs in the water column or on the substrate. Underwater video did not capture Burbot spawning activity, but there may have been some degree of camera avoidance. Therefore, although precise spawning locations were not discovered, the results provide indirect evidence that spawning generally occurs in the Beaton and Shelter Bay areas.

2.If spawning occurs in the mid-Columbia River, will the change in flow regime due to the addition of the fifth generating unit at Revelstoke Dam affect Burbot spawning migration and habitat in the river?

Spawning habitat: The location of the Burbot spawning aggregation did not change after Unit 5 came online (which indirectly suggests that habitat was not affected). The effects of Unit 5 on spawning habitat cannot be tested with the available data. Although we were able to identify the likely location of the main Upper Arrow Lake spawning location, we do not know precisely the geographic extent of the spawning aggregations, or the habitats the Burbot were using. However, it is probable that spawning occurs mainly in deep water areas (>20 m) near the bottom, where they were observed to be present during the day. With additional data, it would be possible to look for changes in the availability of deep water areas in the Beaton area that correlate with the addition of Unit 5.

Spawning migrations: We tested this by showing that spawning migrations (˜seasonal movements) did not vary in a way that could be attributed to the addition of Unit 5.

Flow regime: no change in flow regime could be attributed to the addition of Unit 5.

3.Does winter drawdown of the reservoir cause dewatering of Burbot spawning habitat and affect spawning success?
In the context of ˜present conditions, the question can be answered. It appears that Burbot do not spawn in the areas most affected by drawdown. The locations most expected to be affected by winter drawdown are located immediately downstream of Revelstoke Dam. In this study, winter tracking showed that Burbot move out of these areas. Burbot aggregations were found to be primarily in the Beaton and Shelter Bay areas. During four consecutive winters (the assumed Burbot spawning period), the largest Burbot aggregations were consistently located in these areas. As corroboration, biosampling revealed that Burbot in these aggregation areas were in spawning condition, and that some were spawned-out. From plots of water elevation data, the extent of winter drawdown in the Beaton and Shelter Bay area in February and March 2009-2013 did not appear to be preventing spawning activity.

In a ˜historical context, it may be that Burbot formerly spawned in the drawdown area, but no longer do. Without historic data this question cannot be answered. Clues might be gleaned from strong spawning habitat association data (which are lacking) in conjunction with a map of habitats as they would have been in the drawdown area before the water levels began to be manipulated.

4.Can operation of the Arrow Lakes Reservoir be modified to protect or enhance spawning success of Burbot?
No effects are evident nor anticipated, hence no modifications are required.

1.Where do Arrow Lakes Reservoir Burbot spawn?

Initially, we thought that Burbot would be spawning in relatively shallow tributary areas, which was why we began by using radio tags and aerial tracking. When the first years (aerial) surveys were unsuccessful, we realized that the Burbot must be spawning in relatively deep water, and we switched to acoustic tags.

In the next four study years, we continually documented the Beaton and Shelter Bays areas as the primary areas of Burbot aggregation during the spawning period (Feb/March). Trapping of fish in the aggregation areas showed that fish were expressing or spawned out by March. Plankton tows and egg mats in the aggregation areas did not, however, find Burbot eggs in the water column or on the substrate. Underwater video did not capture Burbot spawning activity, but there may have been some degree of camera avoidance. Therefore, although precise spawning locations were not discovered, the results provide indirect evidence that spawning generally occurs in the Beaton and Shelter Bay areas.

2.If spawning occurs in the mid-Columbia River, will the change in flow regime due to the addition of the fifth generating unit at Revelstoke Dam affect Burbot spawning migration and habitat in the river?

Spawning habitat: The location of the Burbot spawning aggregation did not change after Unit 5 came online (which indirectly suggests that habitat was not affected). The effects of Unit 5 on spawning habitat cannot be tested with the available data. Although we were able to identify the likely location of the main Upper Arrow Lake spawning location, we do not know precisely the geographic extent of the spawning aggregations, or the habitats the Burbot were using. However, it is probable that spawning occurs mainly in deep water areas (>20 m) near the bottom, where they were observed to be present during the day. With additional data, it would be possible to look for changes in the availability of deep water areas in the Beaton area that correlate with the addition of Unit 5.

Spawning migrations: We tested this by showing that spawning migrations (˜seasonal movements) did not vary in a way that could be attributed to the addition of Unit 5.

Flow regime: no change in flow regime could be attributed to the addition of Unit 5.

3.Does winter drawdown of the reservoir cause dewatering of Burbot spawning habitat and affect spawning success?
In the context of ˜present conditions, the question can be answered. It appears that Burbot do not spawn in the areas most affected by drawdown. The locations most expected to be affected by winter drawdown are located immediately downstream of Revelstoke Dam. In this study, winter tracking showed that Burbot move out of these areas. Burbot aggregations were found to be primarily in the Beaton and Shelter Bay areas. During four consecutive winters (the assumed Burbot spawning period), the largest Burbot aggregations were consistently located in these areas. As corroboration, biosampling revealed that Burbot in these aggregation areas were in spawning condition, and that some were spawned-out. From plots of water elevation data, the extent of winter drawdown in the Beaton and Shelter Bay area in February and March 2009-2013 did not appear to be preventing spawning activity.

In a ˜historical context, it may be that Burbot formerly spawned in the drawdown area, but no longer do. Without historic data this question cannot be answered. Clues might be gleaned from strong spawning habitat association data (which are lacking) in conjunction with a map of habitats as they would have been in the drawdown area before the water levels began to be manipulated.

4.Can operation of the Arrow Lakes Reservoir be modified to protect or enhance spawning success of Burbot?
No effects are evident nor anticipated, hence no modifications are required.