Shoal of sea trout viewed with the Didson
ENVIRONMENT AGENCY WALES , FISHERIES ASSESSMENT TEAM
This report presents results from the River Teifi hydro acoustic counter for 2006 (January to August), the eighth year of full operational deployment. During 2006 the performance of the counter was reassessed using the latest advancement in underwater monitoring equipment – a DIDSON acoustic camera. This follows an initial assessment of the counter efficiency (the proportion of fish detected by the counter) undertaken in 2001 using video recordings of fish movement at the site.
Shoal of sea trout viewed with the Didson
Fish Counts
The total provisional validated count for 2006 to the end of August was 22399 fish, with the majority of fish migrating in July and August (see Table 1). Counts during the months of March to June were well below average. The counter was operational for over 90% of the year
DIDSON being deployed during high flows
Table 1: Monthly breakdown of provisional counts from the Glanteifi counter for 2006 (Sept to Dec not yet available)
Month |
Long term validated average (1999-2005) |
Validated count |
Jan |
444 |
1080 |
Feb. |
105 |
663 |
Mar |
151 |
338 |
Apr |
1392 |
169 |
May |
2406 |
677 |
Jun |
6119 |
3229 |
Jul |
6636 |
9063 |
Aug |
4103 |
7181 |
Sep |
2858 |
- |
Oct |
1741 |
- |
Nov |
1031 |
- |
Dec |
930 |
- |
Total |
|
22399 |
The DISON assessment revealed that the counter has been detecting a lower proportion of fish since 2004. The validated counts in Figure 1 have been corrected for the different detection rates over the years and are comparable.
Figure 1: Historical annual estimates of the total number of fish migrating past the counter
(* provisional estimate).
Future Work