Fish Movement at the Springbank Dam - Thames River, Ontario

PHASE 2 - POST-CONSTRUCTION MONITORING - 2008
 

The City of London, Ontario commissioned this study with the objective of comparing post-construction data related to the movement of various fish species during the spring before Springbank dam closure.  Specific objectives were to determine:

1) If the Springbank dam is a barrier to fish movement,

2) Fish attraction to the dam structure,

3) The degree of upstream and downstream fish passage,

4) Timing of fish passage,

5) Fish passage efficiency,

6) Thermal and hydraulic conditions at the dam site during fish passage

7) The duration of migration (i.e. migration windows) for the different species of fish monitored from the Thames River.

The purpose of this report is to summarize fish movement after construction of the new dam gates and to compare post-construction fish-movement data with pre-construction baseline data collected in 2006.

POST-CONSTRUCTION MONITORING OF FISH PASSAGE AT THE SPRINGBANK DAM

 EXECUTIVE SUMMARY

Springbank dam in 2006 pre-construction with stoplog gates (above) and post-construction of hydraulic gates in 2008 (above).

The City of London and the Upper Thames River Conservation Authority originally contracted Biotactic Incorporated in 2006 to design and conduct a study to collect baseline data related to fish movement at the Springbank dam in the spring before stoplogs were installed and the dam operated. The baseline data were compared with similar information collected post-construction in 2008 to address Provincial and Federal directives pertaining to the maintenance or enhancement of the status quo related to fish movement at the Springbank dam. Radio-telemetry was used to track the movement of 120 radiotagged white suckers, shorthead redhorse and smallmouth bass (twenty fish of each species, each monitoring year) at the Springbank dam from April 14, 2006 to June 27, 2006 and again from April 19, 2008 to June 15, 2008. All fish were collected from areas upstream from the dam and released downstream after radio-tag implantation. In 2008, fish approached the dam as readily as they did in 2006, but only half as many fish of each species were eventually able pass over the dam gates. Of the two catostomid species (early migrating white suckers and mid season migrating shorthead redhorse) that were monitored; both readily approached the dam, but white sucker took significantly longer to pass through the dam and shorthead redhorse passed through the dam significantly faster in 2008. Late spring upstream migrating smallmouth bass took longer to pass through the dam in 2008 and some used the structure as habitat. Pre-construction data from 2006, compared with post-construction data from 2008 indicates that the Springbank dam is not a barrier to fish movement prior to dam closure, and can be summarized as follows:

1. Pre-construction attraction efficiencies of white sucker, shorthead redhorse and smallmouth bass in 2006 were statistically similar to post-construction attraction efficiencies in 2008. These values (reported as efficiency with 95 % confidence interval in parentheses) are:

2. Pre-construction passage efficiencies of white sucker, shorthead redhorse and smallmouth bass in 2006 were statistically higher than post-construction passage efficiencies in 2008. These values (reported as efficiency with 95 % confidence interval in parentheses) are:

3. Most fish rapidly approached and swam upstream through the dam structure in 2006. Fish readily approached the dam in 2008, but white sucker and smallmouth bass were more delayed while passing through the dam. The mean time (± standard error) required for each species to pass the Springbank dam was:

4. Environmental factors such as mean river discharge, air temperatures and water temperatures at Springbank dam as well as lengths of individual fish were recorded in 2006 and 2008.  Statistical comparisons were made from the entire study period and one week after release of each species to determine the possible influence of factors external to dam construction.  It was concluded that air and water temperature changes and water level changes were significantly different; however air and water temperatures had a negligible effect on fish behaviour. River level changes reflected different river flow conditions in 2008 compared to 2006. Other water level factors such as hydraulic conditions over the new dam gates did vary over the course of the study due to gate testing and the north gate failed to open fully and did not lie completely flat on the river bottom as designed.

5. Further monitoring is required in 2009 and perhaps 2010/2011, with larger sample sizes of radio-tagged individuals if possible. These additional data are required to refine statistical comparisons related to baseline conditions.  During monitoring, as many factors as possible must be kept constant related to Springbank dam, as well as capturing, handling and release of fish. For example, releases of radio-tagged fish should be conducted under similar thermal and hydraulic conditions, at similar dates and times each year. Dam gates should be lowered as much as possible and remain lowered throughout the study period (except for testing purposes outside of peak periods of upstream fish migration). Upstream fish migration occurred slightly later in 2008 compared to 2006 due to variation in natural environmental conditions.  Some variables, such as river flow, water temperature, and mechanical malfunction are somewhat unpredictable, and control of these dynamic factors will remain a key challenge for this monitoring project.

6. A comparison of the data sets from 2006 and 2008 shows statistically, or mathematically significant differences regarding attraction and passage efficiencies. Observations made either directly or videographically suggest that the biological significance of measured attraction and passage efficiencies may differ from mathematical significance. In other words, there was evidence in both 2006 and 2008 that multiple species other than the selected 3 targeted species, move with relative ease over the Springbank dam gates.

2009 Post-Construction Fish Monitoring Report - HERE