Whatshan Reservoir Bull Trout

Regulation Number: 
2023-04-04
Status: 
Proposed
Region: 
Region 4 - Kootenay
MU: 
4-32
Regulation Type: 
Quota
Species: 
Bull Trout
Closing Date: 
January 6, 2023 at midnight
Decision Statement: 

Pending

Current Regulations: 

Regional regulations with no water-specific entry (trout/char daily quota = 5 any size).

Proposed Regulations: 

Status quo:

Regional regulations with no water-specific entry (trout/char daily quota = 5 any size)

Additional Regulations:

No bull trout under 60 cm.

Rationale: 

Whatshan Reservoir (historic natural lake with raised water level – a reservoir with BC Hydro dam) has an isolated core area of bull trout which is genetically unique and divergent from neighboring populations. This population is considered at risk by provincial status assessment methodology and has a small population that may be currently limited by angler harvest. Other high risk core areas in Region 4 (e.g., Slocan River, Salmo River, Moyie River and Flathead River) are protected by catch and release regulations or 60cm minimum size limits. Redd (spawning) survey data collected on Whatshan Lake between 2016-2018 indicates that the current abundance of the spawning population of bull trout in Whatshan Lake is low (~30 redds per year or <100 fish), with limited distribution throughout the watershed due to migration barriers that restrict movement. Conservation thresholds commonly used in status assessments indicate a spawner abundance of <100 fish is considered a small population that is at higher risk of extirpation. Maintaining spawner abundance well above 50-100 individuals per year is an important consideration that has been discussed extensively in conservation and recovery planning literature for bull trout.  The conservative management strategy aligns with provincial policy to protect wild fish populations. Increasing spawner abundance should result from implementing a 60cm minimum size limit.

A 60cm minimum size limit could initially reduce harvest until equilibrium is reached (i.e., the dynamics between angling and bull trout population responses stabilizes). At equilibrium, an increase in catch rate and mean size of catch is possible, if angling effort increases; however, overall harvest yield may decrease, especially at lower fishing effort. Assuming bull trout grow slowly regardless of density, and effort remains low or is further reduced, there is likely a trade-off in this regulation for the fishery – overall harvest yield will decrease, but quality of the fishery (catch rate and mean size of catch) will increase.

Additional Information: 

Redd survey data collected by Himmer (2018) indicates a small population size.

Creel survey data collected by Andrusak (2016b) suggests potentially high (with high uncertainty due to small sample size) exploitation rates, consistent with those expected to result in spawner abundance limitations.

Gillnet catch data collected by Slaney et al. (1992) suggests low abundance of larger (60 cm) size classes, indicating possible high exploitation of larger, more catchable fish, slow growth rates, or a combination of both.